In view of strong heterogeneity and complex formation and evolution of organic pores,field emission scanning electron microscopy(FESEM),Raman spectrum and fluid injection+CT/SEM imaging technology were used to study t...In view of strong heterogeneity and complex formation and evolution of organic pores,field emission scanning electron microscopy(FESEM),Raman spectrum and fluid injection+CT/SEM imaging technology were used to study the macerals,organic pores and connectivity of organic pores in the lower Paleozoic organic-rich shale samples from Southern China.Combined with the mechanism of hydrocarbon generation and expulsion and pore forming mechanism of organic matter-based activated carbon,the relationships between organic pore development and the organic matter type,hydrocarbon generation process,diagenesis and pore pressure were explored to reveal the controlling factors of the formation,preservation and connectivity of organic pores in shale.(1)The generation of organic pores goes on through the whole hydrocarbon generation process,and is controlled by the type,maturity and decomposition of organic matter;the different hydrocarbon generation components and differential hydrocarbon-generation evolution of kerogen and solid asphalt lead to different pore development characteristics;organic pores mainly develop in solid bitumen and hydrogen-rich kerogen.(2)The preservation of organic pores is controlled by maturity and diagenesis,including the steric hindrance effect of in-situ hydrocarbon retention,rigid mineral framework formed by recrystallization,the coupling mechanism of pore-fluid pressure and shale brittleness-ductility transition.(3)The Ro of 4.0%is the maturity threshold of organic pore extinction,the shale layers with Ro larger than 3.5%have high risk for shale gas exploration,these shale layers have low gas contents,as they were in an open state before uplift,and had high hydrocarbon expulsion efficiency and strong aromatization,thus having the"congenital deficiency"of high maturity and pore densification.(4)The pores in the same organic matter particle have good connectivity;and the effective connectivity between different organic matter pores and inorganic pores and fractures depends on the abundance and distribution of organic matter,and development degree of pores and fractures in the shale;the accumulation,preservation and laminar distribution of different types of organic matter in high abundance is the prerequisite for the development and connection of organic pores,grain margin fractures and bedding fractures in reservoir.展开更多
Based on the results of conventional geochemistry analysis including thin sections and SEM observations, different shapes of bacterial fossils, with size ranging from dozens of nanometers to several microns, were disc...Based on the results of conventional geochemistry analysis including thin sections and SEM observations, different shapes of bacterial fossils, with size ranging from dozens of nanometers to several microns, were discovered in the low-mature marine source rocks and coal seams in South China, of which the Permian source rocks were dominated by the bacterial fossils derived from symbiotic sulphur bacteria with gypsum, and the Chengkou section in the Cambrian strata were occupied by abundant nanoscale bacterial fossils with rod and bar shapes. In contrast, a large quantity of possible bacterial fossils found in the high-mature Permian, Silurian, and Cambrian source rocks using SEM need to be further explored. Despite this,this study has indicated that bacterial fossils were prevalent in the source rocks, such as mudstone, siliceous rock and gypsum-bearing coal seams in South China, which has been ignored before. It also suggests that the bacterial fossils may play an important role in the formation and accumulation of shale gas in the geological history.展开更多
基金Supported by the National Natural Science Foundation of China(41690133)National Oil and Gas Science and Technology Major Project(2017ZX05036-002)。
文摘In view of strong heterogeneity and complex formation and evolution of organic pores,field emission scanning electron microscopy(FESEM),Raman spectrum and fluid injection+CT/SEM imaging technology were used to study the macerals,organic pores and connectivity of organic pores in the lower Paleozoic organic-rich shale samples from Southern China.Combined with the mechanism of hydrocarbon generation and expulsion and pore forming mechanism of organic matter-based activated carbon,the relationships between organic pore development and the organic matter type,hydrocarbon generation process,diagenesis and pore pressure were explored to reveal the controlling factors of the formation,preservation and connectivity of organic pores in shale.(1)The generation of organic pores goes on through the whole hydrocarbon generation process,and is controlled by the type,maturity and decomposition of organic matter;the different hydrocarbon generation components and differential hydrocarbon-generation evolution of kerogen and solid asphalt lead to different pore development characteristics;organic pores mainly develop in solid bitumen and hydrogen-rich kerogen.(2)The preservation of organic pores is controlled by maturity and diagenesis,including the steric hindrance effect of in-situ hydrocarbon retention,rigid mineral framework formed by recrystallization,the coupling mechanism of pore-fluid pressure and shale brittleness-ductility transition.(3)The Ro of 4.0%is the maturity threshold of organic pore extinction,the shale layers with Ro larger than 3.5%have high risk for shale gas exploration,these shale layers have low gas contents,as they were in an open state before uplift,and had high hydrocarbon expulsion efficiency and strong aromatization,thus having the"congenital deficiency"of high maturity and pore densification.(4)The pores in the same organic matter particle have good connectivity;and the effective connectivity between different organic matter pores and inorganic pores and fractures depends on the abundance and distribution of organic matter,and development degree of pores and fractures in the shale;the accumulation,preservation and laminar distribution of different types of organic matter in high abundance is the prerequisite for the development and connection of organic pores,grain margin fractures and bedding fractures in reservoir.
基金supported by Petrochemical Fund (B) for "Research on the effect of gas containing indigenous organic matter in the Paleozoic shale" (No. U1663202)
文摘Based on the results of conventional geochemistry analysis including thin sections and SEM observations, different shapes of bacterial fossils, with size ranging from dozens of nanometers to several microns, were discovered in the low-mature marine source rocks and coal seams in South China, of which the Permian source rocks were dominated by the bacterial fossils derived from symbiotic sulphur bacteria with gypsum, and the Chengkou section in the Cambrian strata were occupied by abundant nanoscale bacterial fossils with rod and bar shapes. In contrast, a large quantity of possible bacterial fossils found in the high-mature Permian, Silurian, and Cambrian source rocks using SEM need to be further explored. Despite this,this study has indicated that bacterial fossils were prevalent in the source rocks, such as mudstone, siliceous rock and gypsum-bearing coal seams in South China, which has been ignored before. It also suggests that the bacterial fossils may play an important role in the formation and accumulation of shale gas in the geological history.
