Diagenetic Process and Pore Evolution of Jurassic Continental Shale in Tarim Basin, Northwest China

Abstract

The Jurassic shale in the Tarim Basin, as one of the important source rocks within the basin, is identified as a set of typical continental sedimentation with big hydrocarbon-generating potential. The diagenetic process and pore evolution characteristics of the Jurassic shale were studied based on geochemical and reservoir bed properties analyses and scanning electron microscope (SEM) observation. The results show that the Jurassic shale shows low-porosity and low-permeability, the mineral composition is mainly of clay mineral and quartz; the shale underwent three diagenetic evolutionary stages, namely syngenetic to Period A of early diagenetic stage, Period B of early diagenetic stage and Period A of middle diagenetic stage; during this process, the shale underwent a series of changes such as hydrocarbon generation of organic matter, conversion from original minerals to illite, formation of authigenic minerals, recrystallization and corrosion; meanwhile, porosity and permeability also underwent the evolutionary processes including rapid reduce of primary pore and development of secondary pore. The pore development within shale is mainly controlled from three aspects, namely material composition of rock, diagenesis and later tectonic reworking.