Cost Effective

Copyright 2001, SPE/IADC Drilling Conference

This paper was prepared for presentation at the SPE/IADC Drilling Conference held inAmsterdam, The Netherlands, 27 February–1 March 2001.This paper was selected for presentation by an SPE/IADC Program Committee followingreview of information contained in an abstract submitted by the author(s). Contents of thepaper, as presented, have not been reviewed by the Society of Petroleum Engineers or theInternational Association of Drilling Contractors and are subject to correction by the author(s).The material, as presented, does not necessarily reflect any position of the SPE or IADC, theirofficers, or members. Papers presented at the SPE/IADC meetings are subject to publicationreview by Editorial Committees of the SPE and IADC. Electronic reproduction, distribution, orstorage of any part of this paper for commercial purposes without the written consent of theSociety of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted toan abstract of not more than 300 words; illustrations may not be copied. The abstract mustcontain conspicuous acknowledgment of where and by whom the paper was presented. WriteLibrarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435.

Abstract

Extended Reach and Deep Water Drilling are constrained bythe weight of the steel drill pipe. Transfer of data between thebottom hole assembly and the well head is currentlycumbersome, slow, and less precise than desired. Recognizingthese limitations, the U.S. Department of Energy, NationalEnergyTechnology Laboratory, has funded a three-yearprogram to develop and qualify a cost-effective compositedrill pipe (CDP). This pipe will provide enabling capability inall three of these areas. The program was started onSeptember 30, 1999 and has the goal of having composite drillpipe approved and commercially available by September 30,2002.This paper reviews the first year of the program, presentsspecifications for the proposed composite drill pipe, andrepresents work-in-progress.

Introduction

Drill pipe weight and friction or drag in the horizontaldeparture of the well limits the maximum distance ofExtended Reach from drilling platforms. Deep Water drillingis limited by maximum length for which steel pipe can supportits own weight. Electronics within the bottom hole assembly

are temperature limited. In steel drill pipe, heat transferthrough the pipe wall from OD fluids to ID fluids is a majorfactor in controlling instrumentation temperatures. LoggingWhile Drilling (LWD) and Mapping While Drilling (MWD)operations are rendered nearly ineffective by the currentinability to transfer data in real time from the bottom holeassembly to the well head. Similarly, direct transfer of powerto the bottom hole assembly is currently a technical challenge.

Cost Effective Composite Drill Pipe (CDP) can reduce costsand improve capabilities in the three major areas now limitingcomplex drilling operations. The composite drill pipe will:

• Provide enabling technology for Extended Reachand Deep Water Drilling by physical/mechanicalcapability comparable to currently availablemetal drill pipe, and

• Provide a weight savings over metal drill pipeby 40% to 50%, thus offering substantial weight-related cost reductions for offshore and land-based operations, and

• Provide substantially reduced heat transferthrough the pipe walls, and

• Provide an opportunity for real time data andpower transmission from well head to bottomhole assembly.

Theory and Definitions

Suitability of Composites for Tubular Applications.Composites can be designed to meet or exceed thephysical/mechanical capabilities of metals in nearly all tubularapplications. An enabling feature is the fact that compositestructures are inherently anisotropic in mechanical and thermalproperties, while metals are isotropic (mechanical propertiesnearly equal in all directions). As a result, the tubular portion

SPE/IADC 67764

Cost Effective Composite Drill Pipe: Increased ERD, Lower Cost Deepwater Drillingand Real-Time LWD/MWD Communication

Dr. J.C. Leslie, Mr. Jeff Jean, Mr. Lee Truong, Mr. Hans Neubert, Mr. James C. Leslie II

Advanced Composite Products & Technology, Inc.

2 DR. J.C. LESLIE, MR. JEFF JEAN, MR. LEE TRUONG, MR. HANS NEUBERT, MR. JAMES C. LESLIE II SPE/IADC 67764

of the drill pipe can be customized and manufactured to meetspecific load conditions. Fiber is placed coincident with theload direction, and of sufficient quantity to satisfy strengthrequirements. As presented later, this will be accomplished bythe cost effective composite drill pipe (CDP) design developedin this program. A typical cross section for the CDP design isshown in Figure 1.

Tool Joints and Metal to Composite Interface. Compositesare ideally suited to plane stress applications and cannot matchthe elastic-plastic behavior of steel in complex 3-D stressfields. For structural efficiency, it is appropriate that the tooljoints be accomplished with metal. For this program, standardsteel pin and box type joints were chosen.

The major design problem in the development of CDP isreduced to that of the interface between the tubular compositepipe and metal tool joints. There are numerous patentsaddressing this problem and ACPT, Inc. has successfullydesigned, produced, and used tubular metal-composite jointsfor power (torque) transmissions for automotive andcommercial applications. ACPT’s previous work has beenapplied to CDP designs, and patents have been applied for.

CDP Reduces Heat Transfer to the Drilling Mud. Datapresented below in Table 1 compares the heat transfercoefficients of 4130 steel, 7075 aluminum, 6Al-4V-Titanium,and the CDP in the thickness direction.

Table 1 Thermal Conductivity (Btu/Hr-Ft-Deg.F)

Steel Alum Titanium CDP 25.0 97 4.6 .50

It is hypothesized that the smooth walls and the absence ofconstrictions within the current CDP design will reduce thetendency toward turbulence in the fresh drill mud, furtherreducing heat transfer and also reducing frictional power(pressure) loss at the drill face.

Material Cost. The primary enabling factor for this programhas been the recent reduction in the price of graphite fibers.This reduction occurred largely through the influence ofZoltek, Inc. on the composites industry. The cost hasdecreased from $30/$35 per pound of fiber to a committedprice of $5/lb. Previous oil patch tubular developments havehad to use combinations of fiberglass and graphite fibers toachieve a lower-cost mechanical design. The current designuses fiberglass only where it does not detract from meeting themechanical/physical specifications set forth for the CDP.Graphite fiber is used for meeting all major load requirements.

Temperature. Resin rheology has limited previous oil patchcomposite applications to maximum temperatures of 250F.Data presented below (Table 2) indicates the current CDP

design can operate up to 300F. The CDP design limitation isthe shear strength of the resin at elevated temperatures. Workis also underway in an effort to extend this capability to 400F.

Table 2 Glass Transition Temperature, ASTM-E-831(TMA Method)

Test 1 Dry Specimen 326FTest 2 After 24hr Water boil 313FTest 3 After 100hr-water boil 296F

Data-Power Transmission Capability Wiring has beenincorporated in the walls of the composite tubular structuresections of CDP. Power and data will be transmitted in realtime through the walls of the CDP. The problem now becomesone of transmission through or around the metal, (API orotherwise) tool joints. At present, this program isconcentrating on demonstrating transmission in a practical,manufacturing capable manner. Feasibility studies areinvestigating methods for transmission through or around themetal joints. Potential transmission methods through tooljoints include direct connect, acoustic and inductive.

CDP Configuration and Specifications

CDP Design. Figures 2 and 3 are schematic illustrations ofthe current cost-effective CDP design. As shown in Figure 2,the overall length is nominally 31.5 feet. The 4.25-inch ID issmooth and uniform throughout. The 5.88-inch ODtransitions to 7.0 inches maximum OD at the tool joint.

Figure 3 schematically illustrates the design of the compositewall and a baseline metal-to-composite interface. Specificdetails have been omitted for patent and proprietary reasons.

Materials

Table 3 summarizes the materials currently used in the CDP

Table 3 CDP Material

1. -FibersCarbon: Commercial Grade Tow Size: 48K to 50KGrade-525 Ksi Fiber Strength, 33-34 Msi Fiber Modulus(ACPT has currently qualified 2 Carbon Fiber types for theCDP)

Fiberglass: E-glass commercial grade, Tow Size: 450 DenierGrade: 225 Ksi Fiber Strength, 10 Msi Fiber Modulus2. -Resin350 F High Performance Resin(Further resin development will be performed for highertemperature wells.)

COST EFFECTIVE COMPOSITE DRILL PIPE: INCREASED ERD, LOWER COST DEEPSPE/IADC 67764 WATER DRILLING, AND REAL TIME LWD AND NWD COMMUNICATION 3

3. -AdhesiveLow Viscosity, High Strength, 350F Service TemperatureEpoxy(Further Adhesive development testing will be performed forhigher temperature wells with the resin research.)

CDP Specifications CDP load capability requirements andspecifications are shown in Table 4. These values wereobtained through direct communications with numerousindustry individuals and major corporations involved inoffshore drilling operations. They have been reviewed andrevised at least quarterly11, since September 30, 1999.

Table 4 CDP Specified Performance Requirements

-Tension-Combined Case Load, Nominal Operation: 20,000 TVD+133,000 lb pull-up load + 30,000 ft-lb torsion +7500 psi internal pressure.-Compression-Combined Case Load, Nominal Operation:

30,000 lb load+30,000 ft-lb torsion+7500 psiinternal pressure.

-Torsion-Maximum Make-up Torque 45,000 ft-lb + 25%for shock-loading and hard-to-breakconnections.

-Tension+Bending-Combined Case Load, NominalOperation:100,000 lb drag load+30,000 ft-lb torsion+7500 psiinternal pressure+10 degrees of bending/100Ft.

-External Pressure-12, 000 psi.-Temperature-350F nominal use.-Fatigue-2, 000,000 cycles (load and frequency TBD)

Manufacture and Marketing of Cost Effective CDPManufacture of the CDP will be accomplished by use offilament winding and CNC machined tool joints, specificallydesigned to accommodate the metal-composite interface.

Initial prototype and field qualification units will be filamentwound at ACPT. It is planned that this pilot plant facility willsupport initial production rates. For full-scale production, adedicated manufacturing plant capable of meeting marketdemands is planned. The number of manufacturing windingstations put into production will be determined by marketrequirements as of 2003 and beyond.

Manufacturing and marketing of the CDP will beaccomplished in cooperation with a well-established majormanufacturer(s) of drill pipe and/or oil patch equipment.Negotiations are in progress toward establishing thiscollaboration(s).

1 Semi-Annual reports are prepared, distributed, and orallyreviewed with contributing members of the CDP team. Formore information on participation in this team effort, pleasecontact Mr. Jeff Jean at ACPT, Inc., (714) 895-5544.

The current program includes on-going manufacturingdevelopment and quality control to assure that the CDP willnot be subjected to property variations through manufacturinginconsistencies. The CDP will be manufactured by the lowestcost process and will be optimally automated.

Data and Results

Overall Plan and Schedule. Table 5 presents a summaryschedule for the 3-year program being followed to achieve thedevelopment and manufacture of Cost Effective CDP. Theprogram is on schedule.

Table 5

Major Schedule Milestones Month Start MonthComplete

Set CDP Mechanical and PerformanceRequirements

1 4

Finite Element Modeling 4 29

Composite Materials Selection andVerification Testing

1 18

Metal-To-Composite Interface (MCI)Design

4 21

Coatings and Liners Research, Testing,and Selection

4 29

1/3 Scale Mechanical Testing 6 12

Full Diameter-10Ft Section MechanicalTesting-Static

12 17

Revised Mechanical/Physical CDPDesign Complete

13 21

Final Design of CDP Complete 29 29

Test 30 Ft CDP Sections-LAB 22 27

Well Site Tests 27 34

First Field Use Available 36 N/A

Materials Test. Mechanical Properties. A materials test planestablished the physical and mechanical composite propertyrequirements to ASTM standards at program initiation.Testing was performed to confirm manufacturers’ publishedresults. In addition, industry input was solicited concerningthe applicability of the selected resin and fiber to down wellconditions. Materials screening was accomplished by use of


NOL Short Beam Shear (SBS) testing. Tests were runcovering temperatures to 400F and with dry and wetspecimens. Wet specimens were conditioned by both 24 hourand 100-hour water boil exposure. Specimen preparation andtesting was accomplished by certified test labs. A summary ofthese test data is presented in Table 6.

Table 6 Short Beam Shear Tests per ASTM D 2344

Dry Avg. Shear (PSI)200F 5800250F 4690300F 4240350F 3920400F 2010

24hr Boil200F 5260250F 4270300F 3820350F 3030400F 1520

100hr Boil200F 4860250F 4180300F 3520350F 2730400F 1210

It has been concluded that composite degradation is caused bymoisture hydrolysis of the resin matrix when subjected toelevated temperature. In order to confirm this hypothesis,additional SBS specimens are currently being subjected tocombined temperature, pressure, and chemical/fluid exposureclosely simulating actual down well conditions. These datawill be provided, as available, at the oral presentation and infuture publications.

It is important to note that the application of ID and OD linersor coatings will also tend to minimize the hydrolysis process,further protecting the resin matrix from molecular bondscission.

Physical Wear of the Composite. Composites are typicallymuch more quickly and severely abraded by physical wearthan steel. This program includes significant effort to protectthe composite drill pipe from abrasion and erosion.

Industry consultations indicate that internal wear is notsignificant with steel drill pipe. It has been pointed out thatthe light plastic coating currently applied to some steel drillpipe to provide lubricity to the interior does not experiencesignificant wear in normal use. An anti-erosion coating willhelp to protect the exterior of the CDP. Several candidateshave been tested using the Slurry Abrasion ResponseDetermination per ASTM G75-95 (SAR Number). Thepurpose of the test is to determine the relative wear resistance

of materials in Simulated Drilling Mud. Other candidatecoatings are still being evaluated. Data is presented in Table 7from tested materials to date. An investigation to find andvalidate the best, most cost-effective erosion/abrasionprotective material for the CDP is an ongoing process.

Table 7 Slurry Abrasion Response Determination Results Per ASTM G75-95

Material 2hr Mass Loss(milligrams)

4130 Steel (Baseline) 252201 XXX 402221 XXX 45UV Urethane 125SPG XXX 1582000 XXX 175

Exterior coatings and other techniques are also beingevaluated to protect the CDP from the much harsher exteriordown well and handling environments. It has been ascertainedthat the exterior wear problem is manageable.

One-Third Scale Testing. Design properties have beenconfirmed by 1/3 scale tubular testing. All specimens werefilament wound and the 1/3 scale requirement was met in towsize, plies, and ply thickness, as well as, all other physicaldimensions, except for total length. The design specificationsfor tension, and torque and compression were confirmed.Figures 4 and 5 show the 1/3 scale compression andtorque/tension specimens.

Table 8 compares the required torsion, tension andcompression capabilities with the 1/3 scale test results. Asshown below, the primary strength levels required by thespecification have been met. Analysis of the 1/3 scale dataleads to the conclusion that the other required mechanicalspecifications will also be met, although not yet tested. Thisconclusion will be verified in the planned testing of full-scale10.0 and 31.5-foot sections of CDP.

Table 8 1/3 Scale Test Averages

1/3 ScaleTest Value

Avg.

Factored toFull-Size

PerformanceRequirement

Tension 63,600 X (9) =572,400 403,000Compression 37,600 X (9) =338,400 30,000Torque 1,960 X (27) =52,920 56,250

Weight Predictions. Based on the current design, it isestimated that a 31.5-foot section of CDP, including steel tooljoints per the ICD drawing (Figure 2), having a constant 4.25


inch ID will weigh 425 pounds, or less. Comparable 135 ksistrength steel tubular, including joints, weighs approximately866 pounds.

Conclusions

ACPT is encouraged by the progress towards meeting all theperformance requirements expected of a fully functional andqualified CDP. Much work, however, remains to beaccomplished. Increased temperature capability remains achallenge, with a goal of meeting 400F service temperature.The metal-to-composite interface (MCI) requires additionalanalysis and testing to guarantee that CDP failure will alwaysoccur in the pipe section. LWD and MWD details, includingreliability issues, need to be demonstrated. Continuation ofthis program, now at the start of the 2nd year, focuses on thesechallenging opportunities.

FIGURE 2 Interface Control Drawing

FIGURE 1 Typical Cross Section of CDP Composite Pipe


FIGURE 3 Metal-Composite Interface (MCI)

FIGURE 4 Subscale Compression Specimens FIGURE 5 Subscale Torsion Specimen


Disclaimer

This report was prepared as an account of work sponsoredby an agency of the United States Government. Neither theUnited States Government nor any agency thereof, nor any oftheir employees, makes any warranty, express or implied, orassumes any legal liability or responsibility for the accuracy,completeness, or usefulness of any information, apparatus,product, or process disclosed, or represents that its use wouldnot infringe privately owned rights. Reference herein to anyspecific commercial product, process, or service by tradename, trademark, manufacturer, or otherwise does notnecessarily constitute or imply its endorsement,recommendation, or favoring by the United StatesGovernment or any agency thereof. The views and opinionsof authors expressed herein do not necessarily state or reflectthose of the United States Government or any agency thereof.

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