Petroleum Accumulation System On Carbonate Rocks, Central Tarim Basin

The exploration of carbonate reservoir is one of hotspots in China in the field of petroleum exploration.As Tarim Basin’s complex accumulation mechanism and the petroleum system theory’s unfitness,the petroleum accumulation system theory and method are used to study the carbonate strata systematically in central Tarim basin, during the study process of marine carbonate rocks,By means of the methods of oil-source correlation and source rock potential analysis,this thesis conducted a comprehensive study for the source rock in central Tarim Basin.It can be concluded that the abundance of organic matter in Cambrian-Lower Ordovician and Middle-Upper Ordovician source rocks are in keeping with the marine carbonate rocks’ evaluation criteria.However,the thermal maturation in Cambrian-Lower Ordovician source rocks is high,and in Middle-Upper Ordovician source rocks is moderate.Oil-source correlation shows that the petroleum near to central Tarim basin uplift originates horizontally from the Cambrian-Lower Ordovician source rocks in northem Manjiaer sag,and migrates through the faults vertically from the Cambrian-Lower Ordovician source rocks in central Tarim Basin uplift.The conduit system of central Tarim basin is mainly composed by fault, fracture and unconformity,which is critical to the migration of petroleum in the study area.And the conduit framework consists of the interaction of fault,fracture and unconformity.It can be concluded that the Ordovician strata petroleum accumulation is dominated by fault,fracture and unconformity.And fault dominates the vertical petroleum migration,unconformity is the petroleum lateral migration passageway and fracture enhances the petroleum fluidity between the reservoirs.The carbonate strata of the central Tarim basin reservoir mostly consist of upper Ordovician limestone,lower Ordovician limestone and dolomite.By means of researching of the reservoir porosity,permeability and other properties,this thesis evaluates the accumulation properties of the reservoir,combining with analysis of reservoir fracture and karsts.It can be concluded that the range of profitability of the upper Ordovician reservoir isfault zone I,and the profitability of lower Ordovician is around the central fault horst zone and the area in southern of central Tarim basin bulge which is along the south of TZ38—TZ52—TB1 well line.According to structural trap,nonstructural trap and complex trap classification,this thesis classifies the traps in this area.On the basis of predecessors’studies,this thesis focuses on dissecting the accumulation conditions of petroleum in central Tarim basin,which includes the study of effective hydrocarbon source rock,conduit system,and reservoir strata,assembling of the generation,accumulation,trapping,and trap classification.Meanwhile this study summaries the laws of petroleum accumulation in carbonate strata and accumulation characteristics of central Tarim basin.Finally,this study classifies the petroleum accumulation system on the basis of above-mentioned studies.In this paper the petroleum accumulation system of Ordovician central Tarim basin district in the Tarim basin has been defined as Ordovician Cambrian—Middle and Lower Ordovician hydrocarbon source rock with a single source ternate-location accumulation system.And the most favorable oil and gas accumulated area is the fault structural beltⅠ.