深水井筒海水聚合物钻井液水合物 生成抑制与堵塞物处理方法.

The methods of preventing and curing gas hydrate in deepwater drilling are too preservative. In the west of the South China Sea, the gas hydrate inhibitive drilling fluid HEM used in the deepwater drilling is quite expensive and the penetration rate is low. To reduce the mud cost and shorten the drilling time, several issues were studied, including the phase equilibrium curves of hydrate generation with different gas components, the regions for gas hydrate generation under different operating conditions, and the methods of dealing with borehole blockage by the gas hydrates. All these studies were conducted with the low cost polymer drilling fluids used in the deepwater drilling in the BD block in the Yinggehai basin (South China Sea). Potential regions for the generation of gas hydrates under different operating conditions were obtained. Based on these studies, poly (M-vinyl caprolactam) was selected as the kinetic gas hydrate inhibitor to inhibit the generation of gas hydrates glycol selected as the thermodynamic inhibitor to remove blockage in a wellbore by gas hydrates. Ten new kinetic inhibitors were designed in laboratory study, of which the DS-A3 inhibitor has good inhibitive capacity for gas hydrate generation. Laboratory study and field (block BD) application showed that: 1) in operating conditions such as normal drilling, circulation and well shut-in, no gas hydrate generation region exists, as such, there is no risks of wellbore blockage. 2) Considering the inhibitive effect and cost together, 0.8% poly (M-vinyl caprolactam) has the best inhibitive effect for gas hydrate generation, and 45% glycol has the best effect for removing blockage of a wellbore by gas hydrate. 3) When there are no complex downhole operating conditions, if the rig down time does not exceed 15 hours, polymer drilling fluids can be directly used in deepwater drilling. In this way the drilling fluid cost for a single well can be reduced by 50%-70%, a good economic benefit. [ABSTRACT FROM AUTHOR]