伊朗Arvand-1井异常高压地层溢流压井技术

Well Kill Technique for Abnormal High Formation Pressure in Well Arvand-1 of Iran

Arvand-1井是一口重点天然气探井,由于钻遇异常高压地层、钻井液密度偏低、不能平衡地层压力,起钻过程中发生了严重的天然气溢流,关井套压高达52.5MPa,关井立压31.7MPa。若对其实施常规压井作业,则存在井内憋压过高极易造成井喷和井漏、钻具不在井底难以进行正常循环压井、人员必须在高空作业而操作不便,以及境外施工井队后勤支持困难等难题,也存在井喷与井喷着火、硫化氢中毒等风险。因此,采取了工程师法、强行下钻法配合置换法的溢流压井配套技术,即先用高密度压井钻井液(最高密度达2.48kg/L)置换压井以降低井内套压,再采用工程师法压井进一步降低套压,然后强行下钻再利用工程师法压井,共历时18d,取得圆满成功。Arvand-1井的压井成功,对于异常高压地层的天然气溢流压井及境外项目的井控工作具有一定的借鉴作用。

Well Arvand-1 is a key gas exploration well,a serious gas kick happened during tripping out due to abnormal high pressure formation.The mud weight is too low to balance the pore pressure.Shut-in casing pressure and shut-in drillpipe pressure are 52.5 and 31.7 MPa respectively.The normal kill technique cannot be used because of potential risks and problems,such as well blow out and lost circulation caused by high pressure.The normal fluid circulation cannot establish since drillpipe does not reach well bottom.It is inconvenient for high-altitude operation.It is difficult to provide good logistics support for overseas wellsites.The risk of blowout and firing as well as poisonous H2S also exist.In order to solve all these problems,engineer method,snubbing and displacement method are combined to kill the well.The displacement method is used first to remove gas and decrease the casing pressure（mud weight up to 2.48 kg/L）,then the wait and weight method is used to further decrease the casing pressure.Snubbing and the engineer method are used again to finish the well killing.It takes 18 days to successfully kill the well.The application experience in Well Arvand-1 can provide reference for well killing in abnormal high formation and well control in overseas project.