Abstract

This paper details the preparation and temporary deployment of a Multiphase Flow Meter (MPFM) for a series of multi-rate well tests carried out on high gas-liquid ratio (GLR) production wells.

The MPFM incorporated specific design features to permit accurate measurement of liquid rates in high Gas Void Fraction (GVF) production streams and was prepared as a skid mounted unit for ease of deployment, hook-up and demobilisation.

MPFMing was chosen in order to eliminate the need to flare or recompress depressurised fluids. This permitted the wells to be flowed at flowrates similar to their normal production rates, which maximised the benefit of the data obtained, without the need to deploy expensive and space consuming additional equipment.

The ease and speed of deployment and hook-up demonstrates that such equipment can provide well performance data similar to that collected by a conventional temporary well test spread.

Cumulative well performance curves generated from the data collected showed good correlation with production station data supporting previous conclusions regarding the accuracy of MPFM's. The maintenance of this accuracy in the difficult high GVF flow regime vindicates the use of the particular equipment model and design chosen.

The small footprint, reduced crew size, and elimination of flaring makes this system an attractive option for testing on unmanned facilities, in environmentally sensitive areas and when space constraints appear prohibitive.

Introduction

The recent redesign of the Pernis West wet gas production gathering system included the provision of a recompression module prior to flow entry to the pipeline transportation system. This gave the opportunity to increase production by utilising lower FTHP pressures. However, the original production test facilities were now undersized for the increased flowrates and a cost-effective alternative to the provision, and permanent installation, of a new test header, separator and meter runs was required.

The provision of permanent multiphase metering on each production flowline was considered technically feasible to provide sufficiently accurate gas and oil and water production data. However, it was considered that periodic production performance data would be sufficient for reservoir management and production forecasting.

The provision of a conventional temporary well test spread, including liquid stabilisation, a gas flare and liquid storage tanks would normally be considered in such circumstances - see figure 1. However, the production gathering complex is sited in an area where the operator wished to ensure that all flaring was eliminated if at all possible.

The alternative of providing a suitable Multiphase flowmeter, on a temporary basis, and returning all produced fluids to the production train, was therefore considered the only effective option available. Such an approach had the potential advantage of minimising costs by reducing manpower requirements, and providing the equipment with regular windows for deployment elsewhere.

Preparation

The first step was to define the meter requirements and confirm the technical feasibility of employing Multiphase metering technology to accurately measure both gas and liquid rates from all the producing wells. The wells at Pernis West provide high GOR gas/oil production, and it was clear that, at the flowing wellhead pressures anticipated (50 to 100 bar),

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