Deepwater Technology

Installing a TAML L-4 multilateral system in deepwater Schiehallion field

BP overcame a complex installation problem by identifying and solving problems before completing a deepwater subsea well.

Ken Horne and Robbie Allam, BP; Mark Glaser and Peter Chandler, Weatherford International Ltd.; Thilo Scharf, Schlumberger

The Schiehallion field lies in 1,150�1,475-ft water depths about 103 nautical miles west of the Shetland Islands. The reservoir was discovered in 1993 and brought on stream in 1998. It is the largest BP-operated field in the region and is one of the UK’s largest producing fields. There are presently 19 production wells and 19 water-injection wells.

Initially, the field’s North West Area Development (NWAD) was to have four wells, two producers with two injectors. However, design and economic reviews indicated that development with a multilateral well and matching injectors was more viable. The selected system consisted of a hollow whipstock through which perforations would be made after installing the completion.

The original well design had the lateral legs produce and commingle through a single completion string. During detailed planning, this design was challenged and adapted for remote Down Hole Flow Control (DHFC) of each lateral’s production. Phase 1a of NWAD was to access reserves in fault block segments 2 and 3 of the T35 sands. The multilateral producer, Well FP02, would have one leg in each segment, each supported by a water injector, Fig. 1. Well FP02 was drilled in summer 2006 and completed with DHFC equipment.

WELL DESIGN

The basis of the TAML L-4 multilateral well was a hollow whipstock through which perforations would be made to produce from the mother bore; however, the design change including intelligent completion control had an effect on the perforation strategy and completion design. The completion tubing spans the junction area; is perforated at the junction and includes a straddle packoff, run to isolate the perforations through the tubing, Fig. 2.