Using High-Resolution MWD Survey Data in Mud Removal Simulations for Effective Cementing Program Design

Abstract

The main objective of this study was to understand the impact high-resolution measurement-while-drilling (MWD) surveys have on casing standoff and mud removal simulations and its impact on final cement program design and risk analysis. High-resolution surveys use a combination of static and continuous MWD inclination data to characterize the well trajectory at 3-m (10-ft) intervals rather than the current industry practices at every stand; i.e., 30 m (100 ft). However, several case studies had demonstrated that surveying the well path at these intervals is often not sufficient to capture the true characterization of the well in question. This result, in some scenarios, leads to significant errors in the final reported dogleg severity (DLS) and tortuosity; therefore, resulting in optimistic well engineering simulations due the hidden additional tortuosity not applied in the models. Two North Sea wells were analyzed when using conventional trajectories defined at each drillstring stand as well as using high-resolution trajectories to evaluate the impact on casing centralization and mud removal simulations. The latest generation cementing software for placement simulation was used in this study. The simulation has the capabilities to deal with computing pipe standoff and angle direction in a 3D annulus, including gravitational forces for accurate mud displacement and removal. This study confirmed that high-resolution MWD survey data can provide additional precise input for casing standoff and mud removal simulation, resulting in a more realistic simulation result due to the appearance of microtortuosity and DLS. Simulation results using high-resolution directional survey data identified conditions where the original mud removal assessment using a standard survey was overestimated due to higher standoff. This result allows an appropriate level of risk assessment and cement job design optimization to improve both the casing standoff and mud removal, which will eventually impact the well integrity quality. This study proved that centralization and mud removal simulations can be, in some scenarios, optimistic if performed using standard trajectories. The results also proved that the risk assessments for the cement program designs will be evaluated differently because the enhanced simulations provide a more accurate result, which impacts the final centralization and mud removal to ensure effective zonal isolation.