Multiphase Flowmeter Performance: A Critical Piece of an Offshore Well Management Toolkit

Abstract

The accurate metering of flow rates across the production chain, from sandface to sales point or custody transfer point is of vital importance. With the use of multiphase flowmeters (MPFMs), measurement of multiphase flow under dynamic conditions is possible. In well tests, the assurance of optimal flowmeter performance is of great importance because test results can significantly impact long-term field development planning and well management. We highlight the integrated approach implemented to improve flowmetering performance for a new oilfield offshore UAE In offshore fields, MPFMs have been installed on production towers to measure production of individual wells. In the first phase of field development, commingled flow from all wells is also metered at the outlet of the manifold tower (MFT) before entering the subsea line to the processing facility. The installed MPFMs eliminate the need for traditional test separators or dedicated test vessels. However, since multiphase flow is complex, turbulent, and chaotic, the acquisition of accurate, reliable, and repeatable rate measurements can be a challenge. Fiscal measurements must also meet statutory requirements for accuracy in hydrocarbon accounting and production allocation. We present the case study of a new field, the initial challenges encountered in achieving quality test data, and the systematic approach established to streamline flowmeter performance. This approach comprises representative fluids description, results validation, and calculation model optimization, which has resulted in improved performance of wellhead and MFT flowmeters. The process of streamlining flowmeter performance verification and optimizing flowmeter utilization to track individual well performance has resulted in cost savings and improved production optimization. Well-specific pressure-volume-temperature (PVT) models have provided optimal conversion of line conditions to standard conditions, with reduced uncertainties introduced by pressure, temperature, and effluent variations. As a consequence, ideal production allocation factors were achieved, yielding confidence in the use of well test data for production and reservoir management purposes. An added benefit is the increased confidence in the data quality for history matching of the dynamic model. Effective production monitoring as new production streams from different reservoirs come on line has enhanced production reconciliation due to reduced uncertainty from commingled flow and improved production forecasting. The principles employed in multiphase flow measurement technology are not new. However, real-time, accurate flow rate measurements are essential for good decision-making, sound engineering analysis, and effective life-of-well management. The application of a case-by-case approach to flowmeter configuration, combined with an efficient monitoring approach, has proved very valuable to achievement of effective reservoir monitoring and well management.