Hydrocarbon Accumulation Regularity In Lower Member Of Ming Formation In Key Oilfield In Bonan Region

Based on studying the structural and sedimentary background and making full use of thestudy area geology, pysical exploration, well logging and all kinds of analysis data, we havestudied all kinds of hydrocarbon accumulation conditions by petrolrum geology, sedimentarypetrology, geochemistry and geophysics in lower member of Ming formation in X-2S/N andY-1/N oilfield.We have summarized the types and distribution of hydrocarbon reservoirs in the lowermember of Ming formation in X and Y oilfield by making use of probing and indication ofhydrocarbons.The types include fault-anticlinal oil reservoir, fault-block oil reservoir andfault-lithologic oil reservoir.In the plane, oil layers(gas layers) mainly distribute in highposition of fault block in a reservoir(small layers) of X-2S/N oilfield and distributions of oillayers or water layers controlled by structure,fault and lithology do not have obvious rule ingeneral in a reservoir(small layers) of Y-1/N oilfield.In the section, hydrocarbon mainlydistribute in the upper part of I,II oil formation in the lower member of Ming formation inX-2S/N oilfield and hydrocarbon mainly distribute in II, III, IV oil formation in in the lowermember of Ming formation in Y-1/N oilfield. Main control factors drawn by superimposingreservoir-forming conditions of hydrocarbon accumulation and distribution in the researcharea include sufficient hydrocarbon source, source fault and regional seal are basicconditions;uplift belt development, local higher location of structure,net sandstonedevelopment and fracture-post strength are dominant factors;fracture cross location,smallscale late fault,fracture shale smear extent and fault lateral sealing are secondary causes.Hydrocarbon migration and accumulation patterns summarized by combinating reservoirtypes and main controlling factors of hydrocarbon distribution are as follows: hydrocarbon ineffective source kitchen vertical migrate to targets good in physical property and lower insmear degree along the bigger displacement gradient of source faults and are influenced byreginal seal and then accumulate in higher location of the structure or anticline structure.Afteraccumulation period, controlling-reservoir fault of high activity intensity lose hydrocarbon insurface and ontrolling-reservoir fault of low activity intensity justify and accumulatehydrocarbon and then form oil,gas and water distribution mode. Based on the main factorscontrolling hydrocarbon accumulation on the five goals of the broken circuit of the drillingrisk analysis and evaluation, evaluation results show, broken circle target drilling risk fromsmall to big order No. two, No. three, No. five, No. one, No. four.