The Challenges of Deepwater Flow Assurance: One Company's Perspective
Authors: Walker David B.L. , McMullen Norman D. 
Published: October 2008

Abstract
This paper is the keynote address for the OTC Special Session on flow assurance.
Huge hydrocarbon resources are being developed in evergreater water depths. There are compelling arguments for wet tree developments and subsea technology will be challenged to perform beyond current capabilities. Greater confidence in flow assurance technology is needed, especially in transient simulation, hydrate inhibition and wax control. Central to achieving this is effective experimentation on existing developments, and more effective collaboration between operators.
The intent of this paper is to provide the context for the remaining papers of this session. It is a general statement of BP's position on flow assurance technology and is intended to help stimulate debate.

Definitions
Only in the past few years has the term flow assurance emerged to describe an important consideration in upstream process design. In BP we use it to address the energy, integrity, and delivery1 aspects of the extraction process from the reservoir sandface to surface process facilities. Energy issues include: the prediction of fluid pressure and temperature as a function of reservoir behaviour over field life, the performance of energy boosting methods and means of reducing pressure and temperature losses. Integrity covers how we manage corrosion, erosion, wax and scale deposition, hydrate formation and the potential for slug flow to impose large loads on pipe bends and separator internal components. Delivery issues include the effect of unsteady flow on the stability of process controls and equipment.
The ability to address these flow assurance questions requires the application of multiple disciplines, in particular a combination of production chemistry, multiphase hydrodynamics, thermodynamics and materials science. Add to that the need to have a strong understanding of operational constraints, and it becomes clear why expertise in flow assurance is so highly valued by the industry.

A BP Perspective
Necessity has driven research and field validation. In BP's case, the emergence of multiphase flow technology really took off with field studies on our Alaskan North Slope production flowlines. We moved on to incorporate the effects of hilly terrain in the flowline design for our Colombian fields, and finally to deepwater, where our West of Shetlands' FPSO production systems employ S-shaped risers in up to 500m (Figure 1). At each stage field trials have been conducted to validate predictive codes, hence building our current capability to address multi-phase flow issues in ultra deepwater developments. Recent code calibration work based on the performance our Troika field in the Gulf of Mexico (Figure 2) suggests that while we have had good success in slug size prediction, our ability to simulate blowdown events is less accurate2.
In parallel, on the production chemistry front, hydrate research and kinetic inhibitor advances have been accomplished through fundamental research combined with partnering with chemical manufacturers. Good headway has been made in kinetic inhibitor development, but they still fail to meet the subcooling requirements demanded by deepwater development.