Evaluation On The Forming Conditions And Favorable Exporation Zones Of Da 43 Block In Yibei Oilfield

The Yibei oilfield is located in the favorable zone of oil and gas accumulation in the Jiyang depression.In order to improve the economic efficiency and reduce the exploration risk,the stereoscopic exploration between coalbed methane and sandstone gas can be realized.This article have studied on accumulation conditions,characteristics and accumulation mechanism and model in D43 block Yibei Oilfield.There are favorable accumulation conditions such as oil generation,reservoir,preservation and so on in Yihe Zhuang uplift to the northeast on the gentle slope.Coal,carbon mudstone and some dark mudstone are preferable source rocks in Paleogene formation with high abundance of organic matter,wide distribution,stable thickness,mainly III kerogen and in moderate and mature stage:all these show fine ability to produce natural oil.Multiple sets of laminated sand bodies are widely distributed with larger cumulative thickness.Beach and dam microfacies of the forth member of Shahejie formation,braided river delta front microfacies and dam microfacies of the second member of Shahejie formation are favorable reservoir facies belts.Porosity and permeability analysis showed that this region is mainly for good sandstone reservoir.In terms of preservation,except suffer the structure belt controlled by Yi Dong large fault and stress field with developing high angle normal faults and smaller dense reverse faults indicates poor preservation conditions.However,in other regions have relatively good preservation conditions considering the thickness and the breakthrough pressure of mudstone caprock,multiple sets of thick mudstone continuous distribution.Based on the comprehensive analysis of the burial history,thermal history,homogenization temperature of fluid inclusions and other quantitative analysis,it is identified that there aretwostages of hydrocarbon accumulation and the mechanism of reservoir formation is explained.In the early Dongying formation,part of the source rock of deep Paleogene became mature and started generating hydrocarbon.Affected by the geothermal gradient,formation completed at the end of Dongying formation.At the same time,the source rock of the Shahejie formation of Guo Ju Zi sag which located at the north part of the Yi he Zhuang uplift to the northeast on the gentle slope became mautre-high mature and the supplement migrated to this block.Consequently,based on the analysis of reservoir forming conditions and hydrocarbon accumulation mechanism,a "multi source with multi reservoirs,new generation with old storage " accumulation model under good preservation condition was establishedFinally,base on the fluid potential analyse the migration mode of oil to divide the area into three migration units.Combinatin of multi conditions such as generation,reservoir,migration and accumulation to classify the three units.Come to the conclusion:the high position of the gentle slope is the most favorable formation area which range is comparable to the present reservoir,and point out the southeastern area and westen area.