Characteristics Of Tight Oil Reservoirs In The Da'anzhai Member Of Gongshanmiao Oilfield In Central Sichuan

The paper is guided by logging geology,reservoir geology,sedimentology and related theories at home and abroad,in combination with previous research results,dissertation has a research on the characteristics of stratum,sedimentary facies and reservoir as well as key control factors and uses a method of a combination of macro and micro analysis as well as dynamic and static data,on a basis of core,logging data and physical data.Research shows that:(1)Da'anzhai Formation(J1dn)of Gongshanmiao in the central region of the Sichuan Basin is divided into three subsections(J1dn1,J,dn2,J1dn3)from the bottom to the top,the top and bottom boundary of the Da'anzhai Formation(J1dn)is obvious,there is no situation of lacuna,the development of the subsegments is relatively stable,longitudinally J1dn2is the thickest,the thickness is from 35 to 60m,J1dn3 is the thinnest,the thickness is from 5 to 15m,the lithology of Jidn3 is coquina and mud shale places between coquina,the lithology of J1dn2 is mud shale and coquina places between mud shale,the lithology of J1dn3 is thick coquina.In the plane,the thickest stratum of Da'anzhai Formation in the study area,which are Wellblock G003-1?G67?G69?G003-11,other areas are relatively thin.(2)The sedimentary environment in Sichuan Basin acts as the lacustrine facies,under the guidance of sedimentary markers,and further divided into two subfacies(both shallow lake,shallow-lake to semi-deep lake)and five microfacies,including the beach core,the beach margin,the lake in front of the beach,mud of the shallow lake and the half-deep lake mud,among which the beach core and the beach margin have advantage of the development of reservoir,they mainly distributed in J1dn1 and J1dn3.(3)The lithology of reservoir in Da'anzhai Formation is mainly all kinds of coquina;Da'anzhai reservoir has a poor physical property,porosity is between 0?1.5%,and with an average porosity of 0.98%,permeability is between 0.0001?1mD,and with an average permeability of 0.138mD,Da'anzhai reservoir is a typical characteristics of extra-low porosity and permeability of tight oil reservoir.But existence of fractures has improved physical property;space types are mainly denudation pores and cracks in all levels of micron and nanometer level;Da'anzhai reservoir has a poor pore structure,which is the characteristic of tight matrix pores;the reservoir of Da'anzhai is mainly fractured-porosity reservoir.(4)The formation and evolution of Da'anzhai reservoir is mainly affected by the sedimentary,diagenesis and tectonic,the beach core and the beach margin determine the distribution of the reservoir;the diagenesis of the compaction and cementation Da'anzhai enables the pore to reduce or even disappear,however,dissolution can improve reservoir physical property,a large number of microcracks developed in Da'anzhai Formation has improved the seepage capacity of tight coquina reservoir to a great extent,it's a key factor of the industrial gas in limestone of Da'anzhai Formation in the central region of the Sichuan Basin.Through the above research,the favorable reservoirs have been selected in the study area,which are Wellblock G39?6003-1,6003-13?G108X and G62?G61.