Journal of Southwest Petroleum University(Science & Technology Edition)

A Study on Distribution of Remaining Oil in the High Water-cut Stage of Delta Front Sand Body

ZHANG Rui, LIU Zongbin, LIAO Xinwu, WANG Gongchang, TIAN Bo

2022, 44(2): 1-18. DOI: 10.11885/j.issn.1674-5086.2020.07.25.01

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SZ Oilfield is a typical delta frontal sediment oilfield in Bohai Sea, it has entered high water-cut period. The residual oil is generally dispersed with accumulation in certain areas. The difficulty of tapping potential is increasing. It is necessary to research the distribution of residual oil in high water-cut period. The study shows: after entering the high water-cut period, the internal relationship between the delta front sedimentary sand body and the injection-production well pattern has a significant controlling effect on the formation and distribution of residual oil. After discussion on the injection-production connectivity between single sand bodies in the study area, according to the situation of injection and production of single sand body in the well, the macroscopic residual oil distribution pattern in the study area is summarized as residual oil caused by imperfect injection-production, and residual oil partially affected by injection-production. The residual oil caused by imperfect injection-production includes unconnected residual oil, connected but obstructed residual oil and residual oil formed by the unobstructed sand body but without oil and water migration; the residual oil that has been partially affected includes local unobstructed residual oil and unobstructed residual oil. According to the distribution scale of the remaining oil level and the longitudinal distribution mode, the practice of irregular directional tapping of a combination of directional wells, horizontal wells and subdivision of layer series under the regular well network of offshore oilfields was carried out. The in-situ application is good and effective. The results of this study have guiding significance for efficient development and adjustment of the delta front sedimentary oilfield in the high water cut period.

Comparison of Delta Sedimentary Characteristics During Rift Depression in Gentle Slope Zone of Xijiang Main Depression

XIANG Qiaowei, LIU Baojun, LI Xiaoyan, WU Yuxiang, CAI Guofu

2022, 44(2): 19-30. DOI: 10.11885/j.issn.1674-5086.2020.03.17.01

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In order to find out the sedimentary patterns and development rules of Wenchang Formation and Enping Formation strata in the gentle slope conversion zone in the south of Xijiang main depression in Pearl River Mouth Basin, the characteristics of the sedimentary systems in the two gentle slope conversion zones are summarized from the aspects of lithology, bedding structure, structural characteristics and geophysical characteristics through drilling, logging, earthquake, core analysis and laboratory tests, and the fracture characteristics in the study area are analyzed. The study shows that during Wenchang period (T$_{80}$-T$_{\rm g}$), NE and NW trending depression-controlling faults are developed and distributed at the basin edge, and the fault combination forms are parallel, stepped and oblique. During the Enping period (T$_{70}$-T$_{80}$), NE, EW and SE faults were developed and distributed in the center of the basin. The fault combinations were in the same direction, reverse direction and oblique crossing. Although it belongs to gentle slope zone, Wenchang Formation has steeper topography, deeper lake basin and braided river delta than Enping Formation. The Enping Formation has a broad and gentle topography, with shallow water deltas, the activities of central faults in the lake basin and the occurrence of seasonal floods, making the underwater branch channels of the shallow water deltas extremely developed. The two different types of deltas have different lithologic combination characteristics: the braided river delta sandstone of Wenchang Formation has coarse and thick grain size and thin mudstone layer, and the shallow water delta sandstone of Enping Formation has coarse and thin grain size, thick mudstone layer and coal bearing, which are all favorable areas for oil and gas exploration.

Classification and Evaluation of Effective Reservoirs in Deep Tight Sandstone Gas Reservoirsin

ZHAO Jun, WU Boshen, WU Yanliang, CHEN Weizhong, ZHAO Xinjian

2022, 44(2): 31-39. DOI: 10.11885/j.issn.1674-5086.2020.01.07.01

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Classification and evaluation of effective reservoirs in deep tight sandstone is an important step in tight sandstone oil and gas evaluation. Due to the extremely low porosity and permeability of tight sandstone and the difficulty in guaranteeing the quality of the data, there are some limitations in the evaluation of reservoir quality by physical property parameters. According to the theory of reservoir filling and the combination relationship between reservoir and cap, based on the capillary pressure data of the study area and the effective stress data of the stratum, the calculation model of pore throat radius of sand and mud in the target stratum is established. It is considered that there is a large capillary pressure difference between the effective reservoir of tight sandstone and the adjacent cap, that is, the ratio of sand to mud pore throat is large. The limit value of sand/mud pore throat ratio of effective reservoir in the study area tends to increase with the increase of depth, and the better the reservoir quality is, the bigger the sand/mud pore throat ratio is. The application of practical data shows that the ratio of pore throat radius of sand and mudstone can effectively indicate the effectiveness of the reservoir, and the established reservoir classification criteria can be used to classify the effective reservoir in the study area by comparing with the tested output.

Study on the Calculated Method of Horizontal In-situ Stress Based on the Kaiser Stress Point Predicted by Acoustic Signal

FAN Xiangyu, YAO Bowei, ZHANG Qiangui, XIA Hongquan

2022, 44(2): 40-48. DOI: 10.11885/j.issn.1674-5086.2020.06.11.01

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The in-situ stress evaluation method by acoustic emission tests needs to carry out acoustic emission tests under the loading condition using four small-size cores drilled from a full-scale stratum rock sample. This method will result in the loss of strata rock samples and the high cost for the in-situ stress evaluation. In the present work, a series rock sores were carried out by acoustic emission tests and acoustic emission tests under the loading condition. According to the concept of the good correlation between acoustic properties and mechanical properties of rock, the relational function between acoustic interval transit time and Kaiser Stress Point of rock sample was obtained using the test results. Next, a new calculated method of horizontal in-situ stress based on the Kaiser stress point predicted by acoustic interval transit times using the relational function was developed based on the calculation model of the in-situ stress evaluation method by acoustic emission tests. Furthermore, using the 360° sonic scan data of the full-scale core, the horizontal in situ stress of a tight oil reservoir was evaluated by the new proposed method, as well as the results were compared with the values of in situ stress evaluated by hydraulic fracturing test data. The results show that the values of the horizontal in situ stress calculated by the proposed method have higher accuracy comparing with the results calculated by the models of Anderson, Eaton and Newberry. Therefore, this new proposed method to evaluate the horizontal in situ stress is not only more accurate comparing with the traditional logging interpretation method, but also have higher economy due to that there is no cost on the tests and rock cores loss.

The Comprehensive Logging Evaluation of "Three Qualities" of Tight Gas

YUAN Long, ZHANG Haining, XIN Yi, HUANG Ruokun, LIU Wei

2022, 44(2): 49-64. DOI: 10.11885/j.issn.1674-5086.2020.02.10.03

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In order to clarify the relationship between source-reservoir allocation of different layers and enrichment high-production area in the Jurassic tight gas of the Kuqa Depression in the Tarim Basin, we make full use of data of geology, core analysis and new logging technology, combined with the logging evaluation methods of the "three quality" factors of tight gas reservoirs, and comprehensively apply the tight reservoirs in the study area using the main control factors. The research shows that the reservoir quality, source rock quality and engineering quality of the high part of the Jurassic tight gas in the Kuqa Depression in the basin are significantly better than those in the east and west, and have a good relationship between source and reservoir; the quality types of source rocks are mainly class Ⅰ and Ⅱ; "three qualities" plays a decisive role in tight gas enrichment and high production. Comprehensive evaluation through close combination of logging, geology and engineering provides a reliable basis for the selection of favorable gas tight zones and fracturing layer selection.

Inversion of Geomechanical Model Parameters Based on KL Expansion and Its Application

QIN Jianhua, YANG Kun, DING Yi, ZHANG Boning, TANG Huiying

2022, 44(2): 65-78. DOI: 10.11885/j.issn.1674-5086.2020.03.02.01

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The distribution of in-situ stresses, as well as geomechanical properties, is critical for wellbore stability analysis, hydraulic fracturing, and sand control in the petroleum industry. In this paper, we propose a data assimilation procedure for matching the in-situ stresses with the hard data (1 D measured or interpreted in-situ stresses) by sequentially adjusting the fields of geomechanical properties and the boundary conditions with optimization algorithms. The distribution of geomechanical properties are generated with the conditional Karhunen—Loève expansion (KL—E), which can reduce the number of unknowns from element-based geomechanical properties to a small set of random variables that significantly save the computing time and accelerate the convergence of the optimization algorithms. The applicability of the proposed procedure has been systematically tested by several synthetic cases and a field case study of a shale gas reservoir in Sichuan Basin. Not only the improvement of stress matching but also a more accurate description of the distribution of geomechanical properties at unmeasured locations is observed. In addition, compared to the inversion of the geomechanical properties, the inversion of boundary conditions is much faster.

Borehole Wall Stabilization Drilling Fluid Technology of Longmaxi Formation Horizontal Section in Chang\-ning Block

BAI Yang, LI Daoxiong, LI Wenzhe, LI Hongbo, LUO Pingya

2022, 44(2): 79-88. DOI: 10.11885/j.issn.1674-5086.2021.08.27.01

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In view of the complicated downhole conditions such as sticking and buried drilling caused by wellbore instability in horizontal section of Longmaxi Formation in Changning Block, it is found that Longmaxi Formation shale is characteristics of strong brittleness and weak water sensitivity. Under the condition of increasing well depth, stress and external force, it is easy to produce micro-cracks. After the filtrate of drilling fluid intrudes into the well wall, micro-cracks continue to expand and lead to the instability of the well wall. According to the characteristics of micro-fractures, a variety of micro-nano materials are used to effectively plug the downhole, and a set of strong plugging oil-based drilling fluid system with adjustable density is established, which has good plugging effect, good hole cleaning, and stable settlement performance. The field experiment shows that the torque of tripping and tripping is significantly reduced when the drilling fluid system is tested from 3 600 m to 4 200 m. It is proved that the drilling fluid system forms a tight plugging layer on the borehole wall, which plays an important role in borehole stability.

A New Method to Calculate the Seepage Law of ASP Flooding

WEI Hongtao, ZHOU Qing, ZHANG Xiaolei, LIU Zhongyuan

2022, 44(2): 89-96. DOI: 10.11885/j.issn.1674-5086.2021.10.31.01

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In order to break through the bottleneck of the study on the seepage law of ASP flooding, the effect of viscosity change on the seepage law is replaced by the change of fluidity, the equation of seepage motion is simplified, and the parameters of the equation are fitted with the experimental data of steady-state method and unsteady method. The two-phase fluidity curve can be processed by this method, and the calculation equation of dimensionless production fluid and oil recovery index is derived considering the fluidity change. The method is proved to be simple and accurate by example verification and comparison. The advantage of this method is that it avoids the influence of complex physical and chemical changes on fluid viscosity in ASP flooding, directly reflects fluid flow capacity, and provides a new idea and method for the study of ASP flooding seepage law.

Comprehensive Evaluation of Coalbed Fracability Based on Dynamic Weight Function

GUO Dali, ZHANG Shuling, WANG Xuan, ZHEN Huaibin, WANG Chengwang

2022, 44(2): 97-104. DOI: 10.11885/j.issn.1674-5086.2020.08.07.01

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The coalbed fracability directly affects the output of coalbed methane gas wells and the production cost of enterprises. In order to scientifically evaluate the fracability of coalbed, we take the coalbed geological parameters as the breakthrough point and use dynamic weight function to comprehensively evaluate the coalbed fracability. Firstly, according to the primary selection of coalbed geological parameters, the main influencing parameters are optimized by mathematical statistics. Secondly, by analyzing the subjective weighting method and the objective weighting method, we compare their advantages and disadvantages, and introduce the dynamic weighting function to evaluate the parameters of coalbed fracability. Thirdly, the weighting bubble sorting method of dynamic weight function is used to comprehensively evaluate the influence parameters, and the relationship between the dynamic weight and the production capacity is obtained according to the fitting. Finally, 26 wells in Block X are evaluated and compared with the actual productivity, the correct rate of fracability evaluation is 88.64%. The accuracy of the comprehensive evaluation model is verified.

Application of Integrated and Efficient Development Model in Mahu Area

LI Xiaoshan, YE Yiping, WANG Shuo, LI Ting, GU Kaifang

2022, 44(2): 105-112. DOI: 10.11885/j.issn.1674-5086.2020.05.21.01

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Mahu area has rich oil and gas resources with found OOIP over 10$\times$10$^8$ t. It is the most realistic main area for the oil and gas production of Xinjiang Oilfield Company. In the early stage of development, there are some problems, such as strong reservoir heterogeneity, low reserve abundance and difficult construction and production efficiency, through innovated applying unconventional concepts, and adopting integrated life-cycle management methods, we carry out exploration-development integration, geology-engineering integration, ground-underground integration, technology-economy integration, experiment-exploration integration research. It aims at increasing well production and recovery by using unconventional development reservoir technical and economic index optimization technology. Through the successful application of the integration practice, Mahu area has achieved good development results. The production capacity of the Mahu area has been built up to 700$\times$10$^4$ t and annual production has reached over 200$\times$10$^4$ t.

Correlation Mining of Hidden Hazards in Drilling Based on Support Matrix Apriori Algorithm

WANG Bing, HUANG Dan, LI Wenjing

2022, 44(2): 113-122. DOI: 10.11885/j.issn.1674-5086.2020.04.20.02

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It is very important to use data mining technology to study the distribution rule and inherent mechanism of hidden trouble in drilling operation. Aiming at frequent itemsets loss of complex hidden danger data and low generation efficiency, an Apriori algorithm based on support matrix is proposed. First, we introduce a boolean matrix in the transaction database to prevent repeated database scanning. Secondly, the support matrix is constructed by multiplying the transaction matrix to obtain support and simplify the calculation method of support. Finally, the connection strategy of the algorithm is optimized, which simplifies the generation process of frequent itemsets, and continuously reduces the matrix structure in the calculation process. Experiments on UCI datasets show that the improved Apriori algorithm can effectively improve the efficiency of execution. This algorithm is applied to the associated mining of historical drilling hazard data, the mining results can provide reasonable basis for safety managers, identify effectively hidden dangers and risk control, which is of great significance and worth of popularization and application.

A Study on Performance Simulation and Optimization of Pressurization System of Wen 23 Gas Storage

SUN Jianhua, ZHOU Jun, PENG Jinghong, XIAO Yao

2022, 44(2): 123-134. DOI: 10.11885/j.issn.1674-5086.2020.06.09.03

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Wen 23 gas storage is one of the largest gas storages in China, and it is primarily responsible for seasonal peak shaving and emergency gas supply tasks in the North China market. Taking Wen 23 gas storage gas injection pressurization system as the research object, we aim to realize the energy saving and consumption reduction of the pressurization system and improve the process level. The simulation calculation model of the reciprocating compressor performance of the booster system is established, and the corresponding simulation calculation program is developed using Java language. On this basis, simulated calculations of the performance comparison of compressors of various manufacturers under the same working conditions and simulation calculations of the effect of changes in working conditions parameters on the compressor performance are carried out respectively. Through simulation calculations, it is found that the compressor of manufacturer A has the highest volume flow and unit energy consumption under the same working conditions. In addition, in terms of the effect of parameter changes on the performance of the compressor, an increase in the first-stage suction pressure of 1 MPa will cause a reduction in unit energy consumption of 75 ${\rm {kW \cdot h}}$/(${\times 10^4} {{\rm {Nm}}^3}$), an increase in the last-stage discharge pressure of 1 MPa will cause a increase in the unit energy consumption by 17 ${\rm {kW \cdot h}}$/(${\times 10^4} {{\rm {Nm}}^3}$), and the increase of the first and second suction temperature will cause a small increase in unit energy consumption. According to the simulation analysis results, corresponding measures for optimizing the compressor start-up plan and optimizing the compressor operating conditions parameters are proposed. The research fully combines the actual operating characteristics of the pressurization system of Wen 23 gas storage, and the obtained research results have important guiding significance for the on-site operation of the gas storage.

Three-dimensional Dynamic Study on Leakage and Diffusion of Natural Gas Pipeline Station

YIN Heng, ZOU Qing, LIAO Kexi, PENG Shanbi

2022, 44(2): 135-147. DOI: 10.11885/j.issn.1674-5086.2021.06.30.02

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In view of the problems caused by the leakage and diffusion of natural gas in natural gas pipeline yards on safe production, a study on the law of natural gas leakage and diffusion in natural gas pipeline yards is carried out. We adopt professional software simulation method, use FLACS software to model, set boundary conditions to solve, study the influence of different wind speeds, different wind directions and different leakage rates on natural gas leakage and diffusion, and combine the relevant standards of the natural gas industry on the combustibility of natural gas pipeline stations in optimizing the position of flammable gas. The research results show that the greater the leakage rate and the lower the wind speed, the larger the volume of combustible gas in the station area, the wider the spread of combustible gas cloud, and the higher the degree of danger. At the same time, the hazard degree of downwind leakage is less than that of other directions. It is recommended that the flammable gas detector in the receiving and dispatching tube area should be set at 1 m away from the receiving tube, and the height should be set at 2 m. This research provides important theoretical support for the safe operation of natural gas pipeline stations.

Bi-nonlinear Fluid-induced Vibration Model of Tubing String in High-yield Gas Well

LI Zhong, WANG Guorong, FANG Dake, WEI Anchao, LIU Jun

2022, 44(2): 148-158. DOI: 10.11885/j.issn.1674-5086.2020.01.05.01

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In view of the damage caused by fluid induced tubing string vibration in high-yield gas wells, the micro element method, energy method and Hamilton variational principle are used to establish the longitudinal and transversal coupling nonlinear fluid-induced vibration (FIV) model of tubing string. Based on the contact collision theory of elastic-plastic body, the nonlinear contact-collision model of tubing string is established and introduced into the fluid induced vibration model to obtain the bi-nonlinear model of tubing string in high-yield gas wells. The bi-nonlinear FIV model of tubing string is solved with the finite element method and Newmark—$\beta$ method. Compared with the experimental data in literatures and the calculation results of single nonlinear model only considering contact impact, the correctness and superiority of the FIV model of tubing string are verified. According to the parameters of a high-yield gas well in the field, a simulation test of fluid induced vibration of the gas well tubing string is carried out by using the similar principle. The vibration response data of the tubing string is measured and compared with the calculation results of the theoretical model, which again verifies the correctness of the bi-nonlinear FIV model of the tubing string. The nonlinear FIV model established in this paper can provide an effective analysis tool for the safety design of tubing string in high-yield gas well.

A Study on Elastoplastic Finite Element Study of Hydraulic Expansion of Lined Composite Pipe

CHEN Junwen, LIAN Zhanghua, TANG Xiaoyong, GU Tianping, SHI Daiyan

2022, 44(2): 159-167. DOI: 10.11885/j.issn.1674-5086.2020.05.08.03

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Hydraulic expansion pressure is a key parameter that affect the forming quality of lined composite pipe. In this paper, based on the experimental data, multi-linear reinforced finite element models of two 316L liner materials are established; based on the Tresca yield criterion, we carried out research on the limit expansion pressure range, expansion pressure and tightness of the lined composite pipe in the process of hydraulic forming. The finite element results are compared with the analytical results. The results show that, when the forming conditions are satisfied, the selection of liner material with lower hardening strength can increase the expansion range and the tightness interval, which is conducive to the design of expansion pressure can be controlled. According to the calculation results, the relationship curve between the tightness and the expansion pressure under the forming condition is fitted, The minimum expansion values of the two materials are obtained to be 113.38 and 126.99 MPa respectively. The finite element model of material multi-linear strengthening established in this paper can accurately consider the strain strengthening process of liner material in the process of expansion joint and provide theoretical basis for the accurate control of the parameters of liquid expansion forming of lined composite pipe.

Effect of Nano-silica on the Viscosity Characteristics of Polymer FRSP—1 Solution

WANG Manxue, HE Jing, ZHAO Xiaoping, WEI Hailong

2022, 44(2): 168-176. DOI: 10.11885/j.issn.1674-5086.2020.10.19.02

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In view of the poor salt resistance of the polymer emulsion, which affects the viscosity and other performance problems of the solution, in this paper, the polymer emulsion FRSP—1 is synthesized, and the dispersion and solubility of FRSP—1 in water, salt resistance, rheological properties, and the influence of nano-SiO$_2$ on the temperature resistance, shear resistance and fluid loss of FRSP—1 solution are studied. The results show that FRSP—1 emulsion has good dispersibility in water, and the viscosity of FRSP—1 emulsion in water can reach more than 90% of the maximum value within 20 seconds; pH has a great influence on the viscosity of FRSP—1 aqueous solution. When the pH of the aqueous solution is between 7 and 9, it is helpful to obtain a high-viscosity FRSP—1 solution; salt has a greater influence on the viscosity of FRSP—1 solution. Divalent salt has a greater influence on the viscosity of FRSP—1 solution than monovalent salt. The greater the salt concentration of the solution, the smaller the viscosity of FRSP—1 solution, and the degree of influence is determined by the order of big to small is CaCl$_2$>NaCl>KCl$\geqslant$NH$_4$Cl; the salt resistance, shear resistance, rheology and fluid loss performance of FRSP—1 solution are significantly improved compared with that without nano SiO$_2$. According to the solution prepared by 1.0%FRSP—1+0.5%NH$_4$Cl+98.5% water+0.025% SiO$_2$, the viscosity after continuous shearing at 90 ℃ and 170 s$^{-1}$ for 60 min is 46 mPa·s, and the fluid loss at 10 min compared with no nano-SiO$_2$, the viscosity of FRSP—1 solution has increased by nearly 40%, and the fluid loss has been reduced by 45%. At the same time, the thixotropic properties of FRSP—1 solution has also been significantly improved.

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