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井—地电位法是利用地下储层注水后岩层电阻率的变化来研究储层剩余油分布和注水的推进前沿、判断油田的注水分布和剩余油分布的一种地球物理方法。本文阐述了井—地电位法监测地下注水裂隙的方法原理,研究和推导了水平管状注水裂隙的井——地电位异常的理论公式,建立了地下裂隙模型并在Matlab中计算地下不同长度、深度和方位的地下裂隙在地面的理论视纯异常值,画出了注水前后电位差视纯异常玫瑰图。数值模拟结果表明,水平管状注水裂隙的井——地电位法视纯异常玫瑰图呈苹果状曲线分布,视纯异常的最小值对应的是苹果状曲线的根部,苹果状曲线的根部所指向的方位对应的就是地下注水裂隙的方位。在供电电流为15A,地下裂隙深度在500 m,裂隙长度为50～100 m时,井——地电位法视纯异常的变化幅值在n×10nV～n×100nV之间。井——地电位法视纯异常的形状、幅值随着水平管状注水裂隙的方位、长度和深度的变化而变化,因此,可以采用井——地电位法,监测地下水平注水裂隙的方位、长度和深度情况,从而为监测地下注水裂隙的注水情况及剩余油的分布情况提供地球物理资料。
Well-to-ground potential method is a geophysical method to study the distribution of remaining oil in reservoirs and the advancement of waterflooding by using the change of formation resistivity after injection of underground reservoirs, and to determine the distribution of waterflooding and remaining oil in oilfields. In this paper, the principle of well-ground potential monitoring of underground waterflooding fissures is expounded. The theoretical formula of well-ground potential anomaly of horizontal tubular waterflooding fissures is researched and deduced. The underground fissure model is established and different subsurface lengths and depths are calculated in Matlab And azimuths of underground fractures in the ground theoretical pure apparent abnormal value, draw the water potential difference before and after the pure abnormal rose figure. The numerical simulation results show that the well-ground potential method of horizontal tubular waterflooding fissures shows an apple-shaped curve, and the minimum of pure anomalies corresponds to the root of the apple-shaped curve. The root of the apple-shaped curve points to The azimuth corresponds to the orientation of underground water fissures. The variation of apparent anomaly in well-ground potential method is between n × 10nV and n × 100nV at a current of 15A, a depth of subterranean fracture of 500 m and a length of 50-100 m of fracture. The well-ground potential method assumes the purely anomalous shape and the amplitude changes with the azimuth, length and depth of the horizontal tubular waterflooding fissure. Therefore, the well-ground potential method can be used to monitor the azimuth of horizontal waterflooding fractures, Length and depth, providing geophysical data for monitoring flooding of underground waterflood fractures and the distribution of remaining oil.