基于层状地层随钻电磁波测井伪解析公式,提出边界最优匹配技术,来实现对钻遇地层结构的自适应截断;同时提出散射场一次反射/透射波高阶渐近与扣除方法,极大地提高了索末菲积分的收敛速度,克服了传统数字滤波积分方法精度低、适用性弱等问题,实现了对随钻电磁波测井正演的加速。利用邻井或导眼井等先验信息,通过对地层模型进行交互式调整,为地层界面的预测提供最优反演初值。结合梯度寻优算法形成水平井随钻电磁波测井实时交互式反演方法。实际资料处理结果表明,随钻电磁波测井实时交互式反演方法很好地解决了井周地层边界位置确定的难题,为水平井钻井轨迹最优化和油藏解释提供了依据。图10表1参18
Based on the pseudo-analytical equation of electromagnetic log for layered formation, an optimal boundary match method is proposed to adaptively truncate the encountered formation structures. An efficient integral method is put forward to significantly accelerate the convergence of Sommerfeld integral. By asymptotically approximating and subtracting the first reflection/transmission waves from the scattered field, the new Sommerfeld integral method has addressed difficulties encountered by the traditional digital filtering method, such as low computational precision and limited operating range, and realized the acceleration of the computation speed of logging-while-drilling electromagnetic measurements (LWD EM). By making use of the priori information from the offset/pilot wells and interactively adjusting the formation model, the optimum initial guesses of the inversion model is determined in order to predict the nearby formation boundaries. The gradient optimization algorithm is developed and an interactive inversion system for the LWD EM data from the horizontal wells is established. The inverted results of field data demonstrated that the real-time interactive inversion method is capable of providing the accurate boundaries of layers around the wellbore from the LWD EM, and it will benefit the wellbore trajectory optimization and reservoir interpretation.
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