基于数字滤波的压裂停泵压降分析方法

Analyzing method of the fracturing pump-off pressure decline based on the digital filtering

水力压裂实践表明,压裂停泵水锤现象会导致压降曲线出现周期性波动,这使得停泵压降的分析变得困难。鉴于此,提出了基于数字滤波的压裂停泵压降分析新方法,即首先采用井筒垂直管流方程将地面压力折算到井底压力,然后采用FIR滤波处理停泵后的压降数据,消除停泵水锤等噪声干扰,从而获得真实反映地层渗流的压降数据。以某低渗透油田的1口水力压裂井为对象,利用新方法开展了停泵压降分析,结果表明诊断结果与其他反演手段的解释结果相近,这在一定程度上验证了该方法的可靠性。本次提出的新方法可用于开展考虑水锤效应的压裂停泵压降分析,对于高效水力压裂实践具有一定指导作用。

Hydraulic fracturing practice shows that the phenomenon of the water hammer in the process of the fracturing pump-off leads to the periodic fluctuation of the pressure decline curve. Thereby, it becomes difficult to analyze the pressure decline. In view of this point, an new analyzing method based on the digital filtering for the fracturing pump-off pressure decline was proposed: First, the ground pressure was converted to the bottom pressure by the vertical pipe flow equation of the wellbore;then FIR filtering was used to deal with the pressure decline data after stopping the pump so as to eliminate the noise interference such as the water hammer of the pump and obtain the pressure decline data that truly reflect the seepage of the formation. Taking one hydraulic fractured well in the low-permeability oilfield as an example, the pump-off pressure decline analysis was carried out with the help of the new method, the diagnostic results were similar to those of the other inverting methods,Which to some extent verify the reliability of the method proposed in this study.The proposed new method in this study can be applied to conduct the analysis of the pump-off pressure decline considering the effect of the water hammer, and furthermore it possesses a certain guidance to the high-efficiency practice of hydraulic fracturing.