基于水击波的页岩油井压裂套变监测原理与应用

Principle and application of monitoring casing deformation in shale oil well fracturing based on water hammer wave

大规模体积压裂导致套管变形是影响页岩油气开采的重要因素之一,国内外对压裂期间的套变一直没有切实可行的方法。通过在井口安装高频压力计监测压裂停泵期间的水击波,通过水击波的波形来判断是否套变这一新方法,实现了对套变的有效监测。建立了压裂停泵水击波完备的方程组,通过对不同管径水击波数值解曲线分析,获得套变情况下波形特征。在管径不变的情况下,井口的压力-时间曲线特征为一条整体光滑的,振幅衰减的波动曲线;在有一处管径变小的情况下,曲线整体趋势不变,但振幅频率变高,且无规律性;在有两处管径变小的情况下,曲线的振幅频率及无规律性增加。通过对柴达木盆地1口井的实例应用验证了方法的正确性。该方法为页岩油气井压裂改造过程中实时监测套变情况提供了一种新的思路和方法。

Casing deformation caused by large-scale volumetric fracturing is one of the important factors affecting shale oil and gas exploitation.There is no practical method for casing deformation during fracturing at home and abroad.In this paper,a new method is put forward to monitor the water hammer wave during the pumping stop of fracturing by installing a high frequency pressure gauge.We establish a complete equation system for the water hammer wave of fracturing pump shutdown.By analyzing the numerical solution curves of water hammer waves with different pipe diameters,the waveform characteristics under casing deformation are obtained.Under the condition of constant pipe diameter,the pressure time curve of the wellhead is characterized by an overall smooth,amplitude attenuated wave curve;In the case where the pipe diameter decreases at one point,the overall trend of the curve remains unchanged,but the amplitude frequency increases without regularity;In two cases where the pipe diameter decreases,the amplitude frequency and irregularity of the curve increase.Finally,the correctness of the method is verified by an example of a well in Qaidam basin.