考虑完井液存在的气井环空带压计算模型研究

Calculation Model of Sustained Casing Pressure in Gas Well Considering the Presence of Completion Fluid

准确预测套管内环空压力上升规律有助于指导现场在压力值达到破坏井筒完整性前采取措施,可有效降低环空带压对注采井安全生产带来的威胁.本文考虑气体在完井液中体积变化及运移规律,建立了完井液存在条件下环空压力计算模型,通过对比实例带压井的环控压力计算值与实际值,验证了模型的准确性.同时,计算分析了完井液液柱高度、完井液压缩系数及水泥环渗透率对最大环空压力值与其变化规律的影响,计算结果表明:较大的水泥环渗透率和较小的完井液压缩系数将会增大环空压力的上升速度,而完井液液柱高度不但对环控压力上升速度产生影响,较小的液柱高度还将导致最大环空压力增加.因此,增加完井液压缩性能、适当降低完井液柱高度、提高固井质量以降低气体在水泥环中的窜流是延缓环空带压的有效措施.

Accurate prediction of annular pressure rise in casing is helpful to guide the field to take measures before the pressure value reaches the goal of destroying wellbore integrity,and can effectively reduce the threat of sustained casing pressure to the safety of production and injection wells.This paper considers the volume change and migration rule of gas in the completion fluid,establishes the annular pressure calculation model under the condition of the presence of completion fluid,and verifies the accuracy of the model by comparing the calculated value of SCP with the actual value of the case.At the same time,with the calculation analysis of the completion fluid liquid column height,completion fluid compressibility and permeability of cement ring on maximum SCP value and its change rule,the calculation results show that the larger permeability of cement ring and smaller completion fluid compressibility will increase the annulus pressure rise speed,and completion fluid liquid column height not only impacts on loop control pressure rise speed,smaller liquid column height will also lead to the maximum annulus pressure increase.Therefore,it is an effective measure to delay the pressure by increasing hydraulic contraction performance,properly reducing the height of completion fluid column and improving cementing quality to reduce gas channeling in cement annulus.