This paper presents an overview of petrophysical research and exploration achievements of low resistivity pay （LRP） zone by well logs in China. It includes geological characteristics and characteristics of well log ...This paper presents an overview of petrophysical research and exploration achievements of low resistivity pay （LRP） zone by well logs in China. It includes geological characteristics and characteristics of well log response of the low resistivity pay zones discovered and evaluated in recent years, as well as the problems in recognizing and evaluating low resistivity pay zones by well logs. The research areas mainly include the Neogene formations in the Bohai Bay Basin, the Triassic formations in the northern Tarim Basin and the Cretaceous formations in the Junggar Basin, The petrophysical research concerning recognition and evaluation of the low resistivity pays, based on their genetic types, is introduced in this paper.展开更多
Fractures are of great significance to tight oil and gas development.Fracture identification using conventional well logs is a feasible way to locate the underground fractures in tight sandstones.However,there are thr...Fractures are of great significance to tight oil and gas development.Fracture identification using conventional well logs is a feasible way to locate the underground fractures in tight sandstones.However,there are three problems affecting its interpretation accuracy and practical application,namely weak well log responses of fractures,a lack of specific logs for fracture prediction,and relative change omission in log responses.To overcome these problems and improve fracture identification accuracy,a fracture indicating parameter(FIP)method composed of a comprehensive index method(CIM)and a comprehensive fractal method(CFM)is introduced.The CIM tries to handle the first problem by amplifying log responses of fractures.The CFM addresses the third one using fractal dimensions.The flexible weight parameters corresponding to logs in the CIM and CFM make the interpretation possible for wells lacking specific logs.The reconstructed logs in the CIM and CFM try to solve the second problem.It is noted that the FIP method can calculate the probability of fracture development at a certain depth,but cannot show the fracture development degree of a new well compared with other wells.In this study,a formation fracture intensity(FFI)method is also introduced to further evaluate fracture development combined with production data.To test the validity of the FIP and FFI methods,fracture identification experiments are implemented in a tight reservoir in the Ordos Basin.The results are consistent with the data of rock core observation and production,indicating the proposed methods are effective for fracture identification and evaluation.展开更多
Multi-type unconventional gas-bearing reservoirs with different lithologies and gas accumulation potential occur in the deep part of the Songliao basin.However,the reservoirs are non-homogeneous,the gas components dif...Multi-type unconventional gas-bearing reservoirs with different lithologies and gas accumulation potential occur in the deep part of the Songliao basin.However,the reservoirs are non-homogeneous,the gas components differ substantially,and not all types of gas-bearing reservoirs have been identified or evaluated.The International Continental Scientific Drilling Program(ICDP)is used as an example to conduct qualitative and quantitative evaluations of deep multi-type unconventional gas-bearing reservoirs using conventional and specialized logging data.The core test data are used to determine the physical properties.The porosity and permeability are compared and analyzed using different methods and models.The results show that the reservoirs have low to ultra-low porosity and ultra-low permeability.Based on the comparison of the rock mechanical parameters and mineral composition,brittleness evaluation parameters are proposed for different types of deep reservoirs in the study region.The mineral brittleness index is highly consistent with the brittleness index based on rock mechanics.An identification method for deep multi-type gas-bearing reservoir and a classification approach for different gas properties are established based on the logging response and parameter interpretation.The methane gas reservoirs have low density(DEN)and low compensated neutron logging(CNL)values and high acoustic(AC)time difference and high resistivity(RT)values.The CO_(2)gas reservoirs have lower RT values and higher CNL values than the hydrocarbon gas reservoirs.The comprehensive analysis of deep gas source rock conditions and of the source-reservoir relationship provides insights for the evaluation of deep multi-type unconventional gas reservoirs.The discovery of high hydrogen content is of significant importance for developing new areas for deep natural gas exploration.展开更多
基金Supported by CNPC Innovation Foundation,Research Projects of PetroChina,Xinjiang and Tarim Oil Companies
文摘This paper presents an overview of petrophysical research and exploration achievements of low resistivity pay （LRP） zone by well logs in China. It includes geological characteristics and characteristics of well log response of the low resistivity pay zones discovered and evaluated in recent years, as well as the problems in recognizing and evaluating low resistivity pay zones by well logs. The research areas mainly include the Neogene formations in the Bohai Bay Basin, the Triassic formations in the northern Tarim Basin and the Cretaceous formations in the Junggar Basin, The petrophysical research concerning recognition and evaluation of the low resistivity pays, based on their genetic types, is introduced in this paper.
基金supported by the National Science and Technology Major Project(Grant No.2017ZX05009001-002 and 2017ZX05013002-004)the Fundamental Research Funds for the Central Universities(Grant No.2462020YJRC005)Science Foundation of China University of Petroleum,Beijing(Grant No.2462020XKJS02).
文摘Fractures are of great significance to tight oil and gas development.Fracture identification using conventional well logs is a feasible way to locate the underground fractures in tight sandstones.However,there are three problems affecting its interpretation accuracy and practical application,namely weak well log responses of fractures,a lack of specific logs for fracture prediction,and relative change omission in log responses.To overcome these problems and improve fracture identification accuracy,a fracture indicating parameter(FIP)method composed of a comprehensive index method(CIM)and a comprehensive fractal method(CFM)is introduced.The CIM tries to handle the first problem by amplifying log responses of fractures.The CFM addresses the third one using fractal dimensions.The flexible weight parameters corresponding to logs in the CIM and CFM make the interpretation possible for wells lacking specific logs.The reconstructed logs in the CIM and CFM try to solve the second problem.It is noted that the FIP method can calculate the probability of fracture development at a certain depth,but cannot show the fracture development degree of a new well compared with other wells.In this study,a formation fracture intensity(FFI)method is also introduced to further evaluate fracture development combined with production data.To test the validity of the FIP and FFI methods,fracture identification experiments are implemented in a tight reservoir in the Ordos Basin.The results are consistent with the data of rock core observation and production,indicating the proposed methods are effective for fracture identification and evaluation.
基金supported by the National Natural Science Foundation of China(Grant Nos.42072168 and 41802156)the National Key R&D Program of China(Grant No.2019YFC0605405)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2022YQDC06)the Foundation of State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing(Grant No.PRP/open2006)。
文摘Multi-type unconventional gas-bearing reservoirs with different lithologies and gas accumulation potential occur in the deep part of the Songliao basin.However,the reservoirs are non-homogeneous,the gas components differ substantially,and not all types of gas-bearing reservoirs have been identified or evaluated.The International Continental Scientific Drilling Program(ICDP)is used as an example to conduct qualitative and quantitative evaluations of deep multi-type unconventional gas-bearing reservoirs using conventional and specialized logging data.The core test data are used to determine the physical properties.The porosity and permeability are compared and analyzed using different methods and models.The results show that the reservoirs have low to ultra-low porosity and ultra-low permeability.Based on the comparison of the rock mechanical parameters and mineral composition,brittleness evaluation parameters are proposed for different types of deep reservoirs in the study region.The mineral brittleness index is highly consistent with the brittleness index based on rock mechanics.An identification method for deep multi-type gas-bearing reservoir and a classification approach for different gas properties are established based on the logging response and parameter interpretation.The methane gas reservoirs have low density(DEN)and low compensated neutron logging(CNL)values and high acoustic(AC)time difference and high resistivity(RT)values.The CO_(2)gas reservoirs have lower RT values and higher CNL values than the hydrocarbon gas reservoirs.The comprehensive analysis of deep gas source rock conditions and of the source-reservoir relationship provides insights for the evaluation of deep multi-type unconventional gas reservoirs.The discovery of high hydrogen content is of significant importance for developing new areas for deep natural gas exploration.
