Eric Kelner, P.E.

Deepwater oil and gas prospects often employ a form of development known as a subsea tie-back. In these applications, wells are completed subsea, and production flows to host facilities for processing, generally in shallower waters, and then on to export markets. In many cases, the host infrastructure already exists, although facilities modifications may be required. Certain of these developments require commingling flow from multiple wells, possibly from multiple fields and an assortment of owners. In order to allocate production in these cases, measurement of the full wellstream fluids may be required. This RP presents a recommended allocation methodology that is technically defensible and mathematically optimized to best fit the application, and that equitably accommodates variances in the uncertainty level between meters in the system.

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.