压裂后不稳定试井早期恢复压力拟合重建方法

Fitting and reconstruction method of early recovery pressure for unstable well testing after fracturing

低渗、特低渗油气藏在大规模压裂后的不稳定试井,会因为关井不及时、井口漏失等原因,造成早期压力恢复数据缺失、跳点等,导致解释误差较大甚至不能解释。基于对压裂后不稳定试井早期压力恢复曲线变化规律的研究,找出压裂后不稳定试井曲线形态特征,简化数学模型;对比拟合效果,优选给出压裂排液关井早期井底恢复压力的经验公式,对缺失或异常的早期压力恢复数据进行外插值重建修正。C904井采用重建后的早期压力恢复数据与压力恢复实测历史数据合并后进行地层参数解释,整合后导入试井软件进行地层参数解释,曲线拟合效果较好,能较准确地解释出地层参数。该方法可较好地对压裂后存在异常的早期不稳定试井恢复压力进行重建,对压裂抽汲后的不稳定试井恢复压力重建亦有较好的的借鉴意义。

Transient well testing after large-scale fracturing in low and ultra-low permeability oil and gas reservoirs will lead to the loss of early pressure build-up data and jump point due to untimely shut-in and wellhead leakage,etc.,and lead to difficulties or errors in model diagnosis.Based on the study of the variation law of the pressure build-up curve in the early stage of the unstable well test after fracturing,the morphological characteristics of the unstable well test curve after fracturing are found out,and the mathematical model is simplified,the empirical formula of early bottom hole build-up pressure is optimized,and the missing or abnormal early pressure build-up data are reconstructed and corrected by interpolation.By comparing the simulated C904 unstable well test data with the measured unstable well test data,the formation parameters are interpreted by combining the reconstructed early pressure build-up data with the measured historical pressure build-up data,the curve shape characteristic is obvious,the explanation result is more accurate.This method can be used to reconstruct the abnormal early instable well test recovery pressure after fracturing,and it can also be used for reference to reconstruct the instable well test recovery pressure after fracturing and swabbing.