The Schiehallion field lies in water depths of 1,150 to 1 475 ft and is situated west of the Shetland Islands. The reservoir was discovered in 1993 and first brought on stream in 1998. It is the largest field operated by BP in the region and is one of the largest producing fields in the UK sector. Currently there are 19 production and 19 water-injection wells in the field, which have yielded more than 250 million BOE to date. At the outset, the North West Area Development (NWAD) of the Schiehallion field was planned to have four penetrations, consisting of two producers, each with its accompanying injector; however, design and economic reviews indicated that development with a multilateral well and matching injectors was more viable. The selected multilateral system consisted of a hollow whipstock through which perforations would be made after the completion was installed. While the perforating gun and low-side weight bias orientation system are not new technologies, they still required substantial qualification because of the unique construction of the well, driven primarily by well control policies and the requirement for an intelligent completion to facilitate independent flow control of both laterals. The resultant integration of technologies supplied by several service companies demanded rigorous testing and qualification of the various components. Several tests were performed to validate the viability of the completion design, such as perforating gun suitability; confirmation that minimal tubing deformation would occur; perforation hole sizes; the likelihood and containment of perforation debris; and testing of a straddle system required to bridge off the tubing perforations to isolate and control the mother bore production. The test program culminated in a full-scale stackup of the intelligent completion within a test well, followed by perforating and subsequent quantification of the debris generated and captured. This paper details the development trials carried out on the perforation system required for this multilateral system to meet the needs of drilling and completing a subsea multilateral producer with an intelligent completion. In addition to discussing the physical testing, this paper summarizes the results obtained from erosion modeling and productivity evaluation, which also influenced the final well design.
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