Operators need a more reliable and efficient method of performing whipstock casing exits, especially in the high cost areas and deepwater environments. Milling through casing collars significantly increases operations time and poses risks for downhole tool failures. In scenarios where casing tallies are inaccurate or missing, wireline Casing Collar Locator (CCL) services are normally utilized to identify casing collar locations to mitigate risks. However, significant rig time is associated with the deployment of wireline service.

A new technology was recently developed to detect and visualize the casing collars in real-time while running in hole on drill pipe with the milling and whipstock assembly. The new capability is developed with the same downhole tool that provides real-time downhole data, such as torque, weight-on-mill, Equivalent Circulating Density (ECD) and downhole dynamics diagnosis, to optimize the milling of the casing window. In combination with the company's Measurement While Drilling (MWD) directional measurements, the technology allows placement of whipstock in an optimal location, orientation of the whipstock and optimized casing window milling in a single run. This new service significantly improves the reliability and efficiency of the casing exit operations, and save the operators substantial rig time, especially in scenarios where a wireline CCL service is otherwise required.

The technology was successfully field tested offshore Norway at the Grane field with a major Norwegian operator. Results from the two field tests from two different sizes of casing exit operations, 18 5/8″ and 13 3/8″, are included in this paper. Casing collars were successfully detected and visualized in real-time and enabled optimal placement of the whipstock. Casing windows were subsequently milled efficiently.

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