Abstract
Modeled side forces exceeding 20,000 lbf per drill pipe joint were exerted on 14″ casing due to an 8°/100 ft sidetrack point in a ~30,000 ft total depth (TD) well in the Gulf of Mexico. This posed a significant risk of rapidly wearing or heat checking the casing, potentially compromising the wellbore's integrity.
After confirming the need to drill two hole sections out of the casing window and establishing the allowable casing wear, it became essential to analyze the wear based on the estimated drill pipe rotations using a realistic wear factor. Given the severity of the side forces, several modeling techniques were employed to accurately predict casing wear, including comparisons between stiff-string and soft-string models, linear and non-linear wear factors, and finite element analysis (FEA) bit depth iterations of various contact points.
Casing wear mitigation was managed using clamped-on Non-Rotating Protectors (NRPs). The NRPs were required to handle additional challenges, such as stripping through the rotating control device (RCD) with backpressure and venturing into open hole to protect the sidetrack point throughout drilling. These factors were evaluated and deemed acceptable based on the casing wear risk evident in the models. The clamped-on design provided the flexibility to install the NRPs at any point along the drill pipe joint, allowing the FEA model to determine optimal locations for minimizing casing wear.
The well was successfully executed after drilling an additional open hole bypass, which increased the initial estimated drill pipe rotations applied to the casing. TD was reached without issues or significant wear to the NRPs, indicating that minimal casing wear was achieved.
