Field production testing is commonly done for the purposes of monitoring field production, observing productivity trends, determining fiscal allocation and field contributions. In Pakistan, production tests are used to measure flow rates to update reservoir parameters, monitor field decline, and to allocate portions of total central facility production to specific fields and wells. A major portion of fields in Pakistan flow from wet gas or gas condensate reservoirs, and these are typically the most challenging to accurately test.
Conventional test separators have long been used for well testing and flow metering. They physically separate the phases and the individual phases are metered using dedicated methods, that have been fine-tuned over decades. Multiple tanks and pumps are used in conjunction with the separators to complete the well test package and handle separated fluids.
Multiphase flowmeters (MPFMs), however, are a much more compact technology with significant operational benefits and have matured and gained acceptance over the past two decades. They continuously measure three-phase flow rates without requiring separation. Many MPFMs have no moving parts, making them more mechanically reliable. The capability for continuous monitoring enables quick, well-informed decisions to be made on well performance.
MPFMs bring distinct advantages over conventional well testing equipment for the purposes of production testing. The unseparated stream can be re-injected into the production line, and there is zero impact on the production plant operations. Use of MPFMs results in faster tests because of quicker parameter stability, wider dynamic range and shorter rig up times. MPFM setups also have smaller, lighter physical footprints, which do not require large pressure-energized vessels, so associated health and safety risks are lower. Often, the costs to the operating company are lower because of reduced equipment and personnel requirements.
In this paper, we present a study where an advanced dual-energy gamma venturi MPFM was used to test multiple wells in multiple complex condensate gas fields. We discuss the performance of the MPFM against a given set of metrological expectations, and provide an analysis of a comparison test done inline with a conventional test separator. Finally, based on these analyses, we present the advantages and challenges of using MPFMs for production testing and surveys in different fields in Pakistan.