高温高压井双封隔器管柱安全评估

Safety assessment on twin-packer string of HTHP well

胡志强 杨进 李中 李文龙 顾岳 李舒展

HU Zhiqiang YANG Jin LI Zhong LI Wenlong GU Yue LI Shuzhan

中国石油大学(北京)石油工程教育部重点实验室 中海石油(中国)有限公司湛江分公司

Key Laboratory of Petroleum Engineering Education Ministry, China University of Petroleum(Beijing), Beijing102249, China CNOOC China Limited Zhanjiang Branch, Zhanjiang524057, Guangdong, China

高温高压油气井投产后受到地层高温流体影响，完井管柱双封隔器密闭空间内的流体介质受热膨胀，导致圈闭憋压，可能造成油管挤溃和油层套管破坏的危险，严重威胁管柱服役周期和井筒完整性。针对密闭空间压力上升带来的安全生产问题，运用弹性力学和传热学理论，分析了温度载荷作用下井筒与地层耦合作用机理，研究了自由段油管和封固段油层套管处管柱位移形变量随温度和压力变化的关系，建立了双封隔器密闭环空压力预测模型，同时对不同生产工况下的封隔器管柱安全性能进行了校核分析。研究结果表明：在开井生产阶段，环空压力随双封隔器的间距增加而增加，不会影响管柱安全；在完井液循环阶段，考虑极端工况情况下，环空压力随双封隔器的间距增加而减小，但均超出油层套管抗内压强度，不能立即坐封，因此等待一段时间后坐封封隔器才能保证管柱的安全性能。

After HTHP (high temperature and high pressure) oil and gas wells are put into production, the fluid medium in the closed space of twin packer of completion string is thermally expanded due to the effect of high temperature reservoir fluids, and leads to confined pressure building.As a result, the tubing may be collapsed and the production casing may be damaged, doing serious harm to string service life and wellbore integrity.To deal with the safe production problems caused by the increasing of pressure in closed space, the coupling mechanism between borehole and strata under the effect of temperature load was analyzed by using the theories of elasticity and thermal conduction.Then, the relationships of string displacement deformation at free tubing and cemented production casing vs.temperature and pressure were investigated.Finally, a pressure prediction model for the closed space of twin packer was established.Meanwhile, the safety performance of packer string in different working conditions was checked and analyzed.It is indicated in the stage of flowing production, the annulus pressure increases with the spacing of twin packer and the safety of strings is not impacted.Inthe stage of completion fluid circulation, the annulus pressure decreases with the increasing of twin packer spacing if the extreme working condition is taken into consideration, but it is always higher than the internal pressure strength of production casing.Therefore, the packer shall not be set at once and its setting shall be performed after a while so as to ensure the safety of strings.

10.13639/j.odpt.2017.03.006