A geopolymer cementing system for oil wells subject to steam injection

Oil wells subjected to cyclic steam injection often present cement sheath failures due to thermal loads. Currently, different Portland based systems are employed to mitigate this risk. We developed and tested geopolymer systems that meet oil well cementing requirements and achieve high mechanical performance. A metakaolin-potassium-based formulation, containing microsilica, mineral fiber and retarder, was adjusted to the desired rheology and thickening time. Triaxial compression and indirect tensile tests were performed and the properties were used in finite element simulations of the life of a model onshore well. Compared to the Portland based system currently in use, the geopolymer has superior uniaxial compressive strength and lower stiffness. Tensile strength increased significantly with the addition of mineral fibers and became higher than that of the Portland system. Numerical simulations show that the geopolymer can withstand steam injection temperatures comparable to a conventional system, remaining in the elastic region. These results show that geopolymers are a viable alternative well cementing system for this application, with significant improvement in mechanical performance.