Table of Content

25 October 2020, Volume 27 Issue 5

Previous Issue    Next Issue

Summary

Prospect of Paleozoic Oil and Gas in Northeast China

Kang Yuzhu, Wang Jiwei

2020, 27(5):  1-6.  DOI: 10.3969/j.issn.1006-6535.2020.05.001

Asbtract ( )   PDF (2145KB) ( )  

References | Related Articles | Metrics

Great progress has been made in Paleozoic oil and gas exploration in China. Several large and medium-sized oil and gas fields have been found in the Tarim, Sichuan and Ordos Basins. However, there are still divergences on the amounts of the Paleozoic oil and gas resources in northeast China. On the basis of predecessors’ studies, this paper summarizes and discusses the Paleozoic stratigraphic sedimentation, hydrocarbon resource potential, oil-forming assemblage and hydrocarbon accumulation conditions in northeast China, and points out the directions of oil and gas exploration. The study shows that:The northeast China during Late Paleozoic consisted of Ergun, Songnen-Zhangguangcai Mt., Jiamusi and Xingkai micro landmasses. The Paleozoic strata in this area are relatively developed completely on the pre-Sinian crystalline metamorphic basement. The Lower Paleozoic is marine sediments, and the Upper Paleozoic is paralic sediments.The magmatic activity in northeast China was very strong with complete lithologies. The Hercynian magmatic activity was the most prominent, mainly intermediate acid volcanic rocks.The Paleozoic strata in northeast China are completely developed with multiple sets of source rock-reservoir-cap rock assemblages. The oil and gas accumulation conditions are favorable, dominated by tight gas. It is the main domain for natural gas exploration in the future.

Geologic Exploration

Characteristics and Controlling Factors of Permian Reef Beach Reservoir in Platform-Depression Margin of Eastern Sichuan Basin

Jiang Yuqiang, Diao Zhilong, Xu Changhai, Feng Liang, Gu Yifan, Yi Juanzi

2020, 27(5):  7-13.  DOI: 10.3969/j.issn.1006-6535.2020.05.002

Asbtract ( )   PDF (3960KB) ( )  

References | Related Articles | Metrics

In view of the unclear understanding of the reservoir characteristics and main controlling factors of the Permian Changxing Formation in the platform-depression margin in eastern Sichuan Basin, this paper discusses the reservoir characteristics of the reef beach and the controlling effect of the reef beach sedimentation and diagenesis transformation on the Changxing Formation reservoir by using the methods of thin section identification, core observation and conventional physical property analysis. The results show that the reservoir rock types of the reef beach reservoir in the study area are bioclastic dolomite and reef dolomite. The main reservoir space types of bioclastic dolomite are intercrystalline pores, intercrystalline dissolved pores and non-fabric selective dissolved pores (vugs), while that of the reef dolomite consists of organic lattice pores and non-fabric selective dissolved pores (vugs). The reservoir physical properties are generally characterized by low-medium porosity and low permeability. The controlling factors of the reservoir include the material basis in the sedimentary stage and the dolomitization transformation in the syndiagenetic stage. In the sedimentary stage, along the high-energy zone in the platform-depression margin, belt-like discontinuous reef beaches were formed, which provided a material basis for dolomitization transformation in the later period. The medium-salinity seawater formed in syndiagenetic stage carries out dolomitization transformation on reef beaches along the primary pore spaces of reef beaches that have not been completely cemented by calcite of the first and second stages, which is the key factor for the formation of reef beach dolomite reservoir. The research results can provide strong support for the exploration expansion of reef beach gas reservoir in the Changxing Formation of eastern Sichuan Basin.

Sedimentary Characteristics and Development Potential of Vendian Transitional Facies in East Siberian Platform

Zhang Yukun, Yang Shuo, Guo Xiao, Wang Shuai, Wang Hui, Song Laiming

2020, 27(5):  14-21.  DOI: 10.3969/j.issn.1006-6535.2020.05.003

Asbtract ( )   PDF (4074KB) ( )  

References | Related Articles | Metrics

The Vendian clastic reservoirs in the East Siberian Platform are an important growth point of oil and gas development in Russia in the future. However, the reservoirs in this area have a long geologic history and complicated geological characteristics, which makes them difficult to develop. Through the analysis of sedimentary characteristics and production performance characteristics, the predominant development reservoirs can be determined. According to the reservoir geological characteristics of the study area, combined with the comprehensive analysis of cores and thin section data, eight types of typical lithofacies are identified in the Lower Vendian Nepa Formation in the target oilfield; three sets of transgressive stratigraphic units and two sets of regressive stratigraphic units formed by periodic transgression during the sedimentary period are divided; a model of transitional facies from alluvial fan to barrier coast on plane is established; the plane distribution characteristics and sedimentary change rules in different periods of the main types of sedimentary facies (such as alluvial fan, tidal flat, barrier island and lagoon) are determined. Based on the production test and physical simulation experiment results, two types of predominant sedimentary facies (alluvial fan and barrier island) are identified; the feasibility of improving reservoir permeability by low-salinity water flooding is demonstrated. This study can provide geological basis for the exploration and development of this kind of clastic reservoirs in transitional facies.

Sedimentary Characteristics and Distinguishing Criteria of Crevasse Splay Reservoir in QHD 32-X Oilfield, Bohai Bay Basin

Chen Xinkai, Chen Cheng, Wang Hu

2020, 27(5):  22-29.  DOI: 10.3969/j.issn.1006-6535.2020.05.004

Asbtract ( )   PDF (1974KB) ( )  

References | Related Articles | Metrics

Fluvial deposits contain a large number of potential reservoirs represented by crevasse splay, but there are few separate discussions on crevasse splay. Taking QHD 32-X Oilfield in the Bohai Bay Basin as an example, the sedimentary characteristics and reservoir physical properties of crevasse splays were studied in detail in combination with core, well logging, and laboratory data. The results show that: in terms of qualitative identification, the grain size of crevasse splays is mainly fine sandstone, and silty-fine sandstone; the content of suspended loads is mostly 20%-50%; the gradation is worse; the roundness is angular to sub-angular; the lithofacies types are mainly massive bedding fine sandstone, sandy bedding fine sandstone/silty fine sandstone and horizontal bedding siltstone; the genetic sequence is mainly reverse rhythm; the thickness of single sand body is 0.2-3.0 m, and the distribution of sand bodies is lobe shaped on plane and wedge shaped on section;deep dual laterolog resistivity (Rd) values of the crevasse splays in the study area are between 1.8-7.5 Ω·m, with GR of 68-82 API; a crevasse splay that is saturated with oil or rich in oil has Rd values between 4.0-7.5 Ω·m, which can be used as a preliminary criterion for quantitative identification;the crevasse splays in the study area have average porosity of 29.26% and average permeability of 207.72 mD, belonging to high-porosity and medium-permeability reservoir, with excellent reservoir potential;however, the permeability of crevasse splay reservoirs is much lower than that of point bar and abandoned channel. In-depth study of crevasse splays is conducive to tapping potential and increasing reserves in old oil fields and prolonging the production life of depleted old wells.

Seismic Response Characteristics of Gas Chimneys in Junction Region of Yinggehai-Qiongdongnan Basins

Song Ruiyou, Hu Lin, Huang Yiwen, Hu Qianwei, Hou Jingxian

2020, 27(5):  30-37.  DOI: 10.3969/j.issn.1006-6535.2020.05.005

Asbtract ( )   PDF (5167KB) ( )  

References | Related Articles | Metrics

There are several anomalies in seismic fuzzy zones at the junction region of the Yinggehai Basin and the Qiongdongnan Basin in the northern South China Sea.There are many types of fuzzy bodies in the peripheral zones. Diapirs, submarine pockmarks and oil and gas seepage systems are developed in the western Yinggehai Basin. Volcanic activity was frequent in the northern Hainan uplift. Buried hill groups and volcanoes are developed in the eastern Qiongdongnan Basin. The exploration degree in this area is low, and the sealing conditions are scarce as the result of being near the provenance. Aiming at the problem that the geological types of the fuzzy zones are not clearly assigned in this area, the seismic response characteristics of the fuzzy zones are summarized. Combined with the formation mechanism and evolution law of various geological anomaly bodies, analogy analysis of seismic facies of the anomaly bodies in the peripheral zones was conducted, and the three-dimensional visualization characterization of the anomaly bodies was carried out. The study shows that these fuzzy zones have the characteristics of small scale, no magma capsule and shallow root, etc. Combined with the analysis of drilling data, these fuzzy zones are characterized as gas chimneys. The gas chimneys in this area are distributed in groups and zones, and are still active during the Late Quaternary, with active oil and gas migration, thus they are favorable oil and gas enrichment zones. The research results show that this area has a better exploration prospect, and the targets with good trap conditions can be used as the breakthrough direction for next exploration.

Technology and Application of Structural-Lithologic Trap Identification and Reservoir Characterization of Paleogene Steep Slope Fans

Yang Dongsheng, Zhao Zhigang, Xu Jianyong, Liu Zhifeng, Li Nan

2020, 27(5):  38-44.  DOI: 10.3969/j.issn.1006-6535.2020.05.006

Asbtract ( )   PDF (7321KB) ( )  

References | Related Articles | Metrics

Due to the lack of bright spot seismic reflection characteristics, it is difficult to identify traps and characterize reservoirs in the process of target evaluation for steep slope fans developed in oil generation sags. Taking LF 1-X target of Paleogene steep slope fan in the Lufeng sag of the Pearl River Mouth Basin as an example, by using various geophysical interpretation techniques such as paleogeomorphological analysis technology, three-dimensional visualization technology and prestack elastic inversion reservoir prediction technology, the technologies for identifying structure-lithologic target traps and characterizing reservoirs in Paleogene steep slope fans in the oil generation sags have been developed, which have effectively identified and characterized the trap and reservoir distribution of this sedimentary type. The research results show that fan delta reservoirs are well developed in the fifth Member of the Wenchang Formation (Wen 5 Member for short) in LF 1-X structure; the enrichment degree of lobes in the west side of the Wen 5 Member reservoir is higher than that of the east side; fan delta front is a favorable development site for high-quality reservoirs. The research results can be referred for the comprehensive evaluation of structural-lithologic targets in steep slope fans of oil generation sags.

Sedimentary Microfacies and Evolution Characteristics of Keshang Formation in Wuxia South Slope

Tu Zhijie

2020, 27(5):  45-52.  DOI: 10.3969/j.issn.1006-6535.2020.05.007

Asbtract ( )   PDF (4020KB) ( )  

References | Related Articles | Metrics

In order to clarify the sedimentary microfacies and evolution characteristics of the Keshang Formation in Wuxia south slope, through core and thin section observation, combined with well logging and mud logging data, the identification marks of rock types, sedimentary structure and logging facies were analyzed, sedimentary microfacies model was established, and sedimentary evolution characteristics were discussed. The research results show that the lithology of the Keshang Formation in Wuxia south slope is composed of glutenite, pebbled medium-fine sandstone, fine sandstone and mudstone, including grain sequence bedding, parallel bedding, massive bedding and scouring filling sedimentary structure. It belongs to delta depositional system, its provenance came from the north, and its channels were NE-SW trending. Sedimentary microfacies include underwater distributary channel, mouth bar, interdistributory bay, shore-shallow lake, sheet sand and crevasse splay. During the early stage of the Middle Triassic, the northwest part of the slope was strongly uplifted, and there were 2-3 main channels and well-developed mouth bars, forming two sets of thick sandstone and glutenite reservoirs. During the late stage of the Middle Triassic, shore lake sedimentary microfacies was developed, the distribution areas of underwater distributary channel and mouth bar microfacies decreased. There is a great potential for exploration of underwater distributary channels and mouth bars of the Keshang Formation, covering an area of 50-110 km². This study deepens cognitions on the sedimentary microfacies of the key strata in the Wuxia south slope of the Junggar Basin, and defines the distribution range of favorable sedimentary sand bodies, which can provide reference for further refining oil and gas exploration and development deployment.

Application of Microbial Geochemical Exploration Technology in Oil and Gas Exploration in Loess Tableland Regions

Cao Jun, Zhou Jinsong, Yin Xiao, Li Yuanyuan, Liu Peng, Ding Li, Liang Yongxing

2020, 27(5):  53-60.  DOI: 10.3969/j.issn.1006-6535.2020.05.008

Asbtract ( )   PDF (4635KB) ( )  

References | Related Articles | Metrics

The northern part of Fuxian County in Yanchang exploration area of the Ordos Basin is located in loess tableland region, and the degree of natural gas exploration is relatively low. Aiming at the problems of weak seismic response, poor applicability and difficult fluid detection in loess tableland region, a comprehensive study was carried out by using microbial geochemical exploration technology combined with oil and gas drilling and geological data. The study results show that: (1) significant microbial anomalies have been detected in the loess tableland region. (2) microbial and geochemical results indicate that the Yanchang exploration area has the characteristics of coexistence of oil and gas. (3) the study area can be divided into 9 microbial abnormal zones and 3 favorable zones. In which, the middle favorable zone indicates a good gas-bearing prospect, the northwest favorable zone has a better gas-bearing property, and the southeast favorable zone may be related to natural gas enrichment. Comprehensive research shows that microbial geochemical exploration technology has certain applicability in the evaluation of hydrocarbon-bearing properties in loess tableland regions. The research results can provide reference for screening favorable oil and gas zones in loess tableland regions.

Formation Mechanism and Distribution Models of Ordovician Reservoirs in Northern Jizhong Depression

Zhao Wenlong, Han Chunyuan, Yan Mengying, Qiao Bo, Luo Jing, Xue Hui, Guo Huiping

2020, 27(5):  61-67.  DOI: 10.3969/j.issn.1006-6535.2020.05.009

Asbtract ( )   PDF (1436KB) ( )  

References | Related Articles | Metrics

In order to solve the problem of unclear understanding of Ordovician buried hill reservoirs in northern Jizhong depression, on the basis of core observation, the basic characteristics, genetic types and main controlling factors of reservoirs in this area were studied by using drilling, well logging, analysis and laboratory data, etc. The results show that 4 sets of dolomite pore type and 1 set of karst fractured-vuggy type reservoirs are developed in this area. Lithology is mainly micritic-powdered crystal dolomite and calcareous dolomite, followed by micritic limestone. The reservoir space mainly includes intercrystalline (dissolution) pores, structural fractures and dissolution pores, etc. Through the study of the basic characteristics of the reservoirs, it is confirmed that the formation of favorable reservoirs is mainly controlled by factors such as rock type, fracture development degree and karstification intensity; rock type is the basis for controlling reservoir formation; fracture development degree is the key to restrict reservoir formation; karstification intensity controls reservoir advantages and disadvantages. Based on this, three reservoir development models of Ordovician in the northern Jizhong depression are established, namely, regional stratified model, regional massive-stratified composite model and local massive model, which provides basis for the establishment of reservoir-forming models and exploration deployment.

Structure Evolution and Middle-Shallow Hydrocarbon Enrichment Patters in the Eastern Wushi Sag

Hu Lin, Jin Qiuyue, Yang Xibing, Hu Desheng, Lu Mei

2020, 27(5):  68-73.  DOI: 10.3969/j.issn.1006-6535.2020.05.010

Asbtract ( )   PDF (1794KB) ( )  

References | Related Articles | Metrics

The stress field, fault properties and structural evolution were analyzed to further understanding the complex faults and high sand content of middle-shallow reservoirs and clarify the hydrocarbon accumulation and enrichment patternsin the eastern Wushi Sag. Research indicates that The extending stress field of Wushi Sag in the Paleocene to Middle-Early Eocene showed a NW-SE direction, and rotated clockwise to near SN direction in Oligocene, and changed to NE-SW direction from the late Oligocene to Miocene. The eastern Wushi Sag successively experienced the Paleozoic-Eocene rift, Oligocene strength slippage and Neogene heat deposition stages. Statistic and analysis of regional drilling, mud logging, oil column height and other data indicate that there are great differences in the lateral and longitudinal hydrocarbon accumulation in the middle-shallow Liu-1 Member and Weizhou Formation in Wushi Sag. Hydrocarbon mainly enriched in the skirt zone far away from the central part of “flower” structure, showing peripheral petal enrichment. The middle-shallow reservoirs in Wushi Sag are characterized by block and toothbrush-like distribution. This research could provide certain guidance for the middle-shallow reservoir exploration deployment in the eastern Wushi Sag.

Quantitative Judgment and Exploration Prospect Analysis of the Mixed-Source Oil of Kenli 16 Oilfield in Laizhouwan Sag

Liu Qingshun, Yang Haifeng, Guo Tao, Wen Honglei, Li Guoying

2020, 27(5):  74-80.  DOI: 10.3969/j.issn.1006-6535.2020.05.011

Asbtract ( )   PDF (1314KB) ( )  

References | Related Articles | Metrics

Kenli 16 Oilfield is located in the Laizhouwan sag with high sulfur content. Crude oil generally has mixed sources, but the degree and distribution characteristics of mixed sources of crude oil are not clear. In view of the above problem, biomarker compounds and saturated hydrocarbon carbon isotope methods were comprehensively used to identify mixed-source oil, and the mixed-source degree is quantitatively analyzed. The results show that the crude oil in Kenli 16 Oilfield generally has the characteristics of mixed sources, and the mixed-source degree of crude oil is basically the same on plane; in vertical direction, the mixed-source degree of crude oil is correlated with the strata. In which, the mixing proportion of salinized crude oil in the upper sub-member of the third Member of the Shahejie Formation is the highest, with an average of 89%; while that in the lower sub-member of the third Member of the Shahejie Formation is the lowest, with an average of 25%. The discovery of the mixed-source oil in Kenli 16 Oilfield confirms the contribution of salinized source rock to the fourth member of the Shahejie Formation in the main trough of the Laizhouwan sag, and indicates that the deep fourth member of the Shahejie Formation in the main trough and the southern slope zone contains great exploration potential. For the first time, the hydrocarbon generation and supply capacity of the southern trough is clearly defined, which is expected to open up the exploration situation in the periphery zones of the southern trough.

Multi-scale Fracture Prediction of Shiniulan Formation in Zheng'an Block of Northern Guizhou Province Based on Post-stack Seismic Attributes

Lan Baofeng, Huang Yi, Zhang Fu, Li Gangquan, Liu Ting, Zhang Jinchuan

2020, 27(5):  81-87.  DOI: 10.3969/j.issn.1006-6535.2020.05.012

Asbtract ( )   PDF (5645KB) ( )  

References | Related Articles | Metrics

The Shiniulan Formation of Anchang syncline in Zheng'an Area of northern Guizhou Province is a set of marl strata deposited in deep-water shelf. Previous drilling results show that the distribution of the typical fractured gas reservoirs in the Shiniulan Formation is closely related to the degree of fracture development. In order to further study the fracture plane distribution law of the Shiniulan reservoir in Anchang syncline, the authors analyzed the fracture development characteristics of the target layers through core and imaging logging data, optimized the seismic attributes sensitive to fracture prediction, and predicted the fracture distribution of the Shiniulan Formation by using the fracture enhancement attribute based on seismic pixel processing. The research results show that the ability to identify fractures using conventional seismic curvature attributes is limited, and the seismic data based on seismic pixel processing can effectively improve the imaging of small faults and structural deformation features. On this basis, the recognition ability of fracture enhancement attributes is greatly improved. The actual drilling results verify that the comprehensive coincidence rate between the fracture prediction results based on post-stack seismic attributes and the leakage points of drilling mud is more than 83.3%, thus the prediction result is reliable. This study provides technical supports for optimizing zones and early warning of drilling risk in the Shiniulan Formation.

Study on the Formation and Evolution Characteristics and Hydrocarbon Enrichment Difference of Fault Concentrated Zones in Qikou Sag

Liu Shirui, Wang Yougong, Liu Haitao, Yu Aixuan

2020, 27(5):  88-93.  DOI: 10.3969/j.issn.1006-6535.2020.05.013

Asbtract ( )   PDF (3646KB) ( )  

References | Related Articles | Metrics

As a landmark product of oblique extension, a fault concentrated zone is the main place for the formation and accumulation of fault block reservoirs. The hydrocarbon enrichment difference in fault concentrated zones with different strike directions in the Qikou Sag was analyzed by statistical analysis of geometric characteristics and structural combination styles of fault concentrated zones in this sag, combined with the formation and evolution law of fault zones. The results show that there are mainly three kinds of fault zones in the Qikou sag: NEE-trending, EW-trending and NNE-trending. Hereinto, the NNE-trending fault zones were formed at the earliest time, the vertical transport ability of the faults are the weakest, and hydrocarbons are enriched in the deep layers; the NEE-trending fault zones were formed later, and the faults have the strongest destructive effect on cap rocks, and hydrocarbons are distributed in both deep and shallow layers; the EW-trending fault zones were formed at the latest, and the vertical transport ability of the faults is between the former and the latter. The research results can provide theoretical support for oil and gas exploration in the Qikou Sag and similar multi-stage rift basins with concentrated fault zones.

Reservoir Engineering

Physical Simulation of Carbonate Particle Migration in Gas Storage

You Lijun, Shao Jiaxin, Wang Du, Wang Han, Kang Yili, Chen Mingjun

2020, 27(5):  94-99.  DOI: 10.3969/j.issn.1006-6535.2020.05.014

Asbtract ( )   PDF (1655KB) ( )  

References | Related Articles | Metrics

Particle migration may be induced due to the excessive pressure during injection and production process in gas storage well.Carbonate reservoir core samples in gas storage were taken to prepare samples with artificial fractures. Stress sensitivity test and velocity sensitivity tests of dry and water-bearing samples were conducted to simulate the fluid flow in dry and water-bearing samples under an increase of gas storage injection production pressure,and the corresponding sample permeabilities were measured during the experiment.Scanning electron microscopy was used to detect the fracture surface before and after stress sensitivity experiment to reveal the particle migration mechanism of gas storage injection-production process.Experiment indicates that the velocity sensitivitiy of dry and water-bearing core samples are medium-weak to medium-strong and medium-strong to strong respectively.The corresponding stress sensitivity is weak to medium-weak.The average permeability loss ratios of dry and water-bearing core samples are 77% and 84% for the particle migration simulation with a increase of gas storage injection-production pressure.Research indicates that the major particle migration mechanisms include the tensile failure of particle on the fracture surface results from high velocity gas flow dragging and rock damage under effective stress in the injection-production process.The rock strength decreases under water condition,which will intensify particle migration.It is recommended to restrict injection-production pressure and reduce fluid flow into gas storage well to prevent the generation of particles an enhance the multi-scale injection-production efficiency of gas storage.This research could provide certain reference for the reasonable injection-production pressure maintenance.

Application of dual-media compound numerical well test technology in fractured reef limestone reservoirs with bottom water

Yang Yong, Xie Ribin, Yan Zhenghe, Sun Changwei, Li Xiaodong

2020, 27(5):  100-105.  DOI: 10.3969/j.issn.1006-6535.2020.05.015

Asbtract ( )   PDF (4722KB) ( )  

References | Related Articles | Metrics

In view of the poor coincidence between analytical well test results and geological and dynamic characteristics in Liuhua 11-1 Oilfield, the dual-media compound numerical well test technology for horizontal wells in fractured reservoirs with bottom water is formed by comprehensively considering geological model, production history, gravity, capillary force and relative permeability curve. Forty wells were selected from the overall pressure build-up test data for dual-media compound numerical well test interpretation. In this method, both bottom water energy and permeability difference between layers are considered. Combines with the existing geological knowledge; The numerical model interpretation results show that:the oilfield pressure build-up well test curves mainly have three flow characteristics: linear flow, bilinear flow and dual-porosity seepage. According to different types of wells, it is suggested that this well can be stimulated by increasing production pressure difference or stabilizing oil and controlling water. This study has a reference for the development of similar reservoirs,which provides references for prodution.

Research on Gel Particles + Polymer Flooding Technology for Quaternary Oil Recovery in Daqing Oilfield

Chen Wenlin

2020, 27(5):  106-112.  DOI: 10.3969/j.issn.1006-6535.2020.05.016

Asbtract ( )   PDF (1964KB) ( )  

References | Related Articles | Metrics

After polymer flooding in Daqing Oilfield, the dominate seepage channels were very developed in the reservoir, the three major interferences, that is interlayer interference, inner layer interference and plane interference, intensified, the consumption of high-concentration polymer for flooding grew, and the economic benefits declined. In view of these problems, PPG gel particles were developed independently, and the PPG+polymer flooding technology were established, realizing the organic combination of "plugging, adjusting and flooding". Through experimental methods such as instrument detection and physical simulation, etc., the seepage characteristics and oil displacement effect of PPG+polymer system were analyzed, and the optimal system formula and injection pattern were screened. The research results show that: PPG for flooding control can increase viscosity, and viscosity retention rate of PPG+polymer system for flooding is as high as 78.9% after 90 days. Compared with pure polymer solution, the viscoelasticity of PPG+polymer system increases significantly, and the system has stronger plugging control properties. The optimal flooding effect can be achieved by firstly injecting PPG+polymer for plugging control with 0.05 PV and then injecting PPG+polymer for flooding control with 0.70 PV, which can save polymer consumption by 24%. After implementing PPG+polymer system for flooding control to the blocks for research and prediction, the recovery rate has increased by 8.57 percentage points. The research can provide technical support for continuous and efficient development of quaternary oil recovery stage.

Response Characteristics of Gas-water Alternate Flooding with CO₂ after Water Flooding in Ultra-low Permeability Reservoirs

Lei Xinhui, Zheng Zigang, Yu Guangming, Zhang Kang

2020, 27(5):  113-117.  DOI: 10.3969/j.issn.1006-6535.2020.05.017

Asbtract ( )   PDF (1329KB) ( )  

References | Related Articles | Metrics

In order to clarify the response characteristics of gas-water alternate flooding with CO₂ after water flooding in ultra-low permeability reservoirs, the research on dynamic characteristics of gas-water alternate flooding with CO₂ was carried out. In the research, through the combination of dynamic and static methods, the dynamic data obtained by physical simulation experiments and the static data of CO₂ solubility in oil-water solution measured in high-temperature and high-pressure phase system were used. The results show that appropriately increasing the gas-oil ratio during the CO₂ flooding process can produce oil and gas to dissolve CO₂, forming a single-phase oil zone under reservoir conditions, and the contribution rate of this stage to the oil displacement effect is 71.98%. It is suggested to appropriately increase the size of the CO₂ slug in the first cycle when designing the reservoir plan, and to select the critical point of gas channeling to inject water, which can effectively increase the utilization rate of CO₂ and improve the oil displacement effect. The research results have a certain guiding significance for the optimization of injection parameters for gas-water alternate flooding.

Classification and Evaluation of Tight Oil Reservoirs Based on Fuzzy C-Means Clustering and Bayes Discrimination

Wang Wei, Kang Shengsong, Gao Feng, Guo Fenzhuan, Zhang Liang

2020, 27(5):  118-124.  DOI: 10.3969/j.issn.1006-6535.2020.05.018

Asbtract ( )   PDF (1400KB) ( )  

References | Related Articles | Metrics

In order to solve the problem that the conventional tight oil reservoirs are difficult to classify and evaluate due to the lack of core analysis data, the optimal type of tight oil reservoirs was classified by fuzzy C-means algorithm through optimizing attribute parameters; then Bayes discriminant analysis was applied to establish the relationship between reservoir types and conventional well logging attributes, and the well logging attributes of conventional oil production wells were utilized to distinguish the reservoir types. Field applications show that the reservoir types of Chang₇ II⁶ and Chang₇ I² perforated sand bodies in Zhidan area of the Ordos Basin are consistent with the oil test results. The coincidence rate of reservoir classification of 203 wells in the study area is 89.7%. This study has a certain guiding significance for the efficient development of tight oil reservoirs.

Study on the Response Characteristics of Fire Flooding in Water-flooded Heavy Oil Reservoirs

Cai Ye

2020, 27(5):  125-131.  DOI: 10.3969/j.issn.1006-6535.2020.05.019

Asbtract ( )   PDF (2077KB) ( )  

References | Related Articles | Metrics

In order to enhance oil recovery after converting from steam huff and puff in water-flooded heavy oil reservoirs, starting from the development mechanism of fire flooding, the research of physical simulation and numerical simulation were carried out. Two kinds of water-flooded models were established, namely strong and weak water-flooded models, respectively. The development mechanism increasing pressure and displacing water of fire flooding in water-flooded reservoirs was revealed. Establish judgement criterions based on evaluation parameters, such as changing law of fluid produced, firing indicator of fire flooding, etc. The fire flooding of water-flooded reservoirs was divided into four stages, and development law of fire flooding in water-flooded heavy oil reservoir was clarified. The research results show that fire flooding in water-flooded heavy oil reservoir has lots of characteristics, such as pressure increasement, water displacement, long water-displacement time, long firing time, high gas injection demand, high heat release, high peak oil production, and good viscosity reduction effect. The research results were successfully implemented in Jin 91 block in Liaohe Oilfield, and the response of fire flooding was obvious. The research has a technical guiding significance in efficient development of reservoirs with edge-bottom water or water-flooded heavy oil reservoirs.

Characterization Model and Experimental Study of Shale Gas Diffusion Capacity Based on Momentum Equation

Chen Lu, Hu Zhiming, Xiong Wei, Yang Hang, Duan Xianggang, Chang Jin

2020, 27(5):  132-138.  DOI: 10.3969/j.issn.1006-6535.2020.05.020

Asbtract ( )   PDF (1290KB) ( )  

References | Related Articles | Metrics

In order to reveal the mechanism of gas diffusion in micro- and nano-pores of shale, aiming at the problem that it is difficult to quantitatively characterize the gas diffusion capacity of shale reservoirs, a new gas diffusion coefficient model considering shale porosity, tortuosity and flow K_n number (ratio of average free path of gas molecules to flow characteristic scale, dimensionless) is established based on differential form momentum equation considering fluid viscosity. The model was verified with the self-developed shale near equilibrium experiment, and then a chart of influencing factors of shale gas diffusion coefficient was formed. The research results show that: considering the porosity, tortuosity and other porous media parameters and flow K_n number of shale gas, the newly established diffusion coefficient model can more accurately characterize the diffusion ability of shale gas, and the coincidence degree with the near equilibrium diffusion flow rate is more than 90%. Diffusion coefficient is negatively related to pressure and positively related to pore diameter. When the pressure is lower than 20 MPa, the pore diameter is lower than 10 nm or the K_n number is higher than 0.2, the influence of the above parameters on the diffusion coefficient must be considered. This study realizes the quantitative calculation of shale gas diffusion flow rate under reservoir conditions, which can be used to establish shale apparent permeability model, and provide scientific basis for the contribution of shale gas diffusion to production in different production stages, adjustment of production system and improvement of single well production.

Drilling & Production Engineering

Development and Field Test of GW-CP194-80M CBM Dual Pressure Coring Tool

Zhu Qingzhong, Su Xuefeng, Yang Liwen, Su Yang, Luo Jun

2020, 27(5):  139-144.  DOI: 10.3969/j.issn.1006-6535.2020.05.021

Asbtract ( )   PDF (1504KB) ( )  

References | Related Articles | Metrics

During the CBM coring process, there is a great variation for the gas content and permeability due to pressure release and sampling operation, which will distort the corresponding test data and seriously influence the formulation of CBM development program. the GW-CP194-80M CBM dual-pressure coring tool was developed to obtain the original core sample under overburden pressure and reduce the test error caused from the formation condition variation. Gas-liquid pressure compensation and a compound rubber pressure-holding cylinder were used to hold the original formation pressure and proper confining pressure to prevent the creation of micro fractures. The sample can be directly used to permeability, critical desorption pressure and other subsequent tests through disassembly under pressure eon the ground. Laboratory field tests indicates that the GW-CP194-80M CBM dual-pressure coring tool is characterized by reliable performance, technical feasibility, effective maintenance of sample structure and favorable dual-pressure performance. This coring tool could provide certain technical reference for the reasonable formulation of CBM development program and accurately determine reserves.

Experiment on Controlling Cone and Increasing Oil with Preset Multi-stage Bottoms in Horizontal Well Annulus

Wang Haidong, Liu Yikun, Meng Wenbo, Zhang Chong

2020, 27(5):  145-150.  DOI: 10.3969/j.issn.1006-6535.2020.05.022

Asbtract ( )   PDF (1729KB) ( )  

References | Related Articles | Metrics

For horizontal wells, in order to reduce the impact of bottom water coning and toe end effect, coning controlling technology with preset multi-stage bottoms in horizontal well annulus was proposed. Simulate development equipment in 3D large-scale bottom water reservoirs. And the experiment on water cresting shape and oil displacement effect was carried out in conventional horizontal wells, horizontal wells with central tube and horizontal wells with multiple bottoms, respectively. Through the experiment, the effectiveness of coning controlling technology with multiple bottoms in annulus was verified. The results show that horizontal wells with multiple bottoms have obvious advantages over conventional horizontal wells and horizontal wells with central tube. The multi-bottom system makes the pressure profile along borehole more balanced, weakens the toe end effect, delays the bottom water breakthrough time, and increases swept volume, whose development effect is 9.98 and 5.95 percentage points higher than that of conventional horizontal wells and horizontal wells with central tube, respectively. The field application of coning controlling and oil stabilizing technology with multiple man-made bottoms in horizontal well annulus shows that the structure of preset multi-stage man-made bottoms in annulus is complicated, while the operation is simple, which has application potential on field. This research can provide technical reference and support for the efficient water controlling development in bottom water reservoirs.

Development of Direct-reading Measurement-adjustment Eccentric Constant-flow Water Distributor

Xiao Guohua, Huang Xiaomeng, Li Huijie, Guan Haifeng

2020, 27(5):  151-156.  DOI: 10.3969/j.issn.1006-6535.2020.05.023

Asbtract ( )   PDF (2175KB) ( )  

References | Related Articles | Metrics

In the separate injection of highly-inclined wells in Jidong Oilfield, the conventional eccentric water distributor has the problems of dropping-fishing difficulty and low measurement-adjustment success rate, while the ordinary concentric water distributor has the problems such as low qualified rate of water distribution when injection volume is small, difficult to keep water injection volume constant, and large measurement-adjustment torque. For this reason, a new type of direct-reading measurement-adjustment eccentric constant-flow water distributor was developed. The water distributor was designed with a V-shaped faucet, a small diameter ceramic plunger and an eccentric regulating valve. The opening of the faucet was adjusted by a gear transmission method, which reduced the leakage flow and improved the adjustment accuracy of water injection. A constant-flow control mechanism was designed to eliminate the influence of water injection pressure fluctuations and realize constant water injection. Bridge channels were designed to continuously provide water flow channels under different working conditions. The water distributor has the advantages such as precise distribution with small injection volume, constant measurement and adjustment, high measurement-adjustment efficiency, and constant water injection volume. The water distributor was applied to 25 highly-inclined wells in Jidong Oilfield, with a measurement-adjustment success rate of 97.6%, and distribution qualified rate of 92.7%, which realized efficient and accurate measurement, adjustment and constant-flow water injection. This technology can meet the needs of highly-inclined wells for multi-stage injection and high-efficiency measurement and adjustment, and can improve the water injection effect.

Wellbore Temperature Calculation Model for Horizontal Wells in Shallow Hydrate Reservoirs in Deep Water

Dong Shengwei, Wang Zijian, Cao Fei, Li Yingjie, Zhang Aixia, Cheng Wan

2020, 27(5):  157-161.  DOI: 10.3969/j.issn.1006-6535.2020.05.024

Asbtract ( )   PDF (1799KB) ( )  

References | Related Articles | Metrics

The development of hydrate reservoirs with horizontal wells has the characteristics of large producing range, high gas production rate, and high economic benefits. However, due to changes in downhole temperature, hydrates are prone to decompose during drilling, which induces instability of borehole wall. Based on the reservoir parameters and basic drilling parameters in the Shenhu area of the South China Sea, the heat transfer process in the wellbore during horizontal well drilling was studied, and the calculation model wellbore temperature profile during the mud circulation process was constructed. The influence law of displacement, density, initial temperature, and horizontal displacement of surface mud on wellbore temperature field was studied. The study finds that the mud injection displacement is the main factor that affects the temperature profile of the wellbore, while the mud density is the secondary factor. The greater the horizontal displacement, the more adequate the heat conduction between the mud and the formation in the wellbore. The research results can provide a reference basis for designing the mud parameters and designing well structure of horizontal wells in hydrate reservoirs in the Shenhu area of the South China Sea.

The Distribution Law of Critical Liquid-carrying Parameters along the Depth of the Gas Wells with Restrictor in Sulige Gas Field

Wang Rui, Wei Meiji, Hu Gaixing, Jiang Dongxing, Ju Yingjun, Zhang Ningsheng

2020, 27(5):  162-166.  DOI: 10.3969/j.issn.1006-6535.2020.05.025

Asbtract ( )   PDF (1306KB) ( )  

References | Related Articles | Metrics

In the low-permeability reservoirs of Sulige Gas Field, aiming at the problem of unclear understanding of critical liquid-carrying parameters in the wellbore of gas wells with restrictor, a pressure distribution model for gas-liquid two-phase flow in gas wells with restrictor was established, and the applicability of four types of critical liquid-carrying models were analyzed. The distribution law of critical liquid-carrying parameters along the depth of gas wells with restrictor was summarized. The research show that: Turner, Coleman, and Peng Zhaomin models are suitable for judging whether the gas wells in Sulige Gas Field have fluid accumulation; the critical fluid-carrying rate of gas wells with restrictor continues to decrease with the increase of well depth, with a sudden drop around the position of the restrictor and a minimum value around the bottom of gas wells; above the restrictor, the critical fluid-carrying volume continues to decrease with the increase of well depth, while below the restrictor, the critical fluid-carrying volume keeps increasing, and the maximum value appears around the wellhead. It is recommended to take the quotient of the integral and the well depth as the final value of critical liquid-carrying volume, where the integral is from the distribution of critical liquid-carrying volume along well depth. This research has a guiding significance for improving the application effect of the critical liquid-carrying model and for stabilizing production of gas wells.

Research on the Mechanical Properties and Borehole Stability of Deep Brittle Shale

Han Zhengbo, Liu Houbin, Zhang Jingtao, Yang Huajian, Shen Xinyu, Yang Qiang

2020, 27(5):  167-174.  DOI: 10.3969/j.issn.1006-6535.2020.05.026

Asbtract ( )   PDF (3073KB) ( )  

References | Related Articles | Metrics

The shale strata of Longmaxi Formation in the central part of Sichuan Basin are highly hard and strongly brittle. During the drilling process, the borehole wall collapses seriously and the pipe is stuck frequently. In order to solve the problem of borehole collapse during drilling, the anisotropy characteristics of deep shale, such as microstructure, physical and chemical properties of water, and mechanical properties, were tested, which was represented by Well Zi201 in Sichuan Basin. Theoretical model of horizontal well borehole stability in deep brittle shale was established considering the factors such as wellbore trajectory, bedding fracture occurrence, wellbore-stratum coupling seepage effect, and the mechanical weak plane effect of bedding fracture. The experimental results show that the content of brittle minerals in deep shale is as high as 70%, the hydration expansibility is extremely low, and the mechanical strength of shale matrix is high. While the strength among bedding fractures is low, so the shale is easy to slip and fall along the bedding fracture. The calculation results of the model show that the influence of mechanical weak plane effect of bedding fracture is obvious. When the angle between the wellbore trajectory and the normal direction of the bedding fracture surface meet a certain degree, collapse and shear slip of the wellbore will tend to occur. The wellbore-stratum effect cannot be ignored. The pressure penetration effect will reduce the effective radial support force of the drilling fluid, which may cause the initiation, extension and even collapse of bedding fracture. So reasonable drilling fluid density and effective plugging property can improve horizontal wellbore stability in deep shale. The research results reveal the collapse mechanism of deep brittle shale wellbore, which can provide a theoretical basis for the design of key engineering parameters of deep brittle shale horizontal wells.