Development of a homogenous cement slurry using synthetic modified phyllosilicate while cementing HPHT wells

Abstract

Cement slurry segregation has a detrimental impact on the cement matrix efficiency in term of zonal isolation. In this study, synthetic modified phyllosilicate (SMP) dispersant, which is known as laponite RD is suggested to reduce the slurry segregation and enhance the vertical homogeneity of the cement matrix in term of density distribution. Seven cement slurries were prepared with different SMP concentrations using molds with different dimensions based on the targeted test, then cured for 24 h at 140 °C and 3000 psi using a high-pressure and high-temperature curing chamber. After that, the samples' density distribution was evaluated using a direct density measurement and computer tomography (CT) scan imaging technique, and the effect of SMP on the cement rheological parameters, permeability, and compressive strength and were also evaluated. The performance of SMP was then compared with a commercial dispersant. As a result, 0.3% by weight of cement (BWOC) of SMP is found to considerably reduce the vertical density variation along the cement column to 0.46% compared with a density variation of 4.78% for the slurry with the commercial dispersant. The CT scan images confirmed the vertical homogeneity of the slurry with 0.3% BWOC of SMP. Addition of 0.3% BWOC of SMP increased the yield point of the cement slurry to 60.6 MPa compared with 20.5 MPa for the slurry with 0.25% of the commercial dispersant. Adding 0.3% BWOC of SMP into the cement formulation decreased the permeability by 37.1% compared with the commercial dispersant. The sample with 0.3% BWOC of SMP has a compressive strength of 43.9 MPa.