_RP_85-2003_2013.pdf

Use of Subsea Wet-gas Flowmeters in Allocation Measurement SystemsAPI RECOMMENDED PRACTICE 85FIRST EDITION,AUGUST 2003REAFFIRMED,OCTOBER 2013Use of Subsea Wet-gas Flowmeters in Allocation Measurement SystemsUpstream SegmentAPI RECOMMENDED PRACTICE 85FIRST EDITION,AUGUST 2003REAFFIRMED,OCTOBER 2013 SPECIAL NOTES API publications necessarily address problems of a general nature.With respect to partic-ular circumstances,local,state,and federal laws and regulations should be reviewed.API is not undertaking to meet the duties of employers,manufacturers,or suppliers towarn and properly train and equip their employees,and others exposed,concerning healthand safety risks and precautions,nor undertaking their obligations under local,state,or fed-eral laws.Information concerning safety and health risks and proper precautions with respect to par-ticular materials and conditions should be obtained from the employer,the manufacturer orsupplier of that material,or the material safety data sheet.Nothing contained in any API publication is to be construed as granting any right,byimplication or otherwise,for the manufacture,sale,or use of any method,apparatus,or prod-uct covered by letters patent.Neither should anything contained in the publication be con-strued as insuring anyone against liability for infringement of letters patent.Generally,API standards are reviewed and revised,reafrmed,or withdrawn at least everyve years.Sometimes a one-time extension of up to two years will be added to this reviewcycle.This publication will no longer be in effect ve years after its publication date as anoperative API standard or,where an extension has been granted,upon republication.Statusof the publication can be ascertained from the API Upstream Segment telephone(202)682-8000.A catalog of API publications and materials is published annually and updated quar-terly by API,1220 L Street,N.W.,Washington,D.C.20005,standardsapi.org.This document was produced under API standardization procedures that ensure appropri-ate notication and participation in the developmental process and is designated as an APIstandard.Questions concerning the interpretation of the content of this standard or com-ments and questions concerning the procedures under which this standard was developedshould be directed in writing to the standardization manager,American Petroleum Institute,1220 L Street,N.W.,Washington,D.C.20005,www.api.org.Requests for permission toreproduce or translate all or any part of the material published herein should also beaddressed to the general manager.API standards are published to facilitate the broad availability of proven,sound engineer-ing and operating practices.These standards are not intended to obviate the need for apply-ing sound engineering judgment regarding when and where these standards should beutilized.The formulation and publication of API standards is not intended in any way toinhibit anyone from using any other practices.Any manufacturer marking equipment or materials in conformance with the markingrequirements of an API standard is solely responsible for complying with all the applicablerequirements of that standard.API does not represent,warrant,or guarantee that such prod-ucts do in fact conform to the applicable API standard.All rights reserved.No part of this work may be reproduced,stored in a retrieval system,or transmitted by any means,electronic,mechanical,photocopying,recording,or otherwise,without prior written permission from the publisher.Contact the Publisher,API Publishing Services,1220 L Street,N.W.,Washington,D.C.20005.Copyright 2003 American Petroleum Institute FOREWORD This Recommended Practice is under the jurisdiction of the API Executive Committee onDrilling and Production Operations.It is intended to advise the user on various aspects of theuse of subsea wet-gas owmeters in allocation measurement systems.Marinization,opera-tion,abnormal operation,and meter testing are important topics included here,but,foremost,this document proposes novel techniques to be used in the allocation of total production toindividual contributing streams.Deepwater oil and gas prospects often employ a form of development known as a subseatie-back.In these applications,wells are completed subsea,and production ows to hostfacilities for processing,generally in shallower waters,and then on to export markets.Inmany cases,the host infrastructure already exists,although facilities modications may berequired.Certain of these developments require commingling ow from multiple wells,pos-sibly from multiple elds and an assortment of owners.In order to allocate production inthese cases,measurement of the full wellstream uids may be required.Add to this the greater uncertainty of,and lack of recognized standards for,multi-phasemeasurement,then place the meters subsea in deep water,and one quickly enters unchartedwaters.Key to the use of multi-phase and wet-gas meters(subsea or topside)is the ability of anallocation system to account f