济阳坳陷车西洼陷二叠系上石盒子组致密砂岩储层成岩-成藏系统演化OA北大核心CSTPCD

The evolution of the diagenetic-accumulation system in tight sandstone reservoirs determines the densification process and the genesis and distribution of high-quality reservoirs.This study examines the tight sandstone reservoir of Permian Upper Shihezi Formation(P2sh)in the Chexi Sag,integrating burial history,tectonic evolution history,and multi-proxy analyses such as thin sections,fluid inclusion analysis,and laser ablation inductively coupled plasma mass spectrometry to systematical-ly study the evolution of the diagenesis-accumulation system.Results indicate that siliceous cement is derived from the pressure dissolution of quartz particles,which contributes the first phase of quartz overgrowth and from feldspar dissolution,which repre-sents the second phase of quartz overgrowth and fills microfractures in quartz particles or intergranular pores.The kaolinite in-cludes a fine-grained kaolinite matrix from the sedimentary period,coarse-grained kaolinite from the leaching of atmospheric freshwater through feldspars,and granular kaolinite from feldspar dissolution in a deep-burial closed system.The evolution process of the diagenesis-hydrocarbon accumulation system of the tight sandstone in the Upper Shihezi Formation,Chexi Sub-sag,follows this sequence:original sedimentary feldspar quartz sandstone with fine-grained kaolinite matrix → coarse-grained kaolinite →yellow fluorescence oil → siliceous cement →natural gas → coarse-grained kaolinite precipitation→ siliceous ce-ment → blue fluorescence oil → natural gas→ authigenic kaolinite precipitation in granular form,illite and chlorite.