Chemical Admixture for Right-Angle Set Wellbore Cements

Abstract

Polyaramid-based chemical admixtures for enhanced gas-tight oil well cements are of interest in the oil and gas industry. Here, a polymer platform is used as the base material for a line of new chemical admixtures in cementing in applications such as small molecule release and particle delivery. Polyaramid-based admixtures provide high-performance for high temperature and high pressure applications in ordinary Portland cement. Experimental results show that a basic cement slurry design responds to the release of admixture by the measure of changes in viscosity and thickening times. Applications in cement design is demonstrated from measurements obtained using oilfield equipment, like the consistometer. Immense efforts towards cement sheath integrity are important for production and safety. Challenges arises during the construction of wells when cement transitions from a slurry into a solid sheath. This transition can span over a significant length of time allowing gases to travel to the surface, causing casing-in-casing (CCA) events and pressure buildup. The ideal scenario is to eliminate the transition time of the slurry by designing cements to set instantaneously into an impermeable sheath. Right-angle set cements are characterized by a 90° set time as measured by a consistometer. The consistency of cement after addition of this new admixture remains at 20 Bc. In all cases, the admixture thereafter remains embedded within set cement and contributes significantly to its mechanical property. Dual performance stems from unique characteristics, such as chemical composition and mechanical integrity of new polymer admixtures. Using these admixtures, gas-tight cement sheaths show enhanced mechanical properties, such as resistance to breakage and fracture propagation, as well.