Reservoir Engineering Analysis Applied to Low Permeability Formations and High Temperature

Abstract

It was found a zone in a Mexican geothermal field whose producers’ wells gradually are changing from two phase flow (mixture water-steam) to one phase (steam). From analysis carried out it was found that normally this behavior is related, among other factors, to unbalance between production mass flow rate and the recharge water entrance. Additionally some relations were found between formation thickness of low permeability and the evolution presented by reservoir. From the evidences found in the analyzed zone, the main conditions prevailing are: existence of high temperature (about 360 °C); and a lack of fluid in the reservoir. Temperature logged is an index of existence a heat source. The analyzed wells were studied in order to carry out their thermodynamic characterization and through correlation between them, a thermal evaluation of the zone. Pressure and temperature profiles measured during drilling stops at different depths were selected as closest conditions to undisturbed state. Were calculated the profiles of thermal gradient along the analyzed wells in the study zone and their corresponding heat flow profiles. The proposed technique in this work allows carry out an integral characterization of the reservoir in order to define the feasibility for using its stored heat for commercial exploitation. The methodology can be applied in geothermal fields with high temperature, but low or null permeability and, low or null recharge water entrance.