基于反褶积的地热井井底压力响应计算方法

Geothermal well bottom hole pressure response calculation based on deconvolution

文章提出了一种根据地热井放喷试验数据计算井底压力响应的方法,解决了放喷试验数据无法进行分析的难题,计算出的井底压力数据反映了地层流动特征,可用于试井分析和产能预测。由于地热井井筒温度、压力变化较大,在计算井筒压力损失时根据流体、水泥环、地层的耦合传热,推导热量损失的微分方程,给出了一种井筒温度、压力、密度分布的计算方法,使计算出的井筒压力损失较准确。在计算井底压力响应时,使用基于反褶积的总体最小二乘方法根据变流量条件下的井底压力计算出单位流量下的井底压力响应,同时把测量误差纳入了目标函数。最后对国内某地热井地面放喷试验数据进行了分析,根据计算出的井底压力响应预测了不同开采条件下的产能,预测的长时间开采时的产量与放喷测试获得的稳定流量吻合,验证了方法的正确性和实用性。

In this paper, a method to calculate well bottom hole pressure response with the data of geo- thermal well open flow test is Presented. The method solves the problem that the open flow test data is not suitable for conventional well test analysis methods, and the analysis result reflects the forma- tion flow characteristics and can be used for well test and productivity prediction. Because the well bore temperature and pressure are rather changeable, the coupled heat of fluid, cement sheath and formation is considered when calculating the well bore pressure drop, and the differential equation of heat loss is deduced. The method accounts for uncertainties including the true error and the pressure drop caused by the temperature, pressure and density distribution. The well bottom hole pressure re- sponse under the condition of unit flow rate is calculated according to the well bottom hole pressure under the condition of variable flow rate by using the total least squares method based on deconvolution. Finally, the open flow test data of a domestic geothermal well is treated by the method and the productivity under different exploitation conditions is provided by using the calculated well bottom hole pressure response. The predicted productivity under long time exploitation accords with the steady flow rate obtained by the open flow test, which verifies the correctness an＆~practicability of this method.