Cement slurry optimization and assessment of additives according to a proposed plan

•A checklist is presented for optimization of cement formulation regarding to gas flow.•The effect of Anti-gas migration agent on controlling gas flow is investigated.•Thixotropic agents improve the performance of slurries facing gas flow significantly.•Thixotropic agents improve the cement transition time, critical hydration time and gel strength profile of the cement.•Thixotropic agents could be used as effective supplementary additives for cement slurries with anti-gas migration agents.

Wellbore cementing is an essential part of every completion plan. The primary target of a cement job is zonal isolation and avoiding formation fluids to invade the well. Failure of cements in this important task result in disasters, significant financial damages and many more consequences. Good Cement slurry design is the key factor of having a gas resistant cement column. The aim of the study was to optimize slurry formulations following a determined checklist of criteria. The performance of two anti-gas migration and thixotropic agents were also assessed. As the final stage of the slurry optimization plan the results were verified using fluid migration analysis (FMA) test. According to the results, total gas migration flow rate of cement slurry optimized using the presented checklist was recorded as 0.23 ml/min. It was also observed that thixotropic agents improved gel strength profile, filtration control, waiting on cement time (WOC), critical hydration time and cement transition time significantly.