Tectonic stress field and its effect on hydrocarbon migration and accumulation in Mesozoic and Cenozoic in Kuqa depression, Tarim basin

Abstract

Through rock acoustic emission experiments and structural deformation analysis, the tectonic stages in Meso-Cenozoic in the Kuqa depression of the Tarim basin are firstly divided. Then, combining with rock magnetic fabric analysis and memory information, the distribution characteristics of tectonic stress field of every tectonic stage are quantificationally resumed. At the same time, according to the distribution relation of tectonic stress field of hydrocarbon formation stage by the finite element numerical simulation method and the known hydrocarbon reservoirs, the effects of tectonic stress field on hydrocarbon migration and accumulation are further analyzed. The Kuqa depression has mainly experienced six tectonic movements since Mesozoic. Except that the tectonic stress field of the Early Yanshan stage (208—135 Ma) showed northeast-southwest extensional stress field where the orientation of the maximum principal compressive stress (σ 1 ) was northwest-southeast, the others were compressive stress field where the orientations of the maximum principal compressive stress (σ 1 ) were near north-south. Along with the closure of the paleo-Tethys ocean, the Kuqa depression in the Indosinian stage (250—208 Ma) was in strong compressive circumstance with apparently big maximum principal stress (σ 1 ) magnitude. Due to the equilibrium adjustment of interior Eurasia, the Kuqa depression in the Early Yanshan stage (208—135 Ma) was in weak extensional circumstance with apparently small maximum principal stress (σ 1 ) magnitude. From the Late Yanshan stage (135—65 Ma) on, with a series of collision events occurring at the south edge of Eurasia, the Kuqa depression was in compressive circumstance again in which the maximum principal stress (σ 1 ) magnitude was from small to big in turn. The Late Himalayan stage (2.6—0.7 Ma) was the main tectonic deformation stage with the biggest principal compressive stress (σ 1 ) magnitude. Tectonic stress field plays a dominant role in hydrocarbon formation, it not only forms migration channels and trap structures for hydrocarbon accumulation, but also is the main drive power for hydrocarbon migration vertically along faults.