Study On The Transporting Capability Of The Sandstone And Unconformity In The Deep Of Bozhong Sub-basin

Bozhong sub-basin experienced a multi-cycle tectonic movement.In the intracontinental fault depression stage,multi-period unconformity surfaces were formed,and a variety of terrigenous clastic sedimentary deposits were developed,resulting in complex and variable distribution of the deep transporting system in central Bozhong sub-basin.Sandstone and unconformity are the transporting to link up deep source rocks and traps.The distribution and capacity of effective sandstone and unconformable transporting in the end of sedimentary period of Minghuazhen Formation are analyzed,providing theoretical support for deep oil and gas exploration in Bozhong sub-basin.Study on sandstone transporting,based on the sedimentary facies,the macroscopic distribution pattern of sand boby was studied,and the characteristics of microscopic porosity and throat was analyzed by combining casting thin sections,SEM and mercury intrusion method.Based on the diagenesis,the porosity and permeability in the critical period was restored,and the capacity of the effective sandstone transporting was evaluated by using storage coefficient and flowage coefficient combined with the hydrocarbon display.Based on seismic data,macroscopic structural patterns of unconformity are identified,combined with logging data,analysis of unconformity longitudinal structures,further use of casting thin sections,fluorescence thin sections,cathodoluminescence and imaging logging data,the characteristics of the porosity and permeability,fracture and secondary pore up and underlying rocks on the unconformity surface are studied to analyze unconformity transporting types and characteristics.Combining the undulating shape of the unconformity surface with the hydrocarbon display,the favorable area of the unconformity transporting is determined.Finally,on the basis of the distribution of the transporting system and fluid potential,the typical area was selected for hydrocarbon geochemical tracing,and combined with the previous research results on fluid potential and fault distribution,the distribution of each transporting in space and time was analyzed,and the hydrocarbon accumulation mode was established.According to the research,the distribution of deep sandstone transporting in Bozhong sub-basin is controlled by sedimentary facies.The sand body in the third member of the Shahejie Formation and the second member of the Dongying are fan-shaped,flower-like and bilt-like under the control of the fan-delta phase.The sand body exhibits a strip shape and a flower shape controlled by braided river delta facies,and the sand body gradually decreases from the protrusion to the depression.Microscopic pore studies show that the residual intergranular pores and dissolution pores are developed,and the pore throat radius is the main factor affecting the transport performance of the sandstone transporting.The diagenesis of the sandstone in the third member of the third member of the Shahejie Formation is controlled by the depth.The sandstone at the edge of the depression is in the B-phase of the A₂-phase.The sandstone above the unconformity surface has favorable porosity and permeability.Under the unconformity surface,the physical factors affecting the semi-weathered rock are mainly lithology,distance from the unconformity surface and tectonic movement.The crack and dissolution pore are the lower half of the unconformity surface.The main transporting space of semi-weathering rock,multi-phase development of oblique joints,high angle joints dominate the migration of hydrocarbon.Combining unconformity macrostructural styles,lithologic configurations,and lithologic properties of unconformity,the unconformity transporting systems are divided into vertical add lateral transporting,lateral transporting,trapped and non-transporting.The distribution of effective sandstone transporting in the end of sedimentary period of Minghuazhen Formation is mainly in the middle of the fan-shaped,flower-like and skirt-like regions.The effective unconformity transporting regions are mainly the unconformity and optimal regions and the superior regions,which are located at the edges of the bulges and depressions,transition zone.The hydrocarbon geochemical tracing shows the migration of hydrocarbon from BZ13-01 to CFD18-01 structure.The transport of deep Paleogene reservoirs is dominated by sandstone transporting;the transport of the former Tertiary buried hill reservoirs is dominated by unconformity transporting.