The low-hanging fruit in even the deepwater provinces of the world has been picked over to a large extent, leaving new discoveries that tend to be smaller and located at increasingly greater distances from production facilities.
Conventional offshore technology also is reaching its deepwater application limits, creating an urgent need for a new development concept that effectively incorporates the use of existing floating systems while opening new avenues for the ultimate production goal: production from subsea systems directly to shore.
This calls for a step-change to "deep-offset" developments that incorporate optimum systems engineering design. Deep-offset implies the combination of production depth and offset that would result in:
• Increased production risk;
• Reduced system availability; and
• Higher development cost using conventional subsea system configurations.
The successful development of long-distance delivery systems (LDDS) will extend the life of existing deepwater floating systems for use as large central production facilities and bring more fields into production that otherwise may sit dormant. In certain instances, expensive topside production facilities may be averted, allowing production from deepwater subsea systems to reach shore facilities entirely via pipeline systems.
To achieve these goals and bring more and more reserves into economic viability, industry needs to work collaboratively, challenging traditional development approaches, closing technology gaps and innovating new engineering possibilities.
Systems perspective
To begin this journey - and for the successful design and operation of subsea multiphase production systems-the industry needs to evaluate an entire offshore development system, from the reservoir to export from the production facility.
This complete system capability - including effective and economic design, construction and operation - requires that system designers consider and control (where possible) reservoir characteristics and production profiles, produced fluids properties and behavior, the design of major system components, operating strategies, and other system variables. Economic penalties for "getting it wrong" can be severe.
To "get it right," the entire system must be engineered with appropriate consideration of interdisciplinary system aspects that affect the work of the entire team. Offshore developments have a myriad of coupled parameters and characteristics that must all be considered concurrently. Some of these, such as reservoir, fluid and seafloor characteristics, constrain the system and must be accommodated. Others, such as wells, wellheads and manifolds, flow lines and risers, and operating strategies are characteristics over which the project development team will have influence and control. In addition, non-technical project constraints, such as economics, project organization, politics and environment, must all be included in a systems perspective.
Long-distance delivery management
For deeper water and longer offset, the challenge is to develop systems that can reliably deliver produced fluids from deep water over long offset distances to remote processing facilities, onshore in some cases. For such systems, it is useful to emphasize "delivery" rather than the more traditional "production." For that reason, Intec has developed the concept of long distance delivery management (LDDM).
For LDDM, the system focus must extend beyond conventional development LLDS for very deep water and long-offset applications. Current technical and economic limitations impede the ability to produce over long distances using conventional methods that use local deepwater production or production-boosting facilities.
Current industry benchmarks for subsea tieback offset distance are about 74.5 miles (120 km) for gas developments and 40 miles (65 km) in the North Sea or 31 miles (50 km) in the Gulf of Mexico for oil/gas condensate developments. Over time, economics will compel the industry to produce subsea developments over longer distances and greater water depths to existing infrastructure, low-cost shallowwater or onshore host facilities for processing.
The move beyond current conventional technology to deep-offset LDDS requires a step-change to long-distance delivery management. LDDM systems engineering will identify the best combination of proven and innovative techniques and equipment to accomplish an optimum system design to suit the attributes and constraints of the development at hand. Depending upon application specifics, goals and benefits of such system designs will:
• Maximize use of prior capital expenditures (Capex) using existing underutilized deepwater facilities. This approach may require extending the reach of subsea developments that can tie into those facilities;
• Reduce Capex expenditures by locating production delivery at shallowwater or onshore facilities rather than on new deepwater facilities;
• Lower the costs associated with locating personnel offshore by removing populated structures from the deepwater offshore environment;
• Optimize deliverability of hydrocarbon fluids in the flow line system and optimize - or even eliminate entirely - the Capex and operating expenditure (Opex) associated with topsides processing, treating and disposing of waste fluids such as produced water by optimizing or minimizing delivery of those waste fluids. Eliminating delivery of produced water may not always optimize delivery of hydrocarbons; and
• Maximize utility of installed subsea long-distance production facilities by configuring them as deepwater hubs - much like current deepwater surface facilities are used as production hubs.
Critical role of systems engineering
While already central to successful execution of offshore pipeline installations, systems engineering will be even more critical with LDDM projects. As a result, the systems engineer will assume important project roles from earliest project conception through production operations. To support development of subsea production systems and long-distance delivery systems in particular, systems engineering activities can be grouped into three primary areas:
• Production system design;
• Equipment application and development; and
• Systems integration.
Production system design encompasses flow line and hardware arrangement and configuration, flow line and pipeline sizing and flow assurance, and operability - all key to the success of most offshore development projects. The issues and interrelationships between them, and other attributes of the total system, must be considered at all levels of field development: early concepts, pre-FEED (front-end engineering design), FEED, detailed design and production operations.
All production modes throughout the system lifecycle, including startup, steady state, rate change and shut-in, must be considered for effective flow assurance and operability. Operating strategies and procedures for successful system designs will be robust; strategies will be developed with system unknowns and uncertainties in mind while being readily adapted to work with an existing system, even when the system is different than that assumed during design.
For long-distance delivery systems, the system will be designed for certain ranges of fluids and production rates. Because precise future operational requirements cannot be known, system design will have to include features that provide operational flexibility to accommodate conditions not initially known. Powered subsea production equipment may enhance this operational robustness.
Equipment application and development focuses on the subsea equipment and subsystems needed to enable deep-offset, long-distance delivery systems. Limited applications of such equipment are now in operation, and the number and type of powered subsea production/processing system components in use is expected to greatly increase in the future.
The emergence of large, reliable subsea multiphase pumps creates opportunities for providing flow energy via pressure boost where the technical challenges of deepwater, remote locations or low reservoir pressure have previously prevented economic development. Opportunities for boosting existing production from subsea tiebacks and prolonging the life of depleted reservoirs also exist.
Electric flow line heating has emerged as a reliable flow assurance technique, with a number of concepts for direct or indirect heating available. Applications for electric flowline heating include intermittent heating for pre-start up heating and wax or hydrate remediation (melting) and continuous heating for prevention of wax deposition or hydrate formation.
Some of the subsea equipment required for new, deep-offset production systems will be proven equipment currently in use, some will be emerging technology and some will be developmental. On a particular project, system engineers will identify equipment requirements, prepare specifications, participate in equipment development and qualification, and provide management and engineering services required to assure that equipment is designed, procured, installed, commissioned and operated in accordance with system requirements.
An integrated, optimized, high-integrity subsea solution, where the benefits of subsea separation, subsea pumping and flow line heating are objectively evaluated and implemented, requires a multidiscipline approach from concept to operation.
Equipment application and development expertise will be applied in specification, selection, design, analysis, test, procurement, installation and operation of powered subsea systems including:
• Pipeline/riser/flow line electric heating systems;
• Subsea/downhole processing equipment;
• Subsea chemical distribution;
• Subsea multiphase pumps, wet gas compressors;
• Subsea single-phase pumps and compressors;
• Control/service/service buoys/mini-spars;
• Long-distance power/communications umbilicals;
• Long-distance wireless communications;
• Subsea power delivery/distribution; and
• Subsea power generation.
Systems integration assures that the total system has been defined, conceived and executed with appropriate attention to system requirements and constraints. Because of the additional complexity, longer life and uncertainties of future system requirements associated with LDDS systems, systems integration will become even more important than with conventional systems.
Systems integration personnel will have to work closely with project team leaders, functional leaders (reservoir, drilling and completions, operations, flow assurance, project engineering, etc.), contractors and the entire project team throughout the life of the project to coordinate, assist and execute system-wide work activities.
With the longer life of such developments, the systems integration function, perhaps embedded within the operations group, will become the "memory" of the project, providing the knowledge of why the system is configured as it is and the understanding of how the system can or cannot be adapted to accommodate desired changes in production requirements.
Conclusion
Expansion in ultradeep water to bring more reserves online requires that the offshore industry move beyond current, conventional technology to deep-offset, long-distance delivery systems. This challenge requires a step-change to long-distance delivery management, which demands even more rigorous attention to an entire system.
While much, if not all, of the equipment identified will be applied in certain developments, equipment currently employed on a limited basis is especially important and will certainly see continuing development and increased application. This equipment includes electric flow line heating, multiphase pumps and meters and control/service/power buoys.
Finally, while minimization of "risk" is usually a top-level project goal, in this context, operators need to re-examine their priorities and likely adopt "optimization" of production and economic risks. This issue will have a very significant impact on development configuration, cost and schedule for deep-offset, long-distance delivery systems, and industry's success in achieving its ultimate production goal: production from subsea systems directly to shore.

Comments