Journal of Southwest Petroleum University(Science & Technology Edition)

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Sedimentary Characteristics of the Maokou Formation of the Permian in Northern Sichuan Basin and Its Petroleum Significance

ZENG Deming, XIE Xiaobin, HUANG Dong, YU Liangzhi, ZHANG Yu

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 1-12. DOI: 10.11885/j.issn.1674-5086.2020.12.24.04

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Based on the fine seismic data interpretation result, combining the field sections and indoor thin-section observation, we study the depositional facies distribution characteristics, by analyzing the main rock types, paleontology, geochemical and seismic characteristics. On the basis of biological (chip) limestone, siliceous rocks and reef limestone development rule of the lithofacies and seismic stratigraphic structures and stratigraphic thickness variation characteristics, we find out that Maokou Formation has developed sedimentary facies of the open sea platform, marginal-platform shoals and slope-basin, summarize four kinds of sedimentary facies association, open sea platform with patch reefs, open sea platform with shaoal patch, the marginal-platform shoals and calcareous-siliceous basins. Land clarify the vertical evolution of sedimentary facies and plane distribution rule. The results show that the high-energy marginal-platform shoals present banding development in the Jiange——Yuanba——Longgang Area. The biological (chip) limestone develops the intercrystalline denudation pore, intergranular dissolved pore and biogenic body cavity pore, which is a high quality reservoir development zone with good physical properties. Maokou Formation (Member 4) in the western Sichuan trough and Guangyuan——Wangcang trough area sedimentary siliceous rock and mudstone is the high quality source rocks, the excellent sedimentary environment providing a favorable conditions for hydrocarbon accumulation oil source and reservoir.

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Geological Conditions and Exploration Potential of Shale Gas in Dalong Formation in Northern Sichuan Basin

WANG Mingfa, WEN Hu, NI Kai, FU Xiaoping, YANG Hongfei

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 13-23. DOI: 10.11885/j.issn.1674-5086.2020.11.05.01

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On the basis of the latest Well LB1 and 7 outcrops data and data of some old wells, the study evaluates the horizontal and vertical distribution law of high-quality shale of Dalong Formation in northern Sichuan Basin. It is considered that the distribution of high-quality shale is controlled by sedimentary facies and shows NW-SE trend. Basin facies have developed in Guangyuan-Wangcang Area with small shale thickness(10~20 m); deep-water shelf facies have developed on both sides of the basin facies, and the thickness of shale is relatively bigger(20~45 m); shallow-water shelf or slope facies have developed in the periphery, and the thickness of shale gradually becomes smaller(0~15 m). From slope facies to shelf facies, then to basin facies, the content of calcareous decreases and the content of silica increases gradually; the thickness of shale is bigger first (deep-water shelf facies) and then smaller (basin facies). In addition, the geochemical characteristics and reservoir microscopic characteristics of Well LB1 are studied, then compared with the Silurian shale fields in Jiaoshiba, Dingshan and Dongxi areas. It is concluded that the high quality shale of Dalong Formation has the characteristics of high organic carbon content, high gas content, good kerogen type, moderate maturity and good compressibility. It is considered that the extensive development of amorphous organic matter is the controlling factor of high organic carbon contentand the anoxic sulfide environment is the key to preservation. The characteristics of high gas content is due to a good correlation between gas content and the specific surface area, and the main contribution of the specific surface area is the content of organic matter. Finally, we have found that the resources of Dalong Formation in SINOPEC mining right have great exploration potential, which is worthy of further exploration.

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Research on Parallel Inverse Q Filtering Methods for Seismic Wave Energy Compensation

ZHANG Quan, WANG Yipin, ZHANG Wei, PENG Bo, XU Lin

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 24-32. DOI: 10.11885/j.issn.1674-5086.2021.02.03.03

Abstract （154）

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In seismic data processing of petroleum exploration, the inverse Q filtering method can effectively perform amplitude compensation and phase correction on seismic waves to provide more accurate information for seismic inversion and reservoir prediction. In large-scale seismic data processing, the inverse Q filtering method takes longer operation time under the CPU computing platform, which affects the efficiency of seismic interpretation. After analysis, it is found that the inverse Q filtering method consumes a lot of time in the short-time Fourier transform and calculates the amplitude and dispersion compensation terms. On the GPU platform, we first parallelizes the amplitude and dispersion compensation calculations, and accelerates the batch short-time Fourier transform with the CUFFT library, and then further optimizes the batch short-time Fourier transform and applies it to the inverse Q filtering method. The results show that compared with the CPU computing environment, the efficiency of the inverse Q filtering parallel algorithm based on the CUFFT library is improved by 3.9 times, and the optimized batch short-time Fourier transform further improves the efficiency of the parallel inverse Q filtering method by 12%.

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A Study on the Characteristics of Reservoir Pore Structure Based on Nand Mercury Injection Data

ZHANG Qian, TANG Haizhong, MU Mingyang, WEI Jun, ZENG Ligang

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 33-42. DOI: 10.11885/j.issn.1674-5086.2020.11.13.11

Abstract （144）

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X1 Wellblock is located in the Changshaling structural belt of Ying'er Sag, Jiuquan Basin. The rock types of this reservoir of the first member in Xiagou Formation of Lower Crataceous are mainly lithic sandstone and feldspar lithic sandstone. Reservoir heterogeneity is strong, and thin interbedded sand and mudstone are especially developed, which brings great difficulties to reservoir comprehensive evaluation. However, fluid identification, reservoir evaluation and later development measures depend on the overall understanding of pore structure of reservoir to a large extent. Taking X1 Wellblock in Changshaling as an example, the statistical analysis was carried out on the mineral composition in the study area, the pore types are classified study of electron microscopic thin section(SEM) observation, and then the key works, under the wellblock of mercury injection and nuclear magnetic resonance T ₂ spectrum of test data, established the quantitative calculation methods of core pore throat radius and the T ₂ relaxation time spectrum, and connecting with the nuclear magnetic resonance (NMR) logging data. A method for continuously and quantitatively characterizing the variation characteristics of reservoir pore-throat radius is developed. The quantitative characterization of pore-throat radius can provide ideas for us to understand the change of reservoir porosity and permeability, and provide more abundant information for the study of reservoir pore structure and reservoir heterogeneity.

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Comprehensive Analysis of Logging and Excavation Effects in Carbonate Reservoirs

WANG Weijun, LIU Hongqi, ZHU Guangya, XIN Jionglong, WANG Youjing

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 43-54. DOI: 10.11885/j.issn.1674-5086.2020.06.26.01

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Due to the large structural changes and complex lithology, there are many contradictions in fluid identification and fluid interface division of carbonate reservoir in H Oilfield. For gas identification, compensated neutron logging mining effect is effective in some blocks, but not in others. Therefore, it is necessary to analyze the influencing factors of mining effect. Firstly, the lithology and pore structure characteristics of carbonate reservoir in H Oilfield are analyzed. Then the physical characteristics of Layer KA and KB such as pore permeability are analyzed. The response characteristics of mining effects formed by neutron logging and density logging in gas reservoirs are summarized by those curves of several Wells, and the reasons of forming true and false mining effects are analyzed. The density log and neutron log correlation was expounded in theory, and two kinds of logging response correlation equation were deduced. The factors affecting the mechanism of the excavation effect were analyzed from the borehole diameter expanding permeability, pore structure, physical property and saturation. Finally, the comprehensive utilization of mining effect judgment analysis method of gas was suggested and the excavation effect of judge true and false of a few basis was put forward. The fluid identification of K Reservoir in H Oilfield is well completed with this method. Therefore, this method can provide reference for the accurate identification of fluid types in H Oilfield and similar complex carbonate reservoirs.

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Research Progress, Challenge and Prospect of Nanoscale Oil-displacing Materials for Enhanced Oil Recovery

ZHANG Chenjun, JIN Xu, YUAN Bin, ZHANG Lei, ZHENG Shaojing

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 55-70. DOI: 10.11885/j.issn.1674-5086.2022.04.27.03

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This review summarizes the research progress of nanoscale oil-displacing materials developed by various researchers, describes the application effect of silica nanoparticles, metal-oxide nanomaterials, polymer nanospheres and carbon nanomaterials, analyses the physical and chemical properties of existing nanoscale oil-displacing agents and their EOR mechanism in porous reservoir media, including nanometer-size effect, wettability alteration, structural disjoining pressure, mobility ratio improvement, and predicts the potential of nanoscale oil-displacing materials in high water cut reservoir, low permeability reservoirs, tight oil and shale oil in China. In addition, the review points out the challenges and research direction in the process of oilfield development, such as testing methods, accuracy of mathematical model, material versatility, economy and industrial production, and provides a theoretical and experimental basis for their large-scale application in EOR.

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Progress of Researches on Self Repairing Hydrogel and Its Application in Oil and Gas Fields

TU Hongjun, ZHOU Ming, LI Tongtong

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 71-80. DOI: 10.11885/j.issn.1674-5086.2020.06.10.04

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In view of the phenomenon that self-healing hydrogels can imitate the damaged parts of plants in nature to repair themselves at the molecular level, the basic principles of design and synthesis of self-healing hydrogels are summarized. Self-healing hydrogels are mainly divided into chemical self-healing hydrogels and physical self-healing hydrogels. In general, chemical self-healing hydrogels can be divided into self-healing hydrogels based on Diels——Alder addition reaction, self-healing hydrogels based on reversible disulfide bond and self-healing hydrogels based on acylhydrazone bond; physical self-healing hydrogels can be divided into self-healing hydrogels based on hydrogen bonding, self-healing hydrogels based on host guest interaction, and self-healing hydrogels based on electrostatic interaction. Self-healing hydrogel not only retains the good water absorption, water retention, biocompatibility and other properties of traditional hydrogel, but also has self-healing properties that can effectively extend the service life of materials and reduce the use cost of materials. On this basis, the potential application value and situation of self-healing hydrogel in oil and gas fields, biomedicine and other fields are analyzed and discussed, and the development trend of self-healing hydrogel in oil and gas fields is prospected.

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Interpretation Model of Gas-injected Tracer for Well Groups in Fracture-vuggy Reservoirs

LIU Xueli, ZOU Ning, LIU Jianyi, XIANG Rui, LIU Zhibin

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 81-88. DOI: 10.11885/j.issn.1674-5086.2020.11.15.01

Abstract （133）

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The conventional gas injection tracer interpretation method for sandstone reservoirs is based on the assumption of continuum, which is not suitable for large-scale fracture-vuggy reservoirs with discrete combinations of fractures and caves. A physical and mathematical model of gas tracer interpretation between injection and production wells in fractured-vuggy reservoirs has been established. The model considers the radial migration and diffusion of gas tracers in large-scale cave areas and the transmission of one-dimensional migration and two-dimensional diffusion in fractures. In this way, the distribution coefficient between wells, phases, and fractures are introduced. The model is solved and the theoretical recovery curve of gas tracer concentration is drawn. The parameter sensitivity analysis of the model is carried out, and the influence of the size of the cavern, the number and length of fractures, the diffusion coefficient, the gas injection rate, and the amount of tracer injection on the output curve is explored. Studies have shown that the larger the cave, the later the peak of the concentration curve appears; the longer the crack length, the lagging of the peak, the more the number of bars and the more the peak. The measured response curve of gas injection tracer in the TK425 Well Group of Tahe Oilfield is fitted and interpreted, and the volume of the karst cave area and the fracture channel between injection and production wells are calculated. The gas injection tracer interpretation model for fractured-vuggy reservoirs can effectively determine the connectivity between wells, calculate formation parameters, understand the distribution of reservoirs, and provide theoretical support for gas injection to improve recovery.

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Characterization and Evaluation Method of Streamline Field in High Water Cut Reservoir

LIU Chaoyang, GUO Qi, LI Gang, HUANG Bo, WANG Zhenyu

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 89-96. DOI: 10.11885/j.issn.1674-5086.2020.10.22.02

Abstract （131）

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By extracting the spatial coordinates and attribute data of particles in streamline field obtained through numerical simulation, we established a characterization method of streamline field with streamline cluster flow rate, streamline cluster potential and streamline cluster oil content. The streamline field is classified and evaluated by density peak algorithm, and the clustering effect of streamline classification is verified by S _Dbw coefficient. Finally the method of quantitative characterization and evaluation of streamline field in high water cut reservoir is formed. The results show that the three parameters can better reflect the distribution relationship and size of flow rate and potential between injection and production wells than conventional methods. Streamline strength grades in different regions can be quantitatively determined by clustering and grading of characterization parameters. The method is applied to an actual block in an eastern oilfield. The whole streamline field is divided into 14 types. The displacement intensity of each region is quite different. Through streamline field reconstruction, the streamline field grade are adjusted from 14 types to 7 types, the flow heterogeneity is weakened, and the reservoir productivity is improved obviously.

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The Expansion and Application of Deviation Factor Chart of Super-high Pressure and High CO ₂ Gas Reservoir

LU Ruibin, WANG Wenjuan, ZHANG Qiaoliang, HU Lin, CHEN Jian

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 97-104. DOI: 10.11885/j.issn.1674-5086.2020.06.13.01

Abstract （171）

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Standing-Katz plate is one of the most common and basic methods to determine the deviation factor of natural gas. However, there are some problems, such as large error in manual reading, limited use of natural gas with super-high pressure ( p _pr>15) and high CO ₂ content. We design a single component deviation factor measurement experiment, and combined with the changing rule of the curve of the Standing-Katz plate, expand the p _pr to 30, the T _pr to 3.6, and digitize the plate. Through different CO ₂ content deviation factor tests, and a new calculation model of pseudo critical pressure and pseudo critical temperature of natural gas considering different CO ₂ content is derived. Compared with the conventional non-hydrocarbon correction model, the new model has higher calculation accuracy and wider application range. Furthermore, the new correction model is embedded in the deviation factor expansion chart, and the software is used. The deviation factor expansion chart considering different CO ₂ content has a smaller error (≤3 %) in the calculation of the deviation factor of HTHP and high CO ₂ content natural gas in the west of South China Sea, and the application effect is better.

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A Study on Fractal Quantitative Characterization Method of Low Permeability Sandstone Pore in DLH Oilfield

SUN Qiang, SUN Zhigang, ZHANG Chao

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 105-116. DOI: 10.11885/j.issn.1674-5086.2020.11.04.03

Abstract （122）

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In view of the difficulty of conventional characterization methods to accurately characterize the complexity and irregularity of pore space distribution in low-permeability sandstone reservoirs, a fractal dimension calculation method is proposed to realize the quantitative characterization of pore characteristics of low-permeability sandstone reservoirs. Based on the analysis of the difference between different fractal dimension calculation methods, the MIFA method is preferably used to solve the fractal dimension of low permeability sandstone reservoirs (between 2.042 and 2.324), with the best correlation. The displacement pressure, average pore throat radius, coefficient of variation, and mean coefficient are determined as the comprehensive characterization parameters of the complexity and heterogeneity of reservoir pore throat distribution. Based on the solution of the fractal dimension of mercury injection at a constant rate, it is found that the heterogeneity of low-permeability sandstone reservoirs presents the following characteristics:small and medium pore throats are larger than small pore throats, and throat distribution is larger than pore distribution. There is certain correlation between the fractal dimension of low-permeability sandstone reservoirs and the experimental results of starting pressure gradient and stress sensitivity damage rate. The larger the fractal dimension, the stronger the heterogeneity of the pore throat distribution and the larger the starting pressure gradient is needed and the damage to the stress sensitivity will increase. The calculation of the fractal dimension of low-permeability sandstone reservoirs can be used for qualitative prediction and judgment of laboratory experimental results, and also as an important criterion for the application of relative permeability curves in reservoir engineering.

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Research on Optimization and Application of Fracturing Perforation Orientation in Directional Wells Based on Minimum Initiation Pressure

WANG Erjun, MA Lei, CAO Feng, FENG Ming, ZENG Fanhui

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 117-126. DOI: 10.11885/j.issn.1674-5086.2021.01.28.02

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Hydraulic fracturing with directional wells in low permeability reservoirs is an important measure to increase production and efficiency and decrease cost in oil and gas fields. Perforation is the first procedure to open a reservoir before fracturing. The quality of perforation directly affects the productivity of directional wells. In order to reduce the fracturing pressure of reservoir and the risk of sand plugging, the perforation azimuth of directional wells fracturing is optimized. Different from previous studies, this paper considers the combined superposition of original ground stress, casing cement ring induced stress, perforation hole induced stress, wellbore injection induced stress and fluid seepage induced stress, and establishes an optimization model for directional well fracturing and perforating azimuth is established based on the minimum fracture initiation pressure(FIP) prediction and the tensile failure criterion. The reliability and rationality of the model are verified by the comparison of indoor physical simulation and theoretical model calculation results. The simulation results show that (1) FIP changes periodically in 360°perforation azimuth, there are two minimum and maximum FIP points, and with the increase of wellbore azimuth, the minimum FIP gradually increases, and the maximum FIP gradually decreases; (2) the perforation directions corresponding to the minimum FIP at different inclination angles and azimuths are quite different, and the optimal perforation direction for inclined wells should take into account the comprehensive effects of the inclination and azimuth angles at the same time; (3) factors such as horizontal principal stress difference and construction displacement have little effect on determining the optimal perforation orientation. The optimal perforation direction angle is 20°and 205°, and the corresponding minimum FIP is 45.5 MPa. Thus, it reduces the construction difficulty and provides reference for the perforation position optimization technique of low permeability reservoir reconstruction.

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Effect of Nonlinear Effective Pressure on Stress Sensitivity in Fracture Sandstones

LIU Xugang, ZHOU Yongyi, ZHANG Junqiang, XIAO Wenlian, REN Xiyao

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 127-135. DOI: 10.11885/j.issn.1674-5086.2020.12.03.01

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To implement the transformation of the relationships between permeability and confining pressures in changing-confining-pressure stress sensitivity experiments into the ones in changing-pore-pressure stress sensitivity experiments, and obtain the relationships between permeability and pore pressure, changing- confining -pressure stress sensitivity experiments and special stress sensitive experiments in tight sandstones with microfractures and artificial fractures are carried out. At the same time, based on the experimental data in changing-confining-pressure stress sensitivity experiments and the effective stress equations, the relationships between permeability and pore pressure are calculated, and are compared with the results in changing-pore-pressure stress sensitivity experiments. The results indicate that calculated permeabilities are larger than those measured directly, which is caused by the Klinkenberg effect, dimensionless permeabilities measured directly are equal to those calculated with the nonlinear effective principle, while larger than those calculated with Terzaghi effective principle. Both effective stress and slippage effect affect the determination of permeability in situ.

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Sand Blocking Mechanisms and Sand Control Parameters Optimization Design in Fine Siltstone Reservoirs

JIA Peifeng, CUI Chuanzhi, ZHAO Yizhong, WU Zhongwei, ZHANG Yuchen

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 136-144. DOI: 10.11885/j.issn.1674-5086.2020.08.04.01

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The siltstone reservoir has many vertical small layers. Well productivity is affected by sand blocking. Based on the existing productivity model of inclined vertical well, the permeability of screen pipe, annulus filling layer, squeeze filling layer and reservoir are described in detail, and the formula of skin coefficient of mechanical sand control is improved. The blocking law of sand control system is analyzed through laboratory experiments. It is considered that with the increase of displacement volume number and displacement flow, the plugging of sand control system intensifies and the maximum permeability decreases by 40%. Reservoir particles enter the casing and block the annulus gravel and sand control screen, resulting in a sharp increase in skin factor and a decrease in production capacity of more than 80%. Expanding the squeeze packing radius can block particles away from the wellbore and help to maintain oil well productivity. Through the optimization analysis of the filling radius of layered sand control wells, it is found that expanding the filling radius in medium and low permeability can improve the interlayer production effect. The filling parameters of sand control wells in typical blocks are optimized, and the filling radius of S4 layer with low permeability is expanded. With the measures, the oil well fluid volume remains stable, and the daily oil production increases by 9.56 t.

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Selection and Optimization of Throttling Process for Ultra-high Pressure Gas Wells

LIU Peng, WANG Chongyang

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 145-154. DOI: 10.11885/j.issn.1674-5086.2020.10.28.04

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The throttling system of ultra-high pressure gas wells plays a vital role in the life cycle of gas wells, and a reasonable throttling process can not only extend the life of gas wells, but also reduce costs. This research introduces the throttling technology used in domestic ultra-high pressure gas wells, and simulates the flow field of different throttling technology in gas wells in Northwest Sichuan Gas Mine based on computational fluid dynamics. The flow field analysis software is used to analyze the internal pressure and flow rate of single-stage and two-stage throttling process systems. The flow field analysis software is used to analyze the internal pressure and flow velocity of single-stage and two-stage throttling process systems. The reasonable CV value and opening degree of different throttling process systems were determined, and the highest flow rate of different throttling process systems was obtained. The throttling parameters selection and use suggestions under different throttling techniques on site are proposed. The research shows that the three throttling processes can meet throttling requirements and on-site production conditions. Among them, the single-stage throttling process is simple, but the flow rate is above 850 m/s, and the valve erosion is serious; one-stage fixed and two-stage adjustable throttling the maximum flow rate is between 550 m/s and 600 m/s, which is lower than the single-stage throttling, but the maximum output is limited; the maximum flow rate of the two-stage adjustable flow is similar to that of the first-stage fixed two-stage adjustable flow, and can be adjusted as needed. Production, but the cost is relatively high.

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Construction and Application of Intelligent Gas Field Integrated Model Data Sharing Platform

LI Yueyang, REN Jingsi, ZHANG Su, JIN Wei

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 155-162. DOI: 10.11885/j.issn.1674-5086.2020.11.19.01

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Integrated simulation model is an important basis for the construction of intelligent gas fields. How to use data-driven model in efficient operation has become a key problem to be solved urgently. In this article, in view of the data source dispersion, poor availability, low level of interaction with model, we carry out the following technical research:(1) combined with data service bus (DSB) and PI OLEDB interface technology, we realize effective integration of multi-source structured data and real-time sampling, meet production data's business requirements in different time dimension of the integration model; (2) we establish data quality rule base and automatic scanning system to realize the effective control of data quality and ensure the normal operation of the integrated model; (3) we develop data exchange tools based on data flow engine technology and has realized the automatic interaction between the comprehensive database and the simulation model. Its advantage is that when the application scene changes, the basic services flexible arrangement method can be used to efficiently reuse the results of data construction in the early stage, which greatly improves the development efficiency. Compared with similar technologies domestic and overseas, the application of data flow engine technology breaks through the interaction barrier between the integrated model and external data resources, breaks the service mode of customized data application development in this field, and lays a technical foundation for the construction of smart gas fields.

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Vibration Response and Fatigue Prediction of Marine Steel Catenary Risers

ZHU Hongjun, DING Zhiqi, GAO Yue, ZHAO Honglei, HU Jie

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 163-179. DOI: 10.11885/j.issn.1674-5086.2020.10.25.02

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Vortex-induced vibration (VIV) is a main factor contributing to the fatigue damage of marine risers. With the aid of Van Der Pol wake oscillator model, the present paper investigates the VIV of pinned-pinned steel catenary risers of different lengths subjected to different shear-flow profiles with the same flow rate. The second-order central difference method is employed to solve the coupled equations in both time and space domain, and the rain flow counting method is used to predict the fatigue life. The vibration presents a blended pattern of standing wave and traveling wave for the response propagation along the span. The vibration shifts from the standing-wave dominated response to the traveling-wave dominated one with the increase of the riser length. The riser experiences multi-frequency oscillation due to the influence of shear flow, and the traveling wave propagates from the riser top to its bottom. Furthermore, the propagation rate of traveling wave varies with the shear degree of flow profile and the riser length. The riser extracts less energy from ambient flow as the shear degree increases, while the energy consumption grows, resulting in the reduction of response amplitude. The fatigue damage is aggravated with the water depth at the same incoming flow profile. The same result is observed as the shear degree of flow profile increases at the same water depth.

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A Study on the Mechanism and Heat Generation Law of PDC Wear Tooth Cutting

YANG Yingxin, XIE Song, CAI Can, CAO Yulei, LI Bangrun

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (1): 180-188. DOI: 10.11885/j.issn.1674-5086.2020.06.04.03

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To explore the cutting process of deep drilling PDC bit cutting teeth in the wear state, the single tooth cutting experiment is carried out by selecting PDC cutting teeth with different wear degrees on the deep drilling PDC bit. The stress state, temperature change law and crack propagation process are analyzed by stress test system, high speed camera and thermal infrared imager. The results show that the cutting force, temperature change and large volume cuttings are more obvious than the non-wear teeth, which will lead to the outburst of drill bit vibration and the sharp acceleration of wear, seriously affecting its service life. On the other hand, when cutting granite, the problem of cutting force increase and heating up is more prominent, but volume breakage is more likely to happen and produce larger block cuttings. The research results will help to re-understand the rock breaking and temperature variation law of real bottom wear teeth, and provide important reference for bit design and downhole life evaluation.

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Current Situation, Challenges and Countermeasures of China's Energy Transformation and Energy Security Under the Goal of Carbon Neutrality

HOU Meifang

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 1-10. DOI: 10.11885/j.issn.1674-5086.2023.01.12.02

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Human society is now in its third stage of energy transformation, with the goal of carbon neutrality and sustainable development, after the first two major energy transformation periods. China's energy development is facing complex situation and severe challenges under the new situation. We must accelerate the low-carbon energy transformation to achieve carbon neutrality, and firmly safeguard the bottom line of energy security at the same time. It is a major issue for China's high-quality energy development to balance energy transformation and energy security. Studies indicate that: 1) the previous two energy transformations were both in line with the traditional law of economic development and accompanied by the industrial revolution. In these two transformations, energy acted as common productive factors, and the energy structure gradually changed under the drive of technology. However, the core reasons of the third energy transformation are to address climate change and guarantee energy security. The ongoing transformation is driven by the strategic measures of sustainable development besides technological development, and it requires multiple efforts. 2) there are lots of risks in China's energy transformation: the total energy consumption is too large, the carbon emission and proportion of coal in energy structure is too high, the domestic production of oil and gas is too low, the dependence ration of overseas oil and gas is too high, and the development of renewable energy is too weak. 3) under the goal of carbon neutrality, China's energy transformation and energy security should focus on "three acceleration": making full use of the advantages of socialist system, speeding up the construction of new energy system through the way of cleaning fossil energy, scaling up renewable energy and developing smart comprehensive energy, speeding up independent innovation of science and technology in the fields of coal, oil, gas and renewable energy, speeding up the implementation of energy conservation.

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Characteristics and Main Controlling Factors of High Quality Channel Sandstone Reservoir in Zhongjiang Gas Field

WANG Yongfei, HENG Yong

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 11-20. DOI: 10.11885/j.issn.1674-5086.2020.11.25.02

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The sandstone reservoirs of Shaximiao Formation in Zhongjiang Gas Field are generally poor in physical properties. High quality reservoirs are one of the main factors controlling oil and gas enrichment and high yield. The characteristics and controlling factors of high quality reservoir are studied by casting thin section, scanning electron microscope, X diffraction and core physical property analysis data. The results show that the pore types of high quality reservoirs are mainly intergranular dissolved pores and residual intergranular pores, and the diagenetic facies are mainly chlorite cemented facies and chlorite cemented dissolution facies. Early lining chlorite cementation and late dissolution are the key to the formation of high quality reservoirs. Microfractures caused by structural fracture can improve the seepage capacity of reservoirs and promote the formation of high quality reservoirs. The main distributary channel has strong hydrodynamic conditions, large particle size, less argillaceous content and more developed chlorite film in the early stage, which is more conducive to the formation of high-quality reservoirs. The secondary dissolution pores are developed in the secondary distributary channels with high feldspar content, and the reservoirs have good physical properties. Therefore, the high quality reservoirs are mostly developed in the main distributary channels and some secondary distributary channel microfacies with high feldspar content.

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A Study on Seismic Reflection Characteristics of Reservoir Under Complex Lithology Background

DAI Ruixue, XI Cheng, RAN Qi, CHEN Kang, LIANG Han

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 21-31. DOI: 10.11885/j.issn.1674-5086.2020.11.27.03

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51.62$\times$10$^4$ m$^3$ of gas was obtained of the risk explororation Well JT1 from the Canglangpu Formation on the northern slope of the paleouplift in Central Sichuan during test. That is the first breakthrough in oil and gas exploration of Canglangpu Formation in Sichuan Basin. However, as the mixed sedimentary facies, the Canglangpu Formation has complex seismic response characteristics of which results in low degree of geophysical study due to its complex lithology. Thus, the seismic reflection characteristics of lithofacies and seismic response model of reservoirs of Cangchuan Formation in central Sichuan Basin are studied based on the drilling data and seismic data. The results show: 1) Canglangpu Formation in Central Sichuan has five lithofacies-seismic reflection modes, among which uniaxial mode and uniaxial complex wave model are the best seismic facies of carbonate rocks. 2) SOM waveform clustering method and wave impedance recursive inversion verify the accuracy of seismic facies, so the carbonate rocks can be further finely depicted. 3) there are two seismic reflection modes of high-quality reservoirs in Canglangpu Formation on the north slope of the paleouplift in central Sichuan Basin. The seismic reflection model of thin-interbedded reservoir is lithologic interface strong axis with complex wave, the seismic reflection model of thick reservoir is lithologic interface strong axis with bright spot. Comprehensive study shows that there are three favorable areas distribute in the shape of stripe in the NW--SE direction in Canglangpu Formation on the north slope and have good conditions for the formation of lithologic traps, with a total area of 1 270 ${\rm {km}}^2$, which is an important area for further exploration. In this paper, one method for research of seismic reflection characteristics of reservoir under complex lithology background is proposed to provide an effective idea for seismic prediction of thin reservoirs as sedimentary facies.

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An Objective Function Optimization Method Based on Multi-frequency Wavelets for Receiver Combination in Seismic Acquisition

PENG Gengxin, XU Feng, XU Kaichi, LIU Fulie, LI Yongjun

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 32-42. DOI: 10.11885/j.issn.1674-5086.2020.12.14.02

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The traditional objective function used to design geophone array parameters often takes single-frequency simple harmonic as the research object, and investigates the local information such as zero point position and suppression band, which does not conform to the actual frequency composition and spatial continuity distribution characteristics of seismic wavelet. Based on the combined energy response of broadband wavelets, using the property that the main bodies of interference waves and seismic reflection signals are continuously distributed in different regions of space, four objective functions with statistical significance are established, each of which has its own emphasis on noise suppression and effective signal protection. Through theoretical analysis, numerical simulation and actual data trial calculation, the differences of different objective functions in noise suppression, reflected signal damage, signal spectrum change and AVO distortion are compared. The analysis shows that the objective function protecting the effective signal, as it has more advantages first can reduce the combined low-pass filtering effect, and has less impact on AVO distortion.

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Self-facies-control Pre-stack Inversion Technology for Turbidite Sandstone Reservoir with Complex Fault System

WANG Zongjun, TIAN Nan, FAN Ting'en, GAO Yunfeng

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 43-57. DOI: 10.11885/j.issn.1674-5086.2021.01.29.01

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Turbidite sandstone reservoir is a typical gravity flow deposit, which is characterized by lateral variation, vertical multi-stage superposition and frequent migration. Seismic inversion is one of the main methods for fine reservoir description, but the complex fault system, lateral abrupt variation and overlimit thickness of the reservoir in E Oilfield restrict the accuracy of reservoir inversion and its subsequent application. In order to solve the problem of reservoir prediction in E Oilfield, a self-facies-control pre-stack inversion technology with complex fault system is proposed in this paper. Firstly, the deep learning algorithm based on the fault contact relationship chart library is used to construct the complex fault system model, and then the high-precision seismic stratigraphic framework is constructed. Secondly, a high-precision self-facies-control low-frequency model is built using the self-facies-control low-frequency model construction technology. Finally, under the constraints of high-precision stratigraphic framework and self-facies-control low-frequency model, self-facies-control pre-stack inversion is realized, which effectively improves the accuracy of sand body prediction near the fault, overlimit thick reservoir characterization and reservoir lateral boundary identification. The application in E Oilfield shows that this method has achieved good results. The thickness coincidence rate of the horizontal length of 16 new drilled development wells is 91%.

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Research on Transient Flow Model of Gas Reservoir Based on Boundary Element Theory

DENG Bo, LU Zhengyuan, ZHAO Na

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 58-66. DOI: 10.11885/j.issn.1674-5086.2020.12.16.02

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The reserves of gas reservoir in Permian Qixia Formation, Shuangyushi Area of northwestern Sichuan Basin is abundant, and the research on transient flow model is difficult due to the development fractures and complex boundary caused by multi-period tectonic movement. On the basis of fundamental principle of seepage theory, a composite dual-porosity physical and mathematical model for vertical well is established by considering arbitrary shape boundary, and then the fundamental and pressure response solution of vertical well in such composite model is derived by point source function and BEM. Combining the principle of superposition and computer programming techniques, the dimensionless pseudo-pressure and its derivative are obtained under different variables, and the gas flow regimes are divided and the parameters sensitives are analyzed. In the end, a field case of Well Shuangyu001—1 in Qixia Formation, Shuangyushi Area in northwestern Sichuan Basin is applied by the method proposed in this paper, and obtained an excellent agreement. It provides a new method for well test interpretation of this kind of complex gas reservoir.

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A Calculation Method of Water Breakthrough Time of 5-Point Well Pattern in Low Permeability Reservoir

LI Chenglong, SUN Pengpeng, WANG Yifei, YANG Guinan

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 67-76. DOI: 10.11885/j.issn.1674-5086.2021.12.24.02

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According to the reservoir development characteristics, fluid seepage law and five-point well pattern characteristics of low permeability reservoirs, a water breakthrough time calculation model considering pressure-sensitive effect, variable starting pressure gradient, well spacing, fracture and well spacing angle, fracture length, heterogeneity and other factors is established, and the influence law of different factors on water breakthrough time is analyzed. Compared with the existing results, the water breakthrough time calculation model established in this paper is more comprehensive and fits the actual situation of the mine better. The analysis results show that the larger the ratio of well spacing to row spacing, the stronger the heterogeneity; the longer the fracture length, the smaller the starting pressure gradient and the original formation pressure, the earlier the water breakthrough time. With the increase of fracture and well row angle, the water breakthrough time changes, when the water saturation is between 0.4~0.5, the water breakthrough occurs early. The research results can provide theoretical support for the development adjustment scheme of low permeability fractured reservoirs.

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Calculation Model of Hydro-mechanical Coupling for Dynamic Width of Deformable Natural Fracture

PENG Hao, LI Qian, GAO Jiajia, YIN Hu, CHEN Yifan

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 77-86. DOI: 10.11885/j.issn.1674-5086.2020.10.28.02

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Aiming at the fact that existing models for calculating the dynamic width of natural fractures fail to consider the compression deformation of the fracture under the net flow pressure in the fracture,the model of hydro-mechanical coupling for dynamic width of natural fracture is studied.Firstly,according to the deformation law of natural fracture wall and the net flow pressure equation in the fracture,a hydro-mechanical coupling leakage dynamic model is established,by which the geometric control equations of the leakage rate and the invasion velocity of the leakage front distance are obtained;then,the self-adaptive search method is used to calculate the equivalent average width of the natural fracture,and the initial width of the natural fracture is obtained based on the volume equivalent principle.The solution method of the natural fracture shape coefficient is established by combining the geometric control equations of leakage rate and the initial width;finally,according to the geometric governing equation of the invasion velocity of the leakage front distance,the natural fracture shape constraint is solved to obtain the normal stiffness,and then the model of hydro-mechanical coupling for dynamic width of natural fracture is obtained.The model of hydro-mechanical coupling for dynamic width of natural fracture has been verified on-site and the calculation results are in good agreement with the on-site measured data.Only the drilling fluid performance,the lost circulation rate sequence and the lost volume sequence measured on-site are needed to predict the dynamic width of natural fractures,which is convenient for on-site application.

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Wellbore Stability Analysis of Drilling Fluid Invading Hydrate Reservoir

WANG Lei

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 87-96. DOI: 10.11885/j.issn.1674-5086.2022.03.29.03

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During the drilling of marine gas hydrate reservoirs, the drilling fluid easily invades the gas hydrate wellbore, causing the collapse and instability of the wellbore. The coupling effect of the collapse pressure of the gas hydrate formation and the hydrate phase equilibrium pressure at low temperature is an important influencing factor. Therefore, it is of great significance for the smooth exploitation of marine gas hydrate to carry out the evaluation experiment of the wellbore stability of hydrate reservoir under the action of low temperature drilling fluid system, and to study the mechanism of gas hydrate wellbore instability caused by drilling fluid invasion. The hydrate cores are prepared by simulating the temperature and pressure at the depth of the ocean, and by injecting drilling fluids of different systems, the temperature, pressure, mechanical characteristic parameters and hydrate mass abundance changes in the gas hydrate cores are monitored, and different conditions are studied. Wellbore stability under influence. The research shows that as the drilling fluid temperature increase, the peak strength near the wellbore after the invasion decrease. Large hydrate mass abundance also causes the fluctuation of hydrate core parameters. Compared with the uninvaded core, the stress peak point of the core decrease by 13.95% on average after 5 min of intrusion.

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Calculation of the Investigation Radius of Producing Well Through Power Law Heavy Oil Sand Reservoir

XIE Mingying, LIU Guotao, YAN Zhenghe, SHI Zhengnan, SUN Xiaona

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 97-106. DOI: 10.11885/j.issn.1674-5086.2021.02.08.08

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The investigation radius is an important parameter in oilfield development. However, the well-known formula of the investigation radius is based on the linear fluid flowing in porous medium, so the formula is out of place for nonlinear fluid, such as power-law fluid. Recently the sand oilfields with power law fluid are discovered in the eastern South China Sea. Based on this, a new numerical method is proposed for studying the investigation radius of power-law heavy oil. This new method avoids the problem of trying to obtain the analytical formula of the investigation radius, and it has wider applicability. On the other hand, the well-known formula does not consider the influence of wellbore storage effect and skin effect. With the help of the relative criterion of investigation radius, using Laplace transform and Stehfest numerical inversion, the influence of power-law index, wellbore storage effect and skin effect on investigation radius is studied by a new method here. A formula for calculating the investigation radius with power-law index between 0.80 and 1.00 is proposed, and the unified form of the formula is formed. At the same time, the relationship between investigation radius and bottom hole pressure drop is also explored. The research results have been used for guiding the optimization design well pattern and injection-production well pattern, and good application results are obtained.

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Stability of Water Annulus Transportation of Heavy Oil in Horizontal Pipeline

YIN Xiaoyun, SU Ming, ZHOU Xin, ZHANG Liang, JING Jiaqiang

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 107-116. DOI: 10.11885/j.issn.1674-5086.2020.12.04.01

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In the present study, simulations for oil-water annular flow through a horizontal pipe were performed by FLUENT software based on VOF two-phase flow model, standard $k-\varepsilon$ turbulence model, and CSF surface tension model. The influences of fluid properties (oil-water density difference, oil-water viscosity ratio, and oil-water interfacial tension) on the distribution of oil-water two-phase and the stability performance of water annulus structure were analyzed. The simulation results indicate that the oil-water properties have no effect on the area-weighted average of the oil volume fraction, which is about 73% in various working conditions. However, they have a significant impact on the volume fraction distribution rules of oil-water two-phase and the stability evaluation indexes of water annulus structure (oil core eccentricity, stable length ratio of annular flow, and pipeline pressure drop). Under the simulated conditions, the oil-water annular flow in a typical eccentric form, where the oil-core located in the upper part of the pipe is wrapped by the upper thin and lower thick water layer. The stability of water annulus is at the best when the oil phase density is 996.4 kg/m$^3$, the oil phase viscosity is 1 743.3 mPa·s, and the oil-water interfacial tension is 22.36 mN/m.

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Study on Wellbore Temperature & Pressure and Phase Control in Supercritical Carbon Dioxide Fracturing

WU Lin, LUO Zhifeng, ZHAO Liqiang, YAO Zhiguang, JIA Yucheng

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 117-125. DOI: 10.11885/j.issn.1674-5086.2021.05.13.01

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Supercritical carbon dioxide fracturing fluid is sensitive to temperature and pressure, and accurate prediction of wellbore temperature, pressure and phase state during fracturing directly affects the final fracturing effect. As a result, a transient wellbore temperature and pressure model of supercritical carbon dioxide fracturing considering axial heat conduction, Joule-Thomson effect, expansion/compression work, and frictional heat was established. Based on the model, the effects of injection temperature, displacement, drag reduction effect, and tubing size on the wellbore temperature, pressure and phase state were analyzed. The results show that the decrease of wellbore temperature leads to an increase in carbon dioxide density and a decrease in flow velocity, which causes the wellhead pressure to decrease simultaneously with the wellbore temperature. The higher the injection temperature, the smaller the displacement, the higher the resistance reduction rate, the larger the tubing size, the higher the bottom hole temperature, and the lower the wellhead pressure. Among them, the wellhead temperature increases by 10℃, and the bottom hole temperature increases by about 7℃; the resistance reduction rate increases by 20%, and the wellhead pressure decreases by about 7MPa. Increasing the injection temperature, the cross-sectional area of the flow channel, and reducing the displacement while using the thickener/resistance reducer can promote the carbon dioxide to reach the supercritical state at the bottom of the well. This article has strong guiding significance for the optimization design and field application of supercritical carbon dioxide fracturing.

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Research on Overflow Intelligent Warning Technology Based on Downhole Annulus Parameters

GE Liang, TENG Yi, XIAO Guoqing, XIAO Xiaoting, DENG Hongxia

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 126-134. DOI: 10.11885/j.issn.1674-5086.2021.03.12.03

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With the development of oil and gas exploration and development toward complex formations, the risk of blowout during drilling has increased, and overflow is the precursor of blowout, so the early warning of overflow becomes a key direction to well control and safety prevention. Aiming at the problem that the traditional prediction algorithm fails to analyze the severity of overflow and the prediction accuracy is not high when performing overflow warning based on ground parameters, through the study of overflow symptoms and the mechanism of overflow, the annulus electromagnetic flow system and other systems are used to directly measure the underground near the bit, and an overflow intelligent early warning model was established based on artificial intelligence algorithm—Random Forest to classify and predict the severity of overflow. In order to verify the feasibility of the early warning model, a simulation experimental platform was built for testing, and compared with the conventional BP neural network. The results show that the accuracy of this method is as high as 92.68%, and the accuracy of classification prediction is significantly higher than that of the BP neural network. The research results verify the reliability of the random forest model for downhole overflow early warning, which well realizes the early warning of overflow, and provides a safety technical guarantee for drilling, and has good application prospects.

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Design of Operating Parameters in MB8 Gas Storage with Edge and Bottom Water

GONG Ruicheng, WANG Aiming, CHEN Fangfang, YU Haitao, LIU Jingun

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 135-144. DOI: 10.11885/j.issn.1674-5086.2021.06.18.01

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The edge-bottom water will affect the injection and production capacity and peak production of gas wells during gas storage operation. There are few cases of underground gas storage building from medium-strength edge-bottom water gas reservoirs at home and abroad. In accordance with the medium intensity edge-bottom water in Wellblock MB8, the formation water will make influence on storage capability when building a gas storage. We evaluate well type by optimizing of gas-water characteristics of injection-production wells, assess gas storage capacity by material balance equation of water drive gas reservoir, analyze well injection-production capacity considering gas-water two phase seepages, and study edge-bottom water transport conditions in the process of injection-production with numerical simulation method. The study shows that it is feasible to transform underground gas storage in Wellblock MB8, and the influence of edge and bottom water on gas storage operation can be reduced by increasing the number of wells, reducing the injection and production of single well, and by optimizing the well location. Considering the influence of edge and bottom water, the effective working gas in MB8 gas storage is 170 million cubic meters, the reasonable number of injection and production wells is 20, and the operating pressure range from 8.1$\sim$10.9 MPa.

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A Review of Offshore Associated Gas Researches and Submarine Associated Gas Storage

LI Qian, ZHOU Xipeng, JIANG Huifeng, MAO Yaling, LUO Xiao

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 145-158. DOI: 10.11885/j.issn.1674-5086.2021.01.04.03

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Aiming at the waste of resources and environmental pollution caused by combustion or discharge of associated gas in offshore oilfields, this paper has carried out research work on the treatment and utilization of associated gas in offshore oilfields. In the research, the existing associated gas processing technology, transportation methods, receiving terminal, etc. are introduced and compared in detail, and the key technologies involved in the associated gas processing method are examined, and focus and direction of future researches on the processing method and technology of marine associated gas is proposed. Focus and development direction. Then, considering small output, high processing cost and insufficient energy supply in the treatment of associated gas in offshore oilfields, we propose the construction and design of submarine associated gas storage using offshore oil and gas reservoir, with reference to onshore natural gas storage, and the gas injection and production process of offshore associated gas storage is established. This research discusses the related technology of associated gas treatment in detail, and proposes to build a submarine associated gas storage to solve the problem of associated gas treatment and utilization in offshore oilfields. The research can be referred to by peer researchersand is of great significance for protecting the environment and improving energy efficiency.

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A Study on the Functional Reliability of Underwater Floating Body Considering the Wear of Joint Clearance

HE Kongde, HU Hao, FANG Zifan, YANG Weihua, LIU Shaopeng

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 159-169. DOI: 10.11885/j.issn.1674-5086.2020.10.22.03

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Aiming at the problem in system functional reliability caused by the wear of joint clearance between the cable and structure of cable-anchored underwater floating body, a system dynamic model considering the ideal hinge and the wear of joint clearance is established based on the method of Archard adhesion wear calculation and reliability calculation. The dynamic equation and the functional reliability are solved by the multi-scale method and Newmark-$\beta$ method. On this basis, the reliability of surging displacement and roll angle is studied. The results show that with the increase of wear, the contact force of the connection reaches 12.0 times and 5.5 times of the ideal hinge value. When the wear volume is greater than 1.5 mm, the mean value and peak value of the rolling angle of floating body caused by the uncertainty contact state are both greater than the ideal articulated state, and the reliability decreases sharply. When the wear volume is greater than 1.82 mm, the reliability is less than 90%. In the state of clearance contact, the reliability of the transverse surging displacement of the floating body will decrease to a certain extent.

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CFD Simulation and Optimization of Electric Submersible Pump Considering the Effect of Heavy Oil Viscosity

LIU Yonghui, XIE Zaixiang, ZHOU Yuchi, PENG Zhenhua, LIU Zhongbo

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 170-177. DOI: 10.11885/j.issn.1674-5086.2021.04.13.06

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Electric submersible pump (ESP) is one of the most common artificial lift techniques. However, when it is applied to heavy oil wells, due to the influence of high viscosity, the performance curves of ESP deviates from the common ones, which caused the effective application window of ESP. Therefore, the centrifugal pump's structural parameters are designed under water flow condition, which is difficult to adapt to the high viscosity environment of heavy oil wells. In view of the above problems, based on the computational fluid dynamics (CFD) numerical simulation method, we study the pressurization characteristics of ESP under the high viscosity condition. The results show that with the increase of fluid viscosity, the frictional force increases, and the interaction effect also shows an increase trend. However, the pressure difference between the impeller inlet and the diffuser outlet decreases, which leads to the flow rate decrease. Meanwhile, the flow regime inside ESP changes from turbulent flow to laminar flow, and recirculation flow area inside the impeller and diffuser blades decrease. Under the same viscosity condition, the head of centrifugal pump decreases with the increase of displacement. Under the same liquid flow rate, the head of centrifugal pump decreases significantly with the increase of viscosity. Based on factor analysis, by taking the effect of viscosity into consideration, the structural parameters of the centrifugal pump are optimized. The optimal structures are as follows: inlet width is 16.6 mm, blade number is 6 pieces, outlet width is 21.9 mm, and blade inclusion angle is 60o. Compared with the original centrifugal pump, when the viscosity is 400 mPa·s, under the submersible electric pump works in allowable flow rate range, the maximum increase of head is 28%.

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A Study on Mechanistic Prediction Model of Gathering Pipelines in CO$_2$ Environment

JIANG Hongye, LIU Yingxue, HE Sha, LUO Jiqing, XU Taolong

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (2): 178-188. DOI: 10.11885/j.issn.1674-5086.2020.11.20.01

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CO$_2$ flooding technology has been widely used in major oil fields because of its ability to significantly improve reservoir recovery. However, the increase of CO$_2$ content in the produced fluid leads to serious corrosion of ground gathering and transportation pipelines. In order to solve the problem of CO$_2$ corrosion of ground gathering and transportation pipelines, the CO$_2$ corrosion rate prediction research under the influence of corrosion product film is carried out. Based on the corrosion thermodynamics and kinetics theory, considering the multifield coupling effects such as fluid flow, electrochemical reaction and mass transfer process, the influence factors of corrosion product film on the diffusion coefficient of ion mass transfer are introduced, and a new corrosion prediction mechanism model is proposed based on the work of Nesic et al, and the chemical, electrochemical and mass transfer calculations are improved. The prediction results of the model are compared and verified by using the experimental data in the literature. The results show that the corrosion prediction model is in good agreement with the experimental data. In the presence of corrosion product film, the corrosion prediction rate can be effectively revised, which further improves the applicability and accuracy of CO$_2$ corrosion prediction mechanistic model, and provides some reference for the design of oil and gas production, processing and transportation pipeline and related facilities.

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The Pore Structure and Controlling Factors of High-porosity and Low-permeability Carbonate

TANG Hongming, PANG Yu, WANG Xiwei, ZHAO Yuchao

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (3): 1-13. DOI: 10.11885/j.issn.1674-5086.2021.04.09.01

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The Upper Cretaceous Khasib Formation carbonate reservoir of X Oilfield in the Middle East is a shallow-sea shelf deposit, it has the characteristics of multiple biological types and rock types, high porosity and low permeability reservoirs, and complex pore structure. Based on the Folk limestone classification scheme, this paper highlights the biological characteristics, and comprehensively compares the pore structure characteristics and control factors of different types of reservoirs on the basis of rock classification. Studies have shown that the reservoir rock types include four types of micrite bioclastic sand-clastic limestone, micrite algal clastic limestone, micrite bioclastic limestone and micritic planktonic foraminifera limestone; the type of pore structure can be divided into three types: high porosity and medium permeability medium throat type, high porosity and low permeability medium fine throat type, high porosity and low permeability fine throat type; the main factors affecting the pore structure are physical properties and structural components. Among different lithologies, the difference in biological species and content affects the development of primary pores and the strength of later diagenesis, resulting in differences in pore structure. Among the same lithology, the content of plasters controls the quality of the pore structure.

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Seismic Sedimentology Characterization of Fan-delta in Slope Belt of Eastern Liaohe Depression

HUANG Derong, ZHANG Xianguo, WANG Youjing, CAI Guogang, XIE Baoguo

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (3): 14-28. DOI: 10.11885/j.issn.1674-5086.2021.11.21.01

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Fan delta is an important type of oil and gas reservoir in slope zone of faulted basin. Lithology and sedimentary facies vary laterally. It is difficult to characterize sedimentary facies distribution inter-wells. A typical fan-delta deposition at Tiejianglu Area in the gentle slope zone of the eastern Liaohe Sag is studied. i. Two work are carried on including isochronicity analysis of seismic reflection, and seismic characterization of sedimentary facies with multi-attributes fusion. The study reveals: 1) in fan delta deposition area, there are diachronous seismic events locally and frequency division dip difference analysis can identify significant diachronous seismic reflection; 2) the root mean square amplitude, energy half-time and skew in amplitude attributes contain the information of sandstone development degree and lithologic combination. RGB fusion of the three attributes provides a simple and effective method for seismic characterization of sedimentary facies in sparse-borehole areas; 3) in study area, there developed 3 fan deltas including 2 large fan deltas of north provenance and a small fan delta of southeast provenance. At present, the exploration and development are concentrated on the fan deltas of north provenance. This study provides an effective method for seismic characterization of fan delta sedimentary facies in gentle slope zone, and provides direction and target for further exploration in the study area.

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Study on Quantitative Well Logging Interpretation of Continental Shale Oil Reservoir in Jimusar Sag

TAN Fengqi, LI Xiankun, GAO Yang, LI Yingyan, ZHANG Fang

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (3): 29-48. DOI: 10.11885/j.issn.1674-5086.2021.04.07.01

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The continental shale oil of Permian Lucaogou Formation in Jimusar Sag is selected as the research object to establish quantitative well logging interpretation models. Core calibration logging and data mining are used to establish the quantitative well logging interpretation models of physical properties, oil-bearing properties, micro pore structure and rock mechanics respectively according to the upper and lower sweet spot. In the field application of well logging interpretation models, the accuracy of reservoir evaluation has been greatly improved, reaching more than 85%. The three well logging curves are selected by the data mining method with the multi-factor permeability calculation model, not only reflect the contribution of absolute porosity to permeability, but also consider the restriction of micro pore structure transformation on permeability, and two well logging curves of natural gamma ray and acoustic time difference are used to characterize respectively the influence of shale content and compaction-cementation effect on seepage path and seepage resistance. Compared with the single factor model, the calculation accuracy is improved by 25.6%. In addition, due to the following influences such as the borehole environment, the gravity differentiation of pore fluid and the anisotropy of formation in different directions, there is a certain deviation between horizontal and vertical well logging curves. So the quantitative well logging interpretation models based on the response characteristics of vertical well logging curves and core analysis data can not be directly applied to the reservoir evaluation of horizontal wells. In view of the above problems, the conversion chart and calculation formula of well logging curves of two measurement methods are established, and the reservoir of the horizontal section can be quantitatively interpreted.

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Stratigraphic Division and Exploration Potential Analysis of Lower Carboniferous in Chepaizi Uplift, Northwestern Junggar Basin

BIAN Baoli, HU Xiuquan, WANG Xueyong, LIU Hailei, CHENG Jinxiang

Journal of Southwest Petroleum University(Science & Technology Edition) 2023, 45 (3): 49-60. DOI: 10.11885/j.issn.1674-5086.2021.04.20.01

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This study uses field outcrops, earthquakes, and the latest drilling and logging data to subdivide the Lower Carboniferous strata in the Chepaizi Uplift, and to conduct exploration potential analysis. Our research indicates that the lower Carboniferous strata in the Chepaizi Uplift have obvious three-division characteristics. From bottom to top, there are volcanic rocks of the Tailegula Formation, interbedded volcanic rocks and sedimentary rocks of the Baogutu Formation, sedimentary rocks of the Xibekulas Formation, and three sets of strata in the rock. There are obvious differences in characteristics, logging response, and seismic reflection. In horizontal direction, the Tailgula Formation is distributed throughout the region, with north-south concave and uplifts alternating. The Baogutu Formation and the Xibekulas Formation spread out in a north-south direction, eroding and pinching east to west. In general, volcanic reservoirs are better than sand-conglomerate reservoirs, and volcanic breccias have better physical properties than andesite. The explosive facies and intermediate-basic overflow facies of the Tailegula Formation are the dominant lithofacies for reservoir development, especially the explosive facies development area in the southeast, which is located in the range of medium magnetic anomalies with wide distribution and great exploration potential.

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