The Rock Reservoir Property Of Lower Triassic Jialingjiang Fm. At Longmendong Of Emei Mountains In Sichuan Province

The Emeishan Longmendong Jialingjiang Formation is located in the Sichuan Basin,it is an important oil and gas producing area.By the end of 2009,the proved reserves were 114.115 billion square meters,accounting for 7.09%of the total proven natural gas reservoirs in the Sichuan Basin.Predecessors have studied the geological features and oil and gas distribution of this area,but mainly concentrated in a larger range,and the comprehensive evaluation of reservoirs and the reservoir's physical properties are less involved.This article focuses on the reservoir of Jialingjiang Formation?T₁j?in Longmendong,Emei Mountain,and based on the field sampling and microscopic identification,combined with multidisciplinary theoretical guidance,such as petrology,sedimentology and petroleum geology,the reservoir properties of the Jialingjiang Formation were systematically studied.Sedimentology and the sedimentary characteristics of the reservoirs in Jialingjiang Formation were analyzed.Comparing petrological characteristics,types of diagenesis and sedimentary characteristics of the minerals in the study area.The diagenesis and control of the sedimentary relative reservoirs were summarized.The reservoir properties such as reservoir space types,porosity and permeability were analyzed in detail.From the bottom to the top,the Emeishan Longmendong Jialingjiang Formation can be divided into five lithological sections,Jia 1?T₁j¹?,Jia 2?T₁j²?,Jia 3?T₁j³?,Jia 4?T₁j⁴?,and Jia 5?T₁j⁵?.It is mainly composed of bright-grained limestone,microcrystalline dolomite and agate-gravel mixed sandstone,and various biological debris such as wormholes,gastropods,and brachiopods,as well as pods and retort.The detailed study of the sedimentary characteristics of the Lower Triassic Jialingjiang Formation in the Longmendong section of Emei Mountain in Sichuan Province and fossils and other sedimentary facies,combining with regional sedimentary backgrounds,It is believed that the Jialingjiang Formation in the area is mainly of the marine-continent transitional type,and the estuary-tidal flat sedimentation system is developed.After studying the types and characteristics of diagenesis in the study area,it was found that dolomitization has important implications for the formation of reservoirs.The recrystallization and compaction are very disadvantageous to the development of pores.In most cases,they block the pores and throats,which is not conducive to the accumulation of oil and gas.Through thin-section microscopic identification,the pore type,throat characteristics,fracture characteristics,porosity,and permeability of the Jialingjiang Formation are studied.The inter-particle pores and Interparticle dissolution hole were found to be the main pore types in the study area.The main cracks are straight seams and oblique seams.The porosity and permeability are better in the segments T₁j¹ and T₁j²,and the segments T₁j¹ and T₁j² are rated as high-quality reservoirs.By analyzing the characteristics of rock pores,caves,and fractures in the Jialingjiang Formation,it was found that the overall reservoir performance was characterized by micropore and low permeability,type III reservoirs mainly,and strong heterogeneity.There are three kinds of reservoir types:pore type,fracture-porosity type,and fracture type.The most common type of reservoir is the fracture-porosity composite reservoir.