INTERPRETATION OF PRODUCTION TESTS IN GEOTHERMAL WELLS WITH T2WELL-EWASG

A crucial aspect of geothermal reservoir engineering is the performance and interpretation of field tests, such as production tests, flowing temperature and pressure logs - both during injection and production, and down-hole pressure transient recording. Such tests are of great importance in order to evaluate the reservoir properties and to predict wells production capacity. However, production tests duration is often limited by environmental constraints related to the disposal of brines, and the running of downhole measurements is constrained by safety and cost considerations related to the use of expensive tools in high temperature high productive wells. From this point of view, the capability to simulate the whole production tests can be extremely useful to improve the data interpretation and reduce the impact of lacking field data. In particular, the coupled simulation of transient fluid flow within the wellbore and the reservoir with the matching of output production curve, flowing logs, and downhole pressure transients, should result in a more reliable evaluation of reservoir properties. This can be done using T2Well, a coupled wellbore-reservoir numerical simulator, with proper equation of state (EOS) modules. EWASG is an EOS module for high enthalpy geothermal fluids consisting of mixtures of water, salts and a non-condensable gas (NCG). We have recently plugged it into T2Well and also improved the analytical computation of heat exchange between the well and the surrounding formations at early time, which may be important for reproducing the transient results of production tests. The resulted wellbore-reservoir simulator, T2Well-EWASG, is capable to simulate high enthalpy geothermal wells. We validated T2Well-EWASG against flowing pressure and temperature logs taken from published literature.