Effects of Thickening Time on the Application of Cement Slurry for High Pressure /High Temperature Drilling.

Abstract

High pressure/High temperature operations remain a high challenge for the industry as deeper reservoir operations are pursued around the globe. In addition to deeper depths, an increasing number of wells are still being drilled and completed in much more hostile down-hole environments. Though high pressure/high temperature wells have always presented drilling challenges, their operations continued to remain very high as the vast reserves of hydrocarbon promised to bridge the gap between demand and supply for energy. The world’s energy demand is rising and favorable economics have allowed oil companies to continue to prospect and drill in these more challenging areas that are actually prone to high pressures / high temperatures than ever before.

This paper addresses some of the challenges relative to cement slurry designs that requires careful engineering practices and needs proper cementing operations and optimization. It presents a simulation study using retarder sensitivity to select thickening time, optimize cement properties and also predict the subsequent HPHT sensitivity on cement slurries. The results showed that the modified Magnesium Oxide(mixture of water-glass and magnesium oxide) was best for slurry design for high pressure/high temperature which gave tighter matrix of cement paste. The application of retarder reduced the thickening time but the Water-Glass Solution improved the Magnesium Oxide cement thickening time, indicating that thickening time was dependent on time of exposure and on temperature. The rheological properties of the slurry showed that at HPHT, there were decreases in plastic viscosity, gel strength and the yield point. The study therefore determined one of the best cement slurry design practices for different down-hole applications in HPHT wells.

KEY WORDS : Cement slurry, Thickening Time, Modified magnium Oxide,High temperature/High Pressure