Thurman B. Carter

Improving Multilateral Drilling and Completion Efficiency with a Hollow Whipstock

A multilateral completion allows one or more laterals to be connected to a parent wellbore so that production from each can be isolated or commingled, and all laterals can be accessed. One of the challenges in multilateral drilling has been in regaining access to the main wellbore after the window has been milled and the lateral drilled. Typically, a solid whipstock has been used to mill the window and drill the lateral; it was then retrieved, and a hollow whipstock run to provide access to the lower main wellbore and allow for the passage of produced fluids. Difficulties were sometimes experienced, however, when retrieving the solid whipstock and realigning the hollow whipstock. This paper will discuss a new single-trip hollow whipstock that can be used for milling a window as well as for production. This innovative design eliminates the risk posed by retrieving the solid whipstock and realigning the hollow whipstock with the window. Since the hollow whipstock is set only once, it remains aligned with the window throughout the life of the well. This assures reentry into the lateral and eliminates any restrictions due to misalignment across the window from a reset whipstock. The discussion in this paper will include information on the design, application, and testing of the new whipstock and will verify its capability to reduce the risks, number of trips, and cost of multilateral installations as well as enhance downhole performance under the challenging conditions inherent with multilateral configurations.