OTC 21476--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 first subsea well of Morvin HPHT field offshore Norwegian Continental Shelf. These improvements are: 1) Using new heavy weight reduced solid oil-based completion fluid for running the lower completion (predrilled liner) and achieving the expected initial productivity ; 2) Extra well cleaning prior to running the lower and upper completion; 3) A designed predrilled liner combined with open hole swell packers for zonal isolation and HPHT tracer-subs for data acquisition; 4) Downhole barrier being installed as an integral part of the lower completion, eliminating the middle completion ; 5) New HPHT permanentretrievable production packer; and 6) Successful installation of downhole P/T gauge with pig tail connection below the tubing hanger. Completion operation on the first well was completed in 40 days (i.e. 12 days less than the planned days) with no major operational set back, safety and environmental incidents. After the well clean up, the well has been flow-tested up to 1500 Sm3/d (limited by rig capacity) and the well testing evaluation shows that the well delivers productivity as expected. Tracer samples analyses also show good production contribution from both reservoirs being penetrated by 1000 m of 8-(1/2)” horizontal hole section. The HPHT reservoir (819 bar / 162 oC) in Morvin wells requires a different approach to completion design and practices in order to avoid well control incidents, operational problems, and achieve full well integrity during its production lifecycle. It demands the use of non conventional materials and fluids, careful equipment selection which is seldom available off-the-shelf in today’s market, equipment qualifications and new procedures1. This paper describes the original completion concept that was much influenced by well completion experiences from the Kristin field, the world’s first HPHT field to be developed subsea from multi-well templates. The paper then discusses the improvements made from the original completion design, challenges and contingencies.