A Research On Reservoir Architecture Of Xujiahe Formation In The Western Sichuan Exploration Area

The Xujiahe Formation implies abundant natural gas resources in Western Sichuan depression, which is the focus horizon of gas reservoir exploration in Sinopec southwest oil and gas branch company. The gas reservoir exploration and development has a long history in Xujiahe formation, and obtains major cognitive achievements. However, because the compact reason is very complexity of the compact sandstone reservoir in western sichuan depression, it brings that gas reservoir is difficult to set up yield, and up grade reserves. In addition the regulation of the gas pattern enrichment is very not clear, various types of gas reservoir and the characteristics has different features. Geological conditions are complex and the main control factors of gas enrichment is not clear. Aim at these prominent problems, preliminary research shows that different lithofacies architectures have different control function for gas accumulation. Consequentily, this paper carrys out lithofacies architecture research in Xujiahe formation of western sichuan area, it is great significant to clear explored direction and to realizes a break through of exploration.The paper adopts the research thought of outcrop-underground-plane-domain (time and space domain). Classify different lithofacies architecture types through the field outcrops sedimentology and analyse the characteristics of different lithofacies architecture,count the characterization parameter of all kinds of architectures, mainly including:sand body morphology, size, direction, superimposed style, sand ratio, thickness of single sand body and interlayer insulation thickness and distribution of diversity. On this basis, accoding to drilling core, cuttings, logging and seismic data. At the same time, by combining thelithofacies combination, lithological profile, sedimentary facies characteristics, carry out the identification and classification of downhole lithofacies and proceed from the downhole one-dimensional profile of pattern standards and parameters system of lithofacies architectureal partition, to compare connecting-well profile of lithofacies architecture with each other, the analyse the lithofacies architectures and space-time evolution characteristics. In addition, it’s analysis and study of typical gas reservoir and purposefully collecting field samples of different architectures to provide the research basis for the high quality reservoir characteristics and forecast and to clear the relationship of existing production reservoir and lithofacies architecture. On this basis, match the relation between the lithofacies architectures and reservoir properties and establish the high quality reservoir concept model of under the control of lithofacies architectureThrough the research of field lithofacies architecture, summarize five sections, a total of 17 kinds of lithofacies wild style and six lithofacies architecture mode which integrates the research of wild field and underground in Xujiahe formation. They are:A: Thick mudstone clip thin-medium thick layer sandstone interbed, B:thick mudstone thin-in-thick sandstone and coal seam, C:clip-thick sandstone in the thick mudstone, D:thick sandstone and glutenite, E:thick layer channel sandstone superimposed, F: thick mudstone facies. On this basis, under the constraint of seismic, set up the comparison framework of connection-well lithofacies architecture framework. According to the results of underground lithofacies architecture, determine planar distribution and characteristics of 7 important sand groups of lithofacies architectures. Within the scope of Work area, different regions of different section distribute different lithofacies architectures..The conclusion is found by combining with production characteristics analysis that each segment layers of high-middle-low yielding wells is controlled by different lithofacies architectures. Basically, have some regularitiries, the high-yield wells is under control of E, C lithofacies architectures, E architectures mode also belong to a good class of reservoir classification and evaluation of the reservoir. While the middle-low-yielding wells, the relationship between reservoir evaluation and classification II, III type and lithofacies architectures is not very close, lithofacies architectures mode of II, III class reservoir and middle-low-yielding reservoirs is diverse, there are five kinds of architectures mode E、D、C、B、A. The middle yielding well is not only controlled solely by E mode or C mode, but also by E+C+D combination control mode. Basically, the fourth section of Xujiahe formation is controlled by combined mode. Low-yielding wells are subject to C+E, A+C+D+E, B combination mode control.