四川盆地东部二叠系吴家坪组地质特征及开发技术对策OA

Well DY1H in eastern Sichuan Basin revealed a high-yield industrial gas flow from the Permian Wujiaping Formation during test.This achievement marks a significant shift in shale gas exploration within the basin from a single-layer system(Silurian Longmaxi Formation)to a multi-layer succession,and creates a new strategic target for shale gas resource replacement in the basin.Taking Well DY1 in the Nanya syncline as an example,based on seismic,drilling,logging and production performance data,this paper studies the geological characteristics and development patterns of the Wujiaping Formation in eastern Sichuan Basin,and proposes the corresponding development strategies.The following results are obtained.First,the Permian Wujiaping Formation in the DY1 well block,deposited in deep-water shelf,contains high-quality shale reservoirs of 15-28 m thick,with the average brittle mineral content of 77.54%,average TOC of 5.41%,average porosity of 5.6%,average total gas content of 6.7 m3/t,and principal buried depth of 4 500-5 000 m.Although the Permian Wujiaping Formation reservoirs are deeper and slightly thinner than the Silurian Longmaxi Formation reservoirs,they exhibit superior static parameters such as gas content,TOC,porosity and brittle mineral content,indicating a great potential for achieving incremental reserves and production.Second,the 4th layer of the third member of Wujiaping Formation is selected as the platinum target,the optimal well spacing is determined as 350-400 m,and the wellbore trajectory/orientation is adjusted properly depending on fracture geometry,helpfully to improve the degree of resource mobilization.Third,through an innovative two-round optimization of casing program and the selection of appropriate bits and rotary steerable systems,the drilling period is minimized to 64.81 d,and the material cost is lowered by more than 4 million CNY per well,implying a significant reduction in investment costs.Fourth,the techniques such as extremely limited entry,fracture pressure reduction with hydrochloric acid,adhead viscous fluid+fast rate enhancement,and supermolecule fracturing fluid are adaptable to the well block and conducive to improving the stimulation effect,making them promising for large-scale application.The Permian Wujiaping Formation is believed to have a potential for serve as a strategic replacement of shale oil resources in the Sichuan Basin.The proposed optimized strategies with respect to well placement,drilling,and fracturing can effectively address the exploitation challenges and provide theoretical and technical support to large-scale and beneficial development of shale gas in the Sichuan Basin.