Sweet spot classification evaluation of tight conglomerate reservoir in Mahu Sag and its engineering application
【Abstract】With the expansion of global oil and gas exploration toward deep, subtle, and unconventional reservoirs, new breakthroughs have been made in oil and gas exploration in China. The Mahu tight conglomerate reservoirs in the Junggar Basin, Xinjiang are rich in oil resources and have great potential for large-scale construction. However, the factors that affect the oil flow capacity in the reservoir are complex and diverse. Also, there are a number of challenges during the development. For example, the reservoir heterogeneity is strong; the determination and classified evaluation of “sweet spot” are difficult; the difference of horizontal principal stress between the two directions is large; the formation and extension mechanism of hydraulic fractures is unclear; the cost is high; the geological conditions are complex. Guided by geology-engineering integration, combining the geological characteristics of the study area with the production practice, we have established the classified evaluation standard of “sweet spots” for this type of reservoirs. By the method of volume fracturing with intensive segments, stereoscopic development technologies and tests of “long horizontal sections, intensive segments, small well spacing, large well clusters and industrialized production” have been explored, forming a set of technical systems for efficient development of tight conglomerate reservoirs and achieving good results. The improvements of accuracy in description of “sweet spots” and 3D geological models have significantly increased the efficiency of drilling and completion engineering. The average number of adjustment times of horizontal section trajectories decreased from 5 m to 2 m and the penetration rate of the oil layer reached up to more than 90%. Moreover, the average cluster spacing in Ma-131 well block decreased from 67 m to 35 m, and the average cumulative production increased by 37.5% in 300 days.
【Keywords】 tight conglomerate; sweet spot classification; small well spacing; intensive segment; stereoscopic development;
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