井喷发生后硬关井的井口压力分析

Wellhead Pressure Analysis of Hard Shut-in after Well Blowout

井涌或井喷发生后,成功关闭防喷器是保护井筒、避免事故恶化的重要措施;而确定关井载荷、界定关井时机对研制与安全运营高压井口装置具有重要意义。以超高压防喷器国产化研制为背景,针对井喷/井涌时地层气体大量侵入井筒、推动钻井液柱加速上行的极端恶劣工况,利用瞬变流理论建立硬关井后井筒环空水击波传播数学模型,计算大量气侵发生后不同时刻实施硬关井引起的井口动载荷,为设计、选用和校核井口装置提供载荷依据。针对防喷器压力等级,给出关井时机界定条件,提出在井口安装钻井液返速监测装置,当流速达到预警值时自动关井,确保井口装置安全。

After a well kick or well blowout occurs,shutting down the blowout preventer(BOP)is an important measure to protect the wellbore and avoid the further deterioration of the accident.It is of great practical significance to determine the shut-in load and delimit the shut-in time for developing and operating high-pressure wellhead equipment.Against the background of domestic development of ultrahighly BOP,in view of an extremely harsh condition,which means that during a blowout/well surge,a large amount of formation gas kicks into wellbore and the drilling fluid is pushed upward faster and faster,mathematical models that describe water hammer wave travelling in the annular space after hard shut-in are established by means of transient flow theory.Extreme loads that the BOP is subjected to are predicted when the hard shut-in happens at different times after massive gas invasion.It provides a basis for designing,selecting and checking wellhead device.The shut-in time is recommended according to the pressure level of the BOP.It is proposed that a monitoring device for return rate of drilling fluid should be installed at wellhead.The well could be shut in automatically when the velocity reaches the warning value,and the safety of the wellhead could be ensured.