RIASSUNTO
ABSTRACT
This paper discusses equipment, completion, production, and maintenance operations utilizing pumpdown (or TFL - through flowline) methods on five subsea wells presently operated by Brunei Shell Petroleum (BSP). These wells include the world's first subsea 4"" x 2"" well (single zone) and among the earliest 3"" x 3"" wells (multiple zones) designed for TFL servicing. All wells utilize remote-operated wet trees installed in 100 to 200 feet of water.
Analysis of procedures, equipment, and costs illustrate that TFL methods provide a practical and reliable means for servicing of subsea wells. Equipment designed for such completions and developed during this project include surface-controlled TFL-retrievable ball valves and the versatile Select-20? system.
Introduction
In the early 1970's, Shell Internationale Petroleum Mij. (SIPM) undertook a series of studies aimed at the development of systems for producing oil fields located in deep water, beyond the continental shelf. An important building block in deep water production systems would be the underwater completed (UWC) well. A principal objective was that the UWC wells would be drilled, completed, produced and serviced using remote control and servicing techniques. Downhole servicing of the well would be done by pumpdown TFL techniques.
In 1971 it was envisaged that the UWC wells would have to be large producers for an economical deep water field development. Downhole, the completion should be as simple as possible; basically a single packer completion without any facilities for gaslifting and a minimum number of functions to be serviced by TFL. A single production tubing string of 4 1/2"" OD was selected for this completion. In 1972 it was decided to install a pilot UWC (Fairley A) offshore Brunei in relatively shallow water permitting easy intervention by divers, if necessary, and for this purpose a project team was set up in Brunei. Since at that time TFL tools and ancillary equipment had been well developed for only 2 3/8"" tubing Shell and Otis Engineering Corporation (a Halliburton company) undertook the development and testing of the various 4"" TFL tools and equipment. Shop tests by Otis in Dallas were followed by extensive testing in a land well in Brunei. The Fairley A completion was installed in March, 1974, and operational experiences with the 4"" TFL tools and associated equipment have, generally, been quite satisfactory since.
In 1974 the requirement for a dual-string multiple-packer completion in medium water depth emerged as a result of the significant increase in the realized price of the oil, making less prolific completions economically viable. A completion scheme was selected that provided dual 3 1/2"" tubing with multiple 9 S/8"" x 3 1/2"" x 3 1/2"" packers and the possibility for gaslifting.
Due to the complexity of the completion a complete new range of TFL tools had to be developed. The Select-20 system, specially designed by Otis, was initially tested in Dallas and subsequently tested and debugged in a landwell in Brunei and was finally installed in four UWC wells in Brunei in 1976 (Fairley-C project).