天然气水合物对深水钻井液的影响及防治

EFFECTS OF NATURAL GAS HYDRATES ON DEEPWATER DRILLING FLUID AND CONTROL MEASURES

随着海洋钻井作业数量和深度的增加,钻井作业难度不断加大,海洋深水钻井作业环境恶劣,操作条件复杂,其中之一便是钻井液(主要是水基钻井液)中易形成天然气水合物。钻井液中一旦形成天然气水合物,会造成井壁失稳、堵塞井筒,钻井液无法循环,造成作业周期延长、钻井成本增加等。为解决钻井中天然气水合物的危害,综述了天然气水合物的形成机理。提出在深水区域钻井作业实施前,要充分估计到井口、防喷器、节流和压井管线中形成天然气水合物的可能性,一旦形成天然气水合物,可通过调节钻井液密度来控制井筒中压力,保持最低的安全钻井液密度来防止天然气水合物的形成。

With the amount and depth of offshore drilling increased,the offshore drilling operations are getting more and more difficult.The drilling environment is harsh and the operation is complicated.One of the challenges is that the drilling fluid(mainly WBM) is likely to produce natural gas hydrate.Once hydrate is formed in drilling fluid,it will results in unstable wellbore,well plugging,no circulation of drilling fluid,elongated drilling cycle,and increased drilling costs.Herein the mechanism of natural gas hydrates is explained,and it is recommended to fully recognize the potential of hydrates formed at wellheads,BOP,and choke/kill lines before deepwater drilling commences,and to control the well pressure through regulating the drilling fluid density so as to keep the minimum safe drilling fluid to prevent the formation of hydrates.