压裂直井压后返排油嘴直径优选方法

随着非常规能源的开发,压裂技术得到了更广泛的应用。压后强制返排技术是保证裂缝高导流能力的有效措施;然而,选取合理的油嘴直径进行返排一直是现场施工的难题。油嘴直径过大,会造成支撑剂大量回流;油嘴直径过小,压裂液向储层大量滤失,对储层造成伤害,不利于油气增产。利用物质平衡原理,在支撑剂回流启动模型的基础上,结合裂缝的闭合特性,导出了压裂液返排过程中井口压力与最优返排油嘴直径的关系式,为现场施工提供指导。分析表明,裂缝闭合时机是油嘴选取的临界状态,裂缝闭合前,支撑剂在裂缝中启动流速低,不宜用大油嘴返排;裂缝闭合后,最优返排油嘴随压降变化敏感,可以及时更换大油嘴进行返排。

Method to Optimize Choke Sizes During Back Flow

As the extensive development of unconventional energy resource, hydraulic fracturing technology is developed and more widely used than before. Technology of forced fracture closure is an effective measure to guarantee high conductivity fractured reservoir. Nevertheless, reasonable choke size during backflow is always an enigma which confuses engineers in oil field. Big choke size may leads to backflow of proppants and small choke size may causes damages to reservoirs. Combining the principle of material balance with model of proppant back flow and considering characteristics of fracture during closure, the paper deduces the equation between well head pressure and reasonable choke size which shows fracture close time is the critical state and small choke size is necessary before fracture close and bigger choke size is reasonable to speed up the rate of backflow.