PETROLEUM EXPLORATION AND DISTRIBUTION CHARACTERISTICS OF CARBONIFEROUS VOLCANIC ROCKS IN NORTH XINJIANG OF CHINA

The Carboniferous marine basins in north Xinjiang of China have a large scale and broad distribution. The sedimental area of prototype basin is more lager than the area of nowadays, with immense thickness of sediments(the thickest arrive at 12000m),which are the fairly strong material bases for hydrocarbon formation. Therefore, there will be great potential for petroleum exploration in this area. Hydrocarbon accumulation of Carboniferous volcanic rocks is closely related to the volcanic rocks in the continental depositional basin in north Xinjiang. The fault depression development degree is the precondition of hydrocarbon generating. When the structural environment was post-collisional extensional stage at Late Carboniferous, plenty of small extensional faults developed, with great segmentation. Till now, three kinds of basins have been kept in this area: remnant-successive basins, successive- superimposed basins and superimposed basins. In successive sedimentary basins, where the sequential deposition were beneficial to the thermal evolution of source rocks, petroleum multiple migration and accumulation as well as petroleum later preservation conditions in this area. The main reservoirs are volcanic rocks, whose physical property were controlled by volcanic apparatus, volcanic facies and dissolutions due to weathering leaching. Effective hydrocarbon generating depression, weathering crust reservoir and the later preservation conditions of the reservoirs are the critical factors to hydrocarbon accumulation in volcanic rocks of Carboniferous. Inherited palaeohigh and fault zones are favorable for the development of volcanic reservoirs and petroleum accumulation. Hydrocarbon accumulation of Carboniferous volcanic rocks mostly followed “source control theory” in Carboniferous. The regions around Carboniferous source rocks are favorable for hydrocarbon accumulation, extension rifts in Late Carboniferous should be the favorable exploration regions. Gas resource of Carboniferous in north Xinjiang can reach 1.2×10¹²m³, with great potential for petroleum exploration.