American Petroleum Institute

Recommended Practice for Measurement of Multiphase Flow - First Edition
 N RP 86

Annotation

This API Recommended Practice arose from a series of meetings that were held during 2003 among measurement experts from several producers who were active offshore in the Gulf of Mexico. This group, the Upstream Allocation Task Group, set out to address the general shortage of standards and recommended practices governing the measurement and allocation of flow in the upstream domain.

The group that developed this Recommended Practice (RP) was called the Well Rate Determination Subgroup, with the charter to make recommendations regarding measurement of flow rates from individual wells. However, as their work unfolded, the charge was slightly broadened to cover the more general subject of multiphase flow measurement, whether that flow was from a single well or the combined flow of two or more wells.

USE WITH OTHER RECOMMENDED PRACTICES

It is intended that this RP be used in conjunction with other similar documents to guide the user toward good measurement practice in upstream hydrocarbon production applications. The term upstream refers to those measurement points prior to, but not including, the custody transfer point.

Specifically this document will address in depth the question of how the user measures (multiphase) flow rates of oil, gas, water, and any other fluids that are present in the effluent stream of a single well. This requires the definition not only of the methodology which is to be employed, but also the provision of evidence that this methodology will produce a quality measurement in the intended environment. Most often, this evidence will take the form of a statement of the uncertainty of the measurement, emphasizing how the uncertainty statement was derived.

This RP will prove especially important when used in conjunction with other similar documents, such as those that address how commingled fluids should be allocated to individual producers. For example API RP 85 Use of Subsea Wet-Gas Flowmeters in Allocation Measurement Systems [Ref. 2] describes a methodology for allocation based on relative uncertainty, the identification of which is discussed in detail in section 8.