Abstract
The cement sheath between casing and formation is required to have long-term sustainability for the longer life of the well. Different formulations based on different additives are prepared and pumped down into the annulus between casing and formation. In the past, sodium silicate and some other silicates had a wide range of applications in conformance control and water shutoff. Mostly silicate-based systems were used as extenders and accelerators in oil well cementing. In this study, a novel silicate system, aqueous alkali alumino silicate (AAAS) was tested in oil well cementing. There have been limited applications of an AAAS-based cement system reported in the literature. Nondestructive compressive strength and rheological properties such as plastic viscosity, yield point, and gel strengths of silicate-based cement slurries were measured. The AAAS was added in (3, 5, and 8) wt % (% by weight of water) into the cement slurry and cured at 50 degrees C and 2000 psi for 24 h in an ultrasonic cement analyzer. The evolution of compressive strength was measured with time. The rheological properties were measured at 50 degrees C and atmospheric pressure using an atmospheric viscometer. The performance of AAAS was compared with 5 wt % sodium silicate and simple Class G cement. The scratch strength of 5 wt % AAAS and sodium-silicate-based cement slurries were tested and compared. It was observed that the addition of a novel silicate system increased the compressive strength. In addition to that, the novel silicate provided an accelerating effect in the development of compressive strength. The rheological properties increased with an increase in concentration. The yield point was mainly affected by the addition of AAAS. The application of a novel silicate could be a strong alternative for sodium silicate in area of oil well cementing because of its promising results of compressive strength and rheology. It has a high tolerance toward contamination as compared to sodium silicate reported in the literature. The nondestructive compressive was increased by 33% upon the ddition of 5 wt % AAAS. Furthermore, AAAS increased the yield point from 15.94 to 24.64 lbf/100 ft(2) at 5 wt % concentration. The AAAS solution is preferable in shallow gas wells of depths less than 3000 feet and 60 degrees C temperature. In those wells, AAAS can be pumped along with cement slurry for its quick setting. The AAAS can also be applied as an extender during cementing of low breakdown pressure formation or depleted zones.