Validation and Operational Experience of a Dualstream II Wet Gas Meter in a Subsea Application on the Statoil Mikkel Field

摘要

Wet Gas flow measurement has now been utilised on many projects over the last decade. Early systems required frequent well testing to enable corrected gas and liquid flow rates to be generated however over more recent years the drive to remove the requirement for well testing has led to the development of 'intelligent' wet gas metering systems. In subsea applications the need to remove well testing requirements cannot be overstated and the use of a proven 'intelligent' measurement technology for royalty allocation may be the only economically viable route for a project to proceed. During 2003 Statoil validated, commissioned and put into operation two Solartron ISA Dualstream II meters for subsea allocation purposes on the Mikkel Field. Mikkel is a gas condensate field located 80 km southeast of the Asgard field. The Mikkel field is connected to the 'mother' platform via a subsea tie-in to the existing flowline from the Midgard field. The meters are installed at a depth of approximately 220m. The "mother" platform is Asgard B. Dualstream II meters have been utilised on several applications to date so this paper will focus primarily on the measurement issues relating to meter validation at a wet gas test facility, commissioning, and also the testing carried out once the meter was installed subsea with reference to the methodologies used and the accuracy obtained. Operational experience to date will be discussed particularly with respect to meter reliability and hydrocarbon mass flow rate accuracy achieved. Because of the tie-in to the existing flowline from Midgard the verification of the Dualstream II meters is challenging and is based on a 'by difference' method using topside instrumentation. In addition we will discuss how the dual redundant instrumentation and hydrate prevention measures, normal operational requirements in subsea applications, can impact measurement uncertainties