Characteristics and genetic mechanism of deep-buried clastic eureservoir in China

Abstract

Systematic researches to the clastic reservoirs in various types and various geological ages basins in China indicate that the present burial depth of deep buried clastic eureservoir ranges from 3000 to 6000 m, and its geological ages from Paleozoic, Mesozoic to Cenozoic. It mainly deposited in delta (including braid delta, fan delta, normal delta), river, also shore, shallow lake, gravity flow channel and turbidity fan facies. The quartzose sandstone is the main reservoir rock of deep-buried clastic eureservoir in the shore facies in Paleozoic, but the arenite and arkose sandstones are the main reservoir rock types in delta, river, shallow lake and gravity flow facies in Mesozoic and Cenozoic. The porosity of most of deep-buried clastic eureservoir is more than 10% and permeability more than 10×10−3 μm2. The formation of the deep-buried eureservoir was related to the paleotectonics, paleotemperature, sedimentary environment, the deep dissolution caused by organic acid or carbonic acid, burial style, the abnormal high pore fluid pressure, early hydrocarbon charging, gyprock sealing, hot convective fluid flow and the mode of sand-mud interbedded, etc. The paleotectonics controls the burial style of sandstones, and the paleotemperature controls the diagenesis process. The sedimentary environment is the precondition and foundation, the dissolution is the direct reason to generate the deep buried clastic eureservoir. The abnormal high pore fluid pressure, gyprock sealing, the mode of sand-mud interbedded, early hydrocarbon charging and the structure fractures were the assistant factors of generating the deep buried clastic eureservoir.