Cement Placement Modeling—A Review

Abstract

SummaryEnsuring cement sheath placement is of paramount importance for the success of a primary cementing operation. Poor mud displacement and fluid contamination can lead to cement isolation failure, loss of production, and even well abandonment. Over time, many cement placement computerized models have been developed, leading to a significant number of theoretical and case history papers. However, using these to design a cement job is difficult because their physical and mathematical assumptions are most of the time unclear, and because their application requires balancing precision with computation time. Models that are too precise may lead to very long runs, while oversimplified models could result in nonpredictive simulations. To the authors’ knowledge, nothing has been published to explain how to perform efficient predictions with a cement placement computerized model. Such is the object of this paper. It presents an extensive analysis of all the available cement placement computerized models, highlighting their advantages and disadvantages and listing their assumptions. This analysis indicates that (1) the actual methods used to estimate the equivalent circulating density window are not rigorous enough; (2) there still exist a lot of uncertainties when predicting the tubular standoff; (3) modeling fluid contamination, especially when the fluids are not compatible, remains very cumbersome, if not impossible, because the true interfaces’ physics is not completely considered; (4) a local contamination observed at an intermediate time can disappear at the end of the simulation due to numerical diffusion, meaning that just looking at the concentration maps at the end of placement is not sufficient to judge the efficiency of a displacement scenario; and (5) changes in geometries along the cement sheath are not considered with precision. This work allows establishing guidelines to help understanding how to manage simulation inputs and analyzing and communicating the produced results.