深水井气侵在不同类型钻井液中运动特征

Movement features of gas in different types of drilling fluid during kicking in deepwater wells

深水井钻井液密度窗口一般小于0.06 g/cm^3,压井过程中容易压漏地层,研究气体在不同钻井液类型中的运动规律有利于正确及时处理井控。通过对多相流的理论研究和计算,采用2口井的钻井液和实钻数据,结合Drillbench软件进行校核,得出了气体在不同钻井液类型中的运动特性;通过研究得出,天然气在水基钻井液中内部表现为气体滑脱和膨胀,长时间的关井会导致压破上层套管鞋;而在油基或者合成基钻井液中,则表现为气体溶解进其中,气体达到泡点压力后再次脱出;而在溢流发现难度上,水基钻井液相对容易发现,而油基钻井液由于气体溶解到钻井液内,溢流不易被发现。研究结果为深水井设计和现场安全处理井控事件奠定理论基础。

The drilling fuids for deepwater drilling can break down the formations easily during well killing for its density window s generally less than 0.06 g/cm3. In order to perform well control accurately in time, it is necessary to study the movement features of gas in different types of drilling fuid. After multiphase fow was theoretically analyzed and calculated, the results were checked by using the Drillbench Software based on drilling fuid and actual drilling data of two wells. In this way, the movement features of gas in different types of drilling fuid were identifed. The gas in water-base drilling fuid is presented in the form of slippage and expansion, and t can break the upper casing shoe after long-term well shut in. In oil-base or synthetic-base drilling fuids, the gas is dissolved and then migrates out when the bubble point pressure is reached. It is easier to detect the kick in water-base drilling fuid than in oil-base drilling fuid, for the gas is dissolved into the latter one. This paper strengthens the understanding on the deepwater well control and provides the heoretical basis for deepwater well design and safe well control operation.