Abstract:

Tarim basin is a huge superposed basin composed of Paleozoic cratonic basin and Meso-Cenozoic foreland basin. The main factors that control the gas accumulation in the cratonic basin are (1) thick source rocks and prolonged low-geotemperature field, which are an important conditions for prolonged hydrocarbon generation and multiphase gas accumultion; (2) palaeohigh and palaeoslope, which control the hydrocarbon migration and accumulation in Paleozoic marine strata; (3) palaeokarst reservoir, which provides reservoir space for the large oil and gas fields in paleozoic carbonate rocks; (4) Paleozoic non-structural trap, which is the main trap type of large oil and gas fields; (5) evolution of closed system of oil and gas accumulation, which controls the distribution of oil and gas resource and its exploration strategy. The condensate reservoir in the ninth block of Tahe oilfield and Hetian river gas field are selected as two examples that illustrate the gas accumulation in cratonic basin. The characteristics of hydrocarbon-generating period of main source rocks indicate that there is a better conditions of gas accumulation in the uplifted belts around the Paleozoic cratonic basin. The potential reservoir rocks near the early Paleozoic source rock are the important targets of gas exploration. Therefore, in Bachu-Maigaiti region and peripheral areas of Manjiaer depression, the exploration activity of mature and overmature gas exploration in marine strata should be increased.

Key words: cratonic basin, hydrocarbon-generating period, natural gas, Tarim