The Study On The Shale Depositional Microfacies Of The Third To Fourth Member Of Shahejie Formation In Lijin Depression

The exploration and development of unconventional oil and gas resources are becoming increasingly important with conventional oil and gas resources gradually decreasing. The shale oil and gas as one of the main types of unconventional oil and gas resources at present, it will become one of the main energy in the future On the basis of the huge resource potential. Dongying Sag is one of the most developed areas of shale hydrocarbon reservoirs in Jiyang Depression, and so far several prospecting wells have produced commercial oil flow in Dongying sag. As the largest sedimentary center in Dongying sag, Lijin Depression has the advantageous resources background. Mud shale formation formed in different environmental conditions, it is quite different among Rock composition, mineral composition, diagenetic characteristics, organic phase and so on which directly affect the process of hydrocarbon enrichment of the shale. In this paper, study the research of sedimentary microfacies of mud shale section with emphasis on the Lijin sag. Clearing the microenvironment of mud shale reservoirs, has the important significance of mud shale oil and gas exploration of Lijin Depression.This paper, using detailed description of core, thin sections identification, analysis of whole rock X-ray diffraction and scanning electron microscopy technologies, based on the integrating various factors such as mineral composition, sedimentary structure, organic matter abundance, color and other foreign matters, sets up a lithofacies classification scheme that suitable for the shale in the 3rd and 4th members of Sha he jie Formation in the west part of Dongying area. The most development of five types of lithofacies include organic-rich laminated limestone, organic-rich calcareous interbedded limestone, organic-contained fine-grained mixed sedimentary rocks,organic-lean massive clay stone and organic-rich laminated clay stone. The main types of reservoir space, including structural fracture、abnormal pressure fracture、inter-laminar fracture、dissolution pore、inter-granular pores of clay mineral and inter-granular pores of calcite layer an so on. The basis of the exploration of the shale is to carry out the advantage(favorable) lithofacies. According to the characters of the lithofacies and the development of reservoir space, determine the intercalation of limestone、laminated limestone and clay stone for advantages(good) lithofacies.In this paper, the high-resolution sequence stratigraphic framework of the 3td and 4th Members of Shahejie Formation in Lijin Sag was established by study on combination with numerous core observations, seismic data, well logging data and well tests. based on the theories of high resolution sequence stratigraphy and sedimentology. According to the rock assemblage features and apparent resistivity curve, divides into 6 parasequence sets including the LST, TST, HST of third member and LST, TST, HST of forth member of Shahejie Formation. From basin center to lake basin peripheral in the order,Within the sequence framework of control, summarizes the main facies types of the shale in the plane distribution features:Clay rock, high organic matter page grain bedded limestone and laminated limestone, grain layer, page fine particle mixed sedimentary rocks, the massive fine grained mixed sedimentary rocks and siltstone.Sedimentary microfacies reflected the changes of sedimentary environment and control the mineral content of the shale, the types of facies and its combination and development of reservoir space types. The main basis of the classification of the sedimentary microfacies of the half deep lake-deep lake area of shale including the lithofacies assemblages, hydrodynamic characteristics, ancient landform and other factors. The mud shale depositional microfacies types of Lijin sag can be divided into the following kinds: Gentle slope dynamic water half deep lake, steep water lake, weak local uplift move weak local uplift of the depth of water in the lake, lake water depth, flat hydrostatic(half) deep lake, in the vast lake deep depression static sounding microfacies.