Use of Synthetic Fluid Inclusions As a Simultaneous Temperature-Pressure Logging Tool in High-Temperature Geothermal Reservoirs

Abstract

Batch autoclave experiments were conducted to evaluate the potential use of synthetic fluid inclusions as a simultaneous temperature-pressure logging tool in high-temperature (>350?C) geothermal systems. The application of synthetic fluid inclusions provides pressure-temperature conditions for deep-seated geothermal systems, which cannot be obtained by conventional tools because of extreme temperature conditions. Fluid inclusions, up to 50 m long were readily synthesized during 5 day-long autoclave experiments conducted at 375 to 475?C, and 39 to 62 MPa in pre-fractured, inclusion/impurity-free artificial quartz. Inferred fluid inclusions trapping conditions are calculated by deducing the intersection of isochores derived from microthermometric data for three sets of simultaneously trapped synthetic fluid inclusions in healed microfractures. Synthetic fluid inclusion logging offers a precise borehole temperature measurement technique with an estimated error of only ±12?C without need of any pressure correction. Pressure estimates are less precise, although the method may be improved by using a combination of H2O-NaCl and H2O-KCl solutions. Saline fluid/quartz/amorphous silica systems, which facilitate crack healing but trap fluids that are not homoge