Novel 3D Fluid Displacement Simulations Improve Cement Job Design and Planning in the Gulf of Mexico

A key to achieving zonal isolation is the complete removal of drilling mud from the annular space between casing and formation and the replacement of the mud by an appropriately designed cement slurry. Although fluid displacement simulators have been available in the industry since the 1990s, a new-generation mud removal simulator has been introduced that provides new levels of details and accuracy. The simulator can be used for all types of wells, but it especially brings value to complex wells such as those found in deepwater Gulf of Mexico. The new fluid displacement simulator comprises a stiff-string centralization model that accurately predicts the casing standoff in a 3D wellbore. It accounts for fluid mixing inside the drillpipe and casing while the fluid travels down the wellbore and includes a high-resolution annular displacement simulator that accounts for the 3D wellbore shape and solves for azimuthal and axial flows. Thanks to these three new features, the simulator generates highly accurate and reliable results with which the cement job design can be optimized, leading to a higher probability of meeting job objectives and achieving zonal isolation. The new generation simulator was used to design and optimize cement jobs in the Gulf of Mexico with strict cement job objectives. The results of the simulator were compared to actual results of post-job wireline cement evaluations logs. The paper includes several case studies of deepwater and shallow water cement jobs in various complex wellbore configurations. Actual cement job data were used to rerun the simulator, and the results were compared with both the prejob cement design and the post-job evaluation logs. The comparison shows that the wireline evaluation results match the fluid displacement simulations very closely when using the stiff-string centralization model in combination with the new fluid displacement simulator, therefore confirming the accuracy of the model. Using the new stiff-string casing centralization and 3D fluid displacement simulator throughout the early planning and design of the cement job allows for an improved cement job design. The simulations highlight possible challenges early in the planning of the cement job so that any required changes or contingencies can be prepared ahead of time, thus resulting in a cement job design that meets the planned objectives.