Performance Evaluation of Local Material Rice Husk Ash under Downhole Conditions with the Addition of Basic Oil Well Additives Antifoam, Fluid Loss, Dispersant and Retarder on Oil Well Cementing

Abstract

The effect of RHA on Compressive Strength as well as other parameters like Consistency and Rheological properties etc. on Class G cement slurry is studied. The following additives were used; Rice Husk Ash (for Compressive Strength), Guinea Corn Husk Ash (Retarder) and other liquid additives which are fluid Loss Additive, Antifoam, Dispersant, Retarder and Water in the formulation of the cement slurry. This research is a comparative analysis based on experimental study on the effectiveness of the various additives on the cement slurry using pure Class G cement slurry combined with all liquid additives as a control. At a Bottomhole Circulating Temperature of 140°C, the Compressive Strength tests carried out on the slurry samples showed that the strength of the concrete increases as the concentration of the RHA increases with time of curing, also the compressive strength started to increase. The best Compressive Strength result was obtained with the percentages of cement replaced by 13.01% RHA. The strength showed impressive increase with time, with highest compressive strength encountered in 24 hours. The Thickening Time of the set Cement Slurry was considered using Class G cement and different percentage of RHA. The final Thickening Time decreases with increase in Rice Husk Ash. Decrease in the setting time was noticeable from 1.87 hrs (at 13.01% RHA) from 40bc to 100 bc. At BHST of 700°C increasing the ash concentration resulted in decrease in the Plastic Viscosities (PV) and increase in the Yield Points of the slurries. The results indicate that the slurries formulated using this ash has viscosities which are within the recommended values showing it is desirable to pump such slurry. For both 124°C and Bottom Hole Pressure of 7700psi the amount of fluid loss increases as the percentage of RHA added increases but it is below 50cp which is acceptable.