| Abstract |
Geothermal wells ordinarily are exploited using the conventional methods similar to those used in oil wells in their primary production stage. However after exploitation starts the productivity decline also appears in higher or lower influence rank. The decline in productivity along exploitation is a function of the reservoir properties, mass flow rate extraction and of recharge water entrance, among other parameters. In the analyzed field it was found that the unbalance caused by the higher mass extracted in comparison with the entrance mass by recharge, is one of the reasons for productivity decline in wells. It has been observed a thermodynamic evolution of some of the wells they will achieve conditions of dry steam. In this work, a section was analyzed of a producer Mexican geothermal field, with high temperature logged, small recharge water entrance and additionally low permeability. The analyzed data show quickly the decline in productivity and in some cases lacking flow. This study is focused to rescue the completed non-producer wells some years before, which are not in use to date. Due to reservoir heterogeneity, producer wells and non producers appear as neighboring along the field. However it was possible to identify a zone, where the non-producer wells but with high temperature appear grouped. The analysis carried out allows establishing a study methodology for zones of high temperature, low permeability and low recharge water entrance, in order to evaluate the stored heat in the rock formation. The evaluation of stored heat in reservoirs that trend to decline represents a technical support for analyzing alternative methods of exploitation different to those conventionally used. The stored heat was evaluated in the analyzed zone using data of three production wells and other three non-producers. In the methodology applied, variation of values in variables was used whose determination could introduce some uncertainty degree. The variation proposed was from 0.75 to 1.25. The obtained results are expressed in MWh and show the feasibility for extending the methodology to other similar fields. |