Tunisian geothermal data from oil wells

Abstract

Since direct measurements of steady‐state temperatures are not readily available in Tunisia, a geothermal investigation has been made using 1319 values of bottom‐hole temperatures (BHTs) obtained from 217 petroleum exploration wells. An empirical relation based on the differences between BHT and DST (drill stem tests) was used to correct BHTs and estimate geothermal gradients. The estimated geothermal gradient of the country varies between 21 and 52 °C/km. A few regions with similar gradients have been identified, and similarities between gradient contours and the main structural directions are noted. Furthermore, for 25 points from 12 wells, it was possible to apply the Horner‐plot method to determine the equilibrium formation temperature (Tf). Comparison of Tf values with those calculated by the estimated gradients reveals a good correlation (r = 97 percent) between the two estimates. This agreement permits greater confidence in the statistical method used and consequently in the estimated gradients for the whole country.