Successful Design and Practices Shaping Up a Robust HPHT Well Completion Concept for Subsea-Horizontal Wells

摘要

Several improvements on fluids, equipment, completion design and practices have been successfully implemented in the firstrnsubsea well of Morvin HPHT field offshore Norwegian Continental Shelf. These improvements are: 1) Using new heavyrnweight reduced solid oil-based completion fluid for running the lower completion (predrilled liner) and achieving the expectedrninitial productivity ; 2) Extra well cleaning prior to running the lower and upper completion; 3) A designed predrilled linerrncombined with open hole swell packers for zonal isolation and HPHT tracer-subs for data acquisition; 4) Downhole barrierrnbeing installed as an integral part of the lower completion, eliminating the middle completion ; 5) New HPHT permanentretrievablernproduction packer; and 6) Successful installation of downhole P/T gauge with pig tail connection below the tubingrnhanger. Completion operation on the first well was completed in 40 days (i.e. 12 days less than the planned days) with nornmajor operational set back, safety and environmental incidents. After the well clean up, the well has been flow-tested up torn1500 Sm3/d (limited by rig capacity) and the well testing evaluation shows that the well delivers productivity as expected.rnTracer samples analyses also show good production contribution from both reservoirs being penetrated by 1000 m of 8-?”rnhorizontal hole section.rnThe HPHT reservoir (819 bar / 162 oC) in Morvin wells requires a different approach to completion design and practices inrnorder to avoid well control incidents, operational problems, and achieve full well integrity during its production lifecycle. Itrndemands the use of non conventional materials and fluids, careful equipment selection which is seldom available off-the-shelfrnin today’s market, equipment qualifications and new procedures1. This paper describes the original completion concept thatrnwas much influenced by well completion experiences from the Kristin field, the world’s first HPHT field to be developedrnsubsea from multi-well templates. The paper then discusses the improvements made from the original completion design,rnchallenges and contingencies.