Tectonic-Fluid Model Of Deep Reservoir Of Cretaceous In The Dabei Block,Kuqa Depression

The deep clastic reservoirs in the Kuqa depression is mainly modified by structure and fluid.Taking the Bashijiqike Formation of the Cretaceous in the Dabei block as the research object,the reservoir characteristics are analyzed according to the core observation,thin section observation,production test,etc.The rock magnetic fabric method,acoustic emission method,structural sedimentology,etc.are carried out to analyze the evolution of tectonic stress field.Tectonic evolution,physical properties and formation pressure are used to explain the effects of tectonic diagenesis.Fluid inclusions analytical skills,carbon and oxygen isotopes analysis,etc.are used to restore the type and perid of fluid.The evolution model is developed to explain the coupling relationship of the tectonic evolution and fluid action,and the effect of that to the reservoir in the form of macroscopic and microscopic.It is of great significance to clarify the characteristics and distribution of favorable reservoirs and to further understand the formation mechanism of deep clastic reservoirs.Results are as follows.?1?The third section of the Bashijiqike Group of the study area is the fan delta sedimentary subfacies,while the second section of the Bashijiqike Group is the braided river delta sedimentary subfacies.The ultra-low porosity and ultra-low permeability sandstone reservoirs are developed.The reservoir space is mainly composed of residual primary intergranular pores and cracks.?2?Before middle Himalayan stage,the target layer is in the weak extension structure setting,the stress is27.4 MPa.There are three-phase near-north-south tectonic compression occured in the middle Himalayan stage,the stress of them are 39.3 MPa,55.7 MPa and 63.6MPa,respectively.The stress in the late Himalayan stage is 79.4 MPa.?3?Structural diagenesis mainly manifests as fault development,tectonic reduction and overpressure.The northward thrust faults are mainly developedin the late Himalayan stage.The third-stage tectonic fractures were developed in the middle Himalayan stage,late Himalayan stage and present tectonic period.?4?The target layer reaches stage A₂ of the middle diagenetic phase.Diagenesis is mainly compaction and cementation,while dissolution is weak.Cement was precipitated in cracks under the action of atmospheric fresh water.The weathering leaching and dissolution occured in the late Himalayan stage.