Challenges faced by the offshore oil and gas industry as it moved into the 2000s have not diminished but, in fact, have remained and new, unexpected challenges have emerged, forcing the industry to redefine itself with the move to even deeper waters.

Recent project requirements for pipe-in-pipe systems for imminent Gulf of Mexico prospects included flowing product temperatures of 350°F (176.6°C), water depths to 10,000 ft (3,050 m), maximum allowable operating pressures of 6,500 psi, and subsea tiebacks extending 40 miles (64 km) and beyond.

Couple this with the fact that the roles of national and international oil and gas companies continue to somewhat blur the market and the search for new oil and gas has intensified to feed the demand of emerging economies, and it becomes quickly evident that technology takes on an even greater position in the industry. This is particularly true of the emerging technologies that are opening the industry’s new frontiers.

As the industry and conceptual advancements move forward, the most significant considerations for any technology today are how it relates to project costs, improves schedules, manages risks, maximizes safety and if it delivers the project’s key objective.
J P Kenny is one of the largest pipeline and subsea engineering and management contractors, with more than 25 years experience and more than 900 staff professionals in 10 worldwide offices. The company has been at the forefront of technological advances currently being used and planned in the offshore market.

Prominent among the emerging technologies discussed here are pipe-in-pipe (PIP) flowlines, pipeline stabilizing spans for steep subsea slopes, high-integrity pressure protection systems (HIPPS), and the standardization of project design and equipment.

PIP

PIP systems are important components of subsea developments where untreated well fluids may have to be transported long distances and wax and hydrate problems have to be managed.

Figure 1. The schematic shows the side elevation view of the anchor stabilization system (patent pending) for a subsea pipeline with respect to a steep sloping seabed below the pipeline. The schematic depicts the side elevation view of the piled pipeline anchor assembly that forms part of the stabilization system. (Graphics courtesy of of J P Kenny)
The advantage of a PIP flowline over traditional wet insulated pipelines is the ability to allow a lower Overall Heat Transfer Coefficient (OHTC) for the system. For long-distance subsea tiebacks, a lower OHTC allows production temperatures of the product being transported to remain above the wax allowable temperature and facilitates longer cool down times to be achieved during a shut down before hydrate conditions develop. A shut-down time in the range of 8 to 10 hours is considered to be the minimum requirement, which is a much larger challenge for tiebacks in excess of 40 miles (64 km).

The pipeline and subsea engineering company has developed a preliminary design solution of a PIP system for high-temperature applications up to 350°F that can be installed using either Reel-lay, S-lay or J-lay methods. The various components anticipated for the PIP system, such as loadshares, centralizers and thermal insulation, have been studied. These designs would be used as a starting point for future deepwater developments.

Key design challenges to the mechanical design and integrity of a PIP system have been identified for PIP components and the insulation material. Insulation material between the inner and outer pipes must provide an adequate thermal barrier to reduce heat loss. Existing insulation materials such as polyurethane foam are not rated for service at the maximum required temperature of 350°F. To handle the high temperature, new high-tech materials such as aerogels and nanogels have been considered for design.

Other important design challenges involve the inner “pipe compressive load” and designing components such as water stops and centralizers. Design studies confirm that a high-temperature PIP design is feasible and merits further consideration.

Steep seabed slopes

Steep, deepwater seabed slopes like those found offshore the Northwest Shelf of Australia and the Continental Shelf offshore Norway and the United States as well as scarps have led to the development of the Vertical Strategic Anchoring System (VSAS), which is designed to anchor and stabilize pipelines.

Basically, VSAS calls for an anchoring system at each end of a pipeline section extending along a seabed and a buoyancy technique utilizing a series of floats that allow the pipe section between the two anchors to maintain a position above the seabed.

Figure 2. Standardized subsea systems can streamline subsea developments.
Each anchoring system is made up of a restraint structure installed on the seabed and an anchor collar that is secured to the pipeline as well as the restraint structure. With this arrangement, the tension induced in the line through lateral movement is transmitted to the seabed through the anchor collar and the restraint structure.

The restraint structure consists of a frame with piles embedded in the seabed. As designed, there is a restraint structure at the upper end of the sloping seabed and a restraint structure at the lower end of the slope. Each structure has restraint faces that are spaced apart to define a gap through which the pipeline extends. On the upper end of the slope the restraint face is curved for controlling the radius of the pipeline curvature.

With this arrangement, the pipeline section between the two anchor structures assumes a profile that is typically curved and somewhat sinusoidal. Any additional lateral pipeline movement induces tension in the line that is transmitted to the anchor system.
The VSAS design provides the means for the buoyant pipeline section between the two anchor locations to remain stable and maintain its position above the seabed.

HIPPS

High pressure has a major impact on the design of well head and other equipment, including flowlines. For flowlines the high pressure can lead to extremely high wall thickness, and for equipment manufacturers line pipe fabrication and installation become more complex.

High Integrity Pressure Protection Systems (HIPPS) provide a solution that enables flowlines to operate at reduced pressures, lowering risk and reducing line cost.

Among the challenges in developing high-pressure oil and gas prospects in deep water is the high capital cost of subsea flowlines and risers. Installing HIPPS in the subsea system allows the flowline to be designed for well flowing pressure.

Although a reasonably new concept for the offshore industry, pipeline design and economic analysis has demonstrated that installing subsea HIPPS can result in significant reductions in the installation cost of flowlines and risers. There is also the payback of higher flow rates.

Of particular importance is the control system, which demands careful design and testing to ensure that the appropriate level of reliability is achieved. Reliability analysis techniques are used to select the appropriate system integrity level and optimum pipe wall thickness.

Deepwater field standardization

Using innovative production technology and standardizing seabed systems and engineering techniques can streamline subsea developments that lead to substantial cost savings and achieve first production faster.

By utilizing standardized techniques, offshore operating companies can bring long-lead delivery items through the supply chain before they even know if hydrocarbons are present. If the company does not find hydrocarbons, they can efficiently move the equipment to the next location, avoiding a backlog of hardware they can’t use.

The standardization system allows the company flexibility in how it is able to pull equipment together long before the project is underway.

This is accomplished by operating companies developing an alignment with supply and service company partners as well as engineering companies with the intent of developing system design and equipment standards that meet requirements from one project to another. It eliminates the need to change specifications for each project.

In essence, the company defines a standard that meets most of its anticipated needs. Keeping to a standard is much more economical than trying to custom-build for each project.
The company, for example, can use standard trees, control system and engineering solutions for each deepwater well and related facilities, achieving substantial cost and schedule benefits to Gulf of Mexico operators and more than 20 tieback developments.

Certainly, the emerging technology discussed above will have a significant impact on moving the offshore industry forward in the production and transportation oil and gas, as will other new technology such as dead hole pumping, simulator tools and cryogenic pipelines.
It is a challenging arena.

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