Advances in research on the genetic mechanisms of intracratonic strike-slip fault system and their control on hydrocarbon accumulation:A case study of the northern Tarim Basin
In recent years,strike-slip fault system over large areas has been identified in multiple cratonic basins in China,representing a significant structural style in interior cratonic basins.With the strike-slip fault system in the northern Tarim Basin in mind,we apply techniques like seismic-geological analysis of the faulted structure,discrete element numerical simulation of the fault dynamic evolution,finite element numerical simulation of off-fault deformations,and structural analysis of the fault cores and associated damage zones(also referred to as the fault core-damage zone architectures)to study.In combination with well production data,new understandings on the origin of the strike-slip fault system and its control on hydrocarbon accumulation are proposed.The results are as follows.(1)The strike-slip fault system in the northern Tarim Basin is formed as a result of northward thrusting of large thrust belts to accommodate regional shortening under the non-coaxial extrusion in the central Tarim Basin,featuring a dynamic genetic mechanism of non-coaxial extrusion and accommodation of regional deformations.(2)With increasing strike-slip fault displacement,the crackle and mosaic breccias in the fault cores gradually evolve into chaotic breccias and cataclasites.The resulted breccias of high evolutionary degree can reduce the fault core-damage zone permeability.(3)The pressure-ridge structures along the strike-slip faults formed under intense strike-slip transpressional stress,is characterized by extension in the upper part and compression in the lower part,resulting in the fault-controlled reservoirs in large scale primarily occurring at depths.(4)The decoupling of the gypsum-salt layer with the overlying strata related to the strike-slip faulting plays an important role in controlling the vertical hydrocarbon migration.(5)Layered deformation,as an inherent characteristic of the strike-slip faults with small displacement at great deeps,governs the vertical migration and accumulation of hydrocarbons in multiple layers along the strike-slip faults.
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