Usability of Geopolymers for Oilwell Cementing Applications, SPE 182354 By ?, 13 Oct 2016

Portland cement has become the prime material used for zonal isolation; sealing annuli between casings, between casing and formation and finally for plug and abandonment (P&A) operations. However, there are concerns regarding Portland cement such as autogenous shrinkage, high permeability after cracks has occurred, gas influx during waiting on cement (WOC) time, instability at high temperature, ductility and durability. Geopolymers have been suggested as an alternative to Portland cement for oil well applications. Geopolymers are inorganic aluminosilicate cementitious materials condensed as result of a complex reaction known as geopolymerization.

The current work presents the usability of a geopolymeric material specially designed for oil well cementing applications, known as aplite rock-based geopolymer. The chemical reaction of the geopolymeric slurries was determined using calorimetry measurements. The rheological behavior of the geopolymers, such as consistometer consistency and viscosity were examined besides their mechanical properties. The investigation of mechanical properties included uniaxial compressive strength, sonic strength and tensile strength. The pumpability and setting time have been studied by changing mix design of the geopolymeric slurries along with the addition of selected retarders. Finally, microstructure of the cured geopolymers was studied using Scanning Electron Microscopy (SEM).

The results show that slurries have a non-Newtonian behavior like a Bingham material with a small yield stress. The curing pressure reduced the pumpability of the geopolymeric slurries; however, the reason remained unclear. Addition of sucrose by 1.2 wt.% of the total solid content resulted in an optimal accumulative heat release, which showed the highest strength development. Pumpability of the mixes was prolonged by introducing sucrose to the geopolymeric slurries. Tensile strength of the geopolymers was found to be approximately 5 percent of their compressive strengths. Based on the obtained result, geopolymers have the potential to be considered as an alternative to Portland cement.