Fracture and cavern hydrocarbon reservoirs in carbonates are an important pool type worldwide. The karst cavern reservoirs are easiest to identify on seismic reflection data. The prediction, exploration, and developme...Fracture and cavern hydrocarbon reservoirs in carbonates are an important pool type worldwide. The karst cavern reservoirs are easiest to identify on seismic reflection data. The prediction, exploration, and development of this type of reservoir require theoretical research on seismic wave fields reflected from complex inhomogeneous media. We compute synthetic seismic sections for fluidfilled cavern reservoirs of various heights and widths using random media models and inhomogeneous media elastic wave equations. Results indicate that even caverns significantly smaller than 1/ 4 wavelength are detectible on conventional band-width seismic sections as diffractions migrated into bead-type events. Diffraction amplitude is a function of cavern height and width. We introduce a width-amplitude factor which can be used to calculate the diffraction amplitude of a cavern with a limited width from the diffraction amplitude computed for an infinitely wide cavern.展开更多
Positive pressure effect is the result of rapid urban development in recent years,which leads to over-exploitation of karst groundwater,coupled with the emergence of extreme weather(such as heavy rainfall,the increase...Positive pressure effect is the result of rapid urban development in recent years,which leads to over-exploitation of karst groundwater,coupled with the emergence of extreme weather(such as heavy rainfall,the increase in the duration of heavy rainfall),leading to the sharp rise of karst water level,the gas in the karst cavity can not be discharged in time to form a high positive pressure in the soil cavity and promote the destruction of the soil layer,which then induces a series of phenomena,such as karst subsidence.As a new collapse mechanism,the positive pressure effect causes geological disasters that seriously affect the safety of people's lives and properties in karst regions.In order to study the damage characteristics and evolution characteristics of karst soil cavities under positive pressure effect,this study is based on the ASCII text provided by FLAC itself,and the orthotropic simulation computation compilation program,which realizes the finite element analysis in FLAC3D,and focuses on the inhomogeneous change of soil displacement,redistribution of stresses,and plastic damage of karst soil cavities in different evolution stages under the action of positive pressure,and summarizes the characteristics and laws of stress,strain and damage in plastic zone of karst soil cave at different stages of evolution.The results will play a positive role in further investigating the potential mechanical effects,development mechanism and critical warning conditions during the evolution of covered karst soil caves,and also have important scientific research value in deepening the theory of prevention and control of collapse disasters in covered karst soil caves.展开更多
基金This research project is sponsored by Nation’s Natural Science Found of China (No. 40174034 and 40274038) as well as theOpening Found Projects of the CNPC geophysical exploration key laboratory (No. GPKL0207).
文摘Fracture and cavern hydrocarbon reservoirs in carbonates are an important pool type worldwide. The karst cavern reservoirs are easiest to identify on seismic reflection data. The prediction, exploration, and development of this type of reservoir require theoretical research on seismic wave fields reflected from complex inhomogeneous media. We compute synthetic seismic sections for fluidfilled cavern reservoirs of various heights and widths using random media models and inhomogeneous media elastic wave equations. Results indicate that even caverns significantly smaller than 1/ 4 wavelength are detectible on conventional band-width seismic sections as diffractions migrated into bead-type events. Diffraction amplitude is a function of cavern height and width. We introduce a width-amplitude factor which can be used to calculate the diffraction amplitude of a cavern with a limited width from the diffraction amplitude computed for an infinitely wide cavern.
基金support provided by the Xuzhou City geological survey and Xuzhou area karst collapse survey projects(China Geological Survey No.12120114022001)The authors also thank Comprehensive geological environment survey projects of key sections in Yellow River flood area of northern Jiangsu province(Special Funds for Geological Survey in Jiangsu Province No.2018.374)Comprehensive Development and Utilization Evaluation of Underground Space Resources in Suzhou Based on Multi-source Data Fusion pilot projects(Jiangsu Province natural resources protection and utilization of special funds No.2200199)for supporting the valuable materials.
文摘Positive pressure effect is the result of rapid urban development in recent years,which leads to over-exploitation of karst groundwater,coupled with the emergence of extreme weather(such as heavy rainfall,the increase in the duration of heavy rainfall),leading to the sharp rise of karst water level,the gas in the karst cavity can not be discharged in time to form a high positive pressure in the soil cavity and promote the destruction of the soil layer,which then induces a series of phenomena,such as karst subsidence.As a new collapse mechanism,the positive pressure effect causes geological disasters that seriously affect the safety of people's lives and properties in karst regions.In order to study the damage characteristics and evolution characteristics of karst soil cavities under positive pressure effect,this study is based on the ASCII text provided by FLAC itself,and the orthotropic simulation computation compilation program,which realizes the finite element analysis in FLAC3D,and focuses on the inhomogeneous change of soil displacement,redistribution of stresses,and plastic damage of karst soil cavities in different evolution stages under the action of positive pressure,and summarizes the characteristics and laws of stress,strain and damage in plastic zone of karst soil cave at different stages of evolution.The results will play a positive role in further investigating the potential mechanical effects,development mechanism and critical warning conditions during the evolution of covered karst soil caves,and also have important scientific research value in deepening the theory of prevention and control of collapse disasters in covered karst soil caves.
