Abstract：If the case of borehole is considered as a layer of medium,people can make,by using mufti-layer radial-stepped medium model,the strict solution of the field of direct current circle in cased borehole to obtain a potential function of any layer;and then the coefficient recursion matrix for potential functions of any two adjacent layers can be derived from boundary condition. This theory can be also used to know some characters of low frequency pseudo-stable field in cased borehole,resistivity measure method for formations around the cased borehole,and the effects of both electric conductivity and thickness of case. Numerical modeling result shows that in terms of field-source distance, field in cased borehole can be divided into near field area,mid field area' and far field area. In the mid field area,second-order derivative of electric potential nearly does not vary with field-source distance,but it changes obviously with formation electric-conductivity. Consequently,the theory can be determined of deriving correct formation electric-conductivity from secondary electric potential difference. Numerical modeling result also says that the secondary electric potential difference is severely influenced by both electric conductivity and thickness of case but slightly affected by electric conductivity of cement.
刘迪仁, 徐建华. 套管井中直流环的响应及其应用研究[J]. 石油地球物理勘探, 1998, 33(4): 519-524.
Liu Diren, Xu Jianhua. Response of direct current circle in a cased borehole and its application research. OGP, 1998, 33(4): 519-524.
