Dynamic elastic parameters of coal are closely linked to crack characteristics and are lithology indicators in seismic exploration. This experimental study measured ultrasonic wave velocity of coal samples considering...Dynamic elastic parameters of coal are closely linked to crack characteristics and are lithology indicators in seismic exploration. This experimental study measured ultrasonic wave velocity of coal samples considering both parallel(90°) and perpendicular(0°) to bedding planes, and then calculated the dynamic elastic parameters(Edand ld) and their anisotropy values(AEdand Ald). The variations of Edand ld,as well as AEdand Aldwere analyzed under various confining stresses. The results show that: Firstly, a critical confining pressure exists, and significant variation in the parameters can be seen below this point and weak variation appears above it. Secondly, a positive correlation exists between Edand the square of P-wave velocity(VP2), and between AEdand the P-wave velocity anisotropy(AEP) as well; however, there is no clear correlation between ldand P-wave velocity(VP). Thirdly, according to the major controlling factors of anisotropy, the coal samples with different Edand ldas well as AEdand Aldcan be divided into two types: one is mainly controlled by bedding and cracks and the other one is mainly controlled by differences of mineral compositions in directions. Consequently, this study can provide theoretical basis for future research on the dynamic elastic parameters and anisotropy of coal.展开更多
Based on ＂true triaxial coal rock permeability of coal sample test system , the permeability under different gas pressure to coal specimen in bedding plane and the vertical bedding directions are tested. The results ...Based on ＂true triaxial coal rock permeability of coal sample test system , the permeability under different gas pressure to coal specimen in bedding plane and the vertical bedding directions are tested. The results show that coal structural anisotropy has a greater impact on gas permeability properties, differences in experimental coal permeability are roughly one order of magnitude. In view of the differences of the gas flow characteristics in the coal bedding plane and vertical bedding, established series and parallel choked flow model of coal sample gas seepage, and made a theoretical analysis to the influences of the bedding structure to gas permeability properties.展开更多
基金provided by the National Key Basic Research Development Program(No.2009CB219603)the Jiangsu Natural Science Fund Project(No.BK20130201)the Jiangsu Graduate Student Innovation Training Project(No.KYLX_1399)
文摘Dynamic elastic parameters of coal are closely linked to crack characteristics and are lithology indicators in seismic exploration. This experimental study measured ultrasonic wave velocity of coal samples considering both parallel(90°) and perpendicular(0°) to bedding planes, and then calculated the dynamic elastic parameters(Edand ld) and their anisotropy values(AEdand Ald). The variations of Edand ld,as well as AEdand Aldwere analyzed under various confining stresses. The results show that: Firstly, a critical confining pressure exists, and significant variation in the parameters can be seen below this point and weak variation appears above it. Secondly, a positive correlation exists between Edand the square of P-wave velocity(VP2), and between AEdand the P-wave velocity anisotropy(AEP) as well; however, there is no clear correlation between ldand P-wave velocity(VP). Thirdly, according to the major controlling factors of anisotropy, the coal samples with different Edand ldas well as AEdand Aldcan be divided into two types: one is mainly controlled by bedding and cracks and the other one is mainly controlled by differences of mineral compositions in directions. Consequently, this study can provide theoretical basis for future research on the dynamic elastic parameters and anisotropy of coal.
文摘Based on ＂true triaxial coal rock permeability of coal sample test system , the permeability under different gas pressure to coal specimen in bedding plane and the vertical bedding directions are tested. The results show that coal structural anisotropy has a greater impact on gas permeability properties, differences in experimental coal permeability are roughly one order of magnitude. In view of the differences of the gas flow characteristics in the coal bedding plane and vertical bedding, established series and parallel choked flow model of coal sample gas seepage, and made a theoretical analysis to the influences of the bedding structure to gas permeability properties.
