Evaluation Of The Favorable Area For Hydrocarbon Accumulation Of Chang 2 In Zhidan Exploration Area

The Zhidan area of Ordos Basin is rich in oil and gas resources,and the Chang-2 oil-bearing formation is one of the important oil-bearing series.Based on the drilling data and the analysis and test results,this paper focuses on the study of sedimentary facies,reservoir conditions and the evaluation of oil and gas reservoir types.Through the analysis of typical oil and gas reservoirs in Zhaike and danba well areas,the types,sources and preservation conditions of oil and gas reservoirs are clarified,and the rules of oil and gas reservoir formation in Chang2 formation of Zhidan area are summarized.The study shows that the sedimentary facies of the Chang 2 oil-bearing formation in the study area belongs to the delta plain subfacies,mainly including distributary channel,floodplain and swamp sediments.The evaluation results of Chang 2 reservoir group indicate that it is a tight sandstone reservoir with low mineral maturity,high structural maturity and strong diagenesis.Chang7 "Zhangjiatan shale" source rock is stably distributed in the study area,with a thickness of 40m and the highest maturity,which can be used as high-quality hydrocarbon source rock.The reservoir types of Chang 2 reservoir group are mainly lithologic reservoirs,mainly including lithologic,lithologic structural and structural lithologic composite reservoirs.The main factors of hydrocarbon accumulation and enrichment in the study area are reservoir conditions,trap conditions and preservation conditions,Delta distributary channel sedimentary sand body provides favorable reservoir space for hydrocarbon accumulation.At the same time,due to the change of sedimentary facies or lateral lithology,the formation of lithologic shelter in the deposition part of the swamp facies or the side of the distributary channel is conducive to hydrocarbon accumulation.For chang-21 reservoir,it is necessary for the overlying Chang-1 formation to be well preserved(that is,to have good caprock).