密集丛式井上部井段防碰设计关键参数临界值计算分析

Calculation and analysis of key parameter critical values in anti-collision design for upper sections of dense cluster wells

井眼轨道整体防碰设计是保障密集丛式井钻井施工安全的关键因素之一,而上部井段井眼轨道设计参数的优选与优化则是降低井眼轨迹碰撞风险的基础。对比分析了国内现行标准对密集丛式井整体井眼轨道防碰设计的指导作用及适用性。针对密集丛式井整体井眼轨道防碰设计问题,应用实钻井眼轨迹碰撞风险分析的分离系数概念,计算分析了分离系数为1时,密集丛式井上部井段造斜点深度、邻井造斜点深度差、造斜率、造斜方位等4个关键参数的临界值。研究结果表明:井口间距是影响密集丛式井上部井段井眼轨道防碰设计参数取值的关键,井口间距越小,临界造斜点深度、造斜深度差及造斜方位差越小,临界造斜率越大;现行标准所规定的邻井造斜点深度差预留了足够的安全余量,加密调整井防碰设计时可适当减小。

One of the key factors ensuring safe drilling of dense cluster wells is the overall anti-collision design of borehole trajectories. To reduce borehole collision risks, parameters for the design of borehole trajectories in upper sections must be properly selected and optimized. China’s standards in prior art were compared to analyze how they guide and apply to the overall anti-collision design of borehole trajectories for dense cluster wells. A separation coefficient in the analysis on collision risks of actual borehole trajectories was introduced. Critical values of four key parameters(KOP depth, offset well KOP depth difference, build-up rate and angle-building azimuth) for upper sections of dense cluster wells were calculated and analyzed with the separation coefficient being 1.Study results show the following: a smaller wellhead spacing delivers a smaller critical KOP depth, a smaller KOP depth difference, a smaller angle-building azimuth and a bigger critical build-up rate;the offset well KOP depth difference defined in existing standards has sufficient safety margins and can be properly decreased for the anti-collision design of infill adjustment wells.