基于小区域地表感知横纵波时差的页岩压裂定位方法研究

Research on shale fracturing localization method based on transverse and longitudinal wave time difference of small-region surface perception

针对页岩油勘探中传统的压裂定位方法存在定位模型复杂、精度低以及技术成本高等不足,提出了基于小区域地表感知横纵波时差的页岩压裂定位模型及其算法。首先,采用变分模态分解的信号处理技术分解微地震波低频响应,可提高原始压裂响应的信噪比。其次,将长短时窗算法(STA/LTA)与赤池信息准则(AIC)算法相结合,有效地识别分解信号的起跳点,从而完成横纵波之间的时差拾取。最后,建立了横纵波时差与压裂源坐标、小区域地表检波器坐标之间定位数学模型,通过最小二乘法,实现基于多个定位数学模型的压裂源坐标计算,其坐标值均值可有效提高定位计算精度。

Aiming at the shortcomings of the traditional shale fracturing localization methods for shale oil exploration,such as the complexity of localization model,low accuracy and high technical cost,both a shale fracturing localization model and its algorithm are proposed based on the time difference of transverse and longitudinal waves of small-area surface sensing.Firstly,the signal processing technology of variational mode decomposition is used to decompose the low frequency response of microseism wave,which can improve the signal-to-noise ratio of the original fracturing response.Secondly,the long and short time window algorithm(STA/LTA)is combined with the Akaike information criterion(AIC)algorithm to effectively identify the take-off point of the decomposed signal,so as to complete the time difference picking between the transverse and longitudinal waves.At last,the localization mathematical model is established among the time difference of transverse and longitudinal waves and the coordinates of fracturing source and the coordinates of small area surface geophones,the calculation of fracturing source coordinates based on various localization mathematical models can be realized by means of the least square method,and the average value of coordinate value can effectively improve the accuracy of localization calculation.