(18c) Pressure and Temperature Optimization for Fluids Produced by Deepwater Oil or Gas Wells: A Study on Current Achievements and Possible Future Developments

The exploitation of deepwater oil and gas reservoirs is a complex and challenging task.  The composition, flow rate and main physical properties (i.e. pressure and temperature) of the produced hydrocarbons change over the time during the life of a field: great care has to be taken in designing and in operating the subsea wells, the subsea production system and the topsides processing facilities which constitute the entire offshore field development. 

To better manage the complexity and the technical challenges that characterize deepwater wells production, and to ensure a greater recovery of hydrocarbons during the field life, actions can be taken, in practice or in principle, to modify the composition, flow rate, pressure and temperature of the produced fluids at the well or when they leave the well and are transported to the host.  Changes may be also required to continue using more conventional construction materials or to limit the cost of the subsea or topsides facilities. 

This study examines the different technologies enabling changes in the composition, pressure and temperature of the produced fluids.  Some of these technologies are field proven and are widely adopted in the industry, such as subsea choke valves.  Others, like subsea multiphase boosting are becoming more and more popular, even if their acceptance does not appear to be general and unconditional.  A few technologies have been used in a more limited way but still have potential for more applications (for example subsea heat exchangers).  New promising technologies are in their infancy and operators look with interest to them to see if they will be able to change the subsea industry: subsea gas compression - now field proven in shallow waters - is possibly the most notable example of these new technologies.

A systematic approach has been followed in mapping and presenting in an ordered way technologies that are not immediately recognizable as related, also due to the fact that they may belong to different disciplines.  Subsea heat exchanger used to reduce the temperature of the gas produced by subsea wells are related to the several different ways of heating a flowline by mean of direct electrical heating or heat tracing: the application is different, but the principle is the same.  In both cases, the temperature of the produced hydrocarbons is modified to obtain operational benefits.

The main focus of this study is on the modification of pressure and temperature of the produced hydrocarbons, but the viable ways of changing their composition and flow rates are also addressed. 

After discussing what is technically feasible today, the study focuses on what appears desirable and may have to be developed in the future.  Ways to improve the transportation of hydrocarbons over long distances are investigated and the impact of new possible technologies on the current way of producing deepwater oil and gas wells is assessed.  For example, increasing the temperature of the produced fluids when they leave the subsea well may reduce the risks of hydrates formation in the flowlines.  Expected benefits of these new possible technical solutions, their perceived risks and costs (although very qualitatively) are also discussed.