| Title | New gel systems to remediate hydraulic short-circuits in heterogenous or fractured heat reservoirs |
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| Authors | D. Rousseau, S. Briton |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | The increasing interest for geothermal operations in highly heterogeneous or fractured reservoirs (such as EGS) highlights the effects of thermal short-circuits between injection and production wells, detrimental to the process efficiency. Remediation methods involving aqueous gels, similar to those implemented for oil production in Conformance Control Operations, are being investigated. A major challenge for adapting these methods to geothermal lies in the impact of high and varying temperatures on gelation kinetics and gel performances. Indeed, operations where short-circuits issues arise often involve deep reservoirs, with higher temperatures than oil reservoirs and significant temperature gradients in circulating fluids. This study introduces a new type of gels made of sulfonated polyacrylamide polymers and inorganic crosslinkers. As gelation requires interactions between crosslinkers and acrylate monomers that are not initially present in the polymer's structure, these systems remain in the sol phase during injection. This means that there is no risk of injection well plugging. When the sol self-propagates in the high conductivity fractures, it is exposed to increasing temperatures: acrylamide hydrolysis leads to formation of acrylates, enabling gelation over the entire fracture width. As gelation kinetics is controlled by both the temperature the ratio between acrylamide and sulfonated units, these versatile gel systems are well adapted for geothermal operations even if the temperature gradient and fracture properties are not precisely known. The experimental study presented includes a set of parametric gelation tubes tests and coreflood experiments performed in artificially fractured plugs, where gelation kinetics, gel parting pressure and gel aging are investigated. |