DOT International goes deep

Large-scale equipment installation is needed as offshore production moves into deeper waters. Descent and positioning of the equipment on the seafloor is quite a challenge, as it must fight the oscillations in the resonance zone. Big, multifunctional installation vessels generally are used to overcome this challenge. However, they are expensive and have a difficult operation window. This paper presents the operational details of the new Y-method and the numerical results that show the feasibility and the efficiency of this new equipment installation method.

This paper examines the economics, sensitivities to volumes, and risks associated with commitments to use pipelines or shuttle tankers for Lower Tertiary prospects in the Gulf of Mexico. It further discusses the impact the export solution may have on field development decisions and timing. These Lower Tertiary prospects are some of the most challenging to drill and produce. Considering the multiple pipeline breaks and incapacitation of shore facilities in 2005 when hurricanes Katrina and Rita blew through the GoM, the paper encourages the use of tankers. Pipelines are a major investment when developing fields in the Lower Tertiary, which is another reason to consider tankers. Lovie also addresses technical and commercial arguments favoring the use of each of the two export modes with respect to the business and field conditions applicable to developments in the Lower Tertiary trend. The author cites economic study data and attempts to weigh up and draw balanced conclusions on how oil export in such deep remote waters may change in the future.

Using a floater for tieback production in deep to ultra deepwater is an economical choice for both marginal and large fields. This paper introduces the principal concepts of a semisubmersible supporting steel catenary risers for tieback production, as well as design requirements and constraints of the hull and riser system. The author examines various aspects of the hull and riser design, including how they improve the system performance, and what their impacts are on execution, installation, cost, and operation safety. Lu presents two design cases for water depths representing the upper and lower bounds of the application range. This systematic analysis compares alternative ways to design the system, and proposes optimal ways to achieve a balanced design of the floating production system with steel catenary risers.

Exploration in frontier, deepwater areas is only possible by pushing enabling drilling technologies into deep and ultra deep waters. Increased operational constraints on drilling equipment and handling have forced the industry to come up with new designs or force application of some of the existing designs in untested territories. This poses unidentified challenges and uncertainties to newly developed technology. Generally, new technology is not covered adequately by established codes and procedures. Therefore, it must be qualified by following a systematic process where the required functionality and reliability is documented. This paper will focus on exploring a structured way for carrying out a qualification process.

The offshore industry has had to foster innovation to face the world’s most challenging environments. The remotely operated vehicle (ROV) gained acceptance as the industry began to understand the possibilities that the new technology delivered. Today the ROV is the workhorse of subsea operations. Rapid expansion into deeper water and harsher environments is pushing resources and current technology to the limit. To meet this challenge, new concepts of operations and novel solutions are required. The presentation will provide the attendees with a picture of how the technology will be used and will show the latest results to demonstrate how close the technology is to being delivered.

This presentation will discuss the method of repairing an SCR in 5,000 to 10,000 ft (1,524 to 3,048 m) of water. The SCR was designed to produce 500 Mcf/d to 1 bcf/d of gas. The riser was damaged or leaking below the surface, past the last shut down valves. TDW Offshore Services performed the repair work while maintaining operating pressure in the remainder of the line to avoid flooding the line and to avoid dewatering and drying. The company did the work in five days versus a potential down time of four to six months. The company pigged a pressure isolation tool down the riser to a point past the leak and controlled it wirelessly from the platform. Once completed, the tool was removed, leaving no holes, no welds, no future leak path, and no trace that any event occurred. Thus an entire repair was performed in several days instead of several months, while the line remained pressurized and gas packed during the repair.

Offshore Brazil fields are mainly in deepwater. To come ashore, pipelines have to contend with an uneven seabed with extremely high inclinations and rocky formations on the continental shelf. Subsea 7 installed the Camarupim pipeline in 2008 in this area. Although the scope was quite conventional, the Camarupim route represented various challenges. The pipeline was initiated in 712 m (2,336 ft) of water on a clayey seabed with about 5.5° lateral inclination. This area was defined as marginal with respect to lateral stability during installation. The pipeline route then approached the live Golfinho 12-in. (30-cm) gas export line that Subsea 7 previously installed. The Camarupim line was laid between 1 to 7 m (3 to 23 ft) from the Golfinho line going up a 40° hill. These conditions required a keen understanding of the seabed conditions, the expected behavior of the catenary, and the capability of the vessel.

Risers, umbilicals, and pipelines applied for deepwater projects are non-redundant components that require high performance reliability due to unacceptable consequences of potential failure. The industry requires reliable design criteria for these components. Based on recent experience, this paper gives an overview of the key issues and challenges with a reliable fatigue design related to deepwater risers, umbilicals, and pipelines. The basis for the analyses methodologies for these components is presented. The paper also includes background for uncertainties of the different parameters involved in the different fatigue analyses and it includes results from the reliability analyses leading to a recommended industry practice for fatigue design of deepwater risers, umbilicals, and pipelines.

Drilling in the deepwater Gulf of Mexico is challenging considering various environmental effects, such as hurricanes and loop currents, which increase drilling and completion costs. The increase in cost is associated with hurricane abandonment operations, including the potential loss of a drilling riser as well as damage to the subsea structures. A free standing drilling riser (FSR) allows the operator to delay hurricane abandonment operations, which has the potential of significant financial savings due to reduction in rig downtime. An FSR has a near surface disconnect point that is used for the planned disconnect only. For emergency disconnect, it is at the interface of the LMRP and BOP as in a conventional riser. This paper presents a feasibility design of an FSR in 7,000 ft (2,134 m) of water near the Sigsbee Escarpment in the GoM. The benefit of using an FSR versus a conventional riser will also be presented based on the loop study.

In addition to the technical sessions, special panel discussions will address the technology and regulatory changes needed to open and develop more of the US outer continental shelf. The panel sessions include speakers from the US Geological Survey, Minerals Management Service, and others to address the issues surrounding the development of new offshore US resources.