| The study area is located in the western Ordos Basin, the most northern is Dengkou in Inner Mongolia, goes through Yinchuan in Ningxia province and Pingliang in Gansu province, ending Long county in Shanxi province, the most eastern is Dingbian, ends the line of the western foot of Helan Mountain and Qingongxia and Guyuan fracture.50-100km from east to west, north and south about600km, covers an area of50000km2, across the four provinces of Shaanxi, Gansu, Ningxia, Inner Mongolia. From the structural point of view, The study area includes the Western obduction zone, Tianhuan depression and part of yishuan downslope. The study area Ordovician strata are epicontinental sea carbonate sedimentary with complete strata and thick formation, Sediment thickness of about1000-3000m, Sedimentary rock through the dolomitization and tectonic development of cracks, which greatly improve its porosity and permeability, have the conditions to develop high-quality effective reservoir. consulting the results from the test gas of the area wells, many wells have gas shows, having Oil and gas exploration and development prospects.But Since1986,when the T1well has produced6.4x104m3gas per day in Ordovician formation lower-paleozoic of Tianchi Structure, and it reached the Industry Standard. A lot of drilling has gas shows, but the vast majority can not get industrial exploitation levels. This is mainly because of overall low degree of exploration in this area, Geological knowledge is not clear enough, Especially due to the deposition, tectonic setting is more complex, Diagenesis and later Diagenesis have a tremendous impact on the reservoir, Bring difficulties to the prediction of high-quality reservoir. In this paper, basing on a large number observing in outcrop,core and thin sections and collecting logging, seismic, well logging data analysis, Come to the area sedimentary facies characteristics, structural characteristics, reservoir physical and lithology characteristics, Thus getting a comprehensive analysis and predicting the distribution of favorable reservoir,ideas and research In this paper:The high-quality carbonate reservoirs are On the basis of sedimentary facies which conducive to pore development and post-transformation, Late ongoing constructive transformation to Form, The main factor is the depositional environment, diagenesis, and tectonic. firstly I made the study of reservoir sedimentary facies analysis through field outcrop, core description, comparison of the associated well, Come to the main types of sedimentary facies and subfacies, Obtained a favorable sedimentary facies belts. Paleokarst enormous impact in the area of reservoir development, The article analyzed the factors affecting the paleokarst, Summary of the types of ancient karst development by means of thin sections and seismic identification. Structural interpretation of weathering crust karst reservoir inversion forecast, That construct and downs, ancient weathering crust karst and dolomite body to control the western margin of the carbonate reservoir traps. Through observation and analysis of field samples and core samples laboratory, Derived lithology physical characteristics, Divided into the main reservoir types based on lithology and pore characteristics. And then analyze the constructive diagenesis and destructive diagenesis diagenesis, As the basis of lithology properties, Combined with post-transformation on the basis of tectonic, Make a comprehensive evaluation and prediction on the reservoir. Identify a number of reliable structural trap by seismic interpretation. The results:Finally, the planar and spatial distribution of high quality reservoir was predicted.Studies suggest that:1two modes of the Ordos Basin, the western margin of the Ordovician sedimentary development, Rimmed carbonate platform model and the carbonate ramp model. Two modes, Types of sedimentary facies is divided into a carbonate platform, slope and basin facies and within a gentle slope, gentle slope, and outside the gentle slope.2The structural characteristics of the structure of the western Ordos Basin show the east-west belt from north to south subsections.in the orientation west to east, Divided from east to west in this article as:western fault subsidence zone, West edge of the thrust belt, Tianhuan syncline zone. in the orientation north to south, Significant difference according to the structural characteristics of the different sections in terms of topography, gravity and magnetic, structural characteristics, deposition. Divided into the northern section and south section of.3Western Ordos Basin Ordovician dolomite reservoir pore types of the collective is divided into three types:①Fine crystalline dolomite intergranular holes-karst hole reservoir.②Hole reservoir powder fine crystalline dolomite intergranular.③Mud rose quartz gray dolomite, limestone fissures cloud-and hidden hole reservoir. From the longitudinal analysis, Zhuozishan group of the best reservoir properties. followed by kelimoli group, And Pingliang group worst. Such as the porosity of the Zhuozishan Group average4.2%, Penetration rate of0.4×10-3μm2, Kelimoli Group porosity average of1.8%, The Kelimoli penetration rate of0.01×10-3μm2, The Pingliang group the porosity only0.8%, Penetration rate of less than0.01×10-3μm2. Ordovician dolomite class reservoir permeability properties are generally better than the particles of limestone classes.4The structural map, dolomite thickness map, the Ordovician weathering crust of the ancient geomorphological map superimposed with, A comprehensive analysis of, Preferred six favorable target, Two one-target, Were northern Majiatan region, Southern sun Gouyan area. |
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