Evaluation of Primary Cementing Operations for a Carbon Capture Storage (CCS) Well: A Case Study

In this case study, we explore a carbon capture storage (CCS) well that is typical of those currently cemented in Alberta, Canada. Storage of carbon dioxide (CO2) deep underground in a safe geological structure, involves the injection of CO2 into well and trapping of CO2 within the formation, without leakage. A key factor contributing to limiting any risk of gas leakage in CCS is a successful primary cementing operation. To retain primary control of the well, the downhole pressure should be less than the fracture pressure and higher than the pore pressure. We use a one-dimensional (1D) hydraulic simulator, to pressure match with recorded pump pressures. While the results illustrate that primary well control is maintained throughout, the pressure comparison to the acquisition data reveals significant differences. This might be due to an increased hole size, due to ellipticity or a washout. Fluid contamination during the annular displacement flow might also alter fluid rheological properties, leading to a higher simulated pump pressure than to the operation data. Secondly, we use a two-dimensional gap-averaged model (2DGA) to determine the positioning of the fluid sequence at the final time of the job. This gives us insights into potential mixing and fluid contamination, possible generation of residual mud wall layers and mud channels at any given depth. The simulated cement job outcomes show a mud channel forming on the narrow side of the annulus. Adding centralizers to the deviated part of the well can enhance the efficiency of the displacement process and reduce the likelihood of mud channel formation.