基于OLGA的深水钻井置换法压井模拟

Killing Simulation of Displacement Method in Deepwater Drilling Based on OLGA

作为一种非常规压井方式,置换法被广泛用于空井、钻具不在井底、水眼堵塞、钻具刺漏等情况下的压井作业。针对目前多采用简化的公式计算、缺乏多相流动模型应用的问题,本文利用一维瞬态多相流模拟软件OLGA,建立了深水钻井置换法压井"注液—等待—放气"过程的模拟方法。该方法解决了钻井数据复杂难以输入和置换法工艺复杂难以模拟的问题,实现了置换法压井流程自动控制,即"注液"过程井筒压力上升到破裂压力前自动停注,"放气"过程井筒压力降低到孔隙压力前自动关阀。计算表明,深水钻井气侵后经过2h关井,气体向上运移并在井口处聚集,具备置换法压井条件。压井过程中,压井液在井筒中不以"液塞"的形式存在;注入阶段井底压力迅速上升,等待阶段井底压力轻微降低,放气阶段井底压力迅速降低;注入时间显著大于放气时间,且随压井的进行逐渐变短。

As an unconventional well killing method,displacement method is widely used in the well killing operation under the conditions of empty well,drilling tool being not in the bottom hole,water hole blocking,drilling tool leakage and so on.In order to solve the problems of simple formula calculation and lacking of application of multiphase flow model at present,displacement method in deepwater drilling was put forward to simulate the process of "injection,waiting and gassing" during the well killing through one-dimensional transient multiphase flow simulation software OLGA in this paper.This method solves the problems that complicated drilling data is difficult to input and the displacement method is complicated and difficult to simulate,and realizes the automatic control of the kill process for the displacement method,that is,the injection will stop automatically before the wellbore pressure rises to the fracture pressure in the process of "fluid injection",and the valve will close automatically before the wellbore pressure decreases to the pore pressure in the pro-cess of "gas discharge".The calculation results show that the well will shut in after gas invasion in deepwa-ter drilling in two hours,and the gas migrates upward and collects at the wellhead,which is suitable for well killing by the displacement method.In the process of well killing,the kill fluid does not exist in the form of "fluid plug" in the wellbore.The bottom hole pressure increases rapidly at the injection stage,and decreases slightly at the waiting stage,and decreases rapidly at the gas discharge stage.The injection time is significantly longer than the blowout time,and gradually shorter with the well killing.