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Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 0-1.

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Quantitative Characterization of Deep-sea Channel Continuity Under Architecture Model Constraints

LIU Fei, ZHAO Xiaoming, FENG Xiaofei, CAO Shuchun, BU Fanqing

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 16-26. DOI: 10.11885/j.issn.1674-5086.2024.08.28.01

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Deep-sea channels are important transportation channels and deposition sites for sedimentary debris to deep-sea basins, and they are the main types of reservoirs in deep-sea sedimentary environments. Aiming at the problems of unclear structural pattern and distribution pattern of sand body inside the channel, and the difficulty of predicting reservoir continuity, we have carried out a research on quantitative characterization method of reservoir continuity in deep-sea channel type. The study takes the deep-sea waterway configuration pattern and characterization results as the constraints, takes the inverse of the product of the lateral and vertical stacking ratio of the sand body as the continuity coefficient, and synthesizes the coupling relationship between the continuity and curvature to realize the quantitative evaluation of the distribution pattern of the continuity of the reservoirs in the deep-sea channel. The study achieves the following insights, the single channel configurations in the study area are divided into three types: isolated (Type Ⅰ), contact (Type Ⅱ), and embedded (Type Ⅲ), corresponding to lateral stacking ratios of >1.00, 0.85~1.00 and <0.85, and vertical stacking ratios of >1.00, 0.80~1.00 and <0.80, and continuity coefficients of 0.96~1.34, 1.37~1.67 and 1.67~2.56, type Ⅰ curvature distribution intervals of 1.00~1.11, type Ⅱ distribution intervals of 1.02~1.28, and type Ⅲ distribution intervals of 1.10~2.28, with continuity decreasing with increasing curvature. The study quantifies the continuity coefficients and curvature distribution ranges of different configuration styles, quantitatively characterizes the stacking relationship between single channel sands, and is of great significance as a geological guide for the efficient production and fine development of deep-sea channel reservoirs.

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Migration Patterns and Genetic Mechanisms of Deep-sea Channels

LIANG Shiqin, WU Wei, XIANG Wei, ZHAO Zhonghui, SUI Yaping

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 27-41. DOI: 10.11885/j.issn.1674-5086.2024.08.31.02

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The deep-sea channel is one of the important conduits for the transport of terrestrial clastic sediments to deep-water basins, and it is also the main depositional site for sand sedimentation in deep-water basins.This study summarizes previous research to clarify the migration and formation mechanisms of deep-sea channels, yielding the following findings: based on the migration mode, deep-sea channels can be categorized into unidirectional migration channels (upstream migration type/downstream migration type) and multidirectional migration channels (downstream migration type/lateral migration type/obstacle migration type). The migration characteristics of the channels can be characterized based on the changes in the channel thalweg, unidirectional migration channels are accompanied by overall changes in the thalweg line, while multidirectional migration channels primarily exhibit local changes. The interaction between bottom currents and gravity currents controls the sedimentary construction of unidirectional migration channels. In addition, self-circulation and upwelling currents also affect the sedimentary evolution of the channels. Multidirectional migration channels, on the other hand, are controlled by multiple factors such as sea level changes, sediment supply, tectonic movements, paleo-topography, and the sedimentary action of the channels themselves. The formation of unidirectional migration channels is mainly controlled by the interaction between gravity flows and contour currents, the self-circulation of flows, and upwelling flows, while multidirectional migration channels are mainly influenced by sea-level changes, sediment supply, tectonic movements, paleotopography, and the self-deposition of channels. The future research and development directions of deep-sea channel migration patterns mainly include three aspects: 1) actively conducting multi-scale quantitative research; 2) exploring the coupling mechanisms of various dynamic factors related to channel migration; 3) strengthening the research on the relationship between channel migration patterns and reservoir development.

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Evolutionary Model of Hydrochemical Lobes in the ABL Block of Campos Basin

YIN Guofeng

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 42-55. DOI: 10.11885/j.issn.1674-5086.2024.09.04.01

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As the major components of submarine fan systems, submarine channels and lobes receive much attention from the sedimentological community. However, studies about the“channel-lobe transitional zone”and the associated channelized lobes are still not enough. This study takes the Block ABL in deep-water areas of Campos Basin of Brazil as the example and recognizes different depositional elements of sandy channels, muddy channels, and sheet lobes, which suggests that channelized lobes are widely developed within the study area. We then characterize the overall deposition and internal architecture of channelized lobes, analyze the associated controlling factors, and establish the evolution model. The results suggest that the overall deposition of channelized lobes show significant variations between different locations; compared with the deposition in southern and downdip area, lobes in northern and proximal areas are more channelized. About the internal architecture, the channelized lobes could be divided into 3 lobe elements, which developed from north to south in terms of sequence. Lobe element 1 was mainly controlled by the source from north, which developed lots of distributaries and was more channelized. Controlled by the main source, Lobe element 2 was oriented along the major feeder channel; due to the gradual decreasing of topographic gradient, the degree of channelization of Lobe element 2 decreased. Lobe element 3 was mainly controlled by the behavior of gravity flow in the major feeder channel; around the bend of major feeder channel, gravity flows were stripped and deposited rapidly, which caused the formation of Lobe element 3 with relatively weak degree of channelization.

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Sedimentary Model and Reservoir Characteristics of the “Three Group” Channel System in the North Sea of UK

BU Fanqing, YANG Li, CAO Shuchun, YANG Baoquan, Lü Wenrui

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 56-66. DOI: 10.11885/j.issn.1674-5086.2024.09.02.05

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There are significant differences in the sedimentary reservoir characteristics of different types of deep-water turbidite channel systems. Taking the restricted deep-water turbidite channel system of the P oil formation in the North Sea G Oilfield in the UK as an example, seismic geomorphology methods, drilling and core data were used to characterize the distribution characteristics of the internal reservoirs in the turbidite channel system, and to clarify the impact of diagenesis on reservoirs in North Sea through thin section and electron microscopy observation. Research indicats that: 1) the P oil formation developed within a restricted U-shaped canyon, forming a typical "three group" sedimentary pattern vertically; 2) the bottom A and B sand formation is composed of coarse-grained sediments. At the bottom, the A sand body is not developed and does not deposit, and is in unconformable contact with the underlying strata; the B sand group is a mud debris flow mixed with plastic flow; the central C sand formation covers the entire canyon and has the best reservoir quality; the top D sand formation is a late stage sedimentation, mainly composed of natural mud embankments; 3) the upper and lower oil groups do not have good physical properties but the middle group does. This study not only has significant theoretical implications for the development of deep-water sedimentology, but also has important practical significance for the exploration and development of similar oil fields.

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Developmental Characteristics and Genesis Mechanisms of Submarine Canyons in the Rovuma Basin, East Africa

MA Hongxia, ZHU Yueyue, XU Xiaoyong, HE Yunlong, WANG Hongping

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 67-79. DOI: 10.11885/j.issn.1674-5086.2024.08.28.07

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The external morphological characteristics, internal filling structure and genetic mechanism of submarine canyons in the Rovuma Basin are not fully understood. We make a study on the external morphological characteristics, internal filling structure and genetic mechanism of submarine canyons by using three-dimensional seismic data, combined with the relevant theories of deep-water sedimentology and previous research results. The results indicate that there are 10 canyons in the Rovuma Basin, trending east-west, with a V-shaped narrow upstream and U-shaped gentle downstream profile vertically, and showing an isolated-merged-dispersed pattern on the horizontal plane. The internal filling sediment types in the canyons include basal lags, slides and MTDs. Outside the canyons, sediment drifts and pockmarks are observed. Considering the developmental background of submarine canyons in the study area, it is believed that there may be two genesis mechanisms at play. One involves the escape of natural gas from the underlying strata, leading to the formation of pockmarks and subsequent erosion of weak layers, with interconnected pockmarks forming the initial shape of the canyon, gradually evolving under the influence of sediment-laden fluid flow and erosion. The second mechanism involves destabilization of sediment on the lower slope due to the activity of large-scale faults, resulting in gravity flow events and subsequent erosion leading to canyon formation.

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Hydrodynamic of the Lower Eocene in the Ruvuma Basin, East Africa

ZHAO Wenkai, XU Xiaoyong, TIAN Dongmei, ZHANG Ying, WU Jianan

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 80-94. DOI: 10.11885/j.issn.1674-5086.2024.09.03.03

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The interaction between gravity flow and underflow can form an asymmetric unidirectional migration channel. The evolution model of unidirectional migration channel has been established by predecessors, but the hydrodynamic mechanism of the interaction between gravity flow and underflow is relatively weak. In this study, the sedimentary hydrodynamic numerical simulation of the interaction between gravity flow and underflow under different conditions in the early and late Lower Eocene in the Ruvuma Basin, East Africa was carried out. The results of the study are as follows: in the early Lower Eocene of the Ruvuma Basin, the restrictive effect of the channel is strong, and the sedimentation of gravity flow is the main effect; in the late period, Under the interaction of gravity flow and bottom current, the fine sediment at the top of gravity flow in the channel drifts northward, forming an asymmetric natural dike on the north side of the channel. Under the action of the crosswise fluid caused by the bottom current, the fine sediment at the top of the gravity flow is transported northward. As sediments gradually accumulate on the north side to form drift deposits, lateral sedimentation steepens the north side of the channel. The two opposite fluids collide in the south side of the channel, the erosion effect is enhanced, in the south side of the strong erosion, the restrictive action is weakened and a new negative terrain is formed. This asymmetric sedimentation pattern gradually migrates the sewers to the south for a long time. By revealing the depositional hydrodynamic processes of the interaction between gravity flow and bottom current in different periods of the Lower Eocene in the Ruvuma Basin, this study elucidates the sediment-erosion mechanism of the fluid structure on the channel and analyzes the genetic mechanism of the asymmetric unidirectional migration channel from the perspective of fluid dynamics.

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Development and Evolution of Deep-sea Channels in Salt Diapir Typed Microbasins

MU Boyu, ZHAO Xiaoming, QI Kun, LIU Fei, LI Fayou

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 95-106. DOI: 10.11885/j.issn.1674-5086.2024.08.28.05

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The unclear development and evolution characteristics of deep-sea channels in salt diapir typed microbasins hinders the exploration and development of deep-sea oil and gas and increases the difficulty of deep-sea oil and gas exploration and development. To solve such problems we made a case study on a Miocene salt diapir typed microbasin in the deep-water area of the continental margin of Angola, based on 3D seismic data and using RGB color blending technique, and analyzed the development and evolution characteristics and evolution model of channels in the basin. The study shows that the structural development of the microbasin controls the development and evolution of the deep-water channel. The channels C1, C2 and C3 developed along the short axis of the microbasin mainly develop the model of overflowing the microbasin, while channels C4 and C5 developed along the long axis of the basin mainly developed the model of filling microbasins. Whether the channel fills or overflows in the microbasin is mainly related to the relationship between the active period of the salt structure and the formation and evolution of the channel, the relative magnitude of the erosion ability of the gravity flow in the channel to the active rate of the salt structure, the structural development characteristics of the microbasin and the angle between channel flow direction and tectonic trend. The channels C4 and C5 flow along the bottom of the structure under the action of gravity flow. With the increase of the accommodation space, the end of the channel gradually begins to lobe and form leaf deposits.

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Deepsea Turbidite Channel Barrier and Interlayer Geomodeling: A Case Study from G Oilfied, Lower Congo Basin, West Africa

XU Rui, LI Fayou, ZHANG Wenbiao, LU Wenming, YUAN Shujin

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 107-118. DOI: 10.11885/j.issn.1674-5086.2024.09.02.03

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As a significant component of turbidite deposition system, turbidite channel has been proven challenging due to its complicated sedimentary hierarchy and strong heterogeneity. Currently, the quantitative research on deep-water turbidite channels mostly focuses on channel reservoirs, but less attention is paid to barrier and interlayer. In the later stage of high water cut development, the influence of interlayer in a single channel on the prediction of remaining oil cannot be ignored, and it is necessary to study the interlayer. In this study, a set of characterization and modeling approach are formed for the barrier and interlayer. First of all, based on core, logging and geophysical techniques, the three-level interlayer architecture levels and models within the reservoir are formed. Then, through the pre-stack shale inversion, the mud interlayer identification data body is formed, and on this basis, the geometric characteristics and scale of the interlayer are quantitatively studied. Finally, a multi-level nested method based on target simulation-sequential indicator simulation-multi-point statistics was used to establish a sedimentary microfacies model of different levels of interlayer in a single turbidite channel, and the quantitative simulation of single sand body level of deep-water turbidite under sparse well pattern conditions was realized. After comparison and verification of posterior wells, the model predicts that the lithology coincidence rate of interlayers is 87%. This modeling approach realizes the quantitative characterization of the interlayer of single sand body, which greatly improves the characterization accuracy of turbidite reservoir, and provides important guidance for remaining oil prediction and production.

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A Study on the Sedimentary Characteristics and Evolution of Mud-rich Deepwater Turbidite Reservoir

Lü Wenrui, CAO Shuchun, BU Fanqing, GUAN Hong, XIAO Peng

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 119-129. DOI: 10.11885/j.issn.1674-5086.2024.09.02.01

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Located in the southern West African Basin, Z Oilfield has low net pay and low net-to-gross ratios, belonging to the mud-rich deep-water gravity-flow deposits. Based on the well penetrations, seismic attributes and production data, the facies types, sedimentary configuration boundaries of the Z Oilfield were identified. The facies distribution characteristics and sedimentary evolution of Z Oilfield were summarized, leading to the following conclusions: 1) the Z Oilfield has developed main channel, levee, main lobe, lobe fringe, shale and slump; 2) channel and lobe configuration boundaries were identified through changes in seismic axis strength, seismic amplitude attributes, and RGB frequency division attributes; 3) for Z Oilfield, the bottom oil group developed unconfined channel-lobe system, dominated by lobes, transitioning upwards to confined channel systems, with strong vertical stacking of channels, and on the top oil groups weakly confined channel systems have developed, with stronger lateral migration, and smaller scales of individual channels.

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Petroleum Geological Characteristics of Transformation-extensional Continental Margin Basins in East Africa

FAN Yuhai, QU Hongjun, ZHU Nan

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 130-146. DOI: 10.11885/j.issn.1674-5086.2024.08.29.01

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In recent years, a series of large gas fields have been discovered in the deepwater areas of the Rovuma Basin and Tanzania Basin on the transform-extensional passive continental margin of East Africa, with recoverable reserves reaching 3.8$\times$10$^{12}$ m$^3$. However, the resource discovery rate in this region is merely 13.1%, indicating a vast potential for undiscovered resources. Based on the comprehensive research achievements of passive continental margin basins in East Africa, this paper summarizes the geological conditions such as source rocks, reservoirs, traps, and migration within the area, and explores the combination patterns of source-reservoir-cap rocks. The results reveal that: 1) The main source rocks in the transform-extensional passive continental margin basins of East Africa are mainly the lagoon facies and restricted marine shale or limestone of the Middle-Upper Jurassic-Cretaceous & the main reservoir rocks are the marine clastic rocks of the Middle-Upper Jurassic-Cretaceous-Neogene. 2) Hydrocarbons are charged into the reservoirs through "vertical charging" or "lateral charging" along faults, and "lateral charging" along unconformities or reservoirs; controlled by the complex tectonic evolution of East Africa, trap types dominated by structures and stratigraphic lithologies have formed. 3) The conditions for hydrocarbon accumulation are most favorable in the Rovuma and Tanzania basins, and the favorable exploration horizons are the sandstone reservoirs of the Cretaceous-Neogene. The Triassic Calub Formation sandstone in the Somali Basin holds promising exploration prospects. With the advancement of exploration degrees and technical levels, significant breakthroughs are expected in the oil and gas exploration of other basins.

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Quantitative Characterization of Evolution and Controlling Factors of Paleo-Rajang Delta in the Zengmu Basin

TANG Zhiyi, XIE Xinong, XU Junjie, WU Jianan, CHEN Beichen

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 147-162. DOI: 10.11885/j.issn.1674-5086.2024.08.28.04

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To clarify the development and evolutionary processes of the large delta complex and slope system on the southern margin of the South China Sea, this paper, based on the interpretation of 2D seismic profile from the region, quantitatively describes the evolution of the Paleo-Rajang Delta in the Zengmu Basin. Key parameters such as the clinoform migration angle $\alpha$, clinoform accretion thickness to clinoform accretion distance ratio $\sigma$, pro-delta width $l$ and pro-delta slope angle $\beta$ are selected to describe the evolution process of the delta. The study explores the controlling effects of various factors on this process. The main body of the delta has undergone five stages of evolution: 1) the early stage of continental shelf delta, forming an oblique prograding clinoforms; 2) the rapid advance stage. when the delta evolved to the marginal shelf delta, and the inflection point trajectory of the prograding clinoforms rose at a medium-high angle while $l$ was small but $\beta$ was large; 3) the stable accretion stage. when the depositional center moved to the slope, and the inflection point of the prograding clinoforms rose at a medium angle while the front of $l$ and $\beta$ were unchanged; 4) the stage of slow progradation. when the inflection point of the prograding clinoforms presented a low angle of progradation while $l$ and $\beta$ gradually decreased; 5) late stage of shelf delta progradation. when climatic conditions coupled with source supply and sea level change affected the rate of change of accommodation $A$ and the rate of sediment supply $S$ and ultimately jointly controled the evolution of the deltaic system and its slope migration.

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Palaeoclimatic and Palaeofloral Evolution and Their Influences on Organic Matter Enrichment of the Early Oligocene-Early Miocene Marine Shales in the Qiongdongnan Basin

DING Wenjing, LI Youchuang, LAN Lei, YANG Shuchun, LIU Haiyu

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (1): 163-180. DOI: 10.11885/j.issn.1674-5086.2024.09.12.02

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Natural gases in the northern South China Sea are predominantly derived from the Late Oligocene-Early Miocene marine shales. The organic matter enrichment and its controlling factors are key points for the natural gas exploration in the Qiongdongnan Basin. The organic matter enrichment from the Oligocene to the Early Miocene marine shales from fifteen wells in the Qiongdongnan Basin was found using the data of total organic carbon measurement and Rock-Eval pyrolysis. During the early Oligocene, the Middle Yacheng Formation shales are enriched in terrigenous organic matter, which was thought to be caused by the flourished tropical/subtropical plants in the more humid environment. During the Late Oligocene-Early Miocene, there is also a terrigenous organic matter enrichment. Analyses of plant-derived biomarkers, palynogical records in shales in combination with regional global climate variations suggest the terrigenous organic matter enrichment was in association with warming and humid climate in the Late Oligocene-Early Miocene, during which higher plants flourished and the East Asian summer monsoon coupled with annual precipitation intensified. The significant extra precipitation brought by intensified East Asian summer monsoon was beneficial for the large amount of scattered plant organic matter enrichment and hence the terrigenously-enriched marine shales were more widely deposited in shallow marine environment. The finding of terrigenous organic matter enrichment in the Late Oligocene-Early Miocene marine source rocks was beneficial for the deep-water natural gas exploration in the deeply buried Ledong Sag and the Lingshui Sag in the Qiongdongnan Basin.

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Study on the Characteristics and Differences of Carbonate Reservoir in Halahatang-Fuman Oilfield

JIANG Tongwen, DENG Xingliang, LI Xuguang, CHANG Shaoying, WANG Peng

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 1-17. DOI: 10.11885/j.issn.1674-5086.2024.04.20.01

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The deep-ultra-deep carbonate reservoirs in the Tarim Basin have already formed a production base of 3 million tons of oil, but there is still controversy over the types of reservoir space and the structural differences of reservoir bodies in deep-ultra-deep carbonate rocks, which affect the optimization of oil and gas reservoir development schemes. Based on field outcrops, cores, seismic, logging, drilling and production data analysis, we conduct a comparative study on the types and structural differences of high-quality carbonate reservoir space and reservoir bodies in the Ordovician deep-ultra-deep strata of the Halahatan-Fuman Oilfield. The results show that: 1) Halahatang-Fuman Oilfield is controlled by the weakening of atmospheric freshwater dissolution from north to south: the main reservoir space types in the northern anticline karst area are karst caves and dissolution pores; the main reservoir space types in the southern interbedded karst area of Halahatan are fractures, pores, and cavity-type reservoirs and karst rivers; the main reservoir space types in the Fuman fault-controlled karst area are angular breccia intercavities and fault voids, and structural fractures. 2) The differences in reservoir space filling characteristics are also quite obvious: the karst caves in the northern anticline karst area and the interbedded karst area of Halahetang are relatively rich in dissolution filling, mainly including sedimentary filling materials, collapse filling materials, and chemical precipitation filling materials; however, the filling characteristics of the reservoir bodies in the Fuman Oilfield are relatively simple, mainly composed of calcite and silica cementation. 3) The differences in the internal structural features of reservoir spaces are as follows: the northern karst area has three layers of dissolution structures, namely, the surface karst belt, the percolation karst belt, and the subterranean karst belt; the southern interbedded karst area of Halahetang has three structural elements composed of the supply area, the percolation belt, and the discharge area; the fault-controlled karst area has four structural models, namely, the single sliding surface structure, the compressional nucleus belt structure, the tensile-torsional cavity nucleus belt structure, and the grille-like fracture network nucleus belt structure. Clearly recognizing the characteristics and internal structural differences of ultra-deep carbonate reservoir spaces is of great significance for the formulation of efficient oil and gas reservoir development plans in the Tarim Basin. It guides the deployment of wells and the optimization of well trajectories, leading to an increase in the success rate of high-yielding wells to over 96%, and provides new ideas for the next phase of efficient oil and gas exploration and development in the study area.

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Distribution of the Thin Reservoir of Shoal Facies at the Top of Member 1 of the Jialingjiang Formation in Luzhou Palaeohigh

TANG Hao, LIAO Zichao, SUN Haofei, XU Chang, CHEN Xiao

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 18-31. DOI: 10.11885/j.issn.1674-5086.2024.04.27.01

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The first Member and second Member of the Lower Triassic Jialingjiang Formation in Luzhou Paleouplift are the main oil resources in Sichuan Basin, however, the reservoir especially the thin shoal reservoir distribution is not clear yet, which restricts oil exploration process. Based on core, cuttings and well logging data, this paper researches reservoir characteristics, reservoir genesis mechanism and paleogeomorphology, and get the following results. The reservoir lithology is mainly composed of thin-middle oolitic and bioclastic limestone, and the main reservoir space is the dissolved intragranular pores and moldic pores. The physical properties are generally poor, but high porosity and permeability layers are developed locally. The leaching of meteoric water is the main reservoir genesis mechanism, while paleouplift is the key to form reservoir by depositing grain shoals and syngenetic karstification. The well logging statistics show that the thickness of granulated rock in the first Member of Jialingjiang Formation is positively correlated with the thickness of strata, which indicates that the thickness of strata reflects the level of sedimentary palaeotopography. Therefore, it is considered that the central of Luzhou palaeouplift, the eastern margin of Kangdian palaeocontinental and the southern area of the central Sichuan palaeouplift are three main favorable areas for reservoir development. This research can be used as reference for the exploration and development of Jialingjiang Formation in Sichuan Basin, and more important it can also provide a case study for the distribution of thin shoal reservoir in the world.

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Characteristics of Iron-bearing Carbonate Cements and Its Impact on Tight Sandstone Reservoirs in the Jurassic of the Taibei Sag

LIN Tong, ZHAO Zhenyu, WU Chao, ZHANG Hua

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 32-49. DOI: 10.11885/j.issn.1674-5086.2024.04.29.01

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The clastic rocks in the Middle-Lower Jurassic coal strata measures are important target for oil and gas exploration and development in Taibei Sag, Turpan-Hami Basin. Iron-bearing carbonate minerals are wildly distributed and the reservoir heterogeneity is strong. In addition, there are significant differences of oil and gas accumulation in different areas. Using various analysis testing. We make a systematic study on the carbonate minerals and paragenetic mineral in the reservoirs and clarify the main causes of reservoir heterogeneity. The study shows that the pores are filled by carbonate minerals to different extent, leading to the decrease of reservoir porosity and the enhancement of heterogeneity reservoir. The mineral assemblage and distribution are affected by the thickness, grain size and composition of sandstone related to sedimentation. The sandstone grain size of underwater distributary channel of braided river in Qiudong Depression is thick, coarse with complex debris and matrix content is poor. The sandstone of underwater distributary channel of braided river in Shengbei Depression is of thin-thickness, of fine grains with high content of plastic debris and matrix. Complex clastic components and high matrix content in sandstone lay the material foundation for the formation of iron-bearing carbonate minerals. The rock texture and quantity of organic matter in sediments determine the diagenetic evolutionary path of reservoirs in different intervals, and further lead to the spatial and temporal disparities of the mineral assemblage associated with iron carbonates.

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Prediction of Pore Sweet Reservoir in Xujiahe Formation with Pre-stack Inversion Technique

SHI Xiulin, LI Ping, LI Jianbo, WANG Chun, REN Haixia

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 50-69. DOI: 10.11885/j.issn.1674-5086.2023.06.01.02

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Reservoir prediction of tight sandstone is always a difficult problem in the industry. Conventional post-stack impedance cannot distinguish between dense surrounding rock and high porosity sandstone effectively, and such problem is particularly typical in the study of tight sandstone reservoir prediction of Xujiahe Formation in Dayi Area, western Sichuan. To solve such problems, this paper carried out research by pre-stack technology. The petrophysical analysis shows that the velocity ratio of P-wave and S-wave has a good distinguishing effect on porous sandstone reservoirs, which indicates that the pre-stack technique can effectively solve the prediction problem. The properties of P-wave impedance, S-wave impedance and the velocity ratio between P-wave and S-wave are obtained by pre-stack inversion. With the help of lithofacies analysis technology, the sweet spot probability body of pore sandstone reservoir is generated, and the plane distribution of pore reservoir is predicted. The results show that the technique is effective and consistent with real drilling, which is of great significance to the exploration and development of tight sandstone field. This paper also elaborates the key technical links of pre-stack prediction, which included pre-stack optimization, partial stacking, petrophysical analysis, probabilistic model building, inversion calculation, and effect analysis of real drilling comparison. Each key link is critical to the reliability of the results. This method provides strong technical support for the study of tight sandstone reservoir prediction and has important guiding significance for continental exploration in western Sichuan.

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Volcanic Reservoir Characteristics and Influencing Factors of Carboniferous Bashan Formation in Shazhang Fault-fold Belt, Eastern Junggar Basin

MAIMAITIYILI Pahading, WEI Bo, LI Xin, TIAN Jijun, ZHANG Zizhao

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 70-83. DOI: 10.11885/j.issn.1674-5086.2022.11.30.02

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The volcanic rocks of the Carboniferous Bashan Formation are widely developed in the Shazhang fault-fold belt in eastern Jungaer Basin, and the exploration and development of the carboniferous volcanic gas field in the adjacent Wucaiwan Sag indicates that the carboniferous volcanic rocks in the study area also have the potential of reservoir formation. To provide support for volcanic oil and gas exploration in this area, this paper comprehensively studies the characteristics of volcanic reservoirs and their influencing factors by using drilling, rock sample, the microscopic chip, imaging logging, analysis data. The results show that: 1) volcanic rock reservoir lithology of Bashan Formation is mainly composed of volcanic lava, fused volcanic breccia, pyroclastic rock, volcanic-sedimentary rock and sub-volcanic rock, which can be identified as eruptive facies, overflow facies, volcanic-sedimentary facies; 2) the main reservoir space is primary reservoir space (primary pores) and secondary reservoir space (secondary pores and fractures), and there are four types of reservoir space combination: pore + dissolved pores in almond body + fracture, pore + dissolution pore, dissolution pore + fracture and fracture; 3) the volcanic rock is of medium-low porosity and medium permeability reservoir with poor overall physical property and heteroqeneity; 4) the development of favorable volcanic reservoir in Bashan Formation is mainly controlled by lithology and lithofacies, weathering and leaching, and tectonic fragmentation.

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A Study on Triaxial Compression Behavior of Digital Core Based on Equivalent Modulus Method

LIN Tiejun, ZENG Xin, SUN Xin, YU Hao, YU Wenshuai

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 84-94. DOI: 10.11885/j.issn.1674-5086.2024.06.24.01

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To address the challenges of coring in deep, hard, and brittle formations, such as difficulties in obtaining complete core samples and the high cost of indoor rock mechanics experiments, a numerical approach is employed. A multi-component digital core model, structured on a Voronoi polyhedron framework is established according to mineral composition content. An equivalent modulus method is proposed to dynamically adjust the mechanical properties of minerals under triaxial compression conditions. The digital core's triaxial compression process is simulated, yielding fracture patterns, stress-strain curves, and elastic modulus values, which align with indoor experimental results. A comparative analysis of the effects of triaxial pressure on the overall rock structure and mineral grains is conducted, focusing on damage and stress distribution. The findings reveal that the impact of triaxial pressure on mineral grains varies depending on the type and spatial distribution of minerals, while also inhibiting crack propagation in the rock. This approach and the results provide new insights into studies on the mechanical and fracture behavior of digital cores, and effectively simulates rock mechanics responses and fracture patterns under complex geological conditions, and offering technical support for solving the coring challenges in deep hard and brittle formations.

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Coalbed Methane Fracturing Effect Prediction Based on FCMFS Feature Selection Algorithm

MIN Chao, GUO Xing, HUA Qing, ZHANG Na, ZHANG Xinhui

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 95-104. DOI: 10.11885/j.issn.1674-5086.2023.02.27.01

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It is difficult to analyze the nonlinear relationship between the fracturing effect and characteristics of coalbed methane from the mechanism level. Aiming at the problem, the internal relationship between the characteristics of coalbed methane fracturing effect is studied, and a prediction method of coalbed methane fracturing effect based on FCMFS feature selection algorithm is proposed. The method uses fuzzy comprehensive evaluation to calibrate the label, and uses genetic programming and XGBoost algorithm to construct and screen the characteristics of influencing factors, including two new structural features (stress ratio and genetic factors of geological construction) and six characteristics of perforation section thickness, permeability, fracture pressure, coal structure, gas saturation and sand strength. The experimental results show that based on the eight features constructed and screened by the FCMFS feature selection algorithm, combined with a variety of machine learning algorithms to predict the effect of coalbed methane fracturing, the accuracy, recall rate, and F1 classification evaluation indicators are improved by about 5%～10%. Among them, the Deep Forest algorithm has the best prediction classification effect on the training set and the test set, and the three classification evaluation indicators are all above 95% and 80%.

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Mechanism and Applicability of AICD Water Control in Fractured Bottom Water Heavy Oil Reservoir

YANG Yong, SUN Changwei, JIANG Renkai, LI Xiaodong, LIU Yuanzhi

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 105-114. DOI: 10.11885/j.issn.1674-5086.2023.04.06.04

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Fractured bottom water heavy oil reservoir is the characteristic of micro-fracture development, high viscosity of crude oil and rapid rise of water cut. It is difficult to ensure the development effect by conventional horizontal well development. The development of such reservoir with strong bottom water control ability by horizontal well is always the main direction of development. Nanhai L Reservoir is a typical reservoir of this type. And has been put into production for more than 20 a, with recovery less than 12%, and comprehensive water cut more than 96%. The results of chemical water plugging and conventional ICD water control are poor. The development of high angle fractures is the main reason for the rapid rise of oilfield bottom water and poor development effect. At the same time, the crude oil in the reservoir matrix is difficult to be effectively used, and a large number of remaining oil still exists in the matrix and isolated karst caves. We analyze the mechanism of AICD water control, studies its applicability in combination with physical model, numerical model and field application, and conclude that AICD technology can improve the production of effective production intervals of horizontal wells in this kind of reservoir, and thus improve the development effect. According to the evaluation of well selection, AICD is a mechanism of controlling water and increasing oil production by controlling the flow of micro fracture and high permeability zone independently, balancing the liquid supply profile of horizontal well, improving the sweep efficiency of horizontal well and increasing the effective well control reserves.

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Control Mechanism of CCUS-EOR for CO ₂-rich Gas Injection in Bailian Condensate Reservoir

CUI Kai, CHEN Qiang, LIU Desheng, SUN Lei, WANG Yong

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 115-126. DOI: 10.11885/j.issn.1674-5086.2022.07.05.01

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To further improve the recovery of the remaining condensate oil and gas reservoirs in the depleted stage of Bailian structural oil and gas reservoir group in Fushan Sag, and to give full play to the comprehensive utilization benefits of the replacement development of CO$_2$-rich gas reservoirs in the Bailian structural belt, based on the development strategy of "carbon peaking and carbon neutralization", combined with the concept of independent carbon emission reduction and carbon neutralization during oil and gas reservoir development, Fushan Oilfield has established a development strategy based on CCUS-EOR technology to directly inject the associated gas recovered from CO$_2$-rich gas reservoirs in the Bailian structural belt into depleted condensate gas reservoirs. The phase analysis of the mixed-phase drive mechanism, the analysis of the long thin tube gas injection drive efficiency and minimum mixed-phase pressure, the analysis of the seepage characteristics of the gas-driven anticondensate in the reservoir core, and the numerical simulation of the gas injection drive components were carried out to study the control mechanism. It is found that gas injection can increase the remaining anticondensate saturation by 1.85 times. When gas injection pressure rises to 20.4 MPa, the mixed fluid can achieve a multiple-contact mixing phase. And the minimum engineering MMP is 21.13 MPa. The condensate recovery of long core mixed phase drive can reach 68.94%. The pilot test scheme of periodic gas injection assisted with gravity miscible flooding was determined and carried out. Numerical simulation and the monitoring of the change of flow composition and PVT phase analysis method in the field show that the control mechanism of the oil and gas transportation and the change of condensate and gas flow direction is the synergistic effect of dissolution and swelling, extraction, gravity mixed-phase drive and reservoir inhomogeneous flow, which provides a reference for the selection of CCUS-EOR technical policy for resuming production of condensate oil in subsequent production wells.

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Influence of Undulating Feature of Horizontal Section of Shale Gas Well on Liquid Accumulation

HE Zhiguo, GAO Shangjun, LIU Yonghui, ZHAO Huiyan, ZAHNG Jing

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 127-136. DOI: 10.11885/j.issn.1674-5086.2023.03.14.01

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Horizontal well technology has been widely used as the main development technology in shale gas exploitation. Horizontal section of shale gas well has ultra-long, complex and changeable well trajectory. At the beginning of production, daily gas production and water production of gas well are large, and then daily gas production and water production rapidly decrease. Affected by many factors such as complex well trajectory, low gas production and low pressure, some gas wells have accumulated liquid in horizontal section. In order to solve the above problems, based on CFD simulation technology, this paper establishes borehole geometry model of typical horizontal section of wells, simulates and calculates gas-water two-phase flow characteristics and influence rules of upset structure in horizontal section under different operating conditions using Eulerian-Eulerian coupling Multi-Fluid VOF mixing method. The results show that with the increase of fluid flow rate, the liquid holdup curve of full borehole in horizontal section of upset structure fluctuates to varying degrees, and the concave point under borehole, At the uphill section of outlet, liquid phase is easy to fall back and causes accumulated liquid. The liquid accumulation height at the downhole of the well bore slowly decreases with the increase of gas flow rate, which can carry the liquid out of the well bore when the gas flow rate reaches 2.2 m/s. When the gas well is in low production period and the gas flow rate reaches the maximum 1.1 m/s, the liquid layer height is also more than half of the size of borehole inner diameter, and $h/D$ is about 0.55.

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Establishment and Verification of the Wall Sticking Occurrence Temperature Calculation Model of Stratified Flow Pipeline

CHENG Xianwen, XIONG Jianhua, HUANG Qiyu, TIAN Jiaxing, YU Le

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 137-150. DOI: 10.11885/j.issn.1674-5086.2022.11.03.02

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Low temperature transportation technology can effectively reduce energy and economic loss for high-water-cut gathering and transportation pipelines. However, with the popularization of gas flooding, the fluids in many gathering pipelines are in the state of three-phase of oil, gas and water. In order to explore the effect of gas on the adhesion of gelled oil on the wall, a self-developed pressure-bearing stirring tank is used to measure the adhesion mass of gelled oil on the wall under different conditions. It is found that the gas dissolved in crude oil can significantly reduce the adhesion of gelled oil, while the temperature does not change with corresponding mass surge; subsequently, a gas injection test is carried out on the high water-cut gathering and transportation pipeline on site, and it shows that with the increase of the gas-oil ratio in the pipeline, the minimum inlet temperature decreases from 29 ℃ to 26 ℃, indicating that the presence of gas improves the fluidity of crude oil; finally, based on the theoretical basis of " wall shear stress=yield stress × coefficient", a stick-wall temperature calculation model that can be used in stratified flow gathering and transportation pipelines is established, and the verification shows that the model has a good calculation effect.

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Stress Test and Analysis for Inlet and Outlet Pipeline System of the Station Under the Foundation Settlement

LIN Ruinan, YANG Hong, MAO Xuebin, HUANG Zhonghong, ZHANG Wen

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 151-163. DOI: 10.11885/j.issn.1674-5086.2022.07.10.02

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The foundation settlement easily leads to the stress concentration and excessive deformation of the inlet and outlet pipeline system of the natural gas station, and in severe cases, the pipeline may be damaged. To this end, a test platform for settlement stress testing of natural gas station inlet and outlet pipeline system including 2 typical structures of inlet and outlet lines, vent pipe and tee pipeline was built. Stress tests of different types of pipelines under foundation settlement were carried out. Based on the test platform, the three-dimensional model of the inlet and outlet pipeline system of the station was established to analyze the influence of internal pressure and diameter thickness ratio on pipeline stress. The results show that: the most serious bending deformation of the inlet and outlet line Ⅰ(buried manifold distribution structure) occurs at the ground elbow and the fixed position of the support, and the maximum tensile stress and compressive stress of the inlet and outlet line Ⅱ(Z-shaped structure) are both at the reducing tee of the pipe, the stress of the inlet and outlet line Ⅱ is smaller than that of the inlet and outlet line Ⅰ under the same settlement conditions; When the pier in the middle of the tee pipeline settles, and the stress of the pipeline at the inner side of the fixed supports at both ends and the settlement point far from the tee increases significantly with the settlement; When the ground-entry end of the vent pipe settles, and the vertical section of the ground-entry end has the most serious deformation, and the joint section between the vent pipe and the main pipeline receives the greatest stress. Reducing pipe diameter thickness ratio and operating internal pressure can reduce the equivalent stress during settlement and improve the pipeline safety. The research results provide a technical basis for the safety assessment, the selection of stress monitoring points and the settlement warning of the inlet and outlet pipeline system in natural gas station.

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Corrosion Characteristics of X70 Steel Under AC-DC Mixed Interference

HE San, YU Rui, ZHANG Jianxiong, LI Bin, XU Huilan

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 164-174. DOI: 10.11885/j.issn.1674-5086.2023.07.31.01

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In certain areas, the cross or parallel installation of oil and gas pipelines, high-voltage transmission lines, and electrified railways creates the risk of AC-DC mixed interference corrosion in buried pipelines. Through electrochemical tests, combined with polarized light microscopy, three-dimensional optical microscopy, and XRD, the AC-DC mixed interference corrosion characteristics of X70 steel in the intersection area of electrified railways, high-voltage transmission lines, and natural gas pipelines were studied. The results show that: 1) the critical current density under AC-DC mixed interference is 120 A/m$^2$; 2) there is no positive correlation between the radius of capacitive reactance arc and current density under AC-DC mixed interference; 3) the AC-DC mixed interference anode area not only continued the corrosion intensity of DC interference, but also played the role of AC oscillation and pitting, resulting in secondary local damage in the corrosion pit, forming a large number of pitting and crevices, and gradually showing the phenomenon of etching which makes the partially corroded X70 steel (partially covered with a corrosion product film) unsupported and exfoliated in solution; 4) at the current density of 180 A/m$^2$, the corrosion depth of the specimen under AC-DC mixed interference reaches 250 μm.

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Structure Design of Tubing Hanger for Deep Subsea Christmas Tree

ZHU Junlong, LI Yufang, RU Mengqi

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (2): 175-184. DOI: 10.11885/j.issn.1674-5086.2023.10.07.03

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The subsea christmas tree is a critical piece of equipment for deep-sea oil and gas development. The tubing hanger, serving as a channel for oil and gas and an electricity, supports the tubing column and seals the annular space between the tubing and casing, making it a core component of the christmas tree. Its structural strength directly impacts the safety of oil and gas production. Taking the tubing hanger from an oil and gas field in the South China Sea as an example, and analyzing foreign tubing hangers, the main structural dimensions of the underwater christmas tree's tubing hanger were designed. Finite element analysis was employed to establish the finite element model of the tubing hanger, and numerical simulations were conducted for its operations during the lowering process, installation, normal production, and locking and unlocking procedures. The results indicated that during the lowering process, the maximum stress of the tubing hanger was 310.43 MPa, with a maximum deformation of 0.450 09 mm. During the installation process, the maximum stress was 310.43 MPa, with a maximum deformation of 0.408 85 mm. Under normal production conditions of 69 MPa and 64 ℃, the maximum stress at the oil outlet of the tubing hanger was 311.13 MPa, with a maximum deformation of 0.581 48 mm. At 69 MPa and 121 ℃, the maximum stress was 586.93 MPa, and the maximum deformation was 1.334 70 mm. The analysis shows that the designed tubing hanger meets the safety strength requirements, exhibits minimal deformation, and has good structural safety. This tubing hanger has been successfully applied to China's first domestically developed underwater christmas tree system, which plays a significant role in advancing the localization of China's underwater oil and gas production systems.

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Researches on and Prospect of ROP Improvement in Deep and Ultra-deep Oil and Gas Drilling

ZHU Xiaohua

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 1-9. DOI: 10.11885/j.issn.1674-5086.2024.09.01.01

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Increasing ROP, controlling complex downhole conditions, and improving drilling-encounter ratio are the three major challenges in deep and ultra-deep oil and gas drilling. Since the “12th Five-Year Plan” period, China has made significant progress in drilling technologies such as rotary steering, precise pressure control, efficient PDC bits, and drilling tools, and a number of ultra-deep wells of about 8 000 meters have been drilled. This paper focuses on the ROP improvement and summarizes the recent research progress in drillstring dynamics, efficient rock breaking and drilling tools, mainly including the review of the development of drillstring dynamics theory, the evaluation methods of drillstring vibration, buckling, and dynamic friction torque. Focusing on the theory of ductile-brittle critical failure of rock, the selection and optimal design method of drill bit based on ductile-brittle critical failure are deeply analyzed. This paper also systematically introduces a series of drilling tools based on impact accelerated crack growth and vibration drag reduction, and the relevant analysis and evaluation method based on CAE numerical calculation. The comprehensive ROP improving method based on efficient energy transfer and utilization is summarized and analyzed. Finally, suggestions are provided for increasing research efforts on downhole power drilling tools and new rock breaking methods. The research work has a certain reference value for improving the drilling speed of deep hard formation and ultra-deep complex structure wells.

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Zoning-grading Analysis and 3D Panoramic Characterization of Thrust Strike-slip Faults

OU Chenghua, WANG Zeyu, LIU Jincheng, LI Zhaoliang, MEI Hua

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 10-24. DOI: 10.11885/j.issn.1674-5086.2023.09.14.02

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The thrust strike-slip fault is widely distributed in the oil-rich structural zone, and quantitative characterization is of great significance to oil and gas exploration and development of oil-bearing basin, superposed coupling of horizontal extrusion stress and compression shear stress, the thrust displacement and slip displacement occur simultaneously in the thrust strike-slip fault system, which cause formation fragmentation, complex fault system, and disorderly logging and seismic response, and increases the difficulty of fault identification, combination, characterization and modeling. Aimed at the formation mechanism and the complexity of the thrust strike-slip fault system, a zoning-grading analysis and 3D panoramic characterization technology is developed to implement the quantitative analysis and 3D panoramic characterization of the study area—the lower plate of the Youshashan fault system of Yingdong Oilfield in Qaidam Basin. Relying on the zoning formation correlation, the key marked formation cross leading and zoning formation calibration technology is established, and solves the problem of difficult calibration and strong multiple solutions of the fragmentation formation, and the effective calibration of the six key marked formation and the full coverage tracking of the whole study area is implemented. The panoramic characterization, multi-scale and multi-type thrust strike-slip fault-fold step grid modeling and panoramic visualization characterization technology are used to the panoramic visual characterization of the thrust strike-slip fault profile-plane-3D multivision space of the study area.

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Interpretation and Identification of Effective Carbonate Reservoir Based on Principal Component Analysis

XU Wensheng, SUN Yaoxi, LIU Qiguang, PANG Xiongqi, ZHANG Hu

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 25-36. DOI: 10.11885/j.issn.1674-5086.2023.09.25.02

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The Kalataer Formation in the Kekeya Area of the Southwest Tarim Depression is a carbonate reservoir, and its pore-fracture system determines the enrichment degree of oil and gas. It is extremely difficult and ineffective to identify and evaluate the pore-fracture system using a single logging parameter. This paper takes the principal component analysis method as the core, couples multiple components under the condition of minimal information loss, and proposes a new method for interpreting and evaluating the storage space of carbonate rock pore-fracture systems based on conventional logging data, aiming to achieve joint quantitative analysis and evaluation of high-density vertical pore-fracture systems in unimaged logging areas. The logging curve data used in this study include sonic logging curves, density logging curves, neutron logging curves, deep lateral logging curves, and shallow lateral logging curves, combined with measured porosity and permeability data, mercury injection test data, etc., to establish a mathematical model for interpreting secondary pore-fracture reservoirs in the Kekeya Area of the southwest Tarim Depression, quantifying the storage space of the carbonate rock pore-fracture system. The research results show that the identification results of the porous-fractured reservoir interpretation model of the Kalataer Formation in the Kerkeya Area are highly consistent with the interpretation results of the imaging logging, with a matching rate of up to 73%, indicating the effectiveness of the method. The research results can provide a solid guarantee for the efficient exploration of tight carbonate oil and gas reservoirs.

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Application of Radial Basis Function Multi-attribute Fusion Technology in the Study of Beach-bar Sand Body Distribution Law

LI Bin, LIANG Yu, ZHAO Hu, YANG Hongwei, WEI Guohua

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 37-47. DOI: 10.11885/j.issn.1674-5086.2022.03.08.01

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Aiming at the difficulty in effective description with the existing seismic resolution due to thin microfacies sand body of the fast changing facies and reservoir heterogeneity, we take the upper E s ₄ sub-member of the Boxing Sag of the Daluhu Oilfield as an example, and use the regional isochronous interface T ₇ under constraints, chronostratigraphic slices to extract typical seismic amplitude attributes, and clarify the response characteristics of beach-bar facies on seismic amplitude attributes. Seismic sedimentology is used to explore the characterization of beach-bar microfacies. The study identifies five seismic reflection characteristics of beach-bar facies in the upper part of the fourth member of Shahejie Formation. The cluster analysis method is used to identify the distribution range of beach-bar facies, and to describe the distribution form of beach-bar microfacies based on colored inversion technology, and explored to use of the radial basis multi-attribute fusion method in thickness sand body prediction. The results show that the sand body in the northwest that interferes with the original seismic attributes is not developed, and is dominated by semi-deep lacustrine mudstone. This prediction result is in good agreement with the actual geological understanding, eliminating the ambiguity of a single seismic attribute. Based on the above results, the study has finely described the distribution of beach-bar microfacies in the study area, showing that the bar sand microfacies in the study area is well-developed and distributed in a wide range, and shows the characteristics of multiple parallel rows of sand bars facing the semi-deep lake area. It is a favorable target area with good potential for unconventional oil and gas exploration and development in the next step.

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Sealing Evaluation of Air Energy Storage in Underground Brine Mining Salt Cavities in Sichuan Basin

MAO Chuan, LIU Li, ZHAO Xiaoming, WANG Peng, ZHOU Ruiqi

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 48-64. DOI: 10.11885/j.issn.1674-5086.2023.12.04.02

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During thousands of years of salt mining in China, a large number of brine-mining salt cavities have been formed. Compared with underground salt cavity gas storage reservoirs, brine-mining salt cavities are characterised by complex geological conditions, extremely irregular cavity morphology, and poor confinement and stability, etc. In order to study the sealing performance of brine-mining salt cavities, this paper with the thin irregular brine mining salt cavity as the research object based on the results of geological, logging and laboratory coretests, a three-dimensional fine geological model and a three-dimensional dynamic geomechanical model of the Y Salt Cavity and wellbore in the Sichuan Basin were established, and numerical simulations of the micro-annularity and fracture extension at the cementing interface were carried out. The results show that: 1) on the basis of clarifying the model permeability and pressure distribution, the simulation results show that the Y Salt Cavity in Sichuan Basin has good closure; 2) the fatigue damage and plastic strain under cyclic loading will be concentrated locally, mainly at the interface between the cement ring and the casing; 3) appropriately lowering the modulus of elasticity of the cement ring and the content of the fibre will enhance the closure ability at the wellbore; 4) when evaluating the closure ability of the salt cavity, the surrounding rock permeability is the main factor. During the construction of the salt cavity gas storage reservoir, a part of the thickness of the top plate of salt rock should be reasonably reserved according to the strength of the closure ability of the rocks in the region to guarantee the cavity tightness.

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Architectural Styles and Depositional Processes of Cenozoic Deep-water Channels in the Lower Congo Basin, West Africa

CAO Shuchun, LIU Fei, BU Fanqing, QI Mingming, GUAN Hong

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 65-75. DOI: 10.11885/j.issn.1674-5086.2025.02.28.02

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The Lower Congo Basin has developed large-scale deep-water channel deposits, which are the primary type of hydrocarbon reservoirs. To address the unclear understanding of the internal channel unit stacking patterns and migration modes, a study on deep-water channel deposition models was conducted. This research utilized three-dimensional seismic data and RGB spectral decomposition attribute fusion techniques to investigate the sedimentary characteristics of different channel architectural levels and reconstructed the depositional process of turbidite channels in the study area. The key findings are as follows: the study area is characterized by a down-stepping confined channel system, comprising three phases of aggradational and progradational complex channels. The lower complex channels exhibit planar straight geometries with vertically stacked individual channels, while the middle complex channels form low-sinusosity belts with laterally stacked individual channels. The upper complex channels show high-sinusosity and meandering planar geometries, with individual channels laterally connected or isolated. These three phases of compound channels correspond to three stages: erosional base, main deposition, and late abandonment. Reservoir formation occurred during the main depositional stage of the channel system. This study clarifies the sedimentary characteristics and stacking patterns of different channel architectural units, and establishes a depositional model for deep-water channels in the study area. The findings hold significant geological implications for the development strategies and efficient production of similar hydrocarbon reservoirs.

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Seismic Wavefield Forward Modeling Study Under Complex Conditions in the Southwest Foreland Belt of the Tarim Basin

PEI Guangping, SHEN Tianjing, PENG Gengxin, JIANG Zelei, CHEN Feixu

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 76-87. DOI: 10.11885/j.issn.1674-5086.2023.05.24.01

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The surface and subsurface structural patterns in the region in front of the southwest foothill area of the Tarim Basin are highly complex, with diverse lithological and structural features. This area is a typical case of “dual complexity” in both surface and subsurface geology, leading to complex seismic wavefields and significant challenges in data processing and imaging accuracy. To clarify the seismic wavefield propagation characteristics in this region and provide a theoretical basis for subsequent data processing, this study constructs a dual-complexity velocity model representative of the area's geological features, based on field seismic data, well logging data, and near-surface outcrop information, and conducts seismic wavefield simulation analysis. During the modeling process, a near-surface velocity model was first developed using near-surface tomography data and elevation information. Then, a structurally complex model was constructed and refined based on seismic interpretation results. These models were subsequently integrated to form the final velocity structure model. To accurately characterize the Q value distribution within the target area, this study proposes a method for constructing a Q model based on sparse well data. Seismic wavefield forward modeling was conducted using the developed velocity and Q models to analyze the effects of surface elevation variation and near-surface velocity distribution on the subsurface wavefield. The findings are expected to provide a theoretical basis for optimizing seismic acquisition system parameters and improving seismic imaging quality in the study area.

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A Feasibility Study of CO ₂ and Associated Gas Mixture Flooding in High Water-cut Reservoirs

ZHANG Lingfeng, LIAO Xinwei, ZHANG Qi, DONG Peng, YANG Zepeng, HOU Shanze

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 88-100. DOI: 10.11885/j.issn.1674-5086.2024.06.23.01

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The Shanshan Block in the Tuha Oilfield has entered a high-water-cut development stage, limiting additional oil recovery by waterflooding, it is imperative to explore novel EOR technologies. Although CO ₂ flooding is proven effective by reseaches home and abord, but it is highly costly for Shanshan Block due to the lack of CO ₂ resources. This study examines mixing hydrocarbon-associated gas with CO ₂ to reduce injection expenses. Minimum miscibility pressures were tested using crude oil, cores, and associated gas in Shanshan Block. Under high temperature and pressure, cores were waterflooded and then displaced with gas mixtures at varying CO ₂ concentrations, tracked by nuclear magnetic resonance and computed tomography. Results show that miscibility occurs above 43% CO ₂ content. At approximately 50% CO ₂, displacement performance is comparable to pure CO ₂ flooding and surpasses pure associated gas, Microscopic analysis reveals that the hybrid CO ₂-associated gas flooding effectively mobilizes remaining oil at the pore scale, demonstrating economic feasibility and technical efficacy. Hence, it offers a promising method for Shanshan Block.

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An Experimental and Numerical Study of In-situ Generated Solvent Assisted SAGD in Heavy Oil Reservoir

CHENG Haiqing, YANG Simin, ZHAO Qinghui, ZAHNG Yong, SU Lei

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 101-111. DOI: 10.11885/j.issn.1674-5086.2023.05.30.01

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In order to solve the problems of low thermal efficiency and high steam consumption in the middle and late stages of steam injection in heavy oil reservoirs, this study proposes an in-situ generated solvent assisted steam assisted gravity drainage technique. This paper studies the feasibility of this new method through a combination of numerical simulation and physical simulation. By conducting experiments on Liaohe Du84 heavy oil, the mechanism of solvent generation during catalytic crac-king of heavy oil was studied. A reaction kinetics model was established based on reaction kinetics theory, and the mechanism of solvent enhanced SAGD in situ production of heavy oil was studied using numerical simulation methods. The research results indicate that over 5% of heavy oil is in-situ converted into solvents in a steam injection environment through catalytic cracking reaction. The solvent composition includes light hydrocarbons and non condensable gases, which have the characteristics of being a solvent medium for SAGD. The concentration also meets the solvent requirements of expanding solvent-SAGD technology. The generated light oil components and gases are recycled in the steam chamber as a solvent medium for gravity drainage, thus improve both recovery efficiency and oil steam ratio.

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Micro Mechanism of Oil Displacement by Water Gas Dispersion System

SHANG Zhenhao, WU Jiazhong, XIONG Wei, ZHANG Moxi, CHEN Xinglong

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 112-123. DOI: 10.11885/j.issn.1674-5086.2022.09.30.02

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Low permeability reservoirs have small pores, fine throats and large seepage resistance, and the recovery percent of conventional water drive is only about 20%. Gas injection development is not only limited by gas sources, but also seriously affected by gas channeling and other problems; therefore, it is urgent to develop key technologies to continuously improve oil recovery in low permeability reservoirs. The oil displacement technology of water gas dispersion system is a new technology to improve oil recovery. This technology can realize the control of seepage resistance and supplement energy at the same time, thus greatly improving the water displacement efficiency of low permeability reservoirs. In order to understand the micro oil displacement mechanism of water gas dispersion system, the flow characteristics and distribution laws of fluid in the displacement process were recorded, identified and quantitatively calculated through water drive, gas drive and water gas dispersion system oil displacement experiments by means of micro etching model, high-speed camera acquisition and ImagePro-Plus6.0 software identification. The experimental study shows that the main producing area of water drive is the main channel, and the remaining oil is mainly distributed in the edges and corners of the model; the characteristics of CO ₂ gas channeling are obvious, the gas mainly flowing in the pore center and forming a water/oil film on the pore wall; the most remarkable feature of water gas dispersion system for oil displacement is that it mixes with the oil phase “highly” after entering the pores. The mixed microbubbles can not only produce “plugging” effect, increasing the seepage resistance of the main channel, but also promote the subsequent fluid to change direction and enter the small pores that are not swept by water drive or gas drive, with obvious effect of expanding the swept volume. And it can significantly displace the remaining oil at the edges and corners, and even recover all the residual oil in the blind end. The oil recovery efficiency of water drive, gas drive and water gas dispersion system drive is 71.6%, 82.0% and 91.0%, and water gas dispersion system plays a prominent role in improving oil displacement efficiency.

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Optimization of Pressure-bearing and Plugging Drilling Fluid System in Mahu 401 Well Area

ZHOU Zenan, WANG Luyi, RONG Kesheng, REN Tao, LIU Xinguo

Journal of Southwest Petroleum University(Science & Technology Edition) 2025, 47 (3): 124-134. DOI: 10.11885/j.issn.1674-5086.2023.05.17.06

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This paper focuses on the problems such as “leakage before flowback” and “leakage in the same layer” when drilling in the horizontal member of Sankai Baijiantan Formation in Mahu 401 Well area, which makes it difficult to greatly improve the pressure bearing capacity. It is found that the Baijiantan Formation has the characteristics of strong permeability and micro-fracture development, and it is easy to produce micro-cracks with the increasing well depth, stress and external force. After the intrusion of drilling fluid filtrate into the well wall, micro-cracks continue to expand, resulting in frequent complications such as well loss. Considering that the crack width of the sampled core of Baijiantan Formation in Mahu 401 Well Area ranges from 1 to 30 μm, multi-micron grade plugging materials are used for optimization, and combined with the optimization of other treatment agents, a set of pressure plugging water-based drilling fluid system and supporting construction technology suitable for this well area are established. The application shows that the maximum leakage velocity, leakage volume and plugging times of the test well are significantly reduced, which indicates that the plugging material has formed an effective sealing and plugging slug, thus improving the pressure bearing capacity of the formation, and its leakage prevention and plugging effect is remarkable.

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