Table of Content

10 October 2023, Volume 45 Issue 5

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GEOLOGY EXPLORATION

Reservoir Characteristics and Formation Mechanism of Sangonghe Formation in the Sag West of Well Pen-1

MA Cong, ZHOU Junjun, HU Liang, QI Jing, WU Haiguang

2023, 45(5):  1-13.  DOI: 10.11885/j.issn.1674-5086.2021.04.21.01

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In this study, the sedimentary characteristics and the formation mechanism of the high-quality reservoir of the sandy debris flow sandbody were investigated. The systematic core, ordinary section and cast section observation, scanning electron microscopy (SEM) and electron probe analysis, and carbon and oxygen isotope measurement were carried out. The results show that the J₁s² sandy debris flow in the sag west of Well Pen-1 contains six different lithologies: Massive fine conglomerate with mud-gravel, massive coarse sandstone with gravel, massive coarse sandstone, massive medium-fine sandstone, stratified fine sandstone and mudstone (or argillaceous siltstone). The physical properties of massive coarse sandstone with gravel, massive coarse sandstone, and massive medium-fine sandstone are the best because they contain a large number of residual intergranular pores and dissolution pores. The “clay mineral coating” composed of single chlorite and the “composite mineral coating” composed of both chlorite and siderite are generally developed in the high-quality reservoirs, which effectively inhibits the secondary increase of quartz and preserves the primary pores in the deep burial process. The dissolution of organic acids and other fluids in the late period also has some positive significance for the improvement of reservoir quality.

Discovery of Carboniferous Platform Margin Slope and Evolution of Regional Sedimentary Facies in Front Belt of Western Kunlun Mountains

WANG Zhenyu, YANG Guang, CHEN Cai, WANG Bin

2023, 45(5):  14-26.  DOI: 10.11885/j.issn.1674-5086.2021.09.26.03

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The Carboniferous formation in front belt of western Kunlun mountains has good potential for hydrocarbon exploration, but no breakthrough has been made so far. The lack of in-depth research on the distribution characteristics and patterns of sedimentary phases is one of the main reasons for this. By systematically analyzing the Carboniferous sedimentary characteristics of 12 field profiles, 3 drillings, and one 2D seismic profile in the front belt of the western Kunlun mountains, we have identified for the first time about the platform margin slope in the Carboniferous, and have defined the type and characteristics of the regional sedimentary phases, as well as the distribution and evolution of the sedimentary phases, based on the idea of “defining the margin along the slope face”. The Carboniferous platform margin slope phase includes slip deposits, debris flow deposits, turbidity flow deposits, and hydrostatic deposits, which spread in an east-west direction along the front belt of western Kunlun mountains of southwestern Tarim Basin. In the Late Early Carboniferous, Heshilafu Formation-Early Late Carboniferous and Kalawuyi Period, the east of the Xin-Tibet Highway was Tiekelike ancient uplift, and the west of the Xinjiang-Tibet Highway located a platform margin face, which stripped from west to east in front belt of western Kunlun mountains, a lagoonal face developed on its inner side, and covered the main area of the Kashgar-Yecheng Sag. In the Azigan-Tahaqi period of Late Carboniferous, marine expanded and ancient uplift disappeared, and platform margin slope-platform margin-restricted platform-evaporative carbonate platform facies developed. Therefore, the Kashgar-Yecheng Sag is the main development area of the high-energy phase face, and has a good combination of source, reservoir and cap; it is the main target area for exploration of the front belt of western Kunlun mountain carboniferous system in southwestern Tarim Basin.

Simulation and Analysis of Tectonic Stress Field of Shale Reservoir in Pengshui Area, Southeast Chongqing

GE Xun, TANG Jiguang, ZHAO Peirong, TANG Yong, XU Qilu

2023, 45(5):  27-42.  DOI: 10.11885/j.issn.1674-5086.2020.12.09.02

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There has been complex structural deformation in Pengshui Area of southeast Chongqing since Mesozoic and Cenozoic. The direction of paleotectonic stress field and tectonic evolution sequence are analyzed in detail, and the quantitative characterization of ground stress is of great guiding significance for the exploration and development of shale gas in Pengshui Area and even in southeast Chongqing. Through analysis and treatment of joint and fault striations in Pengshui Area and its periphery, combined with homogenization temperature of inclusions and apatite dating method, the evolution of paleotectonic stress field in Pengshui Area was reconstructed. Abaqus software is used to quantitatively calculate the stress value of paleotectonic stress field in Wufeng—Longmaxi Formations shale reservoir. The results show that Pengshui Area in southeastern Chongqing mainly experienced two stages of tectonism. In the Middle Yanshan period, it was gradually expanded by SE—NW in Jiangnan uplift. In the Late Yanshanian—Himalayan period, the uplift of Qinghai—Tibet Plateau caused NE-trending compression in Pengshui Area. The numerical simulation of tectonic stress field shows that the high value areas of maximum principal stress are mainly distributed in syncline core, end of fault zone, fault intersection. Stress numerical simulation is the basis of fracture development and deep fracturing research, which can effectively improve the success rate of drilling.

Optimum Selection of Shale Gas Favorable Area of Upper Triassic in the Eastern Margin of Kangdian Uplift

HE Lei, MU Bixin, YANG Ping, CHEN Yang, LIU Zhicheng

2023, 45(5):  43-56.  DOI: 10.11885/j.issn.1674-5086.2021.10.14.01

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Based on the analysis of outcrop profile, drilling and testing data of Xichang Basin in the eastern margin of Kangdian Uplift, the main indexes of organic-rich shale in Baiguawan Formation were evaluated and the shale gas selection was evaluated. The results show that: 1) Organic-rich shale of lacutrine or marsh facies is developed in the first to fourth Member of Ginguowan Formation in Xichang Basin, the thickness of the lower part of the second Member is generally 40~89 m, and the thickness of the lower part of the third member is up to 251 m. 2) Average organic carbon of Baiguowan Formation shale is 1.0%~1.6%, the organic carbon isotope of kerogen is -26.2‰~-23.2‰, and the organic matter type is II₂-III type. The R_o in the eastern Mishi Depression is 1.1%~3.0%, indicating moderate evolution degree. 3) The content of organic matter and the degree of thermal evolution are important factors for the formation of shale gas in the study area. 4) Shale gas content of Baiguowan Formation was estimated to be 1.0~1.5 m³/t with the genetic method. The favorable shale gas areas were selected with the multi-factor overlapping method, and the shale gas resources were evaluated by regions. The total shale gas resources of the favorable shale gas area of Baiguowan Formation in Xichang Basin is 7 106×10⁸ m³, among which the resources of the third Member of Baiguowan Formation is 3 094×10⁸ m³. Shale gas is expected to be discovered in the new zone and new strata in favorable areas such as Terguo and Qiliba in the east of Mishi Depression.

Quantitative Sequence Division and Lacustrine Level Change Based on Wavelet Analysis

DONG Huoxiang, LIU Jingyan, CHEN Zhaoqin

2023, 45(5):  57-68.  DOI: 10.11885/j.issn.1674-5086.2021.08.30.02

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The paleogene of Bohai Bay Basin has always been an important exploration target, which has great potential for oil and gas distribution and accumulation in Changdi Area. However, due to the complex structural conditions in this area, sequence, sedimentation, and other conditions are unknown. In order to explore the sequence development and lacustrine level change in this area, this paper divides the Dongying Formation in Changdi Area into 4 third-order sequences, 10 parasequence sets and 19 parasequences by means of high-resolution sequence division and quantitative sequence division through wavelet analysis. Fischer diagram is drawn on the basis of logging wavelet transform analysis, revealing the change of the accommodation space of Dongying Formation in Changdi Area, which approximately reflects the relative lacustrine level changes in the research area. The Dongying Formation in the research area shows a large-scale lacustrine regression and lacustrine transgression, and the process of small-scale lacustrine transgression and lacustrine regression within the Dongying Formation is consistent with the third-order sequence. In SQ₁ period, the relative lake level reached the maximum, during which there was a small-scale lake invasion and lake retreat, and then slowly lake retreat, reaching the minimum at the end of SQ₂. During SQ₃ period, the lake transgressed rapidly and then retreated rapidly, which fluctuated at a relatively low value. On the whole, the lake basin shrank and was covered by the delta plain.

The Geomechanical Characteristics of the Continental Shale Reservoirs and Their Influence on the Fracturing Effect

XIONG Jian, WU Jun, LIU Xiangjun, ZHANG Lei, LIANG Lixi

2023, 45(5):  69-80.  DOI: 10.11885/j.issn.1674-5086.2021.12.28.01

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According to the reservoir logging data and the post-fracturing oil test data, the reservoir geomechanical characteristics of the Fengcheng Formation continental shale reservoirs in the Mahu Sag, Junggar Basin were analyzed, and the main geomechanical factors affecting the fracturing effect were determined by the grey correlation method. Based on this, the fracturing evaluation index of Fengcheng Formation continental shale reservoirs was constructed by analytic hierarchy process. The results show that the relationships between rock mechanical parameters, acoustic wave and bulk density of Fengcheng Formation continental shale reservoirs are clarified, and the response mechanisms of rock mechanical parameters of continental shale reservoirs in the study area is revealed, so as to establish the calculation models of the reservoir rock mechanical parameters. Based on the drilling fracturing and logging data, the calculation models of formation pressure and in-situ stress of continental shale reservoirs in the study area is established. The main geomechanical factors affecting the fracturing effect of the reservoirs are determined with the grey correlation method, namely, elastic modulus, horizontal stress difference, minimum horizontal principal stress, tensile strength and uniaxial compressive strength. The fracturing evaluation index of the continental shale reservoirs in the study area is constructed by using analytic hierarchy process. The weight coefficients of the main geomechanical control factors are 0.369 6, 0.244 0, 0.209 0, 0.109 3 and 0.068 1.

OIL AND GAS ENGINEERING

Optimization of SAGD Key Parameters for Vertical Assisted Double Horizontal Wells in Super Heavy Oil Reservoir

WANG Qing, YANG Haozhe, LIU Jia, GAO Yu, GAO Liang

2023, 45(5):  81-87.  DOI: 10.11885/j.issn.1674-5086.2021.06.21.01

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In view of the problems of unbalanced development of steam cavity, slow lateral expansion and steam channeling in the development of SAGD in super heavy oil reservoir, multi well combination, multi-media assistance and multi measures are adopted to increase development efficiency on the basis of SAGD. Among them, vertical well assistance SAGD can significantly improve the development of steam cavity, improve oil production rate, and requires less cost and strong operability. At present, the key parameters of vertical well assisted SAGD technology have not been systematically demonstrated. In order to achieve the optimal production effect, the vertical well auxiliary time, perforation parameters considering interlayer, injection production parameters in the preheating stage of vertical well huff and puff, and injection production parameters in the auxiliary stage of vertical well to steam drive in the typical well area Z01 of super heavy oil in Fengcheng Oilfield are optimized through numerical simulation. The research results show that the SAGD measure of vertical well assisted double horizontal wells can effectively improve the production degree and production rate of horizontal well, improve the development effect, and the scheme after parameter optimization is practical and effective. The results provide important technical support for vertical well assisted SAGD efficient development of super heavy oil reservoir.

Pore-scale Simulation of Gas-water Two Phase Flow in Carbonate Reservoir with Different Combinations of Pore, Network and Hole

ZHANG Tao, SUN Tianli, CHEN Weihua, ZHU Guo, WANG Xudong

2023, 45(5):  88-96.  DOI: 10.11885/j.issn.1674-5086.2021.11.26.03

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There are various combinations of pore, network and hole in carbonate reservoir. It is of great significance to understand and characterize the gas-water two phase flow in these different types of reservoirs. A multi-relaxation color-gradient lattice Boltzmann method (LBM) in adaption to the deep-reservoir condition of carbonate reservoir is proposed. Based on the method, the gas-water two phase flow behaviors for different types of carbonate reservoirs under gas accumulation process (gas displacing water) and water invasion process (water displacing gas) are revealed. The results show that, the types of residue water during gas accumulation process include water in dead-end pore, water in side of hole, water film, water in “H” shape and network shape; the types of enclosed gas during water invasion process include gas in dead-end pore, snap off gas, gas enclosed by bypass, gas in “H” shape and network shape. Because the large volume of holes, the residue water (gas accumulation process) or enclosed gas (water invasion process) of network-hole reservoir is highest compared with other two types of carbonate reservoirs. For network reservoir and pore-hole reservoir, with the change of water saturation, the gas percolation capability is fluctuated instead of linear change with water saturation. This work can be a good support for the development of micro-percolation theory and water-invasion-prediction theory for deep carbonate gas reservoir.

Calculation of Depth of Mud Filtrate Invasion Based on Formation Sampling

LIU Haibo, WU Lejun, WANG Meng, ZHANG Hongwei, QIN Xiaofei

2023, 45(5):  97-106.  DOI: 10.11885/j.issn.1674-5086.2021.08.16.01

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Depth of mud filtrate invasion is the basic parameter for evaluating mud filtrate-contaminated formation using conventional logging and for understanding the accuracy of reservoir evaluation parameters. There are various traditional methods to obtain this parameter, but they lack applicability and efficiency. Based on the formation sampling technology, the pumping process can be roughly divided into four stages using of the dynamic curve of the conductivity versus time. They are the startup phase, the initial phase, the transition phase and the stable phase. Based on this, the breakthrough time and stabilization time of formation fluid can be effectively determined. Combining factors of macro-stratum model, reservoir physical properties, pumping parameters, the invasion-depth-volume model has been established to quantitatively calculate the depth of mud-filtrate invasion. The influence of key factors such as formation lithology physical properties, fluid physical properties, instrument parameters, reservoir pollution degree on the calculation results is analyzed. In comparison with the traditional numerical simulation method, the new method is more efficient and reliable. This method has been applied to dozens of exploration wells offshore and have been achieved good results, thus providing an important basis for decision-making of field operation.

An Experimental Study of the Flow Characteristics of Foam Drainage Well

WANG Guisheng, ZHANG Yuhao, WANG Zhibin, WANG Xiang, WANG Jinchang

2023, 45(5):  107-118.  DOI: 10.11885/j.issn.1674-5086.2022.03.10.01

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Foam drainage and gas recovery technology is widely used in various gas fields, especially low permeability gas reservoirs at home and abroad due to its low cost, simple construction and quick results. It plays a leading role in many drainage and gas recovery processes. It is of great significance to accurately reveal the flow pattern and the liquid carrying rule of the bubble discharge well in order to optimize the technological parameters of bubble discharge process and improve the technological level of foam drainage and gas production. Therefore, in this paper, a set of 30 mm diameter visual experimental equipment was set up to carry out the experimental research of surfactant effect on the flow characteristics of gas-liquid twophase flow under different surfactant concentration, inclination angle and gas-liquid ratio. By comparing the flow characteristics with and without surfactant, surfactant effect on flow pattern, structure and transition boundary of gas-liquid two phase flow in vertical pipe were analyzed. The experimental results show that: 1) The addition of surfactant promotes the slug-to-churn and churn-to-annular transition were shifted to somewhat lower gasflow rates. Simultaneously the foam was better able to suppress the intermittent flow, leading to a narrower range of slug flow and churn flow. 2) The pressure gradients of surfactant solutions were lower than those of pure water especially in slugflow and churnflow regimes, with less irregular flow at low gas velocity. However, the pressure difference of annular flow increased rapidly along the increase of concentration. 3) The liquid holdup was much smaller with surfactant, while tended towards stability by the change of concentration at higher gas flow rate. 4) After surfactant addition, the critical gas velocity decreased sharply by over 40% at inclination angle about 50 ° especially.

Dynamic Characteristics and Countermeasures of Sulfur Plugging in Gas Wells of Puguang Gas Field

FU Dekui

2023, 45(5):  119-130.  DOI: 10.11885/j.issn.1674-5086.2022.02.03.01

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Puguang Gas Field is an extremely high sulfur hydrogen gas field. With the development of the gas field, the formation pressure is gradually reduced, the elemental sulfur is gradually separated from the natural gas and deposited on the surface equipment, the gathering and transporting pipelines and on the inner wall of the oil pipeline, which gradually causes the sulfur deposition blockage. At present, sulfur deposition and plugging have occurred in the surface gathering and transportation process and wellbore of Puguang Gas Field, which seriously affects the normal production of gas wells. Aiming at the problem that the dynamic characteristics of sulfur deposition and plugging in gas wells are not clear and the corresponding countermeasures are not available, the mechanism of sulfur plugging in gas wells is studied first. We find that the elemental sulfur is gradually precipitated, then transported and deposited, and finally formed a sulfur plug. Secondly, the dynamic characteristics and changing rules of sulfur deposition plugging in surface flow and wellbore are analyzed, the corresponding countermeasures of sulfur deposition plugging in surface and wellbore are proposed, and the field adaptability of various measures was evaluated. Finally, according to the theoretical research and field practice, it is considered that sulfur plugging will gradually develop to the reservoir, and the countermeasures of sulfur plugging removal are proposed. The research results have a guiding significance for comprehensive control of surface-wellbore-reservoir sulfur shutoff in high sulfur gas wells.

Multifunctional Sustained Annulus Pressure Ground Diagnosis Method and Device

YANG Shunhui, HE Hanping, ZHANG Zhi, DOU Xuefeng, YIN Xilu

2023, 45(5):  131-139.  DOI: 10.11885/j.issn.1674-5086.2022.03.09.01

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In order to break through foreign technology blockade, solve the problems of less functions of domestic technology and the problem of inconvenience in transportation due to large size and heavy mass of the existing devices, we put forward a kind of multi-functional sustained annulus pressure ground diagnosis method, design a set of modular and integration processing plan, and develop a portable device system. The system includes gas-liquid separation and solid phase filtration module, temperature pressure and flow monitoring module, gas phase parameter monitoring module, liquid phase parameter monitoring module and liquid level height monitoring module, which can form an integrated combination scheme with different functions, combined with wireless data transmission technology and supporting analysis software. It has diagnostic analysis functions, such as cause analysis of sustained annulus pressure, calculation of leakage point position, leakage degree assessment and risk degree judgment. The field test results show that the reason for the increase in annulus pressure in the case well is a certain defect in cement ring bonding, the leak point depth is about 3 120 m and a leak rate of 0.012 m³/min. The results measured by the system coincide with the actual situation, which verifies the rationality of the diagnosis method and the reliability of the device.

Operation Optimization of Sichuan East Gas Transmission Pipeline Under Calorific Value Measurement Mode

YUAN Xianzhong

2023, 45(5):  140-151.  DOI: 10.11885/j.issn.1674-5086.2021.09.23.01

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Long distance natural gas pipeline is the main facility connecting upstream gas source and downstream users. Compared with the traditional natural gas volume measurement transaction mode, the calorific value measurement transaction can reflect the energy value of natural gas to a greater extent and realize more fair market competition. On the basis of considering the conversion mode of natural gas from volume measurement to calorific value measurement, this paper creatively establishes the pipeline operation optimization model under calorific value measurement mode. The model aims to maximize the economic benefits of pipeline operation, and takes the air source flow, compressor startup number and compressor speed as decision variables. The established optimization model is applied to the Sichuan-east gas transmission pipeline, and the optimization problem is solved by GAMS modeling system and DICOPT solver. The optimization results show that compared with the traditional volume metering model, the sales profit of east Sichuan Gas Transmission Pipeline under the calorific value measurement model is 10.82% higher, and the energy consumption of compressor station is about 3.4% lower. Although the cost of purchasing gas increases, the increase of gas selling income is higher than that of gas purchasing cost.

PETROLEUM MACHINERY AND OILFIELD CHEMISTRY

Research on Particle Impact and Its Auxiliary Rock-breaking Mechanism

ZHU Xiaohua, HE Ling, LIU Weiji, LUO Yunxu, YANG Feilong

2023, 45(5):  152-163.  DOI: 10.11885/j.issn.1674-5086.2020.12.11.02

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Particle Impact Drilling (PID) is a new and efficient drilling technology, which combines the impact technology and mechanical rock breaking to realize the efficient drilling of the bit in the abrasive hard formation. At present, the mechanism of particle impact assisted rock breaking is not clear enough. In order to optimize drilling parameters with particle impact and improve drilling efficiency, a numerical model of black sandstone with microscopic cluster characteristics was established based on discrete element particle flow method. By analyzing the mineral composition and proportion of black sandstone, the mechanism of single particle impact, multiple particle impact and auxiliary cutting rock breaking under the conditions of different particle size, incident angle and incident velocity were studied. The research shows that particle impact assisted cutting rock-breaking is more efficient than traditional cutting rock-breaking. When particle size is 1.5 mm and 3.0 mm, the rock-breaking specific work will show a sharp decrease, and the rock-breaking specific work has little change when particle size is 1.5~2.5 mm. Particle size, incident angle and incident velocity have important influences on auxiliary rock breaking. In order to improve the efficiency of auxiliary rock breaking, it is recommended to use particles with particle size of 3.0 mm and incident angle of 0°~5°, with increased impact velocity at the same time. It is concluded that the particle impact drilling technology is an effective means to improve the abrasive hard formation drilling efficiency, and the research results can provide some guidance for the development of this technology.

Effect of Repeated-shear on Properties of Oil-containing Foam

SUN Lin, WU Yanping, ZHANG Yongchang, CHEN Dequan, PU Wanfen

2023, 45(5):  164-172.  DOI: 10.11885/j.issn.1674-5086.2021.05.26.02

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In porous media, oil-containing foam is in a dynamic balance between rupture and regeneration. Waring Blender method was used to simulate the regeneration of oil-containing foam by repeatedly shearing zwitterionic surfactant solution (RC) with crude oil. We focused on the solution properties and the change of foaming ability and foam stability after RC solution interaction with different contents of crude oil (0~60%). The results showed that the distribution of RC molecules in the oil phase and at the oil-water interface significantly decreased RC concentration in the foaming system (up to 72%), and the solubilization of crude oil in RC micelles markedly weakened the stability of foam films. Therefore, the performance of regenerated foam from RC solutions was severely damaged. Within an oil content below 40%, as the oil content increased, the foam drainage half-life for the first-sheared oil-containing foam continuously extended to 2.4 times that of the oil-free foam, while for the twice-sheared foam it decreased to 27% of the oil-free foam. During the secondary shearing, the oil phase was emulsified into a large number of small oil droplets due to the reduced oil-aqueous interfacial tension, which could not hinder the drainage and drained easily with water phase. As a result, the oil content in the foam film reduced, and there was little difference between half-lives for first-sheared and twice-sheared oil-containing foams. The research results are expected to provide new insight into the regeneration behavior of oil-contenting foam and contribute to the formulation of oil-tolerant foam system. This study provides new insight into the regeneration behavior of oil-contenting foam, and will contribute to the formulation of oil-tolerant foam system.

Evaluation Study of Shale Water-based Drilling Fluid Plugging Agent in Chang 7 Member of Yanchang Formation

FU Minhao, WANG Pingquan, LU Jinsong, RAN Chao, SU Junlin

2023, 45(5):  173-182.  DOI: 10.11885/j.issn.1674-5086.2023.06.21.02

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In view of the problem of well wall instability in ultra-low porosity and ultra-low permeability shale formations, taking the shale of Chang 7 Member of Yanchang Formation as the reference object, the mineral composition and lithology characteristics are analyzed by means of X-ray diffraction, permeability, porosity, specific surface area, average pore diameter measurement and scanning electron microscopy, and the idea of maintaining wellbore stability of shale is put forward. By using the simulated “standard thick mud cake” plugging evaluation method, the optimal dosage of ZD-1, JB53, EP-2 and ZD-3 plugging agents and the plugging effect of their combination were evaluated, and the effective compound plugging agent SPA-1 was selected. After adding 4.0% SPA-1 to the water-base potassium formate drilling fluid system for Yanchang shale, the rheology is easy to control and the permeability reduction rate reaches 94.20%. The simulated core electron microscopy images before and after the application further verified the plugging effect and analyzed the plugging mechanism of the plugging agent. The results show that SPA-1 set reasonable particle size distribution and the synergistic effect of rigid and flexible particles can achieve effective plugging, which is conducive to the stability of shale wall of Chang 7 Member of Yanchang Formation.