Analysis Of Reservoir Forming Conditions Of Cambrian Buried Hills In Nanpu Sag

According to the heterogeneity of Cambrian buried hills of lower exploration degree in Nanpu sag,with the theories of petroleum geology and structural geology,based on plenty of regional geology,well logging and seismic data applied,combined with the previous research results,analysis of reservoir forming conditions of Cambrian buried hills in Nanpu sag were teken.This paper discussed the structural characteristics,tectonic evolution processes and distribution characteristics of internal formation and reservoir of Cambrian buried hills in Nanpu sag by real seismic data sets analysis results,petroleum tectonics analysis and the prediction as well as the evaluation of reservoir.Moreover,it elaborated the reservoir forming conditions and oil-gas distribution laws of Cambrian buried hills in Nanpu sag by comparative analysis of regional geology data,geochemical data.The results and cognition were gained generally as follows:(1)Cambrian system distributed in Nanpu No.1,2,3,5 buried hills.Cambrian buried hills of Nanpu sag was dominated by three sets of normal faults,with N-E,N-W and E-W trending.Developed double fault-block,reverse tilted fault-block,faulted anticline and corresponding traps.Total area of corresponding traps is close to 160 km2,(2)Structural evolution processes are consist of 5 stages:1)Caledonian-Hercynian period.2)Indo-Chinese epoch.3)Yanshanian.4)paleogene period.5)Neogene.(3)Main lithology of Cambrian system is carbonate rock.The maximum thickness is close to 800m.The thickness becomes thinner gradually from west to east until thinning out.The types of reservoir are mainly fracture type,as well as fracture-pore type,fracture-cave type.Favorable reservoir units are mainly defained as ?1f,?1m,?2m,E 3c,?3f;?,? classes reservoirs are less than ?,? classes reservoirs.Fair reservoir tends to distribute along faults or on the top of buried hills.(4)Sealing ability of cap rock sealing buried hills is excellent.Buried hills preserve stability.Oil and gas migration from adjacent hydrocarbon-rich sags through faults,unconformity surfaces and potentials inside the intervals with high porosity and permeability to traps perpendicularly and laterally,forming upper weathering crust type and inside reservoirs type characterized by new bed generating and old bed storing.Nanpu 1-5well-block,north fault-block of Nanpu No.2 buried hill,Nanpu No.3 buried hill are considered as the most favorable target areas.