Physical Properties Of The Lower Triassic Feixianguan Formation In Longmendong Section Of Mount Emei

In this paper,the lithological characteristics,sedimentary facies and diagenesis of the Feixianguan formation,the Triassic of the Longmendong section of Mount Emei,are supported by various analytical methods,such as the field survey,the observation of the outcrop,the collection of rock samples,and the photographs of the interior mirror and so on.The role of the system is systematically studied.According to the characteristics of lithology,structure,tectonic and occurrence of the formation,the top and bottom boundaries of the Feixianguan formation are judged and divided into four segments,that is,from the Feixianguan one to four segments.One and three segments are mainly carbonate rocks,and the color is green gray-light gray,and two and four segments are mainly marl and plaster rocks,showing purple-red.The analysis of the Lower Triassic Feixianguan formation corresponding to the Longmendong section of mount Emei is not difficult to find that the composition of its carbonate rocks includes three types of minerals: One is carbonates,such as calcite and dolomite;the other is self-generated non-carbonates,such as authigenic quartz,pyrite,and celestite;the third is terrigenous debris,such as feldspar and quartz.There are two types of reservoir rocks in the study area: the first one is the Oolitic limestone;the two is the sand crumb limestone.The diagenesis is mainly dolomitization,recrystallization,dissolution,pressure dissolution and metasomatism.During the formation of reservoir,the first mechanism of reservoir formation is the dissolution of the quasi syngenetic atmospheric water,and the dissolution of the reservoir plays an important role in the expansion of the reservoir and the improvement of the reservoir quality,and the fracture effect improves the permeability of the reservoir.According to the sedimentary environment,the sedimentary facies of Wilson carbonate phase can be divided into continental facies,sea land transitional phase,platform facies and platform edge.The Feixianguan one and three segments are mainly located on the beach body in the edge of the platform,while the Feixianguan two segment is dominated by continental facies and sea land intersections,and the Feixianguan four segment changes into limited platform environment.Therefore,the Feixianguan one and three segments of the reservoir performance is better than the Feixianguan two and four segments.By studying the characteristics of rock pores,holes,and fractures in the Feixianguan formation,the main aspects of the reservoir space are mold pores,intragranular dissolution pores,followed by intergranular pores.The micropores are mainly micropores,and the pore structure is poor.Reservoir porosity is concentrated between 1% and 4%,while permeability is concentrated between 0.001 and 0.1mD,and poor pore connectivity and low permeability.Based on the above analysis,it is considered that the Lower Triassic Feixianguan formation reservoir in the Longmendong section of mount Emei is a type III reservoir.