Introduction. High Performance, Streamline Connections for 4 in. Drill Pipe

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1 Advanced Drill Pipe With Streamline Connections Enhances Slim-hole Drilling Performance Michael J. Jellison, Grant Prideco; Guillaume Plessis, Grant Prideco; Andre Glowacz, Total; John M. Pasnak, Saudi Aramco This paper was prepared for presentation at the IADC World Drilling 2005 Conference & Exhibition held in Rome, Italy, 9-10 June This paper was selected for presentation by an IADC Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the International 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 International Association of Drilling Contractors, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the International Association of Drilling Contractors is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write IADC, P.O. Box 4287, Houston, TX , U.S.A., fax Introduction The trend to drill deeper and longer extended reach slim-hole wells with 6 to 6-1/4 in. final hole sections has revealed serious limitations in the standard 3-1/2 in. drill pipe conventionally used in these applications. Saudi Aramco and Total Indonesia realized significant drilling performance and economic benefits by utilizing 4 in. drill pipe with advanced design, slim-hole connections in place of standard 3-1/2 in. drill pipe. The streamline drill pipe design configuration resulted in successful drilling of longer slimhole intervals with enhanced torsional and tensile strength and improved hydraulic performance at a lower overall cost. Saudi Aramco s QTF field required Extended Reach Drilling to deliver pay zone objectives located at measured depths of 18,000 ft to 25,000 ft with horizontal reach values up to 20,000 ft. Total wanted a drill string design that could deliver higher torsional capacity and improved hydraulic performance to enhance drilling efficiencies and lower drilling times and costs in their Kalimantan field. Use of the larger drill pipe size avoided costly upgrade of the rig pump systems. The slim-hole 4 in. drill string design permitted use of the same drill bit/casing program as employed previously with conventional 3-1/2 in. pipe. A high performance, double shoulder connection for 4 in. drill pipe was selected that maintained a tool joint outside diameter similar to conventional 3-1/2 in. drill pipe tool joints. This streamline connection maintains fishing ability in both cased and open hole sections while providing enhanced torsional strength. The high performance connection provides 22,000 ft-lb working torque, an outside diameter of 4-7/8 in. and an oversized internal bore that promotes hydraulic efficiency. Other major drilling improvements realized included: higher buckling resistance, more available pressure at the bit resulting in better MWD/LWD telemetry transmission, improved hole cleaning and higher penetration rates. In addition, the 4 in. high-performance drill pipe was suitable for drilling larger diameter top-hole sections eliminating a requirement for 5 in. drill pipe. This paper addresses these considerations and provides case histories that clearly illustrate the benefits and savings that can be achieved with this new drill pipe design configuration. High Performance, Streamline Connections for 4 in. Drill Pipe Today s severe ultra-deep and extended reach slim-hole wells require drill pipe with enhanced mechanical performance capabilities and improved hydraulic efficiency relative to standard API 3-1/2 in. drill pipe that has traditionally been used to drill the final 6 to 6-1/4 in. final hole sections of these wells. The desire to utilize 4 in. drill pipe has been confounded by the lack of a connection with a suitable dimensional configuration combined with exceptional mechanical properties. The challenge was to design a high performance, slim-line connection that could be welded to 4 in. drill pipe and provide the same fishing clearance as NC38 connections combined with higher torsional strength, a larger ID bore to improve hydraulic performance and adequate elevator lifting capacity.

2 2 M. JELLISON, G. PLESSIS, A. GLOWACZ, J. PASNAK IADC 2005 Mechanical Performance Properties The drill pipe and tool joint assembly must be capable of withstanding the anticipated service loads including: axial force (tension or compression), torsion, pressure (internal and/or external) and bending. A key consideration that drives connection design and selection is torsional strength. The case histories detailed later in this paper had a basic requirement for maximum anticipated working torque in the range of 20,000 to 22,000 ft-lb. Tables 1, 2 and 3 list dimensional and performance properties of pipe body tubes and connections that were considered for the ERD projects discussed in this paper. 1,2&3 The 4 in. 14 lb/ft drill string design was preferred to improve hydraulic performance and enhanced drilling efficiency. A connection with a restricted outside diameter is required to maintain the ability to fish the connection with a full strength overshot assembly. A maximum outside diameter between 4-7/8 in. and 5 in. must not be exceeded otherwise fishing becomes problematic. The internal diameter will result from the selected type of connection and its ability to transmit torque. Table 3 shows the properties of conventional API as well as first generation (HT) and second-generation (XT) double-shouldered connections. The XT39 connection design, optimized for this pipe configuration, was selected for these challenging well projects because it combined a streamline profile with a slim-hole OD and oversized bore while maintaining the necessary torsional strength to efficiency drill the long extended reach well intervals. Figure 1 depicts a double-shouldered connection. Both members spin up freely from the stab-in to handtight position. In the hand-tight position the primary external shoulder makes contact. 4 As the connection is made-up from the hand-tight to power-tight position the secondary torque stop engages. The secondary torque shoulder provides the increased torsional capacity compared to a standard API rotary shoulder connection. Hydraulic Efficiency The primary driver for moving from 3-1/2 in. drill pipe to 4 in. pipe with streamline connection was to reduce pressure losses through the drill string to improve penetration rates and hole cleaning and lower overall well drilling costs. Numeric hydraulic simulation models were performed. Figures 2 and 3 present the results of these simulations for hole sizes of 6-1/8 in. and 8 ½ in., respectively. With a typical pump rate of 500 gpm for the 8-½ in. bit drilling phase, the pressure drop per unit of length is improved by more than 60% over the API configuration and around 45% over the first generation double shouldered connection. Similar hydraulic performance improvements were realized in the smaller hole size sections and, generally speaking, the larger the pipe for a hole size, the better the hydraulic performance. Therefore, the tube body and tool joint internal diameters are crucial and should be as large as possible provided that increases in equivalent circulating densities (ECD s) do not create well control issues. Consequently, the effect of increased drill pipe size on ECD s must be evaluated for each potential application. In these applications, increasing the drill pipe size from 3-½ in. to 4 in. did not create adverse ECD related issues. Fishing Considerations The need to be able to retrieve the pipe in the event of a failure of the pin connection is the driving factor to the selection of the tool joint outside diameter. The ideal situation is to be able to use a full strength overshot to catch the fish. Having the necessary clearance in a 6 in. or 6-1/8 in. hole, commonly requires that the tool joints OD be 5 in. or less. After compiling and evaluating the information discussed above for the subject well projects, the drilling engineers involved selected the drill pipe design described below: Nominal size 4 in. Weight 14.0 lb/ft Type of upset IU Grade to match environment Connection XT 39 TJ OD 4 7/8 in. or 5 in.

3 IADC 2005 ADVANCED DRILL PIPE WITH STREAMLINE CONNECTIONS ENHANCES SLIM-HOLE DRILLING 3 TJ ID 2 9/16 in. Under certain conditions, the 4 in. drill pipe can be used to drill both the lower, smaller hole sections and the upper larger hole intervals eliminating the requirement for 5 in. drill pipe. 5 The relatively small difference between the tube and the tool joint outside diameters led to a limited elevator surface area for lifting the string of pipe. Figure 4 shows the 4 in lb/ft XT39 drill pipe elevator capacity curve. Although the elevator capacity is somewhat reduced compared to the 3 ½ in. drill pipe configuration, it was more than adequate for the target applications. Note, also if a higher lifting force is required that provide by the elevator shoulder area a sub can be made-up into the top of the string to provide additional lifting capacity. Saudi Aramco QTF Field Case Histories The Saudi Aramco well designs mandated that the hole size in the producing zone be 6-1/8 in. and that 7 in. casing be run from surface to the top of the producing zone. In wells without this design constraint the 7 in. is normally run as a liner thereby allowing a combination of 5 in. x 3 1/2 in. drill pipe to be used. The QTF well design precluded the use of 5 in. drill pipe in the drill string for the 6-1/8 in. hole section. The torque and drag simulation required a high performance slim hole drill string capable of transmitting a torque up to 20,000 ft-lb and withstanding high tension. Another requirement was to give drillers the ability to fish the pipe both in the 7 in. casing and the 6-1/8 in. open hole with a high strength slim-hole overshot. Extended Reach Drilling (ERD) was required for this oilfield due to two main considerations: The proximity of surface infrastructures required that the drill sites be moved away from these facilities. Therefore, to reach the reservoirs underneath these facilities ERD technology was required. Since the field also extends offshore, it was determined that ERD drilling was more cost effective than building offshore platforms. In the typical well design, the kick off depths are usually in the 17 in. hole section below the 18-5/8 in. casing shoe at 700 ft. Long radius build rates are used for both the initial build then the final build into the producing zone following a long tangent section. Intermediate casings strings of 13-3/8 in. and 9-5/8 in. are run prior to the long 7 in. production casing set at the target entry and top of the producing zone. The wells are completed with approximately 5,000 ft of 6 1/8 in. open hole. See figure 5 for a graphic illustration of the well designs. Torque simulations were performed based on three friction factors levels (maximum, expected and target). The anticipated drilling torque was then compared to the drill pipe capacity. The retained option was the 4 in. drill pipe with XT39 connection. Drilling performance was improved with the high torque 4 in. XT39 connection. In particular, the following performance improvements were realized: Higher rotary speeds (and the corresponding higher ROP) could be maintained without fear of twisting off the connections. The torque capacity of the XT39 connection provided sufficient safety margin due to uncertainties of well path tortuosity and friction factors. As drilling progressed, the directional control and friction factors became known and measured depths were increased accordingly. The buckling resistance of the 4 in. drill pipe is higher than that of the 3-1/2 in. drill pipe therefore additional weight on bit could be applied. There was no loss of rig time, which would have been associated with tripping to add additional 3-1/2 in. drill pipe if a combination string of 5 in. x 3 1/2 in. drill pipe were used (as in the case of a 7 in. liner well design). Savings due to the elimination of twist-offs, increased ROP and the ability to tap hydrocarbon reserves at significant lateral distances from the surface location were realized successfully.

4 4 M. JELLISON, G. PLESSIS, A. GLOWACZ, J. PASNAK IADC 2005 Total Indonesia Case Histories Total Indonesia drills S shape wells in East Kalimantan to produce its Tunu field. Starting from existing production structures, there was a need to step out further to reach more remote pay zones. Therefore, the drop off at the end on the 55 degree slanted section was extended to start at a greater depth. The previously used 3-½ in. drill pipe was not able to transmit the required torque, leading to the selection of the above-described pipe. The typical Total Indonesia S shape well starts vertically and turns in a 45 to 55 degree slanted section leading to a final drop off just above the pay zone. The various end sections are typically, equally spaced on a grid with a spacing of about 1600 m (5,250 ft). The first wells drilled, with the 3-½ in. drill pipe had the drop off located as far as 2,000 m (6,562 ft) away from the drilling rig. The latest wells drilled with the 4 in. pipe had the drop off point in the range of 3,000 m (9,842 ft). Total Measured Depth for these new longer wells was approximately 5,500 m (18,045 Ft). Depending on the expected pore pressure, Total Indonesia uses two different well architectures; type 4 for 10,000 psi wells with a mud specific density of 1.55 (12.93 ppg) and type HPHT for higher pressurerated wells of 15,000 psi with a specific density of 2.25 (heavier mud of ppg). See figure 6 for more details on the architecture of both types of wells. Note that a tapered casing string (9-5/8 in. x 7 in.) is set in the type 4 wells that is necessary to safely run the combined 5 in. x 4 in. string of drill pipe in the 6 in. open hole section. With this architecture the 4-½ in. or 3-½ in. tubing will be cemented in the 6 in. hole and the production liner is eliminated. Originally the 4 in. drill pipe was supplied with 5 in. OD x 2-11/16 in. ID tool joints capable of delivering a drilling torque of 22,200 ft-lb, which corresponds to the connection maximum MUT rating (with a standard API 50% zinc compound). In view of the good hydraulic performance, decision was made later to reduce the ID of connections to 2-9/16 in. This brought a small increase in pressure losses that was acceptable and a rise in the maximum MUT up to 24,500 ft-lb, which was the driver for change. Additionally, the use of a copper base thread compound with higher friction factor allowed Total to further increase this torque value by 10%. Regarding fishing of the drill string in the open hole, the objective is to catch a 5 in. OD tool joint in a 6 in. hole using a full strength overshot. A standard tool overshot fishing tool was not available with full strength capability. Consequently a modified stainless steel 5-7/8 in. slim hole overshot, with a skirt to restore it to the full strength rating was utilized. The drilling rigs available on location are equipped with pumps rated to 5,000 PSI or 7,500 PSI. Although hydraulic loss was not the main concern, the selection of 4 in. pipe ensured that sufficient pressure would be available at the bit for reaching the more remote pay zones. The impact on ECD was evaluated before changing the size of the drill pipe from 3-½ to 4 in. Total used its in-house hydraulic model called ECD Elf. On the type of wells drilled in Kalimantan, the variation was found to be of 0.04 sg (0.33 ppg). This was found acceptable. Additionally, on the high-pressure slim hole wells, a system must be available to ensure control of well pressure. It is essential in this configuration to have a hydraulic model developed that allows anticipating the pressure system that will be encountered. Using 4 in. drill pipe instead of 3-½ in. will slightly alter the dynamic pressure in the annulus, due to the reduction of clearance between the formation or casing ID and the pipe body. Total Indonesia developed a model that has been validated in the field and monitors the annular pressure losses very closely during the drilling operation. The cost of drilling, logging and completing one of these highly deviated S-shape wells is found to be in the range of 5.5 million USD, and the typical drilling curve is 30 days. From an economical standpoint, the driver for selecting drill pipe with a second generation double shouldered connection, with its much higher torque rating than the previously used API connection, is the ability to reach more remote pay zones from a single surface facility. It simply removes the need to invest in additional expensive structures and achieve savings that significantly exceed the added investment

5 IADC 2005 ADVANCED DRILL PIPE WITH STREAMLINE CONNECTIONS ENHANCES SLIM-HOLE DRILLING 5 necessary to acquire the pipe and bring minor modifications to the drilling rig. Conclusion The 4 in lb/ft drill pipe with the XT39 second-generation double-shouldered connection has shown its ability to drill slim holes successfully and effectively replace the previously used 3-½ in. and 5 in. drill pipe. This configuration of 4 in. pipe has brought a substantial hydraulic improvement, delivering more pressure at the bit that allows better hole cleaning, significant increases in penetration rates and overall improvement in drilling performance. As a consequence, this drill pipe system can substantially reduce the cost of drilling deep and ERD slim holes. The 4 in. XT39 drill string designs can increase possible step out or reaches distances from the drilling site, permitting the exploitation of previously unreachable pay zones while reducing the number of drilling sites or offshore platforms. Acknowledgements The authors thank J.B. You of Grant Prideco for his contributions to the 4 in. XT39 drill pipe field histories. The authors also express their gratitude to the management of Grant Prideco, Total and Saudi Aramco for their support and encouragement in publishing this paper. The authors also thank Mike Cunnington for allowing us to publish the results of the analysis done by Earth Reach for Saudi Aramco. References 1. API specification 5D, Specification for Drill Pipe, Fifth edition, American Petroleum institute, Washington, D.C. (October, 2001) 2. API specification 7, Specification for Rotary Drill Stem Equipment, Fortieth edition, American Petroleum institute, Washington, D.C. (March, 2002) 3. API recommended practice 7G, Recommended Practice for Drill Stem Design and Operating Limits, Sixteenth edition, American Petroleum institute, Washington, D.C. (August, 1998) 4. Jellison, M.J., Payne, M.L., Shepard, J.S. and Chandler, R.B.: Next Generation Drill Pipe for Extended Reach, Deepwater and Ultra-deep Drilling, paper OTC presented at the 2003 Offshore Technology Conference, Houston, 5-8 May Sachin Mehra, Sedco Forex Schlumberger and J. E Smith, Grant Prideco Replacing 5 inch and 3 ½ inch Drill Pipe with a Single String SPE/IADC 37648

6 6 M. JELLISON, G. PLESSIS, A. GLOWACZ, J. PASNAK IADC 2005 Table 1 Dimensional Data on Drill Pipe Assemblies Evaluated for Slim-Hole ERD Nominal size (tube OD) Nominal weight Connection Tube ID Tool joint OD Tool joint ID Tong space (pin & box) 3 ½ in. (API S-135) 13.3 # NC in. 5 in in in. 3 ½ in. (S135) 13.3 # HT in. 5 in in in. 4 in. (S135) 14.0 # XT in. 5 in in in. Notes: Grade S135 was kept as being the worst configuration. The need for high torsional rating will lead to having the smallest ID at the connection level, meaning higher hydraulic losses. For 3 ½ in. drill pipe, only the most common weight of 13.3# was considered. Actually the 15.5# weight would have a smaller internal diameter that would result in poorer hydraulic characteristics. Table 2 Drill Pipe Tube Performance Properties Nominal size (tube OD) Note: Nominal weight 3 ½ in # 3 ½ in # 4 in # Grade Tensile yield (lb.) Torsional yield (ft.lb) Burst pressure (PSI) Collapse pressure(psi) New Premium New Premium New Premium New Premium G , ,000 26,000 20,100 19,320 18,440 19,758 16,820 S , ,900 33,400 25,900 24,840 23,708 25,404 21,626 G , ,900 29,500 22,600 23,573 22,718 23,484 20,260 S , ,100 38,000 29,100 30,308 29,209 30,194 26,049 G , ,900 32,600 25,500 15,159 14,333 15,896 11,622 S , ,500 41,900 32,800 19,491 18,428 20,141 13,836 The 15.5# weight would have a smaller internal diameter that would result in poorer hydraulic characteristics. Table 3 Tool Joint Connection Performance Properties Connection OD x ID (in) Tensile yield (lb.) Torsional yield (ft.lb) Make up torque (ft.lb) NC 38 (3 ½ IF) 5 x 2 1/8 842,400 26,500 14,000 5 x 2 7/16 708,100 22,200 11,700 HT 38 5 x 2 9/16 649,200 29,600 17,700 XT /8 x 2 9/16 729,700 37,000 22,200 5 x 2 9/16 729,700 40,800 24,500 Figure 1 A second-generation high performance double-shoulder connection provides a streamline configuration and high torsional strength for critical slim-hole drilling applications.

7 IADC 2005 ADVANCED DRILL PIPE WITH STREAMLINE CONNECTIONS ENHANCES SLIM-HOLE DRILLING 7 Pressure Loss Through and Around Drill Pipe Pressure Loss per 1000 ft (psi) 1,200 1, Flow Rate (gal/min) inch Pipe with X Tool Joints with 2 LTS Tong Length. Mud wt lb/gal; Hole Size inches. 3.5 inch Pipe with X Tool Joints with 3 LTS Tong Length. Mud wt lb/gal; Hole Size inches. 4 inch Pipe with X Tool Joints with 3 LTS Tong Length. Mud wt lb/gal; Hole Size inches. Figure 2 Pressure losses are reduced with 4 in. drill pipe with streamline connections compared to 3-1/2 in. drill pipe. Pressure Loss Through and Around Drill Pipe Pressure Loss per 1000 ft (psi) 3,000 2,500 2,000 1,500 1, Flow Rate (gal/min) inch Pipe with X Tool Joints with 2 LTS Tong Length. Mud wt lb/gal; Hole Size inches. 3.5 inch Pipe with X Tool Joints with 3 LTS Tong Length. Mud wt lb/gal; Hole Size inches. 4 inch Pipe with X Tool Joints with 3 LTS Tong Length. Mud wt lb/gal; Hole Size inches. Figure 3 Pressure losses with 4 in. drill pipe are reduced by more than 60% compared to 3-1/2 in. API connection drill pipe and approximately 45% compared to 3-1/2 in pipe with first-generation double-shoulder connections at a typical 500 gpm pump rate.

8 8 M. JELLISON, G. PLESSIS, A. GLOWACZ, J. PASNAK IADC 2005 Figure 4 Elevator capacity curve for 4 in lb/ft S-135 XT39 drill pipe. Figure 5 The long reach of Saudi Aramco QTF field wells puts special demands on the drill string design.

9 IADC 2005 ADVANCED DRILL PIPE WITH STREAMLINE CONNECTIONS ENHANCES SLIM-HOLE DRILLING 9 Figure 6 Depending on the expected well pressures Total Indonesia uses two different well architectures