Multiphase gaps

Michael Reader-Harris, NEL

June 1, 2017

Michael Reader-Harris, of NEL, outlines the risk that absent multiphase flow measurement standards pose to industry.

Michael Reader-Harris

While accurately measuring a complex mixture of oil, water and gas is a major challenge for the oil and gas industry, production from aging fields with reducing reserves has increasingly made it a necessity. Multiphase flow meters were developed in the early 1990s to support more economical development of marginal, deeper and more complex fields, and they will play a major role in the shift to subsea production in deeper waters.

While industry recognizes the vital role that these meters will play in the future, no ISO (International Organization for Standardization) standards have yet been published. This expanding meter market lacks the ISO guidelines that assure both operators and authorities of consistency. Also, international standardization lowers barriers to trade and provides confidence in the product.

A lack of multiphase meter standardization could therefore have a substantially negative impact on accuracy in allocation or well testing for the industry, and discourage introduction of a technology that is required for the development of marginal fields.

However, work has started to fill the gap in international standards. Using the Norwegian Handbook of Multiphase Metering from 1995, which NFOGM has permitted ISO to use as its basis, the new ISO Technical Report, ISO/TR 21354 will provide up-to-date guidance. It will contain sections on multiphase flow, multiphase meter technologies, the aims of multiphase flow measurement, the production envelope, performance specification, testing, field installation and commissioning, and verification during operation. It will also include an annex on inter-comparison between laboratories, which shows the level of agreement between laboratories and reduces retesting.

This Technical Report will show how using a two-phase flow map to plot the trajectory (production envelope) of wells, and then overlaying the measurement envelope of possible multiphase meters, can ensure that the correct one is chosen; moreover, appropriate maintenance and verification strategies will be introduced that will save cost and increase reliability for the user.

ISO committee, ISO/TC 28/SC 2/WG 4: TC 28/SC 2, is responsible for oil flow measurement, within it WG 4 oversees metering and meter calibration. To develop ISO/TR 21354, WG 4 members include myself, and experts from China, France, the Netherlands, Norway, the UK and the US. Some of the experts work for major operators and are including reliable information that has arisen from their experience. Such information, for instance on performance testing requirements, will reduce the risk of poor performance, and ultimately failure, in the field.

The intention is that the technical report will be published in 2018.

Then there will be an internationally agreed document that avoids both inaccuracy through inadequate specification and excessive cost through over-specification.