Table of Content

10 December 2022, Volume 44 Issue 6

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GEOLOGY EXPLORATION

In-situ Stress Logging Interpretation Methods and Reliability Analysis

WANG Zhaosheng, ZENG Lianbo, LI Jing, LIU Daojie, YU Jiangtao

2022, 44(6):  1-9.  DOI: 10.11885/j.issn.1674-5086.2020.11.13.01

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In order to compare the difference in accuracy between borehole breakout, drilling-induced fracture and wave velocity anisotropy methods in interpreting in-situ stress orientation, the theoretical basis, interpretation methods and influencing factors of in-situ stress azimuth analysis by logging data were systematically expounded in this paper. The results show that the present-day maximum principal stress(S_H) orientation of the third section of the Shahejie Formation in Well G6 is 70°~80°, interpreted by imaging logging data and combined with drilling-induced fracture and borehole breakout methods, which is consistent with the micro seismic monitoring results of adjacent wells. While the wave velocity anisotropy method and the borehole breakout method based on six arm dip-logging data interpret that the S_H orientation is 80°~90°. The interpretation accuracy of in-situ stress orientation is affected by natural fracture, fault and formation dip angle, after comprehensive analysis, the in-situ stress orientation results are the most accurate interpreted by drilling-induced fracture method basing on imaging logging. There is a systematic error about 10° of the in-situ stress orientation interpreted by the borehole breakout method basing on the dip-logging in the study area. There are some limitations in the interpretation of in-situ stress orientation with dipole acoustic logging data and wave velocity anisotropy method, which need further correction.

Quantitative Characterization of Sand Body Connectivity in Deepwater Turbidite Channel Reservoir

LI Chenxi, KANG Botao, ZHANG Xu, GAO Yihua, CHEN Guoning

2022, 44(6):  10-20.  DOI: 10.11885/j.issn.1674-5086.2020.08.19.02

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In the development practice of deep-water oilfield, it is found that the composite channel sand body as a development unit bears overall pan-connectivity because of its high sand-ground ratio and good reservoir quality, but there are differences in connectivity in different positions. In order to accurately and finely depict the connectivity of different positions in the channel sand body, and improve the injection-production efficiency and development effect, the reservoir sandbodies are subdivided into configuration units and configuration interfaces by using the method of configuration. The impact of the fine characteristics of gravity flow sedimentary outcrop in the west Qinling Area on connectivity is quantitatively described, and geological model is used to applied it to the development and production. It is found that for turbidite channel reservoirs with high NTG, both channel configuration unit and channel configuration interface affect connectivity at the same time, and generally configuration interface is dominant, the influence of sand body characteristics on connectivity can be described by "configuration unit-interface binary modeling method", the connectivity between sand bodies can be quantitatively described and measured by "connectivity coefficient". The "equivalent substitution" method can be used to calculate the connectivity coefficient.

Application of Rock Physical Template in the Time-lapse Seismic Quantitative Interpretation

HU Yuting

2022, 44(6):  21-28.  DOI: 10.11885/j.issn.1674-5086.2020.06.24.02

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Rock-physical interpretation chart is usually used in quantitative prediction of reservoir lithology and fluid, and has achieved good application effect. Time-lapse seismic is used in reservoir monitoring and qualitative or semi quantitative interpretation of residual oil and gas. With the development of oil or gas fields, more accurately interpretation of remaining oil or gas distribution is required. This paper discusses a method of quantitative interpretation of remaining oil or gas by using time-lapse seismic information. By constructing the relationship chart between the change of reservoir fluid characteristic parameters (such as fluid saturation, pressure, etc.) and the change rate of time-lapse seismic sensitive parameters, the rock-physical interpretation chart representing a static time point is replaced by a dynamic physical interpretation chart changing with fluid, so as to realize the quantitative interpretation of the thickness and distribution of the remaining oil layer and reduce the interpretation ambiguity. The application in S Oilfield has achieved good application effect, and the predicted result of residual oil thickness is highly consistent with the measured result, which effectively guides the optimization of production well location in the study area and reduces the development risk.

Main Controlling Factors and Enrichment Mechanism of Chang 4+5₁ Reservoir in Baibao-Nanliang Area, Ordos Basin

XIAO Zhenglu, LU Jungang, LIAO Jianbo, LI Yong, CHEN Shijia

2022, 44(6):  29-42.  DOI: 10.11885/j.issn.1674-5086.2020.08.26.02

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The high water production rate of Yanchang Formation reservoirs in Ordos Basin is one of the main problems in the fine exploration of oilfield. The Chang 4+5₁ Reservoir in the Baibao-Nanliang Area is taken as the research object. Through the comparative analysis of source rock conditions, sand body types, reservoir characteristics, fracture characteristics, and shielding conditions, the enrichment rules of oil reservoirs are discussed. The results show that the Baibao Area is distributed in the lower delta plain and the near source part of delta front, and the sand body type is mainly underwater distributary channel with large thickness, high permeability, and long lateral extension. Due to the large-scale connectivity sand body with good physical properties, the crude oil migrated laterally to the high part of the structure under the action of buoyancy, resulting in the oil-bearing core producing water. Low amplitude structure is a favorable exploration target in this area. Nanliang Area is distributed at the end of the delta front, mainly composed of mouth-bar sand body. The sand body is relatively isolated, the physical properties are relatively poor and the lithology changes frequently. It is difficult for crude oil to migrate laterally due to the good conditions of authigenic traps in isolated sand bodies. Sand bodies with smooth vertical migration channels and good reservoir physical properties are favorable exploration targets in this area.

The Reason of Limestone Formation Thickering and Its Effect to Reservoir in the North of Oriente Basin

CHEN Jie, TONG Mingsheng, CHEN Guo

2022, 44(6):  43-53.  DOI: 10.11885/j.issn.1674-5086.2020.10.15.01

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The Oriente Basin is one of the most important basin with hydrocarbon source rocks in South American. The major petroleum system is Creatures Napo sandstone. The Napo Formation developed in tide sediment environment with the complex lithology including quartz sandtone, glauconite sandstone, limestone and shale. There are 3 sets of limestone formation in the Napo named as A, B, C limestone from lower to upper which are the marker formation. The A limestone in the north of Oriente Basin develops stably with average thick 40 ft. However several abnormal bodies of A limestone had been found in the northern of Oriente Basin which show the high seismic amplitude. It had been proved that some good sand bodies of A limestone thickened, which makes it difficult to predict the reservoir accurately by seismic data. The regional geology, petrophysics and geophysics data had been used to analysis the reason of A limestone formation thickening. By the seismic forward modeling based on the seismic response character analysis of good sandbody in the normal sedimentation, the seismic response character of sand below the different A limestone had been study. According to the seismic inversion result, many technology had been comparatively analyzed and stack bond seismic data analysis technology based on CRP and spectrum decomposition technology based on tuning body thickness had been used to get off the effect of A limestone thickening. Drilling results have proved the effectiveness of the technologies.

OIL AND GAS ENGINEERING

Research on Managed Pressure Casing Technology in Narrow Safety Pressure Window Formation

XU Bihua, LI Junfu, LI Bin, TIAN Dongcheng, RAO Fujia

2022, 44(6):  54-61.  DOI: 10.11885/j.issn.1674-5086.2020.10.12.03

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Aiming at the problem of high loss risk of casing running in narrow safety pressure window formation, based on transient surge pressure, a wellbore pressure control model for casing running in narrow safety pressure window formation is established, and then a precise pressure control method for casing running is proposed. Firstly, the sensitivity analysis of casing surge pressure is carried out by using the transient surge pressure model. The results show that the higher the casing running speed, the deeper the casing sinking depth, the greater the drilling fluid density and the smaller the annulus clearance, the greater the bottom-hole surge pressure caused by casing. A case study of casing running under precise pressure control shows that this method can not only ensure casing running speed, but also effectively avoid loss in narrow safe pressure window formation. In addition, by comparing the precise pressure control casing running with the conventional casing running, it is found that the maximum speed adjustment range of casing running is very narrow when the casing running with the conventional method is near the bottom of the well, which makes it difficult to maintain the wellbore pressure within the safety pressure window.

The Construction Method of Three-dimensional Dynamic Gas-driven Well Pattern in Fractured-vuggy Reservoirs

ZHU Guiliang, SONG Chuanzhen, ZHANG Hui, CHENG Qian, ZHANG Yun

2022, 44(6):  62-70.  DOI: 10.11885/j.issn.1674-5086.2020.07.02.02

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Gas injection in Tahe fracture-vuggy type reservoir has achieved good oil increase effect, but different gas driven well groups have great difference in oil increase effect, so gas driven well pattern construction technology is urgently needed to guide gas injection on site, so as to improve the proportion of gas injection affected well groups. However, there is no public report on how to construct and evaluate the gas driven well pattern. Based on the analysis of actual well pattern in different karst background and the understanding of gas injection and wave rule, the principle of constructing well pattern of gas-driven three-dimensional structure in fracture-vuggy reservoir is clarified. Factors influencing gas driven pattern can be divided into basic geological conditions factors and advantages and disadvantages of well pattern factors. Using the principal component analysis, basic geological conditions and the evaluation method of the three big background of karst has been established. We put forward the degree of gas driven control, gas drive utilization, gas driven the reserves, plane balanced degree of displacement, vertical displacement equilibrium degree and interleave degree of injection and production layers. Based on the six factors, effects on improving recovery degree, method and standard for quality evaluation of the influence of gas driven patterns. Considering the field practice, the dynamic adjustment method of gas channeling well group is proposed, and the well pattern construction method and flow chart of three-dimensional gas driven structure of fracture-vuggy reservoir are formed. The gas-driven well pattern construction method was applied to W-1 gas-driven well group, increased of 60, 000 tons of accumulated oil and the gas oil change rate of 0.6, verifying the feasibility of the method.

Investigation on the Morphology and Activation Mechanism of Hydraulic Fracture Network in Shale

WANG Qiang, ZHAO Jinzhou, HU Yongquan, ZHAO Chaoneng, FU Chenghao

2022, 44(6):  71-86.  DOI: 10.11885/j.issn.1674-5086.2020.09.24.01

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Aiming at the problem of quantifying the composition of complex fracture network and fracture activation after shale volume fracturing, a complex fracture network model of weak surface of prefabricated structure is established based on finite element method, global embedded cohesive zone model and real shale outcrop. Considering the influence of fully coupled stress/fluid, the effects of weak plane azimuth, horizontal stress difference, fracturing fluid viscosity and displacement on fracture network composition, geometry and SRV are studied. The concept of fracture relative activation, which can quantitatively analyze fracture network composition and fracture activation, is proposed. The results show that the fracture geometry of two kinds of conjugated shale after compaction is controlled by the most weakly mechanical weak-plane, and the fracture network is respectively axisymmetric and centrosymmetric. The fracture network is composed of the weak-plane fractures with the dominant free gas transport and the matrix microfractures with the dominant adsorbed gas transport; the effects of weak-plane azimuth, horizontal stress difference and fracturing fluid viscosity on SRV length are not monotonous, while the increase of the azimuth, horizontal stress difference, fracturing fluid viscosity and the reduction of appropriate displacement will lead to the increase of SRV width; the effect of horizontal stress difference on the relative activation of fractures does not change monotonically, while the increase of weak-plane azimuth, fracturing fluid viscosity and displacement will lead to the increase of the relative activation of matrix microfractures, the increase of the total length of activated fractures and the decrease of the relative activation of weak-plane fractures.

Research on the Flow Characteristics of Micro-bubbles in a Simulated Pore Throat Channel

WU Binbin, WANG Chengsheng, CHEN Ping, HUANG Bo, TANG Engao

2022, 44(6):  87-96.  DOI: 10.11885/j.issn.1674-5086.2020.09.21.04

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In order to study the percolation characteristics of microbubbles in porous media, a microfluidic chip integrated with T micro channel and reducing channel was designed. Flow characteristics of microbubbles formed by "deionized water + air" and "0.02% Tween 20 solution + air" were studied by microfluidic system based on micro imaging. The fluid velocity and pressure changes in the microchannel during bubble fusion were analyzed by CFD method. Experimental results show that when the liquid phase is deionized water, with the change of gas pressure and liquid velocity, the microbubbles will fuse and not fuse when they flow through the reducing channel. The microbubbles generated by "0.02% Tween 20 solution + air" will pass through the reducing channel in turn and will not fuse. When the microbubbles are fused, the surface tension causes the microbubbles to deform, which leads to the large fluctuation of the surrounding fluid velocity, forming velocity "eddy current". When entering the "throat" again, the pressure in the "pore" increases. The experimental study is helpful to further understand the percolation characteristics and displacement mechanism of micro foam flooding.

Research on Automatic History Matching Method Based on Multi Models

LU Yi, HU Hao, CHENG Yabin, XIA Guochao, REN Guangwen

2022, 44(6):  97-104.  DOI: 10.11885/j.issn.1674-5086.2020.11.10.01

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In traditional reservoir numerical simulation, only a single random geological model is established, and the artificial history fitting method is used to obtain the geological model that conforms to reservoir production history and is used for project prediction. However, due to the relative scarcity of geological data and the heterogeneity of reservoir, the historical fitting problem must have multiple solutions, and the single geological model obtained cannot guarantee the accurate reflection of the real underground situation. In the numerical simulation study in this research, static geological data are used to produce a large number of random implementations, PCA dimensionality reduction method is used to reduce the amount of model data, and then the clustering method is used to select a number of implementations with different characteristics as the initial model. The automatic history fitting method based on SPSA algorithm was used to obtain several historical fitting models which conform to reservoir dynamics but contain different characteristics. Multi models can reflect the real underground situation more completely, and the prediction result is no longer a single dynamic curve, but a series of curves with multiple development possibilities, making the prediction more scientific and reliable.

Distortion Influence on Cavern Volume of Jintan Salt Cavern Gas Storage

WANG Jianfu, BA Jinhong, WANG Wenquan

2022, 44(6):  105-113.  DOI: 10.11885/j.issn.1674-5086.2020.10.09.02

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Jintan salt cavern gas storage is constructed in layered salt rock. In the construction, the cavern distortion and leaching often occur, which seriously reduce the effective volume of salt cavern. It is helpful to increase the gas storage capacity by studying its influence on the cavern volume and controlling the leaching method. Based on the actual condition of Jintan salt cavern gas storage, the influence of cavern distortion, partial leaching and sump shape on the effective volume was analyzed. The results show that the distorted and partially-leaching caverns account for about 30% of the total number, the distortion coefficient ranges between (11.8~90.1)×10^-3, and the larger the distortion coefficient, the lower the utilization rate of salt layer; the cross-section of salt cavern is elliptical, and the diameter of cavern varies greatly with different depth, which reduces the utilization rate of salt layer around the cavern; partial leaching reduces the pillar width between adjacent caverns as well as the ratio, so the diameter of cavern is limited, and the cavern volume is seriously reduced; the sump can be divided into "V", "-", " \" and "A" shapes, and the brine discharge efficiency decreases in turn. The last two kinds are the most unfavorable for cavern space utilization and seriously reduce gas storage volume. For the cavern distoration, the means includes reducing the displacement, using positive circulation, natural gas dissolution inhibition technology. For partial leaching, measures such as predicting the direction of partial leaching and reasonably designed well location, reducing P/D and increasing the diameter of cavern can be adopted. There are no effective measures to control the sump deformity and improve the brine discharge efficiency. The research gives a theoretical foundation for the cavern shape control and the improvement of cavern volume, which is helpful to the construction of Jintan salt cavern gas storage.

Experience and Enlightenment of Major Accidents in Underground Gas Storages Rebuilt from Depleted Gas Reservoir Abroad

ZHANG Zhe, XU Changfeng, ZHAO Yong, CHEN Yue'e, ZHANG Xinpeng

2022, 44(6):  114-120.  DOI: 10.11885/j.issn.1674-5086.2022.05.26.03

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Apparently, China is in the primary stage of underground gas storage construction. Experiences in accident preventions and emergency treatments are insufficient. The study of leaking accidents of foreign underground gas storages have been investigated. Analyzing the probability of leaking accidents, main causes and damages of those underground gas storages is a proper method for guiding China's stable and safe underground gas storages operation. The results of study indicate that storage in gas fields is of the highest accident probability with the greatest damage, and that the main types of accidents include surface facilities damage, trap sealing and wellbore integrity failure. The frequency of accidents from the highest to the lowest is the surface facilities, wellbore and trap. The extent of accident damages from the highest to the lowest is the trap, wellbore and surface facilities. Secondly, this paper focuses on the typical leakage cases of foreign storage in gas fields, and concluded that dynamic monitoring of trap sealing in underground gas storages is significant, and evaluating the fractures and old wells sealing condition are of top priorities during the site selection evaluation. In relation to the current constructing and developing situation of underground gas storages in China, five suggestions are proposed to provide an essential guarantee for the efficient construction and safe operation of underground gas storages in China.

Research on the Necessity and Optimization of Supercharging for a Cross-border Gas Field of Amu Darya Right Bank Area

ZHENG Ke, SUN Li, LIU Ronghe, LI Hongxi, ZHANG Li

2022, 44(6):  121-131.  DOI: 10.11885/j.issn.1674-5086.2020.08.04.02

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The gas field lies astride the border between Turkmenistan and Uzbekistan is facing some problems which may affect the completion of productivity construction, such as well head pressure approaching transportation pressure, resource loss, uneven pressure distribution, the huge investment of supercharging and difficult approvals, the lack of personnel. Therefore, this paper did some researches about the necessity and optimization of supercharging. The study shows that supercharging can solve the above problems effectively, the supercharging plan of centralized and staged construction is optimum. Centralized supercharging installs compressors in the same station, but the construction can be carried out in two stages, which can not only minimize the loss of resources, but also alleviate the shortage of infrastructure personnel. By means of optimizing the production capacity profile and installing the flow switching devices in the booster station, the total required power of supercharging can be reduced to 43 MW, the number and utilization ratio of compressor are optimal, minimize investment and maximize benefits. The project has been approved by the resource country and 13 compressors have been put into operation in two stages, the production capacity construction target was successfully completed, effectively guiding the orderly progress of the project, the development effect of the gas field is improved.

FLOW ASSURANCE

Numerical Investigation of the Natural Gas-hydrogen Mixture Stratification Process in an Undulating Pipeline

ZHU Hongjun, CHEN Junwen, SU Huazhong, TANG Tang, HE Shan

2022, 44(6):  132-140.  DOI: 10.11885/j.issn.1674-5086.2022.06.20.02

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The transportation of nature gas mixed with a specific volume of hydrogen is considered to be one of the green and economical ways to transmit hydrogen. In this research, a series of numerical simulations is conducted to capture the stratification process of natural gas mixed with different volume fractions of hydrogen in an undulating pipeline after the shutdown. The effects of the height of undulating pipeline on the process of gas stratification and the maximum hydrogen concentration are examined. An obvious shear effect between gas flows is observed in the inclined tubes of such undulating pipeline. The gas flow in the pipeline could be classified into four stages:initiation and enhancement stage of gas shear effect, vortex formation and shear attenuation stage, vortex extinction and flow stabilization stage, and flow deceleration and vertical stratification stage. The variation of gas concentration depends on the strength of gas flow. The increase of pipeline height or total volume intensifies the shear effect of gas flow, resulting in a longer consuming time for the stable stratification. Therefore, a safety window period for shutdown maintenance is important to be determined according to the risk value of hydrogen concentration.

Response Study of Vortex-induced Vibration of PIP System Based on Wake Oscillator Model

ZHAO Xiang, TAN Ming

2022, 44(6):  141-152.  DOI: 10.11885/j.issn.1674-5086.2022.06.21.01

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The study on the dynamic response of the PIP system under the effect of vortex-induced vibration is carried out for the vortex-induced vibration of the pipe-in-pipe system. The effects of different dimensionless wave numbers, inner and outer pipe diameter ratios, joint layer stiffness, and tension on the displacement response of the marine riser under the action of eddy excitation vibration are also analyzed. In the study, based on the Euler-Bernoulli double-beam theory and using the wake oscillator model, a dynamics model is established, and the expressions of the vibration response of the inner and outer pipes were obtained using the harmonic balance method. The results show that there is instability in the vibration of the PIP under the action of different dimensionless wave numbers and that the vibration of the pipe appears to vibrate at a single frequency in the seventh-order mode. In the high-frequency ratio region, with the increase of the dimensionless connection layer stiffness, the displacements of both internal and external pipes show a trend of first decreasing and then increasing, and gradually stabilizing. The effect of tension on the displacement of the external pipe is relatively complex, and the displacement of the internal pipe shows a decreasing trend with the increase of tension.

Numerical Simulation of Leakage and Diffusion in Hydrogen Mixed Natural Gas Transmission Station

YU Jin, ZHANG Hao, JIA Wenlong, XIE Ping, LI Changjun

2022, 44(6):  153-161.  DOI: 10.11885/j.issn.1674-5086.2020.09.24.03

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Mixing hydrogen into the natural gas pipeline network is currently the most effective way to achieve large-scale hydrogen transportation in the world. The explosion limit of hydrogen is 4.0%~75.6%, the upper and lower limits are wide, and the molecular diameter is smaller than that of methane, which brings great hidden dangers to gas transmission stations. Hydrogen mixed natural gas is the leakage of multi-component system. Based on the modified binary diffusion coefficient and thermodynamic factor calculation method, the Fick diffusion coefficient matrix of three-component system of hydrogen mixed natural gas is calculated, it is used to describe the mass transfer process of molecular motion among components in natural gas mixed with hydrogen. CFD numerical simulation analysis is carried out on the platform of fluent. The results show that the accumulation mode of hydrogen mixed natural gas after leakage is similar to that of natural gas, and its diffusion is affected by obstacles and wind speed; when the same volume of hydrogen mixed natural gas and non hydrogen natural gas leak, the lower explosion limit diffusion radius of hydrogen mixed natural gas is smaller; after the leakage of natural gas with low hydrogen content, the explosion area of hydrogen component is only near the leakage point. The research results can provide early warning and protection guidance for the leakage and diffusion of hydrogen mixed natural gas in the station.

PETROLEUM MACHINERY AND OILFIELD CHEMISTRY

Research Progress of Corrosion During the Exploitation and Gathering-transportation Processes of Shale Gas

ZHONG Xiankang, LI Haonan, HU Junying

2022, 44(6):  162-174.  DOI: 10.11885/j.issn.1674-5086.2020.06.21.01

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Shale gas is a clean energy, which occupies an important position in the energy strategies of many countries. The shale gas exploitation technologies in the United States, Canada and other countries are relatively mature and they are in the leading position across the world. While other countries like in China shale gas exploitation research started later but has developed rapidly in recent years. With the continuous exploitation of shale gas, the corrosion of downhole strings, surface pipelines and equipment occurs frequently, which has seriously affected the normal production of shale gas. Corrosion may occur in shale gas exploration, development, storage and transportation, and different types of corrosion often influence each other, which makes it more difficult to prevent and control. The main corrosion problems involved in shale gas production are sulfate reducing bacteria corrosion, scouring corrosion, CO₂ corrosion, H₂S corrosion and under-scale corrosion. In this paper, the corrosion reasons, corrosion mechanism and anti-corrosion methods in shale gas production are analyzed based on the current research development.

A Study on Profile Control and Flooding Performance of New Crosslinked Polymer Microspheres

ZHOU Haiyan, ZHANG Yunlai, HE Yifan, MIAO Feifei

2022, 44(6):  175-182.  DOI: 10.11885/j.issn.1674-5086.2021.09.09.04

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Bohai Oilfield is characteristic of high porosity and high permeability, loose and fragile, strong heterogeneity. Some well groups have encountered the problems of low efficiency or ineffective circulation of injected water, accelerated water channeling and increased decline rate. Field application test shows that the new cross-linked polymer microsphere P-90 has better profile control and flooding effect for this type of reservoir. In order to better analyze and explain its profile control and flooding mechanism, scanning electron microscopy, laser particle size analyzer, high temperature and high pressure rheometer, microporous filter membrane device, one-dimensional physical model flow device, etc. are employed to evaluate the basic physical and chemical properties and profile control and flooding capability of P-90. The experimental results show that the new crosslinked polymer microsphere P-90 has good swelling effect. After hydration and swelling, a cross-linked spatial network structure is formed between the spheres. The particle size is evenly distributed and remains at 15 μm for a long time. It has good temperature resistance and viscosity retention rate; the membrane with pore size of 5 and 10 μm was effectively blocked. This new crosslinked polymer microsphere P-90 has both the crosslinked network structure of polymer gel and the spherical dispersion structure of polymer microspheres. Its unique microstructure has a significant improvement effect on heterogeneous high porosity and high permeability reservoirs. It has good injectivity, with greatly improved plugging and oil displacement efficiency, and can achieve better deep profile control and flooding effect.