Study On Sealing Property Of Cap Rock In Funing Formation In The Southwest Depression Of Subei Basin

A good cap rock is a key factor in the preservation of hydrocarbon reservoirs.In this paper,we study the seal of the second member of the Funing formation in five oilfields in the northern slope of the Gaoyou depression in the Subei basin(the Shanian oilfield,the Huazhuang oilfield,the Unionzhuang oilfield,the Majiazui oilfield,and the Weizhuang oilfield).In combination with logging,core and drilling datas,the author studies the macroscopic,microscopic and closed mechanisms,and applies grey correlation analysis to comprehensively evaluate and predict favorable exploration areas.Cap rock macroscopic aspects,through the well logging,logging and coring data,the lithology of the second member of the oilfield was identified.The results show that the lithology of the second member of each oilfield is relatively single,mainly gray black and black mudstone.Through statistics of the cumulative thickness of the second member of the oilfield and the thickness of the mudstone member,the ratio of the cover to the mud and land is calculated,and the well is profiled.It is known that the lateral continuity of the cover is good.Cap rock microcosmic aspects,through the measurement of porosity? permeability and displacement pressure of rock sample,and fitting the function with the time difference of acoustic wave,and establishing the model,the relev ant parameter values without measured data can be calculated.Cap rock sealing mechanism aspects,by comparing the displacement pressures of reservoirs and caprocks,the closure of properties is determined;the pressure sealability is determined by the correspondence between the acoustic wave time difference and the abnormal pore fluid high pressure;combined with organic matter maturity and anomalous pores The fluid pressure is high,and the closed hydrocarbon concentration is determined.This determines the type of capping mechanism.This paper uses the grey relational analysis method to calculate the correlation degree and weights of various parameters of the cap rock,establishes a set of evaluation criteria for capping parameters,quantitatively evaluates and classifies the capping grades,and finally divides the favorable zones according to the actual conditions of each oilfield.The study shows that Shanian oilfield is a type I-II cap rock;Huazhuang oilfield is a type II-III cap rock;Unionzhuang oilfield is a type I-II cap rock;Majiazui oilfield is a type II-III cap rockr;Weizhuang oilfield This is a type III-IV cap rock;this shows that the Shanian oilfield and the Unionzhuang oilfield are favorable exploration areas.