Abstract: Based on the widely used electrode array structures and focusing ways in laterolog, effects of three conventional electrode array structures on electrode coefficient, borehole effect and radial investigation have been studied systematically using the finite element method. In addition, we have analyzed the effects of hardware focusing way and software focusing way on logging responses using the contrast of vision. An array measurement method using software focusing has been presented simultaneously, which had been tested using the Oklamoha standard formation. The results show that different electrode array structures and different parts have various effects on the detection characteristics. The status of insulator section should be attached great importance to, because their influence on detection characteristics is extraordinary obvious. The software way not only eliminates the negative influence of remainder potential difference in hardware focusing way, but also realizes array measurement similar to the array laterolog based on the importing of focusing coefficient with the range of 0-1.1, nevertheless, the electrode structure is consistent with the dual laterolog. The electrode coefficient decreases with the increase of focusing coefficient, borehole effect correction ranges from 0.8 to 1.16 and this method improves the radial investigation depth with the largest one exceeding 2.0 m, obtaining more abundant radial formation resistivity information.

Key words: laterolog, electrode array structure, software focusing, focusing coefficient, finite element method, resistivity