Table of Content

25 October 2022, Volume 29 Issue 5

Previous Issue    Next Issue

Summary

Progress and Prospect of Production Profile Testing Technology for Staged Fracturing in Horizontal Wells

Liu Jianfeng

2022, 29(5):  1-8.  DOI: 10.3969/j.issn.1006-6535.2022.05.001

Asbtract ( )   PDF (835KB) ( )  

References | Related Articles | Metrics

In view of the various problems existing in the current production profile testing for horizontal well staged fracturing, the development direction of horizontal well profile testing technology is further clarified by analyzing and comparing the technical principles and adaptability of such three testing technologies as the distributed optical fiber, the production logging and the tracer monitoring to identify advantages and disadvantages of these technologies and providing an outlook on the development trend of each technology. The research shows: The distributed optical fiber monitoring technology is stable and easy to install, but the storage capacity is large and cannot be interpreted quantitatively; the production logging technology has high precision, but it is not applicable in some cases; the tracer logging involves many types, each with its own advantages and disadvantages; In the future, the in-depth research on logging technology can be carried out from the aspects of technical equipment and data interpretation. This research can provide some technical reference for the field test selection, and also provide some new perspectives for the follow-up technical development.

Geologic Exploration

Accumulation Characteristics and Main Controlling Factors of Natural Gas in the He₈ Member of the Upper Paleozoic in the Ningxian-Zhengning Area, Ordos

Zhang Guolong

2022, 29(5):  9-17.  DOI: 10.3969/j.issn.1006-6535.2022.05.002

Asbtract ( )   PDF (2160KB) ( )  

References | Related Articles | Metrics

The natural gas in the He₈ Member of the Upper Paleozoic Shihezi Formation in the Ningxian-Zhengning Area, Ordos shows a good prospect for exploration, but the single-layer thickness of the effective reservoir is thin and the lateral change is rapid, and its natural gas accumulation characteristics and enrichment law are still unclear, which seriously restricts the natural gas exploration and development in this area. To this end, through a comprehensive analysis of the accumulation conditions of gas reservoirs in the study area, such as source bed, reservoir, caprock, trap, and migration, the accumulation characteristics and enrichment laws are summarized, and the gas layer-sensitive logging curves are screened. Combined with the lithology and physical properties of the reservoir, the effective reservoir division standard of the gas reservoir in the He₈ Member of the study area is established, and on this basis, the effective reservoir prediction is carried out by using 3D seismic data. The result shows: The Permian coal-measure source rocks are widely distributed and are in the high-to-over-mature stage, providing good gas source conditions for natural gas accumulation; the branched channel sandstone at the braided river delta front of the He₈ member is distributed in large-scale stripes in the near north-south direction, the lithology is mainly detrital quartz sandstone, followed by quartz sandstone, forming an effective reservoir sand body for natural gas reservoirs; the dominant reservoir in the He₈ Member and the underlying effective source rock form "lower source and upper reservoir" type near-source accumulation assemblages, generating widely distributed tight sandstone lithologic gas reservoirs. The near-source favorable sand body is preferred for accumulation, and the distribution of gas reservoirs and gas abundance are controlled by the distribution of effective sand bodies, the physical properties of the reservoir and the faults leading to the source. Through this study, the distribution of effective reservoirs in the He₈ Member in the area has been identified, which provides a basis for the optimization of the next natural gas exploration targets in this area.

Accumulation Mechanism and Enrichment Law of Tight Gas in Shengbei Structural Zone

Liu Juntian, Xie Dianhe, Peng Yazhong, Jin Jikun, Sun Yufeng, Li Xingliang

2022, 29(5):  18-27.  DOI: 10.3969/j.issn.1006-6535.2022.05.003

Asbtract ( )   PDF (2272KB) ( )  

References | Related Articles | Metrics

The Shengbei structural zone has great potential for tight oil and gas resources, with many oil and gas-bearing formations, and industrial oil and gas have been obtained in several formations including the Middle Jurassic and Cretaceous, and the discovered oil and gas reservoirs are dense. In view of the low degree of research on the oil and gas filling mechanism in the process of oil and gas accumulation, the microscopic testing technology of reservoir fluid inclusions was adopted, combined with the simulation results of formation burial history, thermal evolution history and hydrocarbon source rock maturity history, to analyze the oil and gas filling time and accumulation period, and to study the accumulation mechanism and enrichment law. The results show that the Shengbei structural zone mainly has two oil and gas accumulation periods, namely Late Jurassic-Early Cretaceous and Neogene-Quaternary; the hydrocarbon source rocks of the Shuixigou Group have two times of hydrocarbon generation and expulsion, in the Late Jurassic-Early Cretaceous and Neogene, respectively. The hydrocarbon generation and expulsion period of lacustrine mudstone in Qiketai Formation was dominated by Neogene; the hydrocarbon accumulation was controlled by oil source faults, sand body connectivity and fault sealing. The hydrocarbon source rocks are developed in the northeastern part of the Shengbei Sag, the formation is overpressured, the deep and large faults are developed, and the sandstone reservoirs are superimposed and distributed in different strata, so this area is favorable for oil and gas exploration. The research results have guiding significance for the Middle Jurassic tight gas exploration in the Shengbei Sag, Turpan-Hami Basin.

Key technologies and Applications of Seismic Prediction for Lacustrine Shale Oil in the Fourth Member of Shahejie Formation in Damintun Sag

Chen Chang

2022, 29(5):  28-35.  DOI: 10.3969/j.issn.1006-6535.2022.05.004

Asbtract ( )   PDF (2807KB) ( )  

References | Related Articles | Metrics

The lacustrine shale oil formation in the fourth member of Shahejie Formation in Damintun Sag is complex in lithology, thin in effective thickness, and rapid in reservoir change. The “sweet spots” prediction using the conventional post-stack seismic method has a low accuracy, which restricts the economical and effective production of shale oil resources. In view of the geological characteristics of shale oil in the study area, a number of key technologies such as seismic data optimization processing, joint inversion of pre-stack elastic parameters, and effective fracture prediction have been explored and developed, with the aim of improving the prediction accuracy of “sweet spots”. In terms of seismic data processing, a broadband amplitude preservation processing technology idea with “full Q compensation” as the core has been developed, the gather quality and frequency bandwidth have been effectively improved, enhancing the ability to solve complex geological problems with seismic methods; in terms of reservoir prediction, the pre-stack elastic parameter joint inversion technology and AVOZF inversion technology have been comprehensively applied, so that the high-resolution prediction of geological parameters such as lithology, brittleness, TOC content and effective fractures has been achieved, the favorable areas for the distribution of shale oil “sweet spots” in the fourth member of Damin Tunsha have been identified, and the area of Class Ⅰ and Class Ⅱ “sweet spots” is 143 km². The field practice results show that the geological evaluation results of the newly drilled horizontal wells are highly consistent with the reservoir prediction, and the drilling catching rate of the reservoir is 66.4%. The research results provide strong technical support for the exploration and development of shale oil resources in Damintun Sag.

Characteristics and Indicative Significance of Carbon Isotopes of Marine Shale Gas in Sichuan Basin

Wu Jin, Li Wei, Liu Xin, Xu Hao, Deng Naier, Ren Zihe, Liu Guiying

2022, 29(5):  36-41.  DOI: 10.3969/j.issn.1006-6535.2022.05.005

Asbtract ( )   PDF (1765KB) ( )  

References | Related Articles | Metrics

In order to determine the carbon isotope characteristics and geological significance of shale gas in Sichuan Basin, shale gas samples in Fuling, Changning, Pengshui and Weiyuan were analyzed with gas spectrometer and other analytical methods. As found in the results, the shale gas in the study area was mainly composed of methane with a content ranging from 96.100% to 99.400%, and mixed with a small amount of ethane and propane; the non-hydrocarbon gases were dominated by N₂ and CO₂, and traces of helium from 0.01% to 0.03% were present; the carbon isotope of CO₂ was -12.5‰ to 8.9‰, indicating that CO₂ was sourced from organic and inorganic genesis. At present, carbon isotopic inversion sequence (δ¹³C₃ <δ¹³C₂ <δ¹³C₁) has been found in shale gas fields in Sichuan Basin, which is mainly caused by mixing of hydrocarbon gases from different sources, reaction between gases and minerals, and fractional distillation in alkane desorption/diffusion. The degree of carbon isotope inversion in shale gas is bound up with the confinement of the shale strata, as the self-confinement of the shale strata directly affects the degree of hydrocarbon expulsion and gas diffusion. In addition, there is a positive correlation between shale gas production and inversion degree, indicating that the carbon isotope characteristics of shale gas are important indicators for shale gas production prediction and preservation conditions and enrichment pattern evaluation. The results of the study are of guidance for the further exploration of marine shale gas in Sichuan Basin.

Genesis Analysis of Low Saturation Oil Reservoirs in Badaowan Formation of Mosuowan Bulge in Junggar Basin

Yang Chaohong, Sima Liqiang, Wang Liang, Wang Gang

2022, 29(5):  42-48.  DOI: 10.3969/j.issn.1006-6535.2022.05.006

Asbtract ( )   PDF (1766KB) ( )  

References | Related Articles | Metrics

In view of the lack of reservoir physical properties and the influence of barriers and interlayers on low oil saturation in the previous studies of the genesis of the Badaowan Formation reservoir in the Mosuowan Bulge, Junggar Basin, the analysis of reservoir low-saturation genesis was carried out from the aspects of pore structure, reservoir physical properties and heterogeneous barriers and interlayers, and the influences of structural amplitude on oil-water variation, reservoir physical properties on thickness of oil-water co-producing area, and barriers and interlayer on oil saturation were analyzed. The result shows: (1) The lack of obvious oil-water variation and incomplete oil-water replacement in the reservoir due to poor pore structure are the main reasons for the low oil saturation of the Badaowan Formation reservoir; (2) The relatively large oil-water co-production thickness caused by the physical properties of low porosity and permeability of the reservoir is the secondary reason for the low oil saturation of the Badaowan Formation reservoir; (3) Since the Badaowan Formation does not form regional and continuous barriers and interlayers, the barriers and interlayers have little effect on the low oil saturation of the Badaowan Formation reservoir. The research results will provide a basis for the efficient development of the Badaowan Formation and accelerate the exploration and development process.

Reservoir Characteristics and Main Controlling Factors of the Fourth Member of Shahejie Formation in Niuxintuo Area of Western Liaohe Sag

Zhou Xiaolong

2022, 29(5):  49-56.  DOI: 10.3969/j.issn.1006-6535.2022.05.007

Asbtract ( )   PDF (2962KB) ( )  

References | Related Articles | Metrics

Large-scale conglomerate bodies are developed in the fourth member of the Shahejie Formation in the Niuxintuo Area of the western Liaohe Sag. Influenced by the depositional environment, the reservoir performance of different facies varies greatly, which restricts the in-depth exploration of conglomerate reservoirs in this area. To this end, the petrological characteristics of the reservoir and the main controlling factors of the high-quality reservoir were studied for the clastic rocks of the Shahejie Formation in the Niuxintuo Area using a combination of core, thin section identification, physical property testing and logging and other analytical methods. The result shows: The rock types of the fourth member of the Shahejie Formation in the Niuxintuo Area are dominated by feldspar sandstone and lithic feldspar sandstone, and the reservoir pores are mainly composed of primary pores, secondary dissolution pores and fractures. The reservoir is generally a medium-low porosity and low-permeability reservoir. The physical properties of the reservoir are controlled laterally by deposition and longitudinally by burial depth. The comprehensive analysis shows that sedimentation, burial depth and fracture are the main controlling factors of the high-quality reservoir in the study area, and the front edge of the fan delta is a favorable reservoir facies zone, which is the key area for the next step of exploration. The research results have certain guiding significance for the in-depth exploration of the Niuxintuo Area and similar sags.

Hydrocarbon Accumulation Characteristics and Exploration Potential of Permian Volcanic Rocks in Madong Area

Lian Zhigang, Chang Zhiyong, Li Lulu, Lai Jifeng, Peng Long, Liu Rui

2022, 29(5):  57-65.  DOI: 10.3969/j.issn.1006-6535.2022.05.008

Asbtract ( )   PDF (6719KB) ( )  

References | Related Articles | Metrics

In view of unclear Permian tectonics in Madong Area and unclear favorable hydrocarbon accumulation zone in the target bed series, a comprehensive geological evaluation method and seismic reservoir prediction technology were used to deepen the study on the tectonics, sedimentation and hydrocarbon accumulation of the Permian Jiamuhe-Xiazijie Formation in Madong Area, the geological characteristics of the Permian volcanic rock reservoir in Madong Area were determined, the favorable evaluation targets of Permian reservoir in Madong Area were optimally selected, and finally the wells were deployed and located. The results of the study presented that there were volcanic rock abnormalities developed on large scale in Well Block MD1 in Madong Area under a background of low convex, and the longitudinal favorable oil-bearing stratum was Permian Jiamuhe Formation, with clear characteristics of volcanic rock abnormalities and favorable accumulation conditions. It was recommended to locate Appraisal Well MD103 in Well Block MD1, which urgently needs to be deployed for drilling to achieve a major breakthrough in Permian Formation in Madong Area. The results of the study were of important guidance and reference significance for the exploration of deep volcanic rock abnormalities in Madong Area.

Accumulation Regularity of Clastic Rocks in Ludong Sag of Kailu Basin

Zhang Ruixue

2022, 29(5):  66-71.  DOI: 10.3969/j.issn.1006-6535.2022.05.009

Asbtract ( )   PDF (1323KB) ( )  

References | Related Articles | Metrics

In response to the problem of poor understanding of the accumulation law of clastic rock reservoirs in Ludong Sag of Kailu Basin, the accumulation of clastic rock was explored through the study of sedimentary evolution, reservoir characteristics and pore evolution on the basis of fine tectonic interpretation. The result shows: The uneven development of faulted basins makes most of the oil and gas accumulate in favorable facies zones adjacent to hydrocarbon-generating sags; the clastic rock reservoirs in Ludong Sag has an average pore radius of 4.57-9.56 μm and average throat radius of 3.02-8.33 μm, so it is poor in overall seepage ability, causing difficulties for oil and gas to migrate over long distances, and it is close-sourced and quasi-continuous. Based on the study of clastic sedimentation, reservoir formation and accumulation, the oil and gas accumulation model of Ludong Sag was established. The research results lay a certain theoretical foundation for the exploration of low-permeability oil and gas reservoirs in the Ludong Sag, and have important guiding significance for the oil and gas exploration of similar oil reservoirs.

Study on Geological Evaluation and Key Technologies for Shale Reservoirs in Northern Songliao Basin

Zhang Bing

2022, 29(5):  72-79.  DOI: 10.3969/j.issn.1006-6535.2022.05.010

Asbtract ( )   PDF (1221KB) ( )  

References | Related Articles | Metrics

In recent years, breakthroughs have been made in the exploration and development of shale oil in Northern Songliao Basin. Currently, there is a lack of analysis and summary of the geological conditions for hydrocarbon accumulation and the characteristics of oil and gas reservoirs in Northern part Songliao Basin. To this end, based on the investigation on the exploration and development technologies of shale oil and gas reservoirs at home and abroad, a comparative analysis of six parameters, including burial depth, thickness and reservoir conditions, was performed in combination with the geological and engineering data of shale reservoirs. The results of the study showed that the favorable areas in shale oil and gas reservoirs with high value for commercial development are high pressure shale oil and gas reservoirs rich in organic substances, which are characterized by tectonic stability, high formation pressure coefficient and thick high quality shale. The impact of geological conditions on the development of shale oil and gas reservoirs was also investigated. It was concluded that the degree of thermal evolution, brittleness and burial depth were favorable to the preservation of shale oil and gas, and that drilling and zoning should be done in fractured areas as far as possible to facilitate reservoir stimulation. At the same time, there are some similarities in sequence stratigraphy, geochemical characteristics and production characteristics of shale reservoirs. In terms of development, new technologies and future development of shale oil and gas reservoirs, such as drilling and completion, fracturing stimulation and production optimization, were systematically studied. There is much for reference of the study results to the exploration and development of shale oil and gas reservoirs and large-scale production of Songliao Basin, and to the later selection and well deployment of shale oil and gas zones in Songliao Basin.

Reservoir Engineering

Pore Structure Characteristics and Natural Depletion Law of Deep High-pressure Carbonate Gas Reservoirs

Chen Jianxun

2022, 29(5):  80-87.  DOI: 10.3969/j.issn.1006-6535.2022.05.011

Asbtract ( )   PDF (2540KB) ( )  

References | Related Articles | Metrics

Deep carbonate gas reservoirs with complex pore structure and large variation in productivity challenge the efficient development and long-term stable production, and there is an urgent need to conduct targeted study on the law of natural depletion under stratigraphic conditions. To this end, the pore structure of gas reservoirs was characterized in detail with secondary CT scanning technology, and the influence of pore structure and irreducible water on natural depletion under stratigraphic conditions was investigated by core tests. The results showed that, the uneven development and distribution of pores and fractures was the root cause for the strong heterogeneity and large variation in productivity of this type of gas reservoir; the gas production was mainly controlled by the porosity, and the recovery efficiency was close to a logarithmic relationship with permeability; when the downhole pressure was 15 MPa, the average recovery efficiencies of porous, vuggy, fractured porous and fractured vuggy reservoirs were 47.43%, 48.21%, 59.90% and 62.14%, respectively; the reserve, gas production and recovery efficiency of the fractured porous reservoir were relatively high; the vuggy reservoir was featured by high reserve and low gas production rate, with an obvious characteristic of high porosity and low production; the fractured porous reservoir was characterized by low reserve, fast gas production rate and short stable production period; the porous reserve was relatively low both in reserve and gas production rate. The results of the study provide a theoretical basis for the development plan design of deep high pressure carbonate gas reservoirs.

Characteristic Analysis and Control of Gravity Fire Flooding Based on Numerical Simulation

Yu Xuefeng

2022, 29(5):  88-93.  DOI: 10.3969/j.issn.1006-6535.2022.05.012

Asbtract ( )   PDF (1705KB) ( )  

References | Related Articles | Metrics

The gravity fire flooding is an important replacement method after steam injection in medium-deep thick heavy oil reservoirs. In order to clarify its sweep characteristics and control technology, a numerical simulation model of gravity fire flooding was established based on the relevant data of the gravity fire flooding block in Liaohe Oilfield, and the zonal characteristics, production change law and production control conditions of gravity fire drive were studied. The research shows: The oil production of horizontal wells through gravity fire flooding is mainly caused by vertical flow due to the increase of vertical upward mobility; the production dynamics of gravity fire flooding can be divided into four typical stages: establishment of cavity connectivity, lateral spreading effectiveness, stable combustion for oil drainage, and breakthrough decrement. The minimum gas injection rate can be calculated according to the formula of the ellipsoid model, and it is better to use 2 times of the theoretical calculated gas injection rate for production design; setting a certain back pressure can effectively suppress gas channeling to achieve balanced expansion of the fire line, and the optimal discharge-injection ratio is 1. The research results provide a basis for guiding the engineering design of gravity fire flooding mines.

Characteristics of Multi-Scale Pore-Fracture Structure of Deep Coal Rocks in the Daning-Jixian Block

Yang Xiuchun, Song Bairong, Chen Guohui, He Rui, Zhao Haoyang, Yang Xiao

2022, 29(5):  94-100.  DOI: 10.3969/j.issn.1006-6535.2022.05.013

Asbtract ( )   PDF (2035KB) ( )  

References | Related Articles | Metrics

In response to the problem that it is difficult to quantitatively characterize the complex multi-scale pore-fracture structure of deep coal rock reservoirs in the Daning-Jixian Block with a single technical method, a multi-scale digital core technology is adopted to scan and analyze coal and rock samples based on full-diameter CT scanning, micro-CT scanning, FIB-SEM scanning, and argon ion polishing field emission scanning electron microscopy and other experimental methods. The result shows: The multi-scale pore-fracture systems develop in the deep coal rocks in the Daning-Jixian Block. The nano-scale development is dominated by stomatal and tissue pores, the micro-scale development is dominated by micro-fractures and mineral dissolved pores, and the millimeter-scale development is high-angle fractures and cleat assemblages. The full-diameter CT scanning technology can effectively identify millimeter-scale fractures, cleats and dissolved pores. The core hole-fracture model of the coal section of Well D20 is established, and the calculated fracture porosity is 1.55%, the fracture density is 22.5 pieces/m, and the average opening of fractures is 1.1mm; the average radius of micro-pores is 2.99-4.15 μm, the average radius of micro-throat is 1.16-1.80μm; the average opening of micro-fractures is 3.75-4.84 μm; the average radius of nano-pores is 51.21-80.65 nm, the average radius of the nano-throat is 19.44-32.06 nm; the multi-scale distribution characteristics are obtained through the splicing of micro- and nano-pore data. The number of micro-pores is the largest, with the average surface area accounting for 63.68%, while the number of macro-pores (greater than 103 nm) is small but contributes a large amount of pore volume. The research results can provide technical support for the exploration and development of deep coalbed methane.

Formation Parameter Inversion Method Based on Early Production Decline Analysis of Oil Well

Sun Zhaole, Cheng Linsong, Jia Pin, Jin Ziyi, Zhang Xiangyang

2022, 29(5):  101-106.  DOI: 10.3969/j.issn.1006-6535.2022.05.014

Asbtract ( )   PDF (1509KB) ( )  

References | Related Articles | Metrics

In the initial stage of production of oil wells, affected by the production system, the production is unstable, and the conventional production decline analysis method is not applicable. To solve this problem, by means of transforming the variable production pressure solution of oil wells into the constant production pressure solution under Duhamel’s principle, a data analysis method suitable for early variable output production of oil wells is obtained through introducing material balance time and normalized production, and the mathematical model is used to fit the processed data, so as to obtain the inversion of reservoir parameters. Taking Well P1-2 in Daqing Oilfield as an example, the daily oil production and bottom-hole flow pressure production data were used to quantitatively analyze the production dynamics of a single well, and the regularized production-material balance time double logarithmic curve chart was plotted to perform the quantitative inversion interpretation of the real physical parameters of the formation. The results show that after the method is used to analyze the production data of variable output, the curve exhibits the characteristics of unstable flow and distinct segmentation of the boundary flow in the conventional decline plot. The practical application shows that the average error of this method is less than 10%, and the accuracy is high. This study can provide theoretical guidance for the early productivity analysis of oil wells.

Change Law of Reservoir Characteristics after Water Flooding of C₆ Low Permeability Reservoir in W Oilfield

Shao Xiaoyan, Yang Xuewu, Meng Lingwei, Yue Wencheng, Mo Lei, Cai Tao, Liu An

2022, 29(5):  107-112.  DOI: 10.3969/j.issn.1006-6535.2022.05.015

Asbtract ( )   PDF (2909KB) ( )  

References | Related Articles | Metrics

In response to the problem that the change law of reservoir characteristics before and after water flooding in the C₆ low-permeability reservoir in W Oilfield is unclear, the X-ray diffraction, scanning electron microscope, casting sheet, mercury injection experiment, phase permeability experiment and real sandstone microscopic seepage experiment were applied to study the change law of reservoir lithology, physical properties and seepage characteristics before and after water injection, and to analyze the mechanism and influence reasons of reservoir characteristics change. The research result shows: After water flooding, the total amount of clay minerals shows a decreasing trend as a whole, and the content of calcite increases. Among the clay minerals, the content of illite decreases and the content of chlorite increases slightly; Before and after long-term water flooding of rock samples, the median radius of pore throats of rock samples with good physical properties becomes larger, the permeability increases, and the heterogeneity becomes weak, while the median radius of pore throats of rock samples with poor physical properties becomes smaller, the permeability decreases, and the heterogeneity becomes stronger. The phase-permeability curve after flooding shifts to the left as a whole, the hydrophilicity of the rock weakens, the residual oil saturation increases, the water breakthrough time is earlier, and the water cut rises faster. The long-term scouring of injected water will cause certain damage to the reservoir, and the displacement effect of water-flooding oil will become worse. The research results provide a basis for the description, development effect evaluation and development plan adjustment of low permeability reservoirs.

Simulation Study on the Effect of Gypsum-salt Content on Hydrocarbon Generation in Mature Stage Shale

Meng Qingqiang, Li Jingzhou, Liu Wenhui, Fu Qi, Wang Xiaofeng, Wang Jie

2022, 29(5):  113-118.  DOI: 10.3969/j.issn.1006-6535.2022.05.016

Asbtract ( )   PDF (1289KB) ( )  

References | Related Articles | Metrics

Gypsum-salt rock layers of different thicknesses are developed in the source rock strata of marine and continental basins in China. In order to investigate the influence of the variation of paste rock content on the hydrocarbon generation process and product characteristics of source rocks, taking the shale of Eagle Ford Formation in Permian Basin of the United States as source rock, hydrocarbon generation simulations were made by adding natural gypsum-salt rocks with different mass fractions to analyze the characteristics of the liquid products retained in the solid reactants. The results showed that: with the increase of the mass fraction of gypsum-salt rock, the retained hydrocarbon yield of the marine source rock presented a U-shaped curve of “decreasing then increasing”, and the content of gypsum-salt rock had a linear relationship with the relative content of saturated hydrocarbons, indicating that the gypsum-salt rock could significantly improve the quality of crude oil; the content of gypsum-salt rock was positively correlated with the parameter values of Pr/Ph, U/R and other biomarker compounds, and the influence of gypsum-salt rock content should be fully considered in the application of parameters. The results of the study are important reference for the accurate evaluation of shale oil reserve potential and the identification of the main controlling factors of shale oil quality variation.

Interlayer Interference Pattern and Adjustment Countermeasures of Offshore Thin Interbedded Sandstone Reservoirs

Sun Pengxiao

2022, 29(5):  119-125.  DOI: 10.3969/j.issn.1006-6535.2022.05.017

Asbtract ( )   PDF (1620KB) ( )  

References | Related Articles | Metrics

Thin interbedded sandstone reservoir is disadvantaged by complicated conditions, various main controlling factors of interstratigraphic disturbances, and difficult prediction of interstratigraphic disturbance law, exerting great impact on the overall development efficiency of the oilfield. To address this problem, based on the mechanism of interlayer interference in thin interbedded sandstone reservoirs, the main controlling factors of interlayer interference in thin interbedded sandstone reservoirs were clarified by reservoir engineering methods. According to the dynamic analysis of actual oilfield production, the dynamic and static flow capacities of the sub-bed was quantitatively evaluated, a quantitative prediction chart was prepared for interlayer interference throughout the whole life under the joint action of physical properties, fluid properties, injection and production effects, water logging and other factors of the sub-bed, and targeted countermeasures for bed series adjustment were proposed. It was found in the study that, the interstratigraphic disturbances in thin interbedded sandstone reservoirs exhibited different dynamic patterns under different flow capacities, and the effects of dynamic and static factors should considered comprehensively; interstratigraphic disturbances in sub-beds with flow capacity difference coefficients of 7.0 or less are relatively weak at the initial stage, and such sub-beds could be considered as one system for development; the interstratigraphic disturbances were intensified in the sub-beds under heavy water flooding after the medium and high-water-cut stage. The study results have an exemplary significance regarding the division and adjustment of thin interbedded sandstone reservoirs.

Test of CO₂ Miscible Fracturing and Huff and Puff

Wu Junfeng, Liu Baozhong, Liu Daojie, Wang Changquan, Li Yinghui, Liu Guohua

2022, 29(5):  126-131.  DOI: 10.3969/j.issn.1006-6535.2022.05.018

Asbtract ( )   PDF (1583KB) ( )  

References | Related Articles | Metrics

To address the problem of poor development of conventional hydraulic fracturing in V Formation of Fault Block Gao 5, Nanpu Sag, PVT and core miscible huff and puff tests were conducted to clarify the mechanism of enhancing oil recovery by CO₂ miscible fracturing and huff and puff, and the technical effectiveness was further verified by field tests. The study results showed that: at the current formation pressure (33.00 MPa), CO₂ and crude oil could be mixed, and the crude oil volume was expanded by 41.01%, the viscosity decreased by 33.08%, and the density increased by 7.28% after the injection of CO₂ with a mole fraction of 60%, and CO₂ was effective in solubilization, expansion and viscosity reduction of crude oil; the recovery efficiency could reach more than 60% by miscible fracturing and huff and puff. After CO₂ miscible fracturing and huff and puff, the production of test wells was stable for 26 months, with a cumulative increase of 2 200 t in oil production, and the heavy components of crude oil were effectively utilized. The study provides an effective technical approach for the profitable development of low-permeability tight reservoirs.

Experimental Test Method and Application of High-Pressure Wax-Bearing Condensate Gas Wax Precipitation Point

Xie Yang, Liu Jianyi, Wang Chunpu

2022, 29(5):  132-138.  DOI: 10.3969/j.issn.1006-6535.2022.05.019

Asbtract ( )   PDF (2544KB) ( )  

References | Related Articles | Metrics

To address the problem of low accuracy of wax precipitation point testing of high-pressure wax-bearing condensate gas in the gas phase, a set of high-pressure visualized fluid phase change observation device based on polarized light microscopy method was developed with reference to the preferred viscosity-temperature curve method, differential scanning calorimetry method and polarized light microscopy method to experimentally study on the wax precipitation point law of the wax-bearing condensate gas well fluid and gas-bearing oil under different pressures. The result shows: The wax precipitation point measured by polarized light microscopy method is more accurate than that by the viscosity-temperature curve method and differential scanning calorimetry method. The newly developed high-pressure visualized fluid phase change observation device can accurately test the wax precipitation point of wax-bearing condensate gas well fluid and gas-bearing oil. The wax precipitation point of the wax-bearing condensate gas well fluid first decreases and then increases with the increase of pressure, and then decreases after passing the dew point, and the wax precipitation line divides the well fluid wax precipitation phase diagram into such four parts as the single gas phase, gas-liquid phase, gas-solid phase and gas-liquid-solid phase; the wax precipitation point of gas-bearing oil first decreases with the increase of pressure, and begins to increase linearly when the pressure increases to the saturation pressure. The research results provide a new method for accurate test of the wax precipitation point of high-pressure wax-bearing condensate gas.

Drilling & Production Engineering

Analysis Model and Influencing Factors of Passability of Coiled Tubing Conveying Clustered Perforating String

Liu Jun, Du Zhigang, Mu Shaomin, Wang Muwei, Zhang Min, Yin Teng, Yu Hai, Cao Dayong

2022, 29(5):  139-148.  DOI: 10.3969/j.issn.1006-6535.2022.05.020

Asbtract ( )   PDF (3183KB) ( )  

References | Related Articles | Metrics

To address the problem that the coiled tubing gets stuck in wells when conveying the clustered perforating string, considering the influence of wellbore trajectory, wellbore constraint, tool string variable diameter structure, tool deformation and coiled tubing buckling effect, the micro-element method was adopted to establish an analysis model of the passability of the coiled tubing conveying clustered perforating string to analyze the passability of the coiled tubing conveying 1 bridge plug + 2 clustered perforating guns string in the wellbore. The research shows: The operation tool string will not be stuck during the running process, and the coiled tubing conveying clustered perforating string can go down to the predetermined well depth of 3850m; the longer the vertical section and the shorter the horizontal section, the better the wellbore trajectory is for running the pipe string; the smaller the number of perforation clusters, the smaller the size of the perforating gun, and the larger the coiled tubing size, the better the passability of the tubing string. The analysis method can provide technical support for the operating parameters optimization and operation of the coiled tubing conveying the perforating string on site.

Development and Application of Ball-Actuated Multifunctional Oil Pump

Wu Fei

2022, 29(5):  149-153.  DOI: 10.3969/j.issn.1006-6535.2022.05.021

Asbtract ( )   PDF (3236KB) ( )  

References | Related Articles | Metrics

Multiple trips of the pipe string during sand flushing, water blocking, steam huff and puff, et al. of the heavy oil production wells lead to the problems of high cost of measures and low production rate. To this end, a ball-actuated multifunctional oil pump is developed in consideration of the actual needs of the site. On the basis of the conventional tubular oil pump, an open fixed valve assembly was developed, and the structure of the core components such as the slider sleeve, the support spring, and the fixed valve seat were optimized and designed to form three types of ball-actuated multifunctional oil pumps. Before the ball is actuated, the pump pipe is used to implement the corresponding measures for the oil well. After the measures are implemented, the fixed ball is actuated, the sucker rod and piston are run in, and the pump can be directly transferred to production, which makes the operation link of pulling up the pipe string and running the pump again omitted, and meets the on-site requirements of one-time pipe string completion for oil well steam injection, sand flushing, water blocking and other processes. This technology has been applied for 29 well times in total, with a success rate of 100%. The ball-actuated multifunctional oil pump can effectively simplify the operation and construction process, reduce the operation cost, improve the production rate of oil wells, and provide technical support for the efficient production of heavy oil wells.

Optimal Design of Artificial Fracture Network for Shale Gas Volume Stimulation

Jiang Hai, Xiao Yang, Wang Dong, Liu Ziping, Wang Jiahao, Zhao Di, Zou Longqing

2022, 29(5):  154-160.  DOI: 10.3969/j.issn.1006-6535.2022.05.022

Asbtract ( )   PDF (4785KB) ( )  

References | Related Articles | Metrics

Due to the tight reservoirs in the Weiyuan shale gas block, the local development of natural fractures, and the strong reservoir heterogeneity, the conventional horizontal well staged fracturing technology cannot meet the productivity demand. To address the problem, taking Wei AH1 platform as an example, an integrated fracturing model for the Wei AH1 platform was established based on the technical idea of integrated geological engineering, geological property model and geomechanical model. The model was used to analyze the fracturing displacement, fracturing fluid volume, sand ratio, number of clusters, proppant ratio and injection method, and to determine the optimal parameters of fracturing operation. The research results were applied to 8 wells on the Wei AH1 platform, and the daily gas production was increased by 30% compared with that before the fracturing. This research can provide technical support for the integrated development of shale gas in Weiyuan Area.

Development and Application of Self-Priming Continuous Sand Flushing Technology Supporting Device for Low-Pressure Absorption Wells

Guan Endong

2022, 29(5):  161-165.  DOI: 10.3969/j.issn.1006-6535.2022.05.023

Asbtract ( )   PDF (1464KB) ( )  

References | Related Articles | Metrics

In the middle and late stages of oilfield development, due to the severe formation deficit and the intensified sand production in the oil layer, an effective circulation was not be established through the conventional sand flushing process or the use of temporary plugging agent for sand flushing, thus affecting the normal production of oil wells. The self-priming continuous sand flushing process for low pressure absorption wells is one of the effective technologies to solve this problem, but in actual use, there are problems such as cumbersome procedures, large loss of sand flushing fluid, and sand plugging. To this end, supporting tools such as two-stage integral pipe string and forced circulation valve have been developed, thereby improving and perfecting the self-priming continuous sand flushing technology for low pressure absorption wells. This technology has been applied for 300 well times, restoring oil well productivity up to 5000t, with good application results. This technology can provide technical support for the resumption of production of oil wells with sand production due to formation deficit.

Sensitivity Evaluation of Ultra-low Permeability Sandstone Reservoir and Development of Acidizing Stimulation Fluid

Zhang Jinfa, Li Ting, Wu Jingyu, Guan Yingzhu, Xu Mo, Dan Zhihua, Zhou Mingxiu

2022, 29(5):  166-174.  DOI: 10.3969/j.issn.1006-6535.2022.05.024

Asbtract ( )   PDF (2774KB) ( )  

References | Related Articles | Metrics

Acidizing is an important stimulation measure for ultra-low permeability sandstone reservoirs. If the acid fluid system is not used properly, it will cause sensitive damage to the reservoir. To this end, taking the sandstone reservoir of Sanjianfang Formation in Shanshan Oilfield, Turpan-Hami Basin as an example, the characteristics of reservoir sensitivity and damage mechanism were studied by means of XRD diffraction analysis, scanning electron microscope, reservoir sensitivity evaluation experiment and field data collation, and an acidizing stimulation fluid was developed, which could be used in combination with mud acid to improve the acidizing effect. The research shows: The rock types of the Sanjianfang Formation reservoirs are mainly feldspar lithic sandstone, and the clay minerals are mainly kaolinite and montmorillonite, which belong to high clay mineral reservoirs. The reservoir physical properties as a whole show the characteristics of low porosity and extra-low permeability, the crude oil is light crude oil, and the reservoir is unsaturated reservoir with normal formation pressure. The reservoir has moderate to weak velocity-sensitive, alkali-sensitive, water-sensitive, salinity-sensitive, and weak acid-sensitive properties. The combined acid fluid system of stimulation fluid and soil acid can dissolve pores of various scales such as macropores and micropores to form a pore network system, which can increase the permeability of the target reservoir core to a maximum of 2.68 times the original permeability. The field application effect is remarkable. Compared with that before acidizing, the average daily oil production of a single well increases by 1.29 t/d. The research results can provide technical support for acidizing stimulation of ultra-low permeability sandstone reservoirs.