Chang 7 shale oil play in Qingcheng Oilfield,with widespread water source area and marginal forest area,is difficult to exploit,and hosts a restricted original oil in place(OOIP)of approximately 1.67×108 t.Ultra-long horizontal well can realize a large control of drainage area and reserves,so it can be adopted to effectively exploit the restricted OOIP and enhance the recovery of Chang 7 shale oil.Based on the precise delineation of 3D geological engineering sweet spots,the optimal deployment site of ultra-long horizontal well was determined,and the predominant intervals,potential intervals,fault intervals,and fracture intervals were identified.Then,a fine and differentiated fracturing scheme was prepared to achieve"fracture-controlled reserves maximization".Moreover,an evaluation system for ultra-long horizontal well was established to evaluate the development performance from three indexes:reservoir factor,reservoir development,and economic benefits.Field application shows that with the increase of horizontal section length,the thickness of Class I+II oil reservoirs increases from 623 m to 2 337 m,the well-controlled reserves increase from 16.9×104 t to 45.9×104 t,the initial well production rate increases from 9.6 t/d to 25.1 t/d,and the stage well production increases from 1×104 t to 1.5×104 t.The use of ultra-long horizontal well in Qingcheng Oilfield enables the effective exploitation of different types of reservoirs in environmentally sensitive areas and improves the economic benefits of shale oil development.This technology is referential for the development of similar shale oil reservoirs
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