To evaluate the effect of tectonic deformation on coal reservoir properties, we provide an analysis of the types of tectonically deformed coal, macroand microscopic deformation and discuss pore structural characterist...To evaluate the effect of tectonic deformation on coal reservoir properties, we provide an analysis of the types of tectonically deformed coal, macroand microscopic deformation and discuss pore structural characteristics and connectivity based on samples from the Puhe and Shanchahe coal mines. Our research shows that the tectonically deformed coal mostly includes cataclastic structural coal, mortar structural coal and schistose structural coal of a brittle deformation series. The major pore structures of different types of tectonically deformed coal are transitional pores and micropores. The pore volumes of macropores and visible fracture pores produced by structural deformations vary over a large range and increase with the intensity of tectonic deformation. Mesopores as connecting passages develop well in schistose structural coal. According to the shapes of intrusive mercury curves, tectonically deformed coal can be divided into parallel, open and occluded types. The parallel type has poor connectivity and is relatively closed; the open type reflects uniformly developed open pores with good connectivity while the occluded type is good for coalbed methane enrichment, but has poor connectivity between pores.展开更多
Coal-bearing source rocks of the Pinghu Formation in the Xihu Depression comprise an important material basis of oil and gas resources in the East China Sea Basin.Based on drilling core observation results combined wi...Coal-bearing source rocks of the Pinghu Formation in the Xihu Depression comprise an important material basis of oil and gas resources in the East China Sea Basin.Based on drilling core observation results combined with the analysis and test results of macerals,trace/rare earth elements,and rock pyrolysis,the geochemical characteristics and sedimentary control of coal-bearing source rocks formation are discussed in a high-frequency sequence framework.The results indicate that the macerals composition of the coal-bearing source rocks of the Eocene Pinghu Formation in the Xihu Depression is dominated by vitrinite,with low-medium abundance of exinite and almost no inertinite.The coals and carbonaceous mudstones display higher amounts of total organic carbon(TOC)(14.90%-65.10%),S1+S2(39.24-136.52 mg/g),and IH(191-310 HC/g TOC)respectively,as compared to the mudstones.Organic matter is plotted in typeⅢkerogens and partially in typeⅡ;it is mainly in the low maturity stage.The trace elements results imply that the samples were deposited in a weakly reducing to weakly oxidizing environment and were occasionally affected by seawater.The coal-bearing source rocks were deposited in a relatively oxygen-containing environment.The coal-bearing source rocks development is jointly controlled by the coal accumulation environment,the water conditions affected by ocean currents in offshore basins in China,oxidation-reduction cycles of aqueous media and paleoclimate evolution in a high-frequency sequence framework.展开更多
To predict joint development characteristics of coal seams, joint characteristics of rock seams from 88field stations were observed and comparisons were made between joint characteristics of coal and rock seams at 10 ...To predict joint development characteristics of coal seams, joint characteristics of rock seams from 88field stations were observed and comparisons were made between joint characteristics of coal and rock seams at 10 coal outcrops. Additionally, detailed joint measurements of underground coal seams were taken at two coal mines. This study investigated the effects of seam thickness, lithology, and structure on joint development and established the relationship between joint development of coal and rock seams, which allowed predictions of predominant joint densities for the No.5 coal seam in the southeastern margin of the Ordos basin. The results show that outcrop and underground coal seams exhibit the same joint systems as rock seams. The joints are mainly upright. Predominant joints strike 55° on average, followed by joints striking 320°. The joint density of the coal seam is 18.7–22.5 times that of the sandstone seam at the same thickness. The predominant joint density of the No.5 coal seam, controlled by the structure, is 4–20 joints per meter. Joint densities exhibit high values at intersecting areas of faults and folds and decrease values in structurally stable areas. The permeability increases exponentially with increasing density of the predominant joints.展开更多
Tectonically deformed coal(TDC)develops because of the superimposed deformation and metamorphism of a coal seam by tectonic movements.The migration and accumulation of trace elements in TDC is largely in response to s...Tectonically deformed coal(TDC)develops because of the superimposed deformation and metamorphism of a coal seam by tectonic movements.The migration and accumulation of trace elements in TDC is largely in response to stress-strain conditions.To develop a law governing the migration and aggregation of sensitive elements and investigate the geological controls on TDC,coal samples from different deformation sequences were collected from the Haizi mine,in the Huaibei coalfield in Anhui Province,China,and the concentrations of 49 elements were determined by XRF and ICP-MS,and then microscopically analyzed.The results show that the distribution and morphology of minerals in coal is related to the deformation degree of TDC.The evolutionary process runs from orderly distribution of minerals in a weak brittle deformed coal to disordered distributions in ductile deformed coal.According to the elemental distribution characteristics in TDC,four types of element migration can be identified:stable,aggregate,declining,and undulate types,which are closely related to the deformation degree of TDC.Present data indicate that the overall distribution of rare earth elements(REE)does not change with metamorphism and deformation,but it shows obvious dynamic differentiation phenomena along with the deformation of TDC.Tectonic action after coal-formation,brittle or ductile deformation,and the metamorphic mechanism and its accompanying dynamic thermal effects are the main factors that influence the redistribution of elements in TDC.We conclude that tectonic movements provide the motivation and basis for the redistribution of elements and the paths and modes of element migration are controlled by brittle and ductile deformation metamorphic processes.The dynamic thermal effect has the most significant effect on coal metamorphism and tectonic-stress-accelerated element migration and accumulation.These factors then induce the tectonic-dynamic differentiation phenomenon of element migration.展开更多
基金supported by the National Natural Science Foundation of China (No.40672101)the Key National Natural Science Foundation of China (No.40730422)+1 种基金the National Science and Technology Key Special Project from the Ministry of Technology of China (No. 2008ZX05034)the China Scholarship Council (CSC)
文摘To evaluate the effect of tectonic deformation on coal reservoir properties, we provide an analysis of the types of tectonically deformed coal, macroand microscopic deformation and discuss pore structural characteristics and connectivity based on samples from the Puhe and Shanchahe coal mines. Our research shows that the tectonically deformed coal mostly includes cataclastic structural coal, mortar structural coal and schistose structural coal of a brittle deformation series. The major pore structures of different types of tectonically deformed coal are transitional pores and micropores. The pore volumes of macropores and visible fracture pores produced by structural deformations vary over a large range and increase with the intensity of tectonic deformation. Mesopores as connecting passages develop well in schistose structural coal. According to the shapes of intrusive mercury curves, tectonically deformed coal can be divided into parallel, open and occluded types. The parallel type has poor connectivity and is relatively closed; the open type reflects uniformly developed open pores with good connectivity while the occluded type is good for coalbed methane enrichment, but has poor connectivity between pores.
基金Financial support for this work was provided by the National Key Research Program for Science and Technology of China(No.2011ZX05023-001-008)the Priority Academic Program Development of the Jiangsu Higher Education Institutions(PAPD)。
文摘Coal-bearing source rocks of the Pinghu Formation in the Xihu Depression comprise an important material basis of oil and gas resources in the East China Sea Basin.Based on drilling core observation results combined with the analysis and test results of macerals,trace/rare earth elements,and rock pyrolysis,the geochemical characteristics and sedimentary control of coal-bearing source rocks formation are discussed in a high-frequency sequence framework.The results indicate that the macerals composition of the coal-bearing source rocks of the Eocene Pinghu Formation in the Xihu Depression is dominated by vitrinite,with low-medium abundance of exinite and almost no inertinite.The coals and carbonaceous mudstones display higher amounts of total organic carbon(TOC)(14.90%-65.10%),S1+S2(39.24-136.52 mg/g),and IH(191-310 HC/g TOC)respectively,as compared to the mudstones.Organic matter is plotted in typeⅢkerogens and partially in typeⅡ;it is mainly in the low maturity stage.The trace elements results imply that the samples were deposited in a weakly reducing to weakly oxidizing environment and were occasionally affected by seawater.The coal-bearing source rocks were deposited in a relatively oxygen-containing environment.The coal-bearing source rocks development is jointly controlled by the coal accumulation environment,the water conditions affected by ocean currents in offshore basins in China,oxidation-reduction cycles of aqueous media and paleoclimate evolution in a high-frequency sequence framework.
基金Financial support for this work, provided by the National Science and Technology Major Project (No. 2011ZX05034-001)
文摘To predict joint development characteristics of coal seams, joint characteristics of rock seams from 88field stations were observed and comparisons were made between joint characteristics of coal and rock seams at 10 coal outcrops. Additionally, detailed joint measurements of underground coal seams were taken at two coal mines. This study investigated the effects of seam thickness, lithology, and structure on joint development and established the relationship between joint development of coal and rock seams, which allowed predictions of predominant joint densities for the No.5 coal seam in the southeastern margin of the Ordos basin. The results show that outcrop and underground coal seams exhibit the same joint systems as rock seams. The joints are mainly upright. Predominant joints strike 55° on average, followed by joints striking 320°. The joint density of the coal seam is 18.7–22.5 times that of the sandstone seam at the same thickness. The predominant joint density of the No.5 coal seam, controlled by the structure, is 4–20 joints per meter. Joint densities exhibit high values at intersecting areas of faults and folds and decrease values in structurally stable areas. The permeability increases exponentially with increasing density of the predominant joints.
基金supported by National Science and Technology Major Project(Grant No.2011ZX05034)the Research Fund of Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process,Ministry of Education(Grant No.2013-007)+1 种基金Innovation of Graduate Student Training Project in Jiangsu Province(Grant No.CXZZ13-0944)Fundamental Research Funds for the Central Universities(Grant No.2013XK06)
文摘Tectonically deformed coal(TDC)develops because of the superimposed deformation and metamorphism of a coal seam by tectonic movements.The migration and accumulation of trace elements in TDC is largely in response to stress-strain conditions.To develop a law governing the migration and aggregation of sensitive elements and investigate the geological controls on TDC,coal samples from different deformation sequences were collected from the Haizi mine,in the Huaibei coalfield in Anhui Province,China,and the concentrations of 49 elements were determined by XRF and ICP-MS,and then microscopically analyzed.The results show that the distribution and morphology of minerals in coal is related to the deformation degree of TDC.The evolutionary process runs from orderly distribution of minerals in a weak brittle deformed coal to disordered distributions in ductile deformed coal.According to the elemental distribution characteristics in TDC,four types of element migration can be identified:stable,aggregate,declining,and undulate types,which are closely related to the deformation degree of TDC.Present data indicate that the overall distribution of rare earth elements(REE)does not change with metamorphism and deformation,but it shows obvious dynamic differentiation phenomena along with the deformation of TDC.Tectonic action after coal-formation,brittle or ductile deformation,and the metamorphic mechanism and its accompanying dynamic thermal effects are the main factors that influence the redistribution of elements in TDC.We conclude that tectonic movements provide the motivation and basis for the redistribution of elements and the paths and modes of element migration are controlled by brittle and ductile deformation metamorphic processes.The dynamic thermal effect has the most significant effect on coal metamorphism and tectonic-stress-accelerated element migration and accumulation.These factors then induce the tectonic-dynamic differentiation phenomenon of element migration.
