Investigation of the Effect of Eggshell Additive on Cement Sluryy Quality

Abstract

<p>Cementing oil and gas well requires materials that ensures stability of the cased and cemented wellbore to isolate troubled zones. To achieve this job, the search for alternative material for cementing gas well has increased worldwide. Hence, it is necessary to make use of an appropriate cement programme designed with suitable additive that improves the cement bond strength, durability, resistance to abrasion on the wells life which improve quality of cement to provide zonal isolation. To protect the environment, investment, public trust and reputation, the cement plug sample porosity, permeability must be reduced, also an increase in compressive strength is needed to accomplish this technically. The research is aimed at evaluating the performance of eggshell as additive for gas well cementing operation at ambient condition. Laboratory test were conducted on a base cement sample or check plug mixed with different concentration from 30% to 70% to determine the effect on porosity, permeability and compressive strength of the cement sample. CT scan were conducted to study the composition and internal structure of the cement sample. The results showed that the 50% eggshell addition yielded the best casing integrity and should be used because it is nearly impermeable and non-porous in comparison to the base cement sample or check plug sample. An optimum concentration 50% eggshell/sandstone decreased the porosity and permeability to the barest which the aim of the study stands to achieve. The effect of eggshell and sandstone is prominent to a concentration 50%, this may be due to the equilibrium mixture present in the cement plug with the highest density of the samples obtained, and therefore increasing more than the optimum percentage of eggshell will increase cost of cementing without further improvement in performance. From the CT scan eggshell particle distribute non-uniformly in the mixture to clog the pores, helping to decrease the porosity and permeability only up to a specific quantity. At higher concentration, the result for permeability are found to be reversed whereas porosity keep decreasing. Eggshell does not have significant effect on permeability at higher concentration, while with less or mild concentration of eggshell the permeability reduced drastically. However, it is evident that addition of eggshell as additive resulted in better slurries with higher values of compressive strength greater than 500psi after 48hrs of curing which is the minimum strength before performing any perforation. After 48 hrs of curing the cement, cement sample with eggshell incorporated develop morestrength by 56% to 91% increase in the compressive strength, as the concentration increases compared to the base slurry. All of the prepared cement sample exhibited a sufficient strength required for oil and gas application. Therefore, the material showed potential in making short and long-term wellbore integrity requirement. Eggshell is thought to be responsible for reducing the porosity and permeability of the cement and improving its overall strength.</p><p>Keywords:- Cement Plug Sample, Eggshell Concentration, Porosity, Permeability, Compressive Strength, CT Scan, Zonal Isolation and Wellbore Integrity.</p&gt