Abstract: In order to accurately locate the microseism sources, a thorough knowledge of the velocity model between the treatment well and monitoring well is essential. A new method is developed to invert the velocity model based on Occam inversion algorithm. Instead of the travel times, this method adopts the moveouts of the first arrivals to invert the velocity models, so it can overcome the limitation of conventional approaches when the perforation origin times are unavailable or measured inaccurately. The feasibility of this method is examined on synthetic datasets. The results demonstrate that although the velocity models obtained using this method show some discrepancies, which are caused by the picking errors, they can locate the perforation shots back to their expected positions, so the inverted velocity models can be used to locate the microseism sources.

Key words: microseismic, velocity model, arrival time, travel time, moveout, Occam inversion

摘要： 为了能够对微地震震源进行精确定位, 需要已知压裂井和监测井所在工区内准确的地层速度模型。针对这一问题, 在采用Occam反演算法的基础上, 提出一种利用初至波的走时差信息代替旅行时进行速度模型反演的方法。利用该方法, 可以在无须已知射孔起始时间的情况下反演得到地层速度模型。通过模型数据的处理以及对结果的分析, 表明虽然受到初至到时拾取误差的影响, 采用上述方法反演得到的速度模型会存在一定的误差, 但利用该模型可以将射孔位置定位到其真实位置附近, 表明该速度模型可用于进行微地震震源定位。

关键词: 微地震, 速度模型, 初至到时, 旅行时, 走时差, Occam反演