Proper Appllcatlon Of Borehole Geophysical Techniques To The Evaluation Of A Carbonate Aquifer: A Case Histor

This paper documents a petrographic and petrophysical analysis of a water<br>supply test hole drilled in southwest Texas. The six inch hole penetrated the lower<br>Cretaceous Georgetown and Kiamichi Formations to a depth of 520 feet.<br>Initial analysis of the hole was ambiguous. Density and sonic porosities<br>were as high as 22% and 30%, respectively. However, an air-lift test of the well<br>produced only 35 gallons of water per minute. Further analysis of the well was<br>deemed necessary.<br>A petrographic examination of the drill cuttings was conducted to resolve<br>the discrepancy between the high porosity and low water production rates and to<br>determine if water production could be enhanced by acidizing or fracturing the<br>well. The logs were also analyzed in an attempt to resolve the discrepancy<br>between the density and sonic porosity values. Recommendations were made<br>regarding the most effective methods for evaluating subsequent wells.<br>Petrographic analysis of the cuttings revealed that the rock is a slightly<br>shaly, fossiliferous limestone with isolated moldic and micro-intergranular porosity.<br>While total porosity is high, effective porosity is very low. Neither fracturing nor<br>acidizing the well would significantly increase permeability and specific yield.