THE RESERVOIR TEMPERATURE ESTIMATOR (RTEST): A MULTICOMPONENT GEOTHERMOMETRY TOOL

The Reservoir Temperature Estimator (RTEst) is a multicomponent geothermometry tool for estimating reservoir geochemical parameters including reservoir temperature, CO₂ fugacity, mass of water lost or gained, and a reaction factor. It estimates these parameters and their associated uncertainties by minimizing an objective function that is the weighted sum of squares of the saturation indices of a user-selected set of minerals believed to be equilibrated with the reservoir fluid. RTEst accomplishes these estimates by combining the geochemical modeling capabilities of The Geochemist’s Workbench with the optimization/parameter estimation resources of PEST. Features include 1) multiple weighting methods including an inverse variance method that is based on the conditional variances of the saturation indexes and, 2) an interface to aid the user in selecting the plausible mineral phases to include in the objective function. We demonstrate the capabilities of RTEst through its application to several examples including estimating temperature when the reservoir geochemical signature is modified by mineral equilibrium, reconstructing waters with CO₂ loss, correcting for volatiles loss from boiling, mixing of thermal and non-thermal waters, and using measured water chemistries with missing or unreliable aluminum data.