How Much Is Left of Your Centralizer After Exiting a Casing Window in an Extended- Reach Horizontal Multilateral? Modeling, Yard Tests, and Field Results From Alaska’s West Sak Development

摘要

The West Sak viscous oilfield on the North Slope of Alaska is currently being developed with extended reach multilateral wells, with departure to depth ratios up to 5 to 1, in which horizontal slotted liners are utilized in conjunction with a TAML level 3 multilateral junction system. Centralizers are considered necessary on the slotted liners to avoid slot plugging, reduce drag, and limit differential sticking. Selection of proper centralizers to run through a casing exit, without a whipstock in place, has been key to ensuring a successful multilateral installation. Several failures of centralizers run on liners through casing exits have resulted in significant drilling lost time associated with fishing and milling pieces of centralizers in order to place the wells into proper service. After three such failures, the requirement to study the passage of a centralized liner through a casing exit became essential. A surface test fixture was utilized to simulate liners run through a casing exit to test several potential centralizer candidates using the loads estimated from modeling. Torque and drag modeling provided the side force estimates exerted on the liner and centralizer as they passed through a casing exit. This paper will the discuss the liner centralizer installation problems prior to the testing program, detail the modeling used to determine the loads exerted on the centralizer at the casing exit, show the results of the yard tests conducted on several commonly utilized industry centralizers, and make recommendations for proper liner centralization in multilaterals.