Novel retarder solutions for HPHT well cements

Novel retarder solutions for HPHT well cements Portland cement is todays the main sealant material used for wellbore constructions in O&G and geothermal applications. For the cementing job, well cement is mixed and pumped into the well as a liquid slurry. Accurate slurry design with strong control on cement retardation at high pressure / high temperature (HPHT) conditions is critical in the overall success of drilling and completion well operations to avoid extra costs. Commercial retarders used to increase pumpability of cement slurry are lacking temperature stability and high rate of early strength development during retarded cement setting. In the presented work, novel retarder solutions were developed for sustainable HPHT well applications to ensure reliable cement placement. Cement slurries were prepared following API 10A with different additive concentrations. The setting time of cement slurries was screened in the laboratory using isothermal calorimetry at various temperatures. The thickening time and rheology of the cement slurry with novel retarders are compared with representative benchmarks. The novel retarder solutions are effectively delaying the curing of cement during the initial hydration phase at low temperature and showcased robustness, predictable efficien-cy, and reliability of such tailored systems. Test results have shown higher temperature stability than pure organic admixture solutions, thus qualified for a more reliable cement slurry placement over a broader temperature range (up to 200°C). Thereby, these solutions are of high benefits for well cementing at high BHCT (Bottom Hole Circulating Temperature) and strong temperature gradient along the well depth. A good right-angle-set at high temperature obtained with set cements make the developed solutions attractive for further development to higher technology readiness levels. This R&D work has received funding from the Research Council of Norway (KOMMERS-FORSK Commercialisation Project Qualification / project nº 321355) and from the European Union’s Horizon Europe research and innovation programme under grant agreement nº. 101084623.