Industry-wide research and commercial installations over more than 25 years have advanced subsea completions Into a technically mature option for offshore oil and gas development Field experience now approaches 400 m water depths, with plans under way to go much deeper. As industry progresses into deeper water, a key requirement is the capability for diverless intervention for inspection, maintenance and repair of subsea equipment Esso has been a leader in this area and has undertaken, since the 1960s, several major Research & Development programs as well as commercial projects to advance the state of subsea technology including diverless maintenance systems The latest R&D effort, which draws on more than two decades of experience, is the Esso Deepwater Integrated Production System (EDIPS) development program undertaken in the UK by Esso Exploration and Production UK.
This chapter presents key design features of Esso subsea systems, which have made major contributions to the advancement of subsea technology The evolution of Esso's subsea technology is described and the EDIPS program, as it relates to the subsea theme of this chapter, is also briefly discussed at the end, noting how the programme is pursuing several near-term design challenges
Exxon USA's first subsea well, designated 803 U-3, was completed in early 1964 beneath a platform in 18 m of water in Grand Isle Block 16 field. To simulate satellite well operation, this well was produced to and controlled from a platform one mile away The initial diver-assist tree was later replaced with a more advanced design to prove operational capability without divers The new tree featured
remote flowline connection,
remote riser connection,
internal porting of all hydraulic control and electrical signal lines,
block tree construction utilizing a single casting for the entire tree body,
metal-to-metal seals throughout the production runs,
through flowline, or TFL servicing capability, and
electrical valve position indicators and pressure transducers
All of these features are used to varying degrees on the latest subsea completions today, which are conceptually very similar to this early completion The 803 U-3 well operated successfully, including use of TFL for servicing, until it watered out Exxon USA's next underwater completion, designated 803 U-4, was a true satellite completion located in 18 m of water, again in Grand Isle Block 16 field, two miles from a platform. This project was industry's first completion of an underwater well with the rig off location Prior to the offshore completion, a complete suite of TFL completion and workover tools was developed in an Exxon land test well After the tree was installed and tested on the offshore well, the lack-up drilling rig was removed without completing the well. Then dual flowlines were installed, the well was perforated remotely using a TFL perforating gun, and the producing sand was plasticized using TFL techniques Although some difficulties were experienced with the early design TFL locomotives, the completion was successfully brought on stream using TFL, with no rig intervention required Many of the TFL improvements from this project benefitted Esso and others on later wells
