EVALUATION OF OIL AND GAS EXPLORATION DOMAINS IN BACHU-MAIGAITI AREA OF TARIM BASIN

Due to erosions from Caledonian to early Hercynian,Cambr ian-Middle-Late Ordovician carbonate platform in Bachu-Maigaiti area in the Tarim Basin is thinning northward with the shape of wedge.Different layers of carbonate rock have experienced stages of multi-phase karst effect.From Carboniferous to Permian,a number of sea-level cycles result in alternating layers of carbonate rocks and clastic rocks.Continuing uplifts lead to extensive erosions in Mesozoic.Faults in Bachu region move strongly in Himalayan and Maigaiti region adjust to slope southwards.The strata of Eugene-Pliocene overlap the ancient Bachu uplift of pre-Cenozoic.Taking into consideration of structural characteristics of multi-stage transformation and late-stage strong deformation in Bachu-Maigaiti area,it is pointed out in this paper that,relatively stable region in tectonic movements,long-term targets of hydrocarbon migration and effective sealing belts are the key factors for evaluations of oil and gas tectonic belts.Three tectonic belts with different exploration risks are divided.Four exploration domains are analyzed,including Carboniferous-Permian carbonate reservoir,Middle and Lower Ordovician karst weathering crust reservoir,Upper Ordovician platform edge facies belts and dolomite reservoir under salt in Cambrian.