This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 170853, “Enhancements in Fraction Measurements and Flow Modeling for Multiphase Flowmeters,” by A. Lupeau, OneSubsea, and G. Jolivet, D. Chazal, M. Fiore, C. Toussaint, B. Fournier, and F. Hollaender, Schlumberger, prepared for the 2014 SPE Annual Technical Conference and Exhibition, Amsterdam, 27–29 October. The paper has not been peer reviewed.
With more than a decade of experience acquired using Venturi/gamma ray multiphase flowmeters (MPFMs), further gains in measurement quality and operational robustness have been achieved. This paper will illustrate how enhancements in fraction measurements using multienergy gamma ray attenuation and a more comprehensive analysis of the gamma ray spectrum have been developed and implemented to provide greater measurement accuracy and stability, leading to enhanced performances in multiphase-flow measurements.
Introduction
Increasing industry interest in MPFMs has led to numerous developments in the search for the technology (or, more generally, combination of technologies) most capable of providing multiphase-flow measurements in a wide range of conditions with high levels of accuracy and moderate sensitivity to input parameters and their variations. Several manufacturers have revised their operating principles over the past few years. These revisions include replacing either one or several core-measurement blocks; providing optional added measurements to improve accuracy; or completely changing operating principles, either to replace existing meters or to target specific markets.
Two core technologies have proved very reliable in the field of multiphase metering: Venturi meters for flow velocities and gamma ray measurements to determine flowing fractions. A key benefit of fraction measurements based on gamma ray attenuation is that it offers a straight path of measurement across the fluids independently of their distribution, whether oil-, water-, or gas-continuous, and therefore offers the ability to identify dispersed fluids entrapped in other phases. Such measurements also can be performed at a very high level of accuracy. Venturi meters, for their part, benefit from a simplicity of structure as well as a lack of reliance upon strong assumptions about the distribution and stability of various phases in flow.
While those two technological blocks have been at the core of most multiphase meters, implementations vary somewhat. First, in a majority of cases, a single-energy gamma ray measurement is used, and only a single piece of information is obtained from that measurement, typically related to the split between gas and liquid phases linked to mixture density. Additional information is required to determine the fraction of all three phases; this generally requires performing measurements at multiple locations. In such situations, the multiplicity of measurements raises issues regarding how representative it is to correlate observations performed at multiple locations at the same time in inherently chaotic and unstable flows.
