Self-Repairing Polymer-Modified Wellbore Cements with High Thermal and Chemical Stability for Enhanced Geothermal Systems


Wellbore cement in geothermal environments is subjected to a number of mechanical, thermal (up to 450C), and chemical (CO2, H2S, mineral acids, concentrated brines) stress regimes over its lifetime. As a result, wellbore failure at the cement lining is one of the most common drivers of reservoir intervention during geothermal energy production. Wellbore intervention is expensive and time-intensive since involves production shutdowns and repairs. Intervention costs average $1.5million per wellbore without taking into consideration the economic losses as a result of production stoppage, which can be several million dollars depending on the time frame of plant in non-production mode. To address these problems, we developed thermally stable polymer-cement composites with multiple self-healing capability while maintaining the required rheological (during pumping) and mechanical properties of typical wellbore cement. We demonstrated that these novel composite formulations present all the requirements of standard wellbore cement and introduce self-healing capability as shown by 1) reducing by up to 95% the permeability, and 2) recovery of compressive strength between 70-110% of mechanically induced fractures in the 0.3-0.5mm aperture range.  These polymer-cement composites could then represent a definite solution to wellbore failure, production stoppage and reservoir intervention during geothermal as well as fossil energy production. This presentation will briefly describe the concept and present experimental as well as modeling results obtained this far on this patented technology.

Carlos Fernandez