Comparative Study of Local Cements with Imported Class G Cement at Different Temperatures for Oil Well Cementing Operations in Ghana
The purpose of this research is to determine the suitability of local cements as an alternative to imported class G cement at different temperatures using oil well cement additives. Laboratory investigations on both local and imported cements to determine physical properties such as thickening time, fluid loss, compressive strength, free fluid and rheology were conducted at bottom hole circulating temperature of 27°C (80°F) and 66°C (150°F). The results indicated that locally manufactured cements are compatible with oil well cement additives at 80°F and 150°F and can be used as an alternative to imported class G cement in oil and gas well cementing operations. However, premature gelations of test results were phenomenal at 66°C (150°F) for the entire locally manufactured cements especially sample CEM B. Therefore, for local cements to be used effectively for cementing high temperature operations, stringent quality control during their manufacturing process is imperative.
Evaluation of Thickening Time of Oil Field Class G Cement Slurry at High Temperature and Pressure Using Experimental Design - TI Journals
Abstract: The main objective of cementing technology is to cement casing string so as to facilitate zonal isolation necessary to drill further or control production. To achieve this objective slurries are design by adding certain additives to control density, filtration loss and pumpable/thickening time needed for slurry placement. 
 
Thickening time was evaluated at 6000psi and 400oC using Experimental Design. Four factors which include extender, accelerator, antifoam and dispersant was considered at two levels. Sixteen experiments were conducted with the response replicated twice. The analysis was done using Yates algorithms to determine the influence of different parameters on the thickening time. 
 
A regression equation was developed for pumpable time as a function of the dependent variables. The model developed has a correlation coefficient, R2 of 0.9998, coefficient of variance of 0.0000697 and standard error of 0.08838. The model is simple and easily programmable for initial estimations on the field.
Intensification of Bubble Disintegration and Dispersion by Mechanical Stirring in Gas Injection Refining
Water model experiments were performed for establishing highly efficient gas injection refining processes. Mechanical stirring was applied to disintegrate the injected bubbles and to disperse them widely in the bath. The bubble disintegration and dispersion were investigated by changing rotation mode (direction of rotation), rotation speed, blade size of the impeller and gas flow rate. Forward rotation of the impeller induced a stable tangential flow and could not disperse bubbles in the bath due to formation of a vortex around the impeller shaft. The tangential flow could be suppressed by forward–interrupt rotation, which could reduce the vortex formation to some degree. However, forward–interrupt rotation could not disperse the bubbles widely in the bath. Forward–reverse rotation could prevent the vortex formation completely and create a strong shear stress field, which intensified the bubble disintegration and dispersion in the bath. Higher impeller rotation speed and larger blade length in forward–reverse rotation could enhance the bubble disintegration and make the dispersed bubbles smaller. The bubble dispersion zone became wider with larger blade length. The bubble size tended to be larger at higher gas flow rates. However, its dependence on the gas flow rate became smaller at higher impeller rotation speed.