Technology qualification of deepwater transport shuttle adjustable buoyancy system

Qualification of new technology for deepwater offshore oil and gas exploration and production is needed for the industry adoption process of new equipment and methodologies. Comprehensive programs can alleviate numerous risks associated with new technology through the application of appropriate industry practices such as DNVGL-RP-A203: Qualification of New Technology. Once qualified, innovative designs can provide effective sources of required sustained cost reductions for field developments creating new economic viability. The objective of this paper is to describe the systematic approach developed for the qualification of macro buoyancy spheres used in loose configuration as adjustable buoyancy in deepwater transport shuttles for subsea facilities and chemical transport. The qualification process is designed to examine macro buoyancy sphere structural stability under representative conditions of offshore transport shuttle loading, storage, and unloading at the surface and at depth. An overview of empirical testing procedures, equipment, and the configurations through which sphere performance will be quantified against application requirements is presented. Macro buoyancy spheres have been used for decades in a number of offshore and subsea buoyancy applications such as drilling riser buoyancy modules on marine drilling risers, mid-water distributed buoyancy on production risers and umbilicals, and installation buoyancy for subsea equipment. Their performance in these applications is well understood with wide acceptance in the market. Mass manufactured from high strength, low density materials, sphere performance specifications can be tightly controlled while still being produced in a very cost-effective manner. Once qualified, under the program described in this paper, these same buoyancy spheres have an innovative re-purposed extension within deepwater transport shuttle delivery systems. The readily adjustable and controllable nature of this innovative approach with loose buoyancy spheres, versus a fixed buoyancy system, allows a single subsea transport shuttle to be utilized for a wide variety of loads and service conditions. The buoyancy can be adjusted to match specific payload needs, reliably positioned when and where required, then re-used multiple times in a service delivery mode. This patented feature (patents published and provisional US and world-wide) will enable subsea shuttle transport barges to economically convey equipment from the sea's surface to the mudline and vice versa, especially in remote locations for smaller subsea projects where a typical heavy-lift vessel may prove to be cost prohibiting.