高温高压气井关井期间井底压力计算方法

常规的井底压力预测方法认为,气井关井后压力恢复初期井口测压受到井筒储集效应影响,后期受温度降低引起的续流影响,并且在压力恢复期间井筒中不存在流体的流动。但是,新疆克拉2气田部分高温高压气井的实测结果表明,关井后测得的井口压力恢复曲线总体呈下降趋势,与常规方法所计算的压力曲线并不一致。对高温高压气井关井后的井筒温度特征、井筒续流特征和井筒流体参数变化特征进行了分析,认为,关井期间井口(底)压力同时受到井筒储集效应和温度变化的影响,并且在压力恢复过程中井筒内一直存在续流流动,需要进行流动气柱压力计算。为此,综合考虑井筒续流、井筒温度及井筒流体参数的变化特征,基于井筒压力恢复原理,建立了关井期间的井底压力计算模型,并对该模型进行了实例计算验证。实例验证表明,该模型计算出的压力恢复曲线正常,可用于产能试井解释。 

The Calculation Method of Bottomhole Pressure during Shut-in Period in High Temperature and High Pressure Gas Well

In the conventional method of bottomhole pressure prediction it is assumed that the wellhead pressure is affected by the wellbore storage at the beginning of pressure buildup and by the afterflow in the late stage because of the temperature drop.And it is also assumed that there is no fluid flow in the wellbore after shut-in.However,according to testing results of some high pressure and high temperature wells in Kela2 Gas Field,there was a pressure drop in the wellhead pressure build-up curve which is different from the conventional pressure build-up curve.The changing characteristics of wellbore temperature,the wellbore afterflow and the fluid parameters during the pressure build-up test then were analyzed.It is believed that the wellhead pressure or bottomhole pressure would be affected by both wellbore storage and wellbore temperature simultaneously.And there was afterflow in the wellbore during the whole test.So,the bottomhole pressure needs to be calculated by the flowing pressure equation.Based on the wellbore pressure build-up theory,the bottomhole pressure calculating model is established considering the effect of wellbore afterflow,the wellbore temperature changing and the fluid parameters changing.Taking one gas well for example,the pressure buildup curve calculated by this model is normal,and it can be applied for interpretation in the deliverability test.