The Characteristics Of Ordovician Hydrocarbon Accumulation And Controlling Effects In Tazhong No.1 Slope Zone And No.10 Zone

From 2003 to the present,the large reef-beach reservoir of upper Ordovician in Tazhong No.1 slope zone and quasi-layered karst reservoirs of Middle-Lower Ordovician in Tazhong north-slope zone have been found.Controlled by the distribution of reservoirs and faults,it has big hydrocarbon possibility differences in different structural zones.Therefore,Tazhong No.1 slope zone and Tazhong No.10 structural zone are selected as studied areas.Based on a number of geological,logging,seismic,geochemical analysis data,the study focused on the characteristics of faults and reservoirs and their controlling on hydrocarbon accumulation in these two structural zones.The study shows that:(1)It shows better oil and gas possibility of Lianglitage Formation in the Tazhong No.1 slope zone,while in the Tazhong No.10 structural zone,it shows better potential of Yingshan Formation.The distribution of reservoir and development of faults are the main keys controlling the hydrocarbon distribution.(2)According to the analysis of reservoir characteristics,during the deposition of Lianglitage Formation,thick reef-grain beach complex and mound-grain beach complex which form high-quality reservoir are deposited in the Tazhong No.1 slope zone.To the Yingshan Formation depositied,Tazhong No.10 structural zone is located in karst highland where develops large grain banks.Influenced by the late karstification,a large number of dissolved pores and cracks are formed.(3)Based on analysis of faults,Tazhong No.1 fault has a feature of violent activity obvious segmentation,which can be divided into four segments.While Tazhong No.10 fault belongs to the secondary fault,whose activity is much weaker.Strike-slip faults can be divided into four combinations in the map and three flowers shape with six zone in the section.Negative flower structure are more developed in study area.Based on the evidence of formation water,it has a better fluid communication between upper Ordovician and lower Ordovician in the Tazhong No.1 slope zone,which shows that the faults are open.(4)Lianglitage Formation reservoirs are controlled by the distribution of high energy sedimentary sub-facies.While the distribution of palaeo-geomorphology and karstification are the two factors affected the distribution of Yingshan Formation reservoir.Because of the shorter distance to Manjiaer depression,the oil and gas injection point,fault dip and throw of Tahzong No.1 fault play a significant role in controlling effects.In the map,high-yield wells are mainly distributed in strike-slip fault fracture zone and horsetail plume strike-slip zone,and the oil and gas production will be higher with the closer distance to the strike-slip faults.