The Study For Reservoir Character Of Ⅱ Oil Group Of Lower Xingouzui Formation In Xingou Area

Half of the world’s oil and gas resources reservoir in carbonate rock, the study status of lacustrine carbonate rocks in the continental petroliferous basin is more and more attention. Development of lacustrine carbonate sedimentary, reservoir characteristics and favorable reservoir area prediction study has an important significance for guiding the exploration of oil and gas. In this paper, based on the previous study results on the detailed investigation, the carbonate sedimentology, reservoir geology and petroleum geology, logging geology, statistics and other basic theory as guidance, making full use of drilling, core, logging, seismic and organic and inorganic geochemical characteristics analysis and so on, carried out a systematic study of a series of characteristics of II oil group in Lower Xingouzui Formation, Xingou area, Qianjiang Depression dolomite Stratigraphic features,sedimentary reservoir characteristics and distribution of favorable reservoir prediction.Based on microscopic identification of the rock samples in the study area, combined with the X diffraction analysis, study area mainly developed seven types lithology mud-crystal dolomite, terrigenous detrital mud crystal dolomite, argillaceous micrite dolomite, dolomitic mudstone, argillaceous gypsum rock, gypsum mudstone and siltstone rock. By coring depth homing core segment, statistical analysis of different types of lithology logging response characteristics, taking into account the accuracy of identification of lithology logs and purpose of identifying the main reservoir section, the seven types of lithology merged into four categories:dolomite rock, shale rock, argillaceous gypsum rock and siltstone rock.On this basis, the establishment of different types of logging lithology identification model and using Fisher discriminant analysis method, a clear dolomite reservoir development and variation in the whole region.Sedimentary facies in the study area is divided into shallow lake facies, and further to shallow lake facies are divided into three subfacies:Lake flat, shallow lake sand bar and limitations depression. Lake flat subfacie can be divided into dolomite flat and mud flat microfacies, the limitations depression subfacies can be divided into argillaceous depression and dolomitic depression microfacies. Dolomite flat microfacies and dolomitic microfacies depression is the main dolomite microfacies types:Dolomite flat microfacies mainly developed in relatively high-lying parts of the internal configuration of the source rocks and reservoir relations, dolomite reservoir quality is good, is conducive to the flow of oil and gas in the interior, as the study area favorable reservoir development of micro phase type; Dolomitic depressions formed microfacies in the low-lying parts of the internal configuration of the source rocks and reservoir relationship is poor, large dolomite reservoir thickness, and material of the poor, the strong internal heterogeneity, is not conducive to the flow of oil and gas in the interior, not as favorable reservoir development microfacies in the study area. According to a comprehensive analysis of sedimentary characteristics, the development of lacustrine carbonate rocks in the study area is mainly affected by provenance, ancient landscapes and lake level fluctuation.Through the reservoir characteristics study:in study area Ⅱ oil group in Lower Xingouzui formation Carbonate Reservoir porosity medium ultra-low permeability reservoirs, reservoir properties of carbonate reservoirs from good to bad:terrigenous detrital mud crystal dolomite>mud crystal dolomite> argillaceous micritic dolomite. Sedimentary facies is the main controlling factor in reservoir properties. intercrystal pore of the secondary porosity as the main reservoir space in the study area, the native microbial pore, large pores, moldic pore and corroded fissure as the secondary reservoir space, has little effect on reservoir properties.Integrated oil layer have been found, the oil displayed, the palaeogeomorphology, sedimentary facies characteristics, dolomite effective thickness, reservoir development characteristics of the study area to predict the distribution of II oil group in Lower Xingouzui formation carbonate reservoirs. In xinyi area and xiner area enclosed "C" shaped area, relatively high structural parts in the structure is effective composite parts dolomite reservoir of three oil layer. The "C" shaped area is favorable reservoir development area in the study area; In addition, seismic attributes, sedimentary and tectonic setting background of the oval area surrounded by qiao2,xin61,xi2 wells are very similar with the predicted favorable zone. This area may be beneficial exploration prospect area.