Table of Content

10 December 2025, Volume 47 Issue 6

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SPECIALIST FORUM

Application and Development of Big Data in Well Engineering

ZHANG Zhi, WANG Xianghui, DING Jian, ZHAO Jie, WU Linfang, HOU Zhenyong

2025, 47(6):  1-14.  DOI: 10.11885/j.issn.1674-5086.2023.10.29.31

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Industrial 4.0 technological revolution promotes the oil and gas industry to enter a new stage of smart oilfields, which is characterized by digitalization and intelligence. China has made great progress in digital construction and application integration in the oil field, carrying out a number of big data analysis on massive exploration and development data collected, such as drilling, logging, well testing, analysis and testing, oil and gas production, and accelerating automated construction and intelligent decision-making. However, there are some challenges, such as inconsistent standards of well engineering database, difficulties in in-depth data sharing, severe data isolation and so on. In order to accelerate the construction and application of geology–engineering integration and better leverage the big data of well engineering for the construction of smart oilfield, the following work has been carried out: the relationship and difference between big data of well engineering and traditional big data are analyzed; the current situation of oil and gas big data platforms at home and abroad is counted; the characteristics and levels of well data are introduced; the big data algorithm of common well engineering problems is summarized; the scheme of algorithm optimization according to business requirements is proposed. Finally, the development suggestions are put forward for the current problems existing in the application of current big data technology in well engineering.

GEOLOGY EXPLORATION

Characteristics of Late Miocene Deepwater Sedimentary and the Exploration Prospect in the Shuangfeng Basin

YANG Zhili, WU Jia'nan, FAN Guozhang, LI Li, ZHANG Yuanze

2025, 47(6):  15-26.  DOI: 10.11885/j.issn.1674-5086.2024.08.30.02

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Shuangfeng Basin is the sediment unloading area of the central canyon of Qiongdongnan Basin, with a huge scale of deep-water sedimentary system. With the acceleration of exploration in the deep water area of the northern South China Sea, the oil and gas exploration prospects in the Shuangfeng Basin are increasingly receiving attention. A systematic study was conducted on the development characteristics and oil and gas geological conditions of the late Miocene deep-water sedimentary bodies in the Shuangfeng Basin through comprehensive analysis of sea level rise and fall, seismic data reflection characteristics, etc. The research results indicate that the deep-water sedimentary bodies in the Shuangfeng Basin were mainly developed in the Late Miocene, with branch channels, channel complexes, channel—levee complexes, lobe etc. The distribution area of deepwater sedimentary bodies reach ten thousands of square kilometers, making it a potential area for ultra large scale reservoirs. Meanwhile, the western and northern depressions of the Shuangfeng Basin have good conditions of source, reservoir, and cap rocks. Due to the Shuangfeng Basin located in the deep-water to ultra deep-water zone, the quality of source rocks, the scale of hydrocarbon generation and expulsion, and the economic viability of exploration targets are uncertain factors in oil and gas exploration in this area. The result has important guiding significance for the analysis of oil and gas exploration prospects, strategic selection of areas and zones in the Shuangfeng Basin.

Indicators of Fluid Change in 4D Seismic: An Case Study of 4D Seismic Interpretation in P Oilfield

LI Meng, LI Fayou, ZHANG Wenbiao, LU Wenming, ZHAO Huawei, XU Rui

2025, 47(6):  27-36.  DOI: 10.11885/j.issn.1674-5086.2024.09.03.01

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Fluid dynamic monitoring is a key technology for the efficient development of oil and gas reservoirs. 4D seismic can directly image fluid changes and enable 3D spatial fluid dynamic monitoring, and is therefore widely used in the development of deepwater oil and gas fields, thermal recovery of heavy oil, carbon dioxide sequestration. However, mainstream 4D seismic interpretation methods suffer from high ambiguity and poor reliability when characterizing complex fluid changes. To overcome these technical challenges, this study, based on theoretical models and 4D seismic forward modeling and using phase transformation technology, establishes the relationship between 4D seismic response and different fluid changes, proposes 4D seismic fluid change indicators, and achieves dynamic interpretation of complex fluid change patterns and ranges. The new method proposed in this paper was used to interpret the fluid changes in the 4D seismic data of the deepwater P Oilfield in Angola, West Africa. The interpretation results are consistent with production dynamic information. The fluid change interpretation results show that the differences in seepage characteristics of oil, gas, and water, along with reservoir structural features, control the movement paths of gas and water. Effective monitoring of fluid dynamic changes provides a reliable basis for development plan adjustment.

Diagenesis and Pore Evolution in Low-permeability Reservoirs of the Baodao A Deepwater Gas Field

YANG Li, LI Hua, WANG Panrong, PENG Zhichun, PAN Yan

2025, 47(6):  37-46.  DOI: 10.11885/j.issn.1674-5086.2024.09.12.01

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Baodao A Gas Field is the first deep water and deep gas field discovered in Baodao Depression. The main gas group of the Baodao A Gas Field is the third member of the Lingshui Formation. The water depth of the gas field varies greatly, the fault system is well developed, the reservoir highly heterogeneous, and the diagenetic phenomena abundant. Affected by the diagenetic transformation, the physical properties of the gas field are poor and the distribution law is complex. Therefore, based on the experimental data of thin section of rock, X-ray diffraction of clay minerals, and oxygen isotope analysis, the reservoir physical property, diagenetic characteristics and quantitative evolution of pores of the low permeability reservoir in the third member of Lingshui Formation in the study area are systematically described. The results show that: mechanical compaction reduces the porosity of the reservoir by 22.0%, which is the main factor of reservoir compaction in the third member of Lingshui Formation in the study area. The porosity of the reservoir is increased by 11.9% by solution and decreased by 13.7% by cementation. The process of pore evolution reveals that compaction is the primary factor contributing to early changes in reservoir physical properties, while mineral dissolution during the middle and late stages of oil and gas charging enhances reservoir space. Subsequently, late-stage carbonate cementation further densifies the reservoir. This research achievement effectively guides the prediction research of favorable reservoirs, provides geological basis for the efficient development of gas fields, and lays a foundation for ensuring the country’s accelerated advancement into the deep sea.

Distribution Patterns and Controlling Factors of Axial Submarine Fan Sandbodies in the X Oilfield, North Sea, UK

CAO Shuchun, YU Jitao, QI Mingming, BU Fanqing, WU Shenghe, SHEN Mo

2025, 47(6):  47-59.  DOI: 10.11885/j.issn.1674-5086.2025.02.21.03

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Submarine fan reservoirs are a hotspot for oil and gas exploration and development in the world. The distribution pattern and genesis of sand bodies are complex. At present, there is a lack of research on the axial submarine fan sand bodies in deepwater grabens. Taking the B Formation of Upper Jurassic of the X Oilfield in the North Sea, UK as an example, this paper attempts to investigate the distribution patterns and controlling factors of axial submarine fan in the deep-water graben environment, by well and seismic data mining. The results show that submarine fan sand bodies are mainly of proximal bypass type, presenting banded, lobate or tongue shapes. Lobate sandbodies are thick and wide with a low length-width ratio of 5, which were formed by lateral migration or retrogradation superposition, commonly seen in B4 Oil Group. In contrast, banded sandbodies are relatively thin and narrow with a high length-width ratio of 10, which were formed by vertical superposition. This type of sandbodies is developed in the B2 Oil Group. The distribution of submarine fan sand bodies is mainly controlled by paleogeomorphology. The longitudinal steep slope (greater than 6°) driven by the differential subsidence of the graben, causes the submarine fan sand bodies to present proximal bypass type. The limitation of the internal graben affects the morphology and superposition style of the submarine fan. Compared with the thin mud-rich submarine fan sand bodies, the thick sand-rich submarine fan sand bodies are relatively less restricted, which are mostly lobate and tongue-shaped, and are lateral superposed. The lateral symmetry of the graben landform affects the lateral development position and migration direction of the submarine fan.

Intelligent Classification of Deep-water Submarine Fan Lithofacies Based on Small Sample

ZHEN Yan, LIU Xiaowei, ZHANG Yihao, ZHAO Zhen, XIAO Yifei, ZHAO Xiaoming

2025, 47(6):  60-71.  DOI: 10.11885/j.issn.1674-5086.2024.09.15.02

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Aiming at the problems of high cost, difficulty in operation, high technical requirements, limited number of rock core-taking and small number of lithofacies samples obtained in the exploration and development of deep-water submarine fan reservoir, an intelligent classification method of deep-water submarine fan lithofacies based on small samples was proposed. First, the Empirical Mode Decomposition (EMD) and sliding window are used to construct multi-layer image styles input for each well point as inputs. Secondly, the lithofacies recognition model is constructed by using Long Short-Term Memory (LSTM) and Convolutional Neural Networks (CNN) algorithms. The Generative Adversarial Networks (GAN) model was used to expand a few class samples. Finally, a Genetic Algorithm (GA) was introduced to optimize the model parameters. Taking Akpo Oilfield in the Niger Delta Basin of West Africa as the research area, this method is used to carry out the intelligent identification of lithofacies. Research shows that the lithofacies classification accuracy of the GAN-GA-CNN model proposed in this paper can reach 94.22%, which greatly improves the prediction accuracy compared with the original CNN model, proving the feasibility of the proposed method.

OIL AND GAS ENGINEERING

The Influence of Supercritical Retrograde Condensate on Gas Well Productivity in BZ19-6 Condensate Gas Reservoir

JIANG Weijun, YANG Zhicheng, MA Yue, ZHANG Caiqi, YU Xiyan, SUN Lei, LIU Yang

2025, 47(6):  72-82.  DOI: 10.11885/j.issn.1674-5086.2023.07.27.01

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During the two-year production test of the four well sections in the ultra-large BZ19-6 condensate gas reservoir, near-wellbore reservoir damage and productivity decline occurred due to the supercritical reverse strong retrograde condensation behavior of the formation fluid. To clarify the impact mechanism of supercritical retrograde condensation on gas well productivity, this study integrates experimental methods including phase behavior evolution analysis of formation fluids, core damage tests, and numerical simulation of gas-oil two-phase seepage dynamics, combined with supercritical fluid extraction technology and near-critical non-equilibrium thermodynamics theory. The results reveal the saturation distribution of retrograde condensate in the near-well zone and its constraining effect on gas-phase seepage capacity, quantifying the specific impact of condensation damage on well inflow performance. The findings provide technical support for dynamic analysis, rational production allocation, and development adjustment in the early production test stage of the BZ19-6 condensate gas reservoir and similar reservoirs.

The Research of Fracture and Pore Dual-media Reservoir Gas Well Production Capacity Formula

PENG Peng, WANG Xiaopei, ZHANG Yongling, ZHAO Boyong, LIU Zhaolong

2025, 47(6):  83-93.  DOI: 10.11885/j.issn.1674-5086.2023.12.18.03

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Reasonable evaluation of production capacity is very important for gas well production. It is the foundation for the long-term development of gas field. The ultra-deep and ultra-high-pressure fractured tight sandstone gas reservoirs in front of Kuche mountain of Tarim Oilfield is characteristic of tight matrix and developed fractures. The seepage characteristics often manifest as the dual-media reservoir features of fractures and matrix. The entire flow process is divided into three stages: fracture flow, transitional flow and overall system flow. In response to the lack of targeted production capacity evaluation methods, the research has been conducted on the early production capacity evaluation formula corresponding to the fracture flow stage, transitional stage and on the long-term stable production capacity corresponding to the fracture porosity flow stage. The production capacity evaluation formula for dual-media reservoir gas wells considering the skin factor and the high speed non-Darcy coefficient has been theoretically established. The examples of calculation show that the result of production capacity formula is closer to the testing production than the conventional point method empirical formula, demonstrating good applicability in ultra-deep and ultra-high-pressure fractured tight sandstone gas reservoirs.

A Study on Hole Initiation Pressure and Orientation of Perforated Well in High Stress Reservoir

LIU Hu, LU Qianli, DUAN Hua, XIAO Bin, ZHANG Hang

2025, 47(6):  94-106.  DOI: 10.11885/j.issn.1674-5086.2024.01.01.01

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It is difficult to accurately predict breakdown pressure of high stress reservoir or reservoirs with complex in-situ stress conditions, which leads to problems such as difficulties in reservoir fracturing, risk of liquid pumping and difficulties in sand pumping. Perforation hole is an important channel connecting wellbore and formation. Studying the initiation pressure and orientation of perforation hole is helpful to the understanding of the breakdown behavior of high stress reservoir or reservoir with complex in-situ stress conditions, and provides a basis for subsequent optimization of sand fracturing process. In this paper, based on the theory of elastic mechanics, the stress field model around the casing perforation well and the perforation hole are established. Based on this model, the initiation pressure and orientation of perforation hole are determined. Compared with the field data of a high stress reservoir, the reliability of the model is proved. Hole initiation pressure and orientation in vertical well under different in-situ stress conditions of high stress reservoir are also analyzed. The results show that for in-situ stress state in both strike-slip fault and reverse fault, when perforating along the direction of the maximum horizontal principal stress, the hole always fracture horizontally, forming a horizontal fracture near the hole, and the initiation pressure is the lowest, and the pattern of near-wellbore fracture on strike-slip fault is more tortuous; when perforating along the direction of the minimum horizontal principal stress, the smaller the horizontal ground stress difference is, the easier the hole is to fracture horizontally, forming a horizontal fracture near the hole, and the initiation pressure is higher, and the pattern of near-wellbore fracture on strike-slip fault is more tortuous; the larger the horizontal stress difference is, the easier the hole is to fracture longitudinally, which tends to form vertical fracture near the hole, and the initiation pressure is lower, and the pattern of near-wellbore fracture on reverse fault is more tortuous. The results of this study are conducive to the efficient development of high stress reservoirs or reservoirs with complex in-situ stress conditions.

Physical Model Experiment on Wellbore Deformation and Failure of Coalbed Methane Horizontal Well Considering the Influence of In-situ Stresses

ZHANG Qiangui, DENG Jian, FAN Xiangyu, JIA Lichun, GUO Xiaowei

2025, 47(6):  107-118.  DOI: 10.11885/j.issn.1674-5086.2024.11.04.02

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Understanding wellbore instability mechanisms in coalbed methane (CBM) horizontal wells under complex stress conditions is crucial for optimizing CBM reservoir drilling. Using a self-developed true triaxial device to simulate surrounding rock deformation, this study examines how differential horizontal stresses and vertical stress variations affect deformation and failure in CBM horizontal wellbores, and obtains the following results: 1) Wellbore deformation can be divided into three stages: slow shrinkage deformation stage, stable shrinkage deformation stage, and accelerated shrinkage until closure stage. 2) In the latter two stages of wellbore deformation, the deformation of the specimen in three directions is mainly controlled by wellbore deformation and failure. 3) As the maximum or minimum horizontal principal stress increases, the slope of the vertical principal stress-deformation curve during the stable shrinkage deformation stage of the wellbore significantly increases, and the strain in all three directions per unit stress increment decreases; simultaneously, the cross-sectional area at wellbore failure increases, with a corresponding increase in critical vertical principal stress and a decrease in vertical strain. 4) When the two horizontal principal stresses increase simultaneously, the aforementioned trends become more pronounced, which is more conducive to maintaining wellbore stability. The findings of this study can provide guidance for the drilling design of CBM horizontal wells.

Prediction of the Effect of Pressure-bearing Plugging of Fractured Formation Under Non-uniform In-situ Stress

LIU Yang, ZHANG Pei, MA Qi, WANG Junli, MA Tianshou

2025, 47(6):  119-128.  DOI: 10.11885/j.issn.1674-5086.2023.09.04.01

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Pressure-bearing plugging is an important method to solve the problem of lost circulation in fractured formation. Accurate prediction of pressure-bearing capacity of leakage formation is the core basis of scientific application of pressure-bearing plugging technology. For this purpose, on the basis of analyzing the variation of fracture width under non-uniform in-situ stress, the crack tip stress intensity factor when considering in-fracture plugging is derived based on superposition principle, and an analytical model for predicting the pressure-bearing capacity of plugged fractured formation is established. Compared with the traditional model, the prediction results of this model have higher accuracy and reliability. Finally, the influence of different engineering and geological parameters on the pressure-bearing capacity of plugged fracture is analyzed. The results show that increasing the fracture tip length and reducing the fluid pressure at the fracture tip during plugging treatment are beneficial to improving pressure-bearing capacity of fractured formation. When a low-permeable plugging zone is formed in the vicinity of borehole wall, it is necessary to optimize the length of the plugging zone to maximize the pressure-bearing capacity of plugged fracture. When the formation permeability is determined, pressure-bearing capacity of plugged fracture decreases with the increase of the ratio of in-situ stresses, and increases with the increase of elastic modulus, Poisson's ratio and fracture toughness.

Gas Entrapment Characteristics and Its Recovery Mechanisms During Water Invasion Process for Deep Carbonate Gas Reservoirs

ZHANG Ruihan, HU Yuhan, LI Tao, LU Guang, ZHANG Tao, ZHANG Liehui

2025, 47(6):  129-140.  DOI: 10.11885/j.issn.1674-5086.2023.11.03.34

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Carbonate gas reservoir is usually deposited along with aquifer. Water invasion during the development of these reservoirs results in larger amount of gas trapped within the reservoirs. Therefore, it has great theoretical and practical significance to characterize and understand the pore-scale gas entrapment characteristics and its recovery mechanisms during water invasion process. Based on the CT scanning images for real carbonate reservoir, the characteristics of fractures and pores in fracture-pore type reservoir were extracted. The corresponding etched-glass model was manufactured to conduct gas-water two-phase flow experiments. The invasion dynamics and gas entrapment characteristics were revealed. Furthermore, the effects of pore structure, wettability and pressure gradient on water invasion dynamics were evaluated based on the Lattice Boltzmann Method (LBM). Finally, the mechanism of trapped gas recovery is revealed. The results show that more strongly hydrophobic carbonate reservoirs lead to a larger volume of trapped gas after water invasion. The types of trapped gas include dead-end/corner trapped gas, side-flow trapped gas, snap-off trapped gas, H-shaped trapped gas, and network-shaped trapped gas. When the invasion pressure gradient increases (well production increase), a large volume of gas will be trapped inside the formation in the form of network-shaped trapped gas. In flooded gas reservoirs, intermittent well production(intermittent depressurization and pressurization) can lead to the recovery of the snap-off trapped gas and network-shaped trapped gas.

A New Method for Sand Production Prediction of Gas Storage Wells Based on Fuzzy Comprehensive Evaluation

LIAO Wei, HUANG Haibing, HU Shuyong, ZHANG Shijie, LI Xinlu

2025, 47(6):  141-150.  DOI: 10.11885/j.issn.1674-5086.2024.11.11.32

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Affected by the operation mode of gas storage with strong injection and production, the risk of sand production is prone to occur in the reservoir during peak shaving and gas production. Once sand is produced, it will seriously affect the life and peak shaving capacity of the gas storage. The commonly used qualitative empirical sand prediction methods lack intuitive and comprehensive results, and a single prediction index has great limitations. In response to this problem, qualitative experience sand prediction methods such as porosity method, acoustic time difference method, combined modulus method, sand production index method and Schlumberger ratio method are considered comprehensively, and analytic hierarchy process and fuzzy comprehensive evaluation decision-making are adopted to establish qualitative experience. The fuzzy comprehensive evaluation model for sand production prediction can predict and analyze the sand production results of different perforation sections. Application examples show that this method has realized the prediction of formation sand production results in different perforation sections, improved the accuracy and comprehensiveness of formation sand production prediction, which is of great significance to the long-term safe operation of gas storage.

PETROLEUM MACHINERY AND OILFIELD CHEMISTRY

Research and Improvement of Interface Mechanical Behavior of Screw Motor Based on Cohesive Zone Model

REN Meipeng, XIE Renjun, ZHU Xiaohua, SHI Changshuai, ZHANG Xingquan

2025, 47(6):  151-167.  DOI: 10.11885/j.issn.1674-5086.2023.10.16.02

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Aiming at the problem of debonding failure of the stator rubber bushing of the screw motor, the failure mechanism of the stator bushing of the 7/8 head conventional and equal wall thickness screw motor was studied. The principle of rubber-metal interface cohesion was adopted in the study. Through rubber-metal bonding mechanics test and rubber uniaxial tensile test, and finite element and numerical analysis, the interface shear stress was found to be the main factor causing the bushing bonding failure, and the minimum arc radius $R$ of the bushing profile was the main reason for the change of the maximum interface shear stress. The drilling fluid and interference have a significant effect on the shear stress at the interface of the equal wall thickness bushing. When the drilling fluid pressure increases from 15 MPa to 60 MPa, the maximum shear stress at the interface of the equal wall thickness bushing increases by 146%, and the equal wall thickness screw motor is more prone to bonding failure. Finally, the different wall thickness bushing structure is proposed. The interface shear stress of the different wall thickness bushing is less than that of the equal wall thickness bushing, and decreases with the increase of the minimum arc radius $R$, which has good heat dissipation. The service life of the bushing with different wall thickness is proportional to the minimum arc radius when fatigue failure occurs. The maxi-mum service life is predicted to be 240.99 h when fatigue failure occurs. The first fatigue failure area is the inner cavity arc top of the bushing, which is consistent with the actual failure phenomenon. This paper provides a theoretical basis for the design optimization of screw motor, and makes an important contribution to improve the working life of screw motor.

The Influence of Transportation Environment on the Quantization Accuracy of Ultrasonic Internal Detection

CAI Liangxue, ZHENG Yuejun, LU Yifeng, XU Guangli

2025, 47(6):  168-177.  DOI: 10.11885/j.issn.1674-5086.2024.01.15.02

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Ultrasonic internal detection has been widely used in the field of pipeline detection and monitoring due to its advantages of easy operation and accurate detection. The echo signal contains a lot of information, but the change of working conditions will affect the echo signal. In order to explore the influence of pipe pressure or flow rate on the measurement accuracy of wall thickness, an ultrasonic internal detection simulation experiment system was used to carry out experiments. Under different pipeline transport conditions, ultrasonic internal detection signals are collected and characteristic parameters are extracted to analyze the fluctuation of echo signals. The wall thickness of the pipeline is calculated by using the transit-time method, and the influence of different pipeline transport environments on the calculation accuracy of wall thickness is analyzed. The results show that with the change of pressure and flow rate, the moment of receiving the echo signal is advanced or delayed, and its amplitude fluctuates. The fluctuation range of the wall thickness accuracy error is between -0.71% and 0.96%. This indicates that the pipe flow state (0.3~1.2 MPa, 8.129~15.023 m³/h) has no significant influence on the measurement accuracy of wall thickness, and the influence of pipeline transportation environment on the accuracy of ultrasonic internal detection of pipe wall thickness can be ignored, which provides theoretical support for accurate analysis of ultrasonic internal detection data.

An Experimental Study on Start-up Mechanism of Micro-residual Oil by New Chemical System

WEI Hongtao, ZHANG Xiaoqin, GUAN Wenting, YANG Fengrui, ZHOU Yu

2025, 47(6):  178-186.  DOI: 10.11885/j.issn.1674-5086.2023.12.11.01

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Based on the microfluidic glass model of three typical oil layers in Daqing Oilfield, the start-up mechanism of the new alkali-free medium phase system on the micro residual oil was studied by means of microscopic oil displacement visualization, contact angle wettability measurement and interfacial tension measurement instruments. The new system has smaller particle size and stronger solubilization effect of emulsified oil droplets, and significantly improves the swept volume and oil washing efficiency. Compared with other composite systems, the new system has stronger wettability and can achieve rapid wettability reversal in a very short time to change the wettability. In this paper, the rapid deformation ability of the new system is studied by means of visual experiment. Compared with other chemical systems, this property is more conducive to the start-up and migration of micro-residual oil, increases the injection performance of the system, and provides help for the expansion of the sweep volume of the system. Another existing form of corner micro-residual oil in the reservoir is proposed, and the mechanism that the new system starts this kind of residual oil by breaking the regional pressure field balance is given. Through the research, the micro-residual oil start-up and migration mechanism of the new alkali-free system is defined, which provides technical means and support for further research on the oil displacement mechanism of the new alkali-free system.