The Characteristic Of Fractured Dolomite Oil And Gas Reservoir In Biyan Depression

The oil and gas reservoirs constructed by limestone, mudstone, and dolomite, belong to the typically unconventional oil and gas reservoirs. If having no the fracture, pores, or solution cavity in these reservoirs, they are non-effective oil and gas reservoir. The dolomite reservoir, in BiYang Depression, belongs to the fractured, pores, and cavity lacustrine dolomite reservoir. Series of strata thickness is up to 2km, and the typical lithology is lacustrine argillaceous dolomite interlayer with several layers of of trona. Former scholars processing some studied at the reservoir in this district. But some problems still have not been solved, such as the oil storage ability of the dolomite, the space distribution of reservoir body, the types of reservoir layer, the character of fracture and the distribution of the fracture. In all this problems, the distribution of fracture in dolomite reservoir is the most important problem, which is signality for evaluating and exploiting the reservoir. This paper study aim at the problem of identify and forecasting of the fracture in dolomite stone reservoir. In this paper, we utilized the fractured carbonate reservoir characterize method. First summarizing the geology character of the dolomite reservoir by observing the drilling core, logging data processing and the rock slice. Then setting up a credible quantify model to identify the types of fracture, the logging character of fracture and the growth layer of fracture. Third, using the mathematical simulation method to forecasting the growth zone of fracture, also including the first usage of Gaussian curvature method. Also forecasting the distributing of oil and gas energy by studying the paleo-stress field. At last, evaluating the grade of reservoir and the property of oiliness and providing the dependence for advanced exploration and exploitation.Firstly using the cycle strange method of base-level to correlate the formation cycle. The second member of HeTaoYuan formation is divided into four scale base-level cycle, which include one long cycle, six medium cycles, fifteen short cycles (according to the drilling core of well Yun2), and many more super-short cycles. By observing the drilling core and basing on the former researcher's work, resulted the complex lithology correlation as five common lithology correlations. The result is that the main dolomite mineral is dolomite stone, calcite, and other little iron pyrites, analcime, etc, analyzing by the microscope, scanning electron microscope, X ray diffract, and electron probe. Affecting by Diageneses, such as dissolving and fractureing, making a great contribution to the fractured reservoir. Filling action is sub-important. The proportion of non-filled fracture is 60.5 %, bitumen-filled fracture is 7%, alkali-filled is 11.6 %.The reservoir's macro solution pores is divided into five types, pinhole size, mung to soybean size, bull-eye size, water-eroded cave, and hole in this studied zone. The distinguished fracture types from the drilling core include seven types, syndepositted slumping fracture, syndepositted dry shrink reservoir, level fracture, X types conjugate shear fracture, low anglefracture, forepart high angle fracture, and late age high angle fracture, etc. Micro-porosity contains four types, inter particle porosity, micro-pinhole, corrosion porosity, and corrugated porosity. The microfracture contains four types, interlaminate micro-fracture, conjugate crossing shear fracture, high angle inclined fracture and micro-seam. And the x type shear fracture is the key factor for the reservoir, which approved by observing the oil layer in well Yun2. The fracture is growth main in argillaceous dolomite that adjacent the trona. Identifying granular porosity sandstone reservoir, low porosity and low permeability porosity dolomite reservoir and fractured dolomite reservoir, three reservoir types. The shear fracture, solution hole reservoir is most avail reservoir.First, summing up the correlation between the logging and lithology of the well of Yun1, Yun2...