Multiphase Flow Measurements Sensitivity Assessment and Management - A Cost Effective Methodology for Surveillance Engineers and Field Operators

Multiphase flow measurements (MPFM) have gained the oil and gas industry focus since the early 90’s(1) due to its continuous improved performance and ease of remote operations (1). Different MPFM systems have been developed but none of them can be referred to as absolutely accurate (3). One of the commonly used systems combines Venturi meter with gamma ray fraction meter (4). The latter is simple, robust and extremely accurate for a given composition based on physical measurements. However, the sensitivity of the nuclear attenuation to heavy atoms can lead to drastic uncertainties on Water Liquid Ratio (WLR) measurements. Therefore, applications where heavy atoms composition changes with time represent an operational and economical shortcoming for surveillance engineers and field operators due to the need to frequently update the configuration data set of such MPFM systems every time the wellstream composition changes. This paper provides surveillance engineers and field operators with a methodology that has been developed and validated while commissioning new permanent MPFM units on three major onshore fields in the UAE. Several sensitivity studies were carried out to determine the impact of lumping well configuration profiles into groups and assess the MPFM measurements sensitivity to various physical and compositional flow parameters such as phase densities, viscosities, %H2S, %CO2 and water salinity. It also offers a cost effective solution in order to optimize the time and cost required for initial and/or frequent MPFM configuration work by introducing pre-determined configuration data sets that takes into account the wellstream compositional variation with time. The suggested methodology was applied on 247 wells producing from five different reservoirs. It has significantly reduced the man-hour required to complete the individual well profile configuration from 60 days to 8 days. Once the methodology is implemented, it requires no further vendor support and no frequent physical reconfiguration. For MPFM systems that do not rely on nuclear attenuation technology, the methodology still can be applied to identify measurements sensitivity envelope to any physical, chemical and/or mechanical parameters.