Experimental and Numerical Evaluation of the Integrity of Cement and Geopolymer Under Low and Elevated Temperature Well Conditions

ABSTRACT Rock-based geopolymer is an inorganic polymer consisting of granite mine waste and metallurgical industry by-products. Previous studies have investigated that the rock-based geopolymer has a potential to be an alternative to Portland cement for preventing long-term degradation. In this paper, instead of mechanical well integrity, the performance of mud displacement using the rock-based geopolymer with different retarding additives is evaluated. The investigation includes experimental and simulated studies. In the experiments, rheological properties (i.e., shear stress-shear rate curves and thickening time) are measured. A 3D computational fluid dynamic (CFD) model is developed to simulate the mud displacement in the annulus between the casing and formation. Since previous reports and publications presented that the well inclination was a major challenge in cementing procedures due to gravity effects, this paper focuses on the displacement in horizontal and high-inclined wells. Oil-base drilling fluidwas used as the representative fluid. The effect of different cement additives adding to the geopolymer on the mud displacement, including gluconic acid, sucrose, calcium chelator, and sodium poly-naphthalene as dispersant and retarder are evaluated to provide a recommendation for rock-based geopolymer additives. Wellbore geometries is another investigating parameter. The paper compares the performance of normal, rectangle, and real-shape annulus. The real-shape well geometry was developed based on the caliper log generated from a well in Tuscaloosa Marine Shale (TMS) area. Compared with the ideal annulus, the model can provide an accurate recommendation for applying rock-based geopolymer in field conditions. The results aim to provide more information on the application and mud displacement performance of rock-based geopolymer in high-inclined and horizontal wells. Recommended additives were proposed for the optimization of pumpability and displacement efficiency. Evaluations of different wellbore geometries provide a more realistic model. INTRODUCTION Cement placement is becoming a major challenge as more unconventional reservoirs have been developed due to the complicated lithology, drilling strategies, and innovative cementitious materials. An excellent cement system is expected to provide casing supports, producing zone isolations and leakage preventions. Poor quality of cement can lead to well integrity issues and negative impacts on the environment and human safety, such as casing damage, blowout, groundwater contaminations, and greenhouse gas leakage. To achieve the goal of a high-quality cementing job, mechanical and hydraulic cement integrity considerations should be involved during the analysis. Mechanical considerations should satisfy the requirements of structural failure prevention in the cement under different wellbore conditions, such as high-temperature high-pressure (HTHP). Hydraulic integrity is required for quality evaluations of cement slurry, specifically in the mud displacement processes.