水合物钻探井筒多相流动及井底压力变化规律  

Multiphase flow in wellbores and variation laws of the bottom hole pressure in gas hydrate drilling

作　　者：高永海 孙宝江 赵欣欣 王志远 殷志明 王金波 

机构地区：[1]中国石油大学石油工程学院,山东青岛266580 [2]中海油研究总院,北京100027

出　　处：《石油学报》2012年第5期881-886,共6页Acta Petrolei Sinica

基　　金：国家自然科学基金项目(No.50874116;No.51034007;No.51004113);山东省自然科学基金项目(ZR2009FQ005);国家重大科技专项(2011ZX05026-001-02);教育部创新团队项目(IRT1086)资助

摘　　要：天然气水合物钻探过程中,破碎后的水合物碎屑伴随钻井液上升到一定位置后开始分解,分解出的天然气使井筒流动变为复杂的多相流,导致井底压力预测困难,甚至可能引发井涌等复杂情况。针对这一问题,考虑水合物分解和相变热的影响,建立了水合物层钻井中的井筒多相流动模型和传热模型。通过对模型的求解,分析了水合物分解临界点和井底压力的变化规律。结果表明,降低钻速和钻井液入口温度,有助于抑制水合物分解,稳定井底压力;增大排量,水合物临界分解位置降低,整个井筒中气体体积分数较小,井底压力较稳定;适当提高钻井液密度控制井底压力能够有效抑制水合物分解。在水合物层钻井时,应对以上参数进行优化,以避免因水合物分解而引发的事故。During the process of gas hydrate drilling, hydrate cuttings continuously rise along with drilling fluid and start to decom- pose at a certain position, the decomposed natural gas will change the wellbore flow into a complex multiphase flow, which makes it difficult to predict the bottom hole pressure and possibly arouses the occurrence of some complex situations, such as well kick. Ai- ming at these situations, we established models for wellbore multiphase flow and heat transfer in gas hydrate drilling by taking the effect of hydrate decomposition and the thermal effect of phase transition into consideration. Variation laws of critical points for hy- drate decomposition and the bottom hole pressure were investigated through computation with the models. The result shows that the reduction in drilling rate and the inlet temperature of drilling fluids will help to restrain hydrate decomposition and stabilize the bot- tom hole pressure. Besides, the enhancement of delivery capacity will lower down the position of the hydrate decomposition critical point, yet with a lower gas volume fraction and a steady bottom hole pressure in the whole wellbore. Moreover, to control the bot- tom hole pressure by properly raising the mud density can restrain hydrate decomposition effectively. In order to avoid accidents re- suiting from hydrate decomposition, we should optimize the above-mentioned parameters while conducting gas hydrate drilling.

关 键 词：水合物 井底压力 分解 临界点 多相流动 

分 类 号：TE521[石油与天然气工程—油气田开发工程]