最小二乘曲线拟合的微地震初至优化拾取方法及应用

Microseismic first arrival picking based on least square curve fitting

水力压裂改造中微地震事件具有能量弱、信噪比变化大、干扰源复杂等特点,对微地震信号进行快速精确的初至拾取是微地震实时监测、指导压裂生产急需解决的关键问题。针对微地震事件时窗能量比法拾取精度低、不同信噪比事件适应性差的特点。首先应用能量比法粗略拾取初至位置。然后应用最小二乘曲线拟合法拟合理论曲线,在拟合曲线定义的前、后时窗范围内二次优化拾取初至。通过实际数据测试,并与能量比法对比,验证了本文方法的有效性与可行性。基于最小二乘曲线拟合的微地震初至优化拾取方法能较快速、准确地拾取不同波形特征、不同信噪比的微地震事件初至,有效提高微地震实时定位的准确性与效率。

Microseismic events are characterized by weak energy,variable signal-to-noise ratio(SNR),and complicated source interferences.So it is very difficult to do rapid and accurate microseismic first arrival picking in real-time monitoring to guide fracturing operation,and the energy ratio method has low accuracy and poor adaptability to different SNR events.To solve this problem,we propose a new microseismic first arrival picking method.First,an initial picking is carried out with the energy ratio method.Then the theoretical curve is fitted with the least square curve fitting.In the time window range before and after curve fit setting,the secondary optimized picking is conducted based on the initial picking.Real data tests verify the validity and feasibility of the proposed method.Comparing with the energy ratio method,the proposed method can quickly and accurately pick first arrivals from microseismic events with different waveform characteristics and different SNR,and effectively improve the accuracy of microseismic realtime positioning.