Interpretation of Schlumberger Sounding Data in Geothermal Areas

Abstract

Various authors have studied the methods of automatic interpretation known as the resistivity inversion, in which the adjustments of layer parameters are made by the computer based on the least squares method, starting from the initial guess parameters. The method is at present the most excellent tool for the interpretation of Vertical Electric Sounding (VES) curves.

In the present paper, the method of interpretation of VES curves is developed by the use of the linear filter method for the forward problem and the nonlinear least squares method for the inverse problem. The method is applied to the VES data over the present production area and to the data of the survey line D in a new area of Hatchobaru geothermal field, Ohita, Japan.

The section of resistivity layers derived from the inversion were compared with the drilling data from the production wells. As a result of this comparison, an acceptable geoelectric model was obtained for the fractured type of geothermal reservoir. Judging from the type of VES curve, it was found that the most of production wells are located on and near the VES stations where apparent resistivity curves show less than 10 ohm-m values against the moderate electrode separation.