1、Selection of Centralizers for Primary Cementing OperationsAPI TECHNICAL REPORT 10TR4FIRST EDITION, MAY 2008Selection of Centralizers forPrimary Cementing OperationsUpstream DepartmentAPI TECHNICAL REPORT 10TR4FIRST EDITION, MAY 2008Special NotesAPI publications necessarily address problems of a gene
2、ral nature. With respect to particular circumstances, local,state, and federal laws and regulations should be reviewed.Neither API nor any of APIs employees, subcontractors, consultants, committees, or other assignees make anywarranty or representation, either express or implied, with respect to the
3、 accuracy, completeness, or usefulness ofthe information contained herein, or assume any liability or responsibility for any use, or the results of such use, of anyinformation or process disclosed in this publication. Neither API nor any of APIs employees, subcontractors,consultants, or other assign
4、ees represent that use of this publication would not infringe upon privately owned rights.API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure theaccuracy and reliability of the data contained in them; however, the Institute makes no represe
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7、nsis not intended in any way to inhibit anyone from using any other practices.Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standardis solely responsible for complying with all the applicable requirements of that standard. API does not represe
8、nt,warrant, or guarantee that such products 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 p
9、ermission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005.Copyright 2008 American Petroleum InstituteForewordNothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for themanufact
10、ure, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anythingcontained in the publication be construed as insuring anyone against liability for infringement of letters patent.Suggested revisions are invited and should be submitted to the Standards Departme
11、nt, API, 1220 L Street, NW,Washington, D.C. 20005, standardsapi.org.iiiContentsPage1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Benefits of Centralization . . . . . . . . .
12、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1 Definition of Standoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Casing Centraliza
13、tion and Centralizing Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 General Discussion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.1 Centrali
14、zer Types Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.2 Advantages and Limitations of Centralizer Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.3 Sel
15、ecting the Type of Centralizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.4 Drag Force vs Standoff Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
16、03.5 Location and Number of Centralizers to Obtain a Desired Standoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.6 Estimated Drag and Torque When Using Rigid and Solid Centralizers . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.7 Friction Coefficients . . . . . . . .
17、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.8 Potential Benefit of Centralizer-induced Swirl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.9 Centralizer Installatio
18、n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.10 Use of Dissimilar Materials: Casing-centralizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.11 Centraliz
19、er-formation Interactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.12 Stop Collar and Integral Collar Holding Forces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.13 Centr
20、alizer Quality Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.14 Effect of Expansion Coefficient of the Stop Collar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.
21、15 Potential Impact of Centralizers on Casing String Stiffness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.16 Compatibility of the Centralizers with Wellbore Fluids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.17 Thermal Stabili
22、ty of the Centralizer Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233.18 Potential Carbon Steel and Chrome Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233.19 Potential Generation
23、 of Gases from Materials Under Downhole Conditions. . . . . . . . . . . . . . . . . . . . . . . 233.20 Centralizer Wear During Running in the Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Figures1 Definition of Sandoff . . . . . . . . . . . .
24、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Example of a Bow-spring Centralizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Example of a Double Bow-spring
25、 Centralizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Example of a Rigid Centralizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Example of a Rigid Centralize
26、ra Slim-hole Centralizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Example of a Rigid Centralizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Example of Steel Spiral Solid Centr
27、alizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Example of Steel Spiral Solid Centralizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Example of an Integral Solid Cent
28、ralizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 Example of Solid-roller Centralizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611 Example of Centralizers Bo
29、nded Directly onto the Pipe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612 Example of Limited OD Bow-spring Centralizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713 Computer Simulation for Case with Bow-spring
30、 Centralizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914 Computer Simulation for Case with Rigid Centralizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915 Example of the Effect of Normal Forces on Selection of Centralizer Type
31、. . . . . . . . . . . . . . . . . . . . . . . . . 1016 Typical Swirl Angle vs Distance Away from the Centralizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1317 Swirl-inducing Centralizer in a Deviated, Enlarged Hole . . . . . . . . . . . . . . . . . . . . . . . . . . .
32、 . . . . . . . . . . . . 1418 Swirl-inducing Centralizer in an Inclined, Non-enlarged Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1419 Effect of Bow-spring Centralizer in Proximity of the Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
33、20 Example of Bow Centralizer with Fins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1521 Centralizer Installations for Casing Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16v
34、Page22 A Type of Rigid Centralizer Installed for Casing Rotation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1623 Four Centralizer Installation Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1724
35、 Visualization of a Centralizer Embedded into the Formation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1825 Testing of Unconsolidated Sand Under Hydrostatic Pressure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1926 Impact of Centralizers on Casing
36、String Stiffness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Tables1 Example of Parameters Used in Generated Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Standoff of Rigid or Solid Centralizers vs Hole
37、Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Holding Forces of Different Type Stop Collars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 Wear Measurements in Micrometers. . . . . . . . . . . . . . .
38、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Selection of Centralizers for Primary Cementing Operations Acknowledgment API Subcommittee 10 acknowledges the assistance from industry manufacturers in compiling this document. Many of them provided photos of their
39、centralizers, and those illustrations are included in this document. 1 Introduction The proper centralization of the casing for primary cementing has long been a critical step in quality cementing. Lack of proper centralization can lead to severe cementing problems, including lack of zonal isolation
40、 and improper casing support. The goal of this document is to provide the petroleum industry with information for three types of centralizers, their selection and application, and their advantages and limitations. 2 Benefits of Centralization When performing primary cementing jobs, the casing should
41、 be centralized in the wellbore for three reasons: 1. to help get the casing to bottom (this includes reduction of the potential for sticking of the string); 2. to help move the casing during mud conditioning and during the cementing job; 3. to provide an optimal path for fluid flow during mud condi
42、tioning and cementing allowing for effective mud removal to achieve zonal isolation. Field experiences, numerous large-scale experiments and computer simulations have shown that poor casing centralization can be detrimental to the cement job, particularly in narrow annuli. Therefore, a good centrali
43、zation program should aim for high levels of standoff, which produces improved mud removal, particularly across critical areas of the wellbore, that is, those areas where isolation is required. It is imperative the user investigate the standoff at all points, especially between the centralizers. 2.1
44、 Definition of Standoff Standoff is defined by API/ISO documents (e.g. ISO 10427-2) as the smallest distance between the outside diameter of the casing and the wellbore. The standoff ratio is defined by the same documents as the ratio of standoff to the annular clearance for perfectly centered casin
45、g expressed as a percentage (%). Annular clearance for perfectly centered casing is the wellbore diameter minus the casing outside diameter divided by two. Figure 1 illustrates standoff and annular clearance. 1 2 API TECHNICAL REPORT 10TR4 AB C Formation Casing Cement Mud BAC=Standoff % x 100 A = Di
46、stance from center of Wellbore to Formation B = Distance from center of Casing to OD of Casing C = Smallest distance from OD of Casing to Formation NOTE Failure to place cement completely around the casing, as portrayed in the figure, is a likely result of inadequate standoff (centralization) and re
47、sults in failure to achieve isolation. Figure 1Definition of Standoff 2.2 Casing Centralization and Centralizing Devices Casing centralization requires mechanical devices (centralizers) to keep the casing away from the wellbore and/or from the cased sections of the well. Significant issues include:
48、1. the centralizer must provide enough load support to overcome the normal forces tending to lay the casing against the formation wall, particularly in deviated holes, horizontal holes and through doglegs; 2. enough centralizers should be used to provide good casing centralization over the needed in
49、tervals (including at points between the centralizers); 3. it is normally assumed (however not always the case) that the formation can provide enough support for the tools (minimum centralizer embedment). SELECTION OF CENTRALIZERS FOR PRIMARY CEMENTING OPERATIONS 3 3 General Discussion 3.1 Centralizer Types Available The industry has developed three main types of centralizers: bow-spring, rigid, and solid. 3.1.1 Bow-spring Centralizer The bow-spring centralizer is composed of flexible spring bows (heat-treated steel springs) attached to two collars. By design the bows are
