Analysis Of Carboniferous Igneous Hydrocarbon Accumulation Characteristics And Controlling Factors In Hashan Area

The exploration degree of sub-mountain complicate structure zone of northwestmargin in Junggar Basin is relatively low, and the study of hydrocarbon accumulationconditions and reservoirs characteristics for Carboniferous igneous-rock reservoirs inHashan area is weak, result in the hydrocarbon accumulation control factors is not clear. Inaccordance with these problems exist in the study area, under the guidance of the theory ofpetroleum geology and petroleum geochemistry, we fully use the present logging, seismicdata, and use technical means and research methods of geological statistics andgeochemical analysis, focusing on the research of Carboniferous oil source andhydrocarbon migration, to discuss the hydrocarbon accumulation characteristics and clearthe accumulation controlling factors for building hydrocarbon accumulation model. Basedon the research above, we come up with the exploration direction and target next.There are mainly6faults and several unconformities in Hashan area which hasexperienced a number of tectonic movements. The predecessors build the structural modelof early overthrusting and late strike-slip under the constraint of piedmont zone geologicalstructure model. The Carboniferous strata of external nappe system cover on the Permiansource rocks after the early overthrusting action. They form beneficial accumulationcombination of source rock below and reservoir rocks above which has great explorationpotential. The well drilling of Haqian6, Hashan1etc. confirmed that Permian FengchengFormation source rock exists below the thrust block of Hashan area. The source rock isevaluated as a good source rock. The oil and source rocks correlation shows that the oil inCarboniferous System comes from Permian Fengcheng Formation source rock. Thelithology of reservoir is tuff, volcanic breccia, basalt, andesite etc. There are various typesof reservoir space. The main types are tectonic fractures and dissolution pores. The reservoir can be evaluated as low to middle porosity and low permeability reservoir.Migration path analysis suggests that the crude oil of Carboniferous System comes fromPermian Fengcheng Formation source rock of deep par-autochthonous stacking system,and the migration direction is from bottom to top. F3thrust fault links up the lower part ofthe Permian source rock and the upper part of the Carboniferous igneous fracturedreservoir. It is a good path for oil and gas migration. The study area develops various typesof traps. The main types are fractured trap, anticline trap, fault trap, etc. The Carboniferousigneous rock strata overthrusting and stacking with each other formed a special igneousreservoir-seal assemblage.Based on the research of accumulation conditions and according to the characteristicsof hydrocarbon enrichment, we consider that there three types factors control thehydrocarbon accumulation of Carboniferous System in the study, they are source rock,faults and reservoir. Source rock locates underneath, micro-fracture system and faultmigrates as irregular dual passages and the oil riches along the fault zone where fracturesdeveloped are the hydrocarbon accumulation characteristics of the external thrust system.In this foundation, we build the fractured hydrocarbon accumulation model of igneous rockreservoirs in complex thrust belt: source rock below and reservoir rocks above, dualmigration and enriched along fault zone.