Shasta/Mustique Subsea Equipment Platform Interface and Operability

Abstract

SUMMARY The economic benefits of all inclusive systems engineering approach is now recognized in the offshore industry. Nowhere is this more evident than in the area of deepwater subsea tiebacks to existing facilities. This type of development requires effectivemanagement of the interfaces between personnel on the existing facility and the new project team, the interfaces between the new subsea facilities and the existing platform, and the interface of the new operating procedures with the existing platform daily routine. A second factor in tie economic viability of many of these projects is the need to minimize operating costs by avoiding the need fm subsea .system repair intervention, An operability analysis focusing on the subsea system and platform interface engineering was used on the Hardy projects to address the concern with the potential for interventions, With minimum operating costs as a primary goal, Hardy encouraged participation from both host platform operating groups from the outset of both projects. This cooperation was critical since both projects were planned to mow than double the throughput for both host platforms without adding platform operating personal. The approach of operator involvement also ensured a safe, reliable, and economic transition between the installation and operating phases of the developments. INTRODUCTION This paper describes the operability and interface management effort on the SHASTA and MUSTIQUE developments in [he Gulf of Mexico. Hardy's project management approach was apply 10 both developments, however (his paper focuses on the SHASTA development specifically for the installation and operation phase. The SHASTA field is located in Green Canyon block 136 in approximately 1000ft of water. Hardy Oil & Gas USA inc. was the development opera[or with responsibility for the design, drilling. and installation cycles of the project. Texaco Exploration & Production INC (TEPI) took over as operator of all facilities on production start up. Equity ownership of the field is 50% TEPI, 25% Hardy, and 25% Samedan. Subsea wells produce gas and condensate through Iwo export flowlines to the Green Canyon block 6 Texaco platform in 612 tl of water. The # 6 well is located in 860 ft of water while the # 7 well is in I(M2 R. The two wells are located 1-1/2 miles apart with the closest well (#6) being 9-1/2 miles from the platform. The SHASTA subsea wells are controlled from the platform using a multiplexed electro-hydraulic control system. The production facilities added to the platform specifically for S1IASTA have a throughput capacity of 60MMSCFD and include dedicated provisions for flowline pigging and continuous methanol and corrosion inhibitor inject ion. Figure I illustrates the overall field arrangement.