Evaluation of different test methods for the detemination of rheological parameters in cement slurries for HPHT wells
Rheology, Cementing, HPHT Oil Wells
Temperature is an important factor for the determination of rheological properties of a cement slurry. The American Petroleum Institute (API) recommends in its RP 10B-2 standard that rheological parameters of cement slurries, at bottom hole circulation temperature (BHCT) greater than 190 °F, must be determined in two steps: (i) the slurry must be conditioned at BHCT conditions using a pressurized consistometer and (ii) cooled down to 190 °F and depressurized to atmospheric conditions so an atmospheric viscometer can be used. In this work, rheology tests of HPHT (High Pressure High Temperature) slurries were carried out on a pressurized viscometer, which allows the tests to be entirely executed at the BHCT conditions. This way, there was no need for cooling, depressurizing and transferring the slurry between equipments. The results were compared to what was obtained with the API RP 10B-2 procedures. Significantly different rheological parameters were observed between these two methods. In addition, hydraulic simulations were performed to evaluate the impact of those differences on cement slurry displacement in a cementing job. The simulation revealed that the difference between the rheological parameters obtained with each method influences the result of the operation, considering indicators such as the maximum equivalent circulation density (ECD) and slurry displacement efficiency.