Whilst permanent downhole pressure measurement is now accepted as routine, the increased technical challenge and complexity of downhole multiphase flow measurement has delayed introduction until recently. Successful field trials with over one year of operation show that design integration and deployment in both new and mature fields is imminent. We present here a discussion of the wider impact of this technology on our industry.
Downhole flow monitoring at the most basic level can be considered as simply an alternative flow measurement required for well production optimisation. In subsea environments a downhole meter can be the most cost-effective option for adequate data gathering, however, the decision to meter production downhole, rather than at surface should be based upon total value, rather than the cost of the installed device. In some production situations (such as gas lift) factors associated with the downhole measurement of produced fluids, rather than the surface flow rates, allow direct measurement of well production efficiency, and hence allow near real-time production optimisation.
In the advanced completions of the future, a reservoir-integrated system of both downhole (moving to individual branch monitoring in multi-branch wells) and surface flow measurements allows the ultimate flexibility, both to optimise production systems and to cope with variations of reservoir behaviour that would otherwise require well interventions or unplanned shutdowns.
Hydrocarbon surface (fiscal) production rates are the ultimate "bottom line" of total asset production, but do not diagnose individual well productivity. Downhole flow rates are the most basic measure of well and reservoir performance, which coupled with the classic techniques of pressure analysis, allow optimisation of well and asset production.
Introduction to It is now widely accepted that multiphase metering is here to stay, and that the old technology of Multiphase Flow Metering test separators will gradually be replaced in more and more installations. Test separators are bulky and expensive in themselves, and if a dedicated, separate test line is also needed the capital cost and maintenance of the test line and manifold should be added to the separator cost when a comparison is made with a Multi-Phase Flow Meter (MPFM) installation. Surface and downhole MPFMs are designed to be virtually maintenance-free, and have demonstrated significant longevity since their introduction nearly twenty years ago. They also offer quantifiable reductions in operational expenditure (OPEX) in topside and subsea installations when compared with conventional test separators1.
Considering measurement quality, test separators measure cumulative volumes at discrete points in time, often requiring time to stabilise and (being affected by slugging) suffering from flow re