高压深井分段改造管柱封隔器间压力预测及应用

针对高压深井分段改造过程中封隔器间环空压力下降造成的改造管柱和封隔器受力状况恶化问题,基于能量守恒原理和井筒传热理论,建立了考虑摩擦生热和对流换热等影响的注入工况井筒温度场二维瞬态预测模型,并分析了井筒温度和压力变化对封隔器间环空体积的影响;然后结合井筒温度瞬态预测模型、环空流体PVT状态方程、油管柱径向变形计算模型和地层瞬态渗流方程,建立了典型高压深井封隔器间环空压力预测模型。最后,以塔里木油田1口高压气井为例开展了封隔器间环空压力预测。分析结果表明:常规设计方法认为安全的管柱,考虑封隔器间环空压力下降后就存在非常大的失效风险,高压深井分段改造管柱设计过程中必须充分考虑该因素。该研究成果为高压深井分段改造管柱的优化设计提供了新思路。

Prediction of pressure between packers of pipe strings for high-pressure deep-well staged stimulation and its application

In view of the deteriorated loading conditions of working strings and packers caused by annulus pressure drop between packers during the staged stimulation of high-pressure deep wells, one 2D temperature field transient prediction model was set up for borehole under injecting conditions which considers friction heat, convection heat exchange, etc. based on the energy conservation principle and the borehole heat transferring theory. By analyzing the influences of borehole temperature and pressure changes on the annulus volume between packers, and in combination with borehole temperature transient prediction model, annulus fluid PVT equations of state, radial deformation model of tubing and formation transient seepage equation, a typical high-pressure deep well inter-packer annulus pressure prediction model was established. Taking a high-pressure gas well in the Tarim Oilfield for example, the inter-packer annulus pressure prediction was conducted. The analysis results show that although the pipe string is safe according to the conventional design method, it is still susceptible to failures when the annulus pressure drop between packers are taken into consideration, so this factor should be considered in the design of pipe strings for staged stimulation. This prediction model provides a new idea for the optimal design of pipe strings for the staged stimulation of high-pressure deep wells.