Advanced Slip Crushing Considerations for Deepwater Drilling

Abstract Deepwater drilling trends are moving towards deeper water depths as well as deeper exploration horizons and reservoirs below the mudline. These trends have created various operational and well design challenges. This paper addresses a serious problem pertinent to the design of landing strings and drill strings for deepwater operations. These strings are designed to run long and heavy casings, tiebacks, or liners (typically including deep intermediate and production tubulars). The total weight of these strings may approach or exceed 1,000 klb<SUB>f</SUB> at the mudline. Adding in the additional weight of the landing string back to the rotary results in a serious design problem regarding both the landing string itself and the handling equipment. Slip-based handling systems work well in most instances, but lead to bi-axial loading from the tension and radial loads exerted by slip inserts. As a result of biaxial loads, the axial load rating of the landing string is reduced. The current understanding of slip crushing phenomena is based on testing and modeling work dating to 1959. This paper examines recent tests in the light of more advanced models and presents an improved understanding of slip crushing loads.