体积法压井现场试验研究

Field experimental research on volumetric method for well killing

为了更加精细地描述体积法压井过程中井内气体的分布和运移规律,针对体积控制法压井开展了试验研究,通过在试验井井底注气的方式,模拟气侵并实施体积法压井;测量并分析压井过程中套压、立压、出口流量及注气速率等参数的变化规律。研究结果表明:体积法压井控制过程中,由于井筒内气侵气体以多个短气柱和弥散型气泡分布为主,在钻井液泄流过程中套压很难实现理想状态的稳定控制;井口出现气体并不代表气侵气体以气柱形式全部到达井口,通过气液混合泄流,可有效控制井底压力实现井底准恒压;当部分气体在井口形成气柱后,可提前启动置换流程,这种体积控制流程和置换流程结合的方式可有效降低地层破裂风险;置换流程中压井液的注入会产生井底附加压力,针对薄弱地层,需考虑此参数以降低风险。

In order to describe the distribution and migration laws of gas in the well during the volumetric well killing process more finely,the experimental research on the volumetric control method for well killing was carried out.The gas cut was simulated and the volumetric method for well killing was implemented through the way of gas injection at the bottom of experimental well,then the variation of casing pressure,standpipe pressure,outlet flow rate,gas injection rate and other parameters during the well killing process were measured and analyzed.The results showed that during the volumetric control process of well killing,the cutting gas in the wellbore mainly distributed in the forms of multiple short gas columns and dispersive bubbles,so it was very difficult to achieve the stable control of ideal status for the casing pressure during the discharge process of drilling fluid.The appearance of gas at the wellhead did not represent that the cutting gas would all arrive the wellhead with the form of gas column,and the quasi constant pressure at well bottom could be achieved by controlling the pressure of well bottom through the gas-liquid mixed discharge.After partial gas formed the gas column at the wellhead,the replacement procedure could be started in advance,and the combined method of volumetric control procedure and replacement procedure could reduce the risk of formation damage.The injection of well killing fluid in the replacement procedure would generate the additional pressure of well bottom,and this parameter should be considered to reduce the risk aiming at the weak formation.