This paper outlines the history of traditional offshore drilling with subsea Blowout Preventer (BOP) stacks and conventional riser and then illustrates the new method of surface stack drilling using the Environment Safe Guard (ESG). Introduction With the high cost of drilling in deepwater (greater than 2,500 feet/760 meters) and the limited number of available rigs with the capability of drilling in these water depths, a new approach to deepwater drilling was needed to try to reduce drilling costs to a more manageable level. As the water depth capability of new rigs increased, so have the costs. These high costs have resulted in many small, deepwater fields being rendered uneconomical to produce. In an effort to bring these fields back to economic viability, drillers have tried several ways to reduce their deep-water drilling costs. One of the most promising of these methods is to relocate the subsea BOP Stack to the surface and replace the large bore, low pressure drilling riser with conventional casing as the high pressure riser between the seabed and the rig. However, use of this method must be limited to the most benign sea state and weather conditions because of the risk of damage to the casing riser, which could result in environmental contamination. Surface Stack drilling has been successfully implemented in the south Pacific, but only during the summer months. In this area and under this weather window limitation, exploration drilling costs have been reduced by up to 35% with only a few emergencies arising. In order to continue and broaden the use of this proven cost saving drilling approach, a means of increasing the safety of the overall system, by reducing the risk in case of riser failure was required. If the riser could be sealed off at the seabed, the risk of riser failure could be completely eliminated. Also, if the riser could be disconnected just above the seabed sealing mechanism, overall rig safety could actually be increased beyond current levels. This is easily achieved using an assortment of existing, field proven components located on the seabed. Background The idea of locating a BOP Stack on the ocean surface to provide well control while drilling for offshore oil is not new. Figure 1, Typical Jack-up Rig When the first land rig was mounted on a barge decades ago, these systems were common. Later, Jack-up rigs (Figure 1) were outfitted with such systems. Jack-up rig evolution allowed their water depth capability to be expanded to 650 ft. Then, Semi-submersible rigs (Figure 2) and Drillships were developed and the BOPs were moved to the sea floor allowing a relatively low-pressure (and thus, less expensive) riser to transport the drilling mud returns back to the mud processing equipment located in the rig by way of the Riser annulus. This seabed BOP configuration facilitated the original water depth expansion to 1500 ft. with second generation rigs, and later to 3,000 ft. with third generation rigs.

The Malampaya field development in the South China Sea comprises subsea wells in 820 metres water-depth producing via a subsea manifold and two 16 inch diameter inconel clad flowlines to a shallow water platform 30 km distant in 43 metres water-depth. Condensate is removed on the platform and the dry gas is then transported via a 24 inch diameter, 504km long export pipeline to an onshore gas plant at Tabangao (Batangas, Luzon Island) for extraction of H 2 S. The condensate is stored in the platform concrete gravity structure (CGS) caisson prior to export via shuttle tanker from a catenary anchor leg mooring (CALM) buoy located 3km from the platform.Two umbilicals are installed between the Malampaya platform and the ten slot subsea production manifold. Each umbilical provides methanol injection, annulus vent service and electric and hydraulic control.The dual umbilical solution for Malampaya is perhaps unique in that the cross sections are identical and the system design features redundancy within each umbilical and between the two umbilicals. The services are routed subsea to facilitate safe isolation and permit limited production in the event that all services in one umbilical are not available. This availability objective was driven by the high priority placed on cost effectively minimizing downtime across the entire system and the discipline to concentrate on lifecycle cost rather than capital expenditure (this subsea development is the sole source of gas to a major electrical power generation network and downtime is a major concern). The majority of steel tubes in the cross section were required for methanol service to the subsea manifold for injection at the manifold headers and the trees. Unlike common methanol injection lines for hydrate prevention, the tubes were required to transport regenerated methanol with potential H 2 S carryover from the produced gas stream.To prepare for the installation campaign in a region with minimal supporting infrastructure, contingency planning was emphasized and included an onshore full scale evaluation of vessel tensioner holding capacity in order to safely increase the operating envelope of the vessel lay spread.The paper concentrates on the numerous challenges associated with design and logistics; material selection, the novel procurement strategy for steel tubes, delivery logistics for 768km of tubes, the extensive welding campaign and the remote installation.

Over the previous decade a rapid and significant design evolution has occurred in Shell's subsea umbilical and distribution systems. This design evolution is principally the result of key drivers including more stringent flow assurance requirements, increasing water depth, continuous cost improvement and standardization. This paper will address these key drivers and their influence on the design of Shell's subsea umbilicals and distribution system as well as how the umbilical and distribution system has been integrated into Shell's standard subsea system overall. Improvements, advancements and lessons learned since Shell's first deepwater subsea development in the early 1990's will be reviewed. Also addressed are significant technology andimprovement areas. The creation of a group to specifically focus on the umbilical and subsea distribution system has resulted in a unique team of experts within Shell and its Subsea Alliance partner, FMC, that has demonstrably added value to the subsea system design process. Managing the umbilicals and subsea distribution on a portfolio basis has enabled this group to improved reliability and cost of these deepwater systems. Introduction The umbilical is the "lifeline" of the subsea system. Together with the local subsea network of hydraulic and electrical flying leads it provides the electrical power, communications, chemical injection and hydraulic fluid power necessary to control and operate subsea wells. In the last decade a rapid and fascinating design evolution of Shell's umbilicals and subsea distribution systems has occurred. This evolution has been driven by several key factors, namely evolution of the flow assurance requirements, increasing water depth, cost improvement and standardization of subsea equipment. These challenges have been met through the efforts of a dedicated team responsible for the umbilicals and associated subsea distribution network. By focusing on the umbilicals and standard subsea equipment for all ongoing subsea projects, the team has been able to transcend traditional project boundaries and leverage innovations and standardization across the entire portfolio of projects laying the foundation for continuous technical and cost improvement. Several advances in umbilical technology and cost improvements have resulted from this focused effort including the use of large, steel tube umbilicals, the introduction of new materials for steel tube umbilicals, the design and standardization of modular subsea distribution system and the standardization of umbilical design. Of course, along with the achievements and advances come some lessons that will also be discussed. Evolution of Umbilical Design Requirements Flow assurance requirements have changed dramatically as we have moved beyond the subsea gas wells developed initially into more difficult oil developments containing paraffin and asphaltenes. Standardization and cost improvement have also been predominant themes in evolution of subsea developments and have had a significant influence on the umbilical system design as have deeper water and flow assurance. Flow Assurance Requirements. Flow assurance, as it is used here, refers to the means by which continuous hydrocarbon flow throughout the subsea system from the well tubing to flowlines and ultimately the host is ensured.

The Mensa Project is a remote satellite subsea production system located in the Gulf of Mexico, Mississippi Canyon 687, in approximately 5300 ft. of water.The development of this field required a production control umbilical for hydraulic and chemical injection service to the subsea wells.A steel tube umbilical design utilizing relatively large diameter, carbon steel tubing was selected for this project. Design verification testing was conducted and the umbilical was successfully manufactured and installed. TIle viability of utilizing continuous carbon steel tubing for subsea hydraulic umbilicals as well as the fabrication and installation of large steel tube umbilicals in ultra-deepwater has been demonstrated on the Mensa project.

The umbilical infrastructure for the Na Kika Development is comprised of four dynamic umbilicals from the host platform and five static umbilicals between subsea fields to provide injection chemicals, power and communication services to five subsea fields. An additional umbilical was also installed to tie back a sixth field, Coulomb, to the Na Kika host. Shell contracted directly with the installation contractor for transportation and installation of 123km of steel tube umbilicals. A hybrid transportation solution was adopted and multiple lay spread configurations were employed. The campaign marked the largest and most complex umbilical installation campaign undertaken by Shell in the GoM and the first installation of lazy wave umbilical risers from a floating host. A rigorous approach was applied during the planning phase in order to identify and reduce the risks associated with the novel installation aspects. Contingency plans were prepared and key equipment procured to minimize schedule impact in the event of installation delays or damage. The risk mitigation measures employed, the difficulties encountered and the lessons learned during the installation campaign are expanded in the paper. Introduction Execution of the umbilical scope for Na Kika represented a contractual challenge as well as a technical challenge. The numerous novel installation requirements were augmented by the complexities and constant interface evolution inherent with a new green field development project of this magnitude. The nine umbilicals for the Na Kika subsea development and the single umbilical for the Coulomb development were transported from Norway to the Gulf of Mexico during April and August 2003. Installation of the umbilicals was performed during September and October 2003 by the MSV Toisa Perseus using three different lay spread configurations. A selection of highlights and difficulties encountered during the campaign are presented, concluding with some of the main lessons learned. Umbilical Configuration All Na Kika umbilicals and the Coulomb umbilical were manufactured with varying quantities of three core materials - zinc extruded carbon steel tubes, zinc extruded Nitronic 19D duplex steel tubes and electric quad cables. All the umbilicals, with the exception of KGL, followed a common construction specification with the carbon steel tubes layed-up in a central bundle and the duplex steel tubes, electric quad cables and fillers layed-up around this central bundle as the second pass. Static umbilicals were jacketed with polypropylene (PP) roving and the dynamic umbilicals were extruded with polyethylene (PE) sheath for the dynamic section only. A summary of dimensional data for the ten umbilicals is presented in Tables 1 and 2. Dry weights are quoted "in air, fluid filled" and submerged weights are quoted "in seawater, fluid filled". Diameters and weights for the dynamic umbilicals are stated for the PE sheathed dynamic section. Table 1 Static Umbilical Summary (Available in full paper) Table 2 - Dynamic Umbilical Summary (Available in full paper) Contract Strategy A strategy to contract three well-defined scopes; tube supply, umbilical manufacture and umbilical transportation/ installation (T&I) with the project team retaining overall project management was followed.