Measurement performance assurance for subsea multiphase flow meters (MPFM) can derive motivation from several sources of technical and/or business need, ranging from well surveillance to flow assurance monitoring, to production allocation among commingled sources of varying royalty, taxation, or ownership. Often, the more sensitive the subsea MPFM measurement is to a technical or business driver the more difficult it can be to initiate a comparison to a reference measurement or reference fluids such as topside measurement. Thus, providing assurance for subsea MPFM measurement performance requires a coordinated effort of MPFM performance surveillance – a combination of data and activities that can enable continuous indication of MPFM measurement performance, with or without periodic comparisons with reference measurements. However, utilizing MPFM performance surveillance information – which can come from a multitude of sources – can be confusing and potentially misinformative if a rigorous methodology to systematize the information isn't applied. It was in this context that a surveillance methodology using data validation and reconciliation (DVR) was chosen to leverage the disparate surveillance information available and provide quantitative measurement performance assurance results for a subsea MPFM.
DVR was applied to assess the performance of a subsea MPFM incorporated within a subsea/topside field. Multiple sources of surveillance data and information were utilized in the application including the subsea MPFM, independent water-liquid ratio measurement, pressures and temperatures throughout the network, fluid properties, inlet separator flow measurements, and well test results.
Three main objectives were established to demonstrate efficacy of the applied DVR methodology for subsea MPFM measurement performance assurance: 1) quantified DVR results for direct MPFM validation via well test; 2) continuous DVR condition-based monitoring (CBM) of the subsea MPFM within a defined subsea/topsides topology during normal operations, and 3) DVR-derived uncertainty estimates for the subsea MPFM. Several case studies using DVR surveillance are presented to address subsea measurement performance assurance through direct validation, CBM and uncertainty estimation. Each case study describes the workflow and detailed explanations for the steps taken in the DVR surveillance methodology.
Implementation challenges and lessons learned are also presented, along with a strategy for sustained subsea MPFM measurement performance assurance using a DVR-based surveillance approach.