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Recursive matrix method for simulating response of through-casing resistivity logging |
WEI Bao-jun1,2,TIAN Kun1,ZHANG Xu1,UU Kun1
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(1.College of Physical Science and Technology in China University of Petroleum,Qingdao 266555, China;2. Key Laboratory of New Energy Physics & Material Science in Universities of Shandong, Chirui University of Petroleum,Qingdao 266555,China)
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Abstract: |
A modified transmission line equation ( MTLE) for simulating the response of through-casing resistivity logging was computed by a recursive matrix method. The response of different formation models was simulated by the method, and the influence of such factors as cement layer,electrode spacing and heterogeneous casing was analyzed by the method. The influence of formation with multiple boundaries in radial direction was included in the coefficients of the transmission line equation, so the distribution of potential can be given for formation models which are layered in axial-direction and stair-stepped in radial direction. The method has the virtue of little computational amount,convenient programming and no overflow. The simulation results show that the method has a high resolution of axial formation boundaries. The low-conductivity cement layer has a great influence on the response in high-conductivity formation. The computed apparent conductivity is a composition of conductivities of all the layers in radial direction as there are many layers in this direction. It has some influence on the logging response whether the casing becomes thinner or thicker, and the abnormality of logging response appears near the points where the casing suddenly changes. The simulation results also show that the electrode spacing has some influence on the response of through-casing resistivity logging. |
Key words: electric logging electric conductivity casing transmission line equation recursive matrix method |
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