Copyright 2006, IADC/SPE Drilling Conference This paper was prepared for presentation at the IADC/SPE Drilling Conference held in Miami, Florida, U.S.A., 2123 February 2006. This paper was selected for presentation by an IADC/SPE Program Committee following review of information contained in a proposal submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the International Association of Drilling Contractors or Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the IADC, SPE, their 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 and Society of Petroleum Engineers 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 Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 1.972.952.9435.

Abstract World class ERD wells are being used in the Russian Far East to develop an offshore reservoir from an onshore location. These wells have reaches of 9-11 km. While drilling the initial wells into the reservoir, high torque was experienced even while using a nonaqueous drilling fluid (NAF). The torque was sufficiently high that concerns arose about the feasibility of being able to drill longer wells later in the development. Consequently, finding techniques to reduce drilling torque became a major focus for the drilling phase of the project. A systematic R&D process was initiated to look for solutions to the torque problem. The scope of the investigations included consideration of different drilling fluid base oils, solid/liquid lubricants, and mechanical means to reduce torque. Small-scale screening lubricity testing was performed in a controlled laboratory environment to identify potential lubricant candidates. Full-size laboratory testing was then performed on the leading products. Various mechanical means to reduce torque were also evaluated. Finally, field trials were performed using solid and liquid lubricants and different types of mechanical torque-reduction tools. Solid lubricants caused plugging problems with BHA components and their use was discontinued. Liquid lubricants achieved torque reductions of 5-15%, which was sufficient to drill the longest throw wells. The mechanical tools when added to the drill string showed the greatest reductions in torque, but were very expensive. Since the liquid lubricants represented a significant addition to the cost of the wells, other means of reducing torque were investigated. Eventually, it was discovered that the use of 4,500 m of range II drill pipe instead of range III caused a reduction in the torque. This is believed to be related to the

larger tube body-casing contact area of the range III pipe joints compared to the range II pipe joints. Further evidence that the large contact area between the casing and the range III drill pipe was causing both excessive wear and torque was provided when drill pipe inspections revealed an alarming increase in rejections due to excessive tube wear near the middle of many joints. Ongoing investigations are attempting to find mechanical solutions to the drill pipe-casing contact problem. New orders of drill pipe could be range II pipe, but the existing large inventory of range III drill pipe needs to be protected from excessive wear, while at the same time reducing the drilling torque. Several types of drill pipe stand-off bands are under investigation and may represent a viable solution to both problems.

Introduction The Sakhalin-1 project will develop about 2.4 billion bbl of oil and approximately 17 TCF of gas. For the initial phase, 15 ERD wells are planned from the land well site (Figure 1), and an additional 18 ERD wells will be drilled from an offshore location1, as shown in Figure 2. These wells will be used to develop the Chayvo field reservoirs.

The well design for the land-based wells, shown in Figure 3, has the following features:

Very shallow KOP at app. 200 m 18-5/8-in. surface casing at 800 m 13-5/8-in. intermediate casing at 3300 m 4,500-6,300 m long tangent section at a 76-81 deg

sail angle 9-5/8-in. production casing run to the top of the

pay at 7,800-9,600 m MD A 1,300-3,200 m long horizontal section cased

with a 6 5/8 in. or 7-in. liner The horizontal section crosses multiple hydrocarbon intervals before reaching total depth (TD) from 9,100 - 11,134 m. The wells are drilled with rotary steerable systems (RSS) from the 17-1/2-in. hole down to TD. These tools contribute significantly to the success of the wells. They enable a smooth borehole to be drilled along the planned directional path. On the eight wells drilled to date, all of the 13-5/8-in. and 9-5/8-in. casings and the 7-in. liners have reached their target depth

IADC/SPE 98969

Torque Reduction Techniques in ERD WellsJ.H. Schamp and B.L. Estes, SPE, ExxonMobil Development Co., and S.R. Keller, SPE, ExxonMobil Upstream Research Co.

2 IADC/SPE 98969

using normal (mud-filled), floated (air-filled), and selectively floated (mud over air) casing installation methods.

Chayvo Pilot Wells. While drilling the first of two pilot wells, high torque was encountered while drilling out the 9-5/8-in. casing shoe track. The high torque continued through the 8-1/2-in. hole section and approached the make-up torque of the 5-7/8-in. drill pipe (56,000 ft-lb) and the nominal working capacity of the top drive system (~56,000 ft-lb at 110 RPM). Concerns about being able to drill to TD arose. A solid fibrous lubricant was added to the NAF system to reduce the coefficient of friction (CoF). This lubricant caused issues with both the MWD system and the cuttings injection well and required constant additions due to screening out by the solids control equipment. Therefore its use had to be discontinued. Two other available asphaltene-based lubricants also showed little success. The first well was eventually TD'd at the planned depth of 9,276 m MD. Drilling torque had not increased significantly while drilling the 8-1/2-in. hole section most probably due to a polishing effect in the long 9-5/8-in. production casing.

On the second pilot well, similar high torque was encountered despite a lower cumulative-dogleg down to the 9-5/8-in. casing shoe. After the top drive stalled several times, non-rotating drill pipe protectors (NRDPPs) were installed on the DP which lowered the torque significantly. Unfortunately, these tools could not withstand the side loads in the tangent section, and they had to be removed after experiencing considerable damage. This well was TD'd at 10,181 m, and it became evident that alternative solutions to the torque problem were needed.

Chayvo ERD Challenges. The longest land well was planned at 11,134 m and presented a significant step-out from the two pilot wells. Also, after proving the feasibility of drilling Sakhalin ERD wells from onshore, a potential need to drill even longer wells was realized. Within this scenario, the need for a systematic research effort to identify ways to reduce drilling torque became evident. A special task force consisting of drilling, mud, and R&D specialists was put together to search for solutions.

The next four wells (Chayvo Z-1, Z-2, ZG-1, ZG-2) were planned to be drilled in batch mode. This opened a time window of 6-8 months for the research work before the next 8-1/2-in. section was to be drilled. This group of wells included the two longest oil wells and two slightly shorter gas wells.

Drilling Torque Considerations The torque required to rotate generally arises from two sources: the frictional resistance between the rotating drill string and the casing or borehole and the bit/stabilizer torque. For ERD wells, as the measured depth increases, most of the torque comes from the frictional resistance. Frictional resistance is affected by many factors including the drilling fluid properties, hole cleaning, drill string surface roughness, and side loads on the drill string.

Drilling Fluid Properties. The properties of the drilling fluid, including viscosity and chemical composition, can effect torque. However, trying to adjust these properties to reduce torque can be challenging because the fluid properties impact many other aspects of drilling. For example, the mud viscosity effects not only torque but also solids suspension, hole cleaning, and circulating fluid pressures. The oil/water ratio (OWR) in a NAF is known to affect drilling torque5, but changing the OWR can affect fluid stability, cost, and other properties.

For Chayvo, all hole sections (with the exception of the 24-in. surface hole) are drilled with a low-toxicity mineral oil-based NAF system The mineral base oil has a low viscosity even at colder temperatures which is beneficial for equivalent circulating density (ECD) control in the long, horizontal hole sections. Lubricants. In the past, the use of drilling fluid additives to reduce the torque required to rotate the drill string has typically been associated with water-base muds (WBMs). Both chemical and solid (e.g., beads) additives have been used. NAFs are generally thought to provide lower torque values than WBMs primarily due to the lower coefficient of friction of the base fluid. Typical NAF base oils have a steel-on-steel coefficient of friction (CoF) 20%-40% lower than that of water under similar temperature and pressure conditions. However, as wells with longer throws (e.g., 11 km) are being drilled, the need has arisen to examine lubricants for NAF systems. A great deal of work has been performed to identify additives for oils to reduce friction and wear in applications such as internal combustion engines and machinery. However, these are relatively clean applications. In a drilling fluid, there is typically a large concentration (e.g., 10-40 % by volume) of solid particles from the weighting material and drilled cuttings. Also, the surfaces of the drill string and the casing or borehole can be very rough. Very little research has been performed on lubricants to reduce friction in these "dirty" applications. While some anecdotal reports on the effectiveness of various NAF lubricants have been reported2-5, a systematic study on NAF lubricants does not appear to have been documented in the literature. Hole Cleaning. Another consideration for reducing torque in high-angle wells is hole cleaning. The drill string is often embedded in cuttings, and this can hinder rotation both by increasing mechanical friction and by wedging in the gap between the drill string and the surrounding casing or borehole as the string rotates. It is often noted that surface torque is reduced after performing operations to improve hole cleaning. (Such operations might include circulating several bottoms up, increasing the flow rate, increasing the rotation rate, and/or pumping sweeps.) For the Chayvo wells, however, high torques were observed inside casing prior to drilling out indicating that hole cleaning is unlikely to be the cause of the observed high torque values.

IADC/SPE 98969 3

Surface Roughness. The surface conditions of the drill string and casing can also affect torque. Hardbanding to reduce tool joint and casing wear has been used for years, and often a reduction in torque due to a polishing effect is noted in ERD wells. Openhole spiraling or tortuosity can also contribute to high friction and torque values. However, for the Chayvo wells, more than 75% of the hole is cased while drilling the 8-1/2-in. hole section where the highest torque values are seen. Side Loads. The side loads are the distributed normal (lateral) forces acting on the drill string. These loads, when combined with the local CoF, effect the torque required to rotate the string. The side loads are primarily effected by the well path and the weight of the drill string. A number of studies4, 5 have indicated that a catenary well path helps reduce torque. However, the selection of the well path is influenced by a number of factors, including hole stability considerations, performance of directional equipment in various hole sizes, simplicity, and the required completion interval trajectory. For these reasons, a well path with an initial build section, a long tangent interval, and a final build to horizontal was chosen for the majority of the Chayvo wells drilled to date. Pre-drill modeling studies indicated that there was not a significant difference in torque between the chosen well path and a catenary profile. Doglegs or other local variations in the actual well path compared to the desired path can also contribute to the side loads and hence torque. To minimize these effects, as mentioned earlier, RSS are used to drill the Chayvo wells below the surface pipe. Because they can build angle continuously while rotating, RSSs generally provide a smoother well trajectory than alternative directional drilling methods. It is also well known that side loads can be increased by buckling of the drill string due to compressive loads. For the Chayvo wells, torque and drag modeling is used to ensure that the string does not experience excessive buckling. Research Approach. After considering the factors effecting torque for the Sakhalin I ERD wells, the team decided to initially focus on two approaches for torque reduction:

drilling fluid additives to reduce the CoF by

improving the lubricity of the mud system, and mechanical drill string tools to reduce the

frictional resistance to rotation.

The goal was to identify one or two lubricants, or mechanical torque reduction devices, that would give enough torque reduction to allow drilling all wells to TD. Constraints included avoiding plugging of any downhole tools, additional equivalent circulating density (ECD), extensive surface equipment modifications, excessive additive costs, costly tool failures, or high tool mob/demob and rental charges in this remote location.

Lubricant Testing There are two categories of drilling fluid additives (lubricants) that may reduce the CoF: solids and chemicals. Solids act like ball or roller bearings in the mud to keep the metal-to-metal or metal-to-rock interface from occurring. The end result is a metal-to-solid or rock-to-solid contact thus reducing the CoF. Chemical lubricants are believed to adhere to or modify the surface of the metal and/or borehole thus reducing the CoF. Testing Procedures. In testing lubricants, one of the most important factors is using consistent test procedures and consistent drilling fluid. During the initial testing, it was found that the results were significantly effected if the procedures were not followed exactly (mixing time, order of addition, letting the mud cool down before testing, etc.). This led to the writing of detailed testing procedures (including duplicate testing) and lab technician signoff to ensure accurate and consistent data. The drilling fluid was built in the same laboratory using the same procedures to ensure a consistent lab-prepared drilling fluid. Testing Fluids. A 55-gallon drum of drilling fluid from a recent Sakhalin well was shipped to Houston for lubricity testing, as this is a more representative sample of fluid than a lab-prepared sample. Due to the limited volume, only the small scale testing was performed using the field drilling fluid. Lab-prepared muds were used for the large scale testing (described later). Screening Process. There are several laboratory lubricity measuring devices on the market; most of them measure metal-to-metal interfaces. The performed testing focused on metal-to-metal testing as more than 75% of the hole is cased while drilling the 8--in. hole section where the highest torque values are seen. After evaluating six lubricity devices, three were chosen for the planned work. These were a Baroid lubricity meter (Figure 4), a special lubricity tester built by MI/Westport (Figure 5), and a Falex lubricity meter located at Southwest Research Institute (SWRI) (Figure 6). Over 40 different lubricants and base oils and seven drilling fluid systems were tested to determine which one provided the lowest CoF. Lubricants included vegetable oils, fatty acids, alcohols, esters, and other chemical groups. Base oils included mineral oils, diesel, esters, olefins, and mixtures of the last two. Preliminary lubricant tests were performed on the Baroid lubricity meter and the Falex device as results could be obtained quickly and easily. These data were used to narrow down the products being tested. The MI/Westport lubricity meter was also used for the same purpose, but not as extensively as the Baroid and Falex devices due to the volume requirements and cost of using the device.

4 IADC/SPE 98969

Once the lubricant choices were narrowed down, optimization testing was performed on the Falex and Baroid devices. This testing involved varying the applied sideload, and varying product concentration, to determine the optimum quantity to achieve the maximum effectiveness. Testing Results. Figure 7 and 8 show Falex testing results from the screening testing (CoF for different fluid systems vs. side load, and CoF for various liquid lubricants vs. side load). Important observations from screening and optimization testing are:

1. No single chemical group consistently tested better; the results are scattered, and each product needs to be evaluated on its own.

2. The results are valid only for the particular combination of base oil and lubricant. Other base oils (drilling systems) may show different results.

3. A few products increased the CoF. 4. Higher lubricant concentrations beyond a certain

threshold did not provide further reductions of the CoF.

5. The best alternative fluid system had similar CoFs to the current fluid system plus the best lubricant.

6. In the Falex device, the CoF decreases with increased loads. This is believed to be due to a polishing effect.

Based on this testing (plus logistical and other consi-derations), it was decided to stay with the current NAF system. However, the best performing lubricants were taken to the next step: full-scale testing. Full-Scale Testing. Final testing was performed on a full- scale test device (Figure 9). Modifications to an existing device that had been used to measure riser wear due to tool joint rotation were made. These modifications included enabling the interface between a fullsize 5-7/8- in. tool joint (7-in. OD) and a piece of Chayvo 9-5/8-in. casing to be submerged in a circulating NAF at an elevated temperature. This device rotates a tool joint at ~150 RPM, applies a side load up to 3,200 lb/ft to the 9-5/8-in. casing as it is pressed against the tool joint, and measures the torque imparted to the casing using a load cell (Figure 10). The device is configured with mud mixers and a circulation pump so that after a baseline torque is measured, a lubricant can be added to the drilling fluid on-the-fly so that the effect of the lubricant can be measured without any other changes to the test setup. Testing was done using a NAF designed to be similar to that being used at Chayvo including incorporation of appropriately-sized sand particles. All testing was done at the Chayvo downhole circulating temperature of ~150 F. The large-scale testing was used as a final verification of the lubricants to be used in the field. Figure 11 shows typical test results from the modified large-scale apparatus. Lubricant Testing Results. Recognizing the differences in the design of the test equipment, the goal of the lubricity testing was to obtain similar trends in the results of all the lubricity testing devices to help ensure that a selected lubricant would

reduce the CoF in the field. The testing showed that each of the devices had its own range of CoFs and % improvement. In general, the laboratory lubricant testing indicated that, under ideal conditions, certain lubricants added to the NAF could reduce the CoF by up to 50%. However, it is recognized that the results in the field may be different due to a variety of factors including the presence of a cuttings bed, different side loads, drilling fluid contaminants, different surface roughness conditions, and adsorption of the lubricants on both cuttings and other surfaces. Two of the best performing lubricants were shipped to Sakhalin for a field trial. The lubricants selected were also based on availability, logistics, and price. (The field results are discussed in a later section.) Limited testing of drill beads was also conducted on the large-scale testing device. The results indicate that beads can reduce the coefficient of friction. However, due to operational constraints, drill beads have not been used in Chayvo field operations. Mechanical Tool Evaluation Drill String Subs. Mechanical torque reduction subs have been successfully used in other ERD projects4-8. The limited use of mechanical torque reduction devices in the Z-4 well had also proven the concept, but the test showed that the tool used was not robust enough to withstand the requirements of the Chayvo downhole conditions. A quick survey of the current market indicated several additional designs were available for 5-7/8-in. drill pipe. These tools have an inner mandrel and outer sleeve and are designed as an integral part of the drill string. The tools were evaluated for their robustness and the inherent risk of loosing parts in the hole. Out of this pre-screening, one tool was eventually selected for further studies. A study was conducted with the scope to estimate the margin of safety of the sub under static design loading conditions using finite element analysis (FEA). Not included in the study were cyclic (fatigue) or dynamic loading conditions and effects of wear. During the study, FEA models were developed for the mandrel and the sleeve, and a mechanical analysis was performed for the locking collar and pins to estimate shear, crush and breakthrough limits. The general conclusion was that the structural performance of all parts exceeded the capacity required for expected levels of tension, torque, bending, side- and drag loads. Consequently, a recommendation to build 200 tools for a pilot test at Chayvo was made. Field Testing of Lubricants and Tools While drilling the two longest wells of the Chayvo drilling campaign:

- Chayvo Z-1 with a TD of 10,995 m, and - Chayvo Z-2 with a TD of 11,134 m,

IADC/SPE 98969 5

two of the liquid lubricants were added to the drilling fluid. Initially, the mud was treated with 5-6 volume percent of the lubricant. This typically resulted in a 5-15% reduction in torque. When the effect of the lubricant diminished and torque started to increase above acceptable levels, more lubricant was added to maintain a constant concentration. Also, 150 of the mechanical torque reduction subs were field-tested in one of the two wells. In the subsequent wells, more of the best performing lubricant was used:

- Chayvo ZG-1 with 10,537 m TD, - Chayvo ZG-2 with 10,523 m TD, - Chayvo Z-5 with 9,168 m TD, and - Chayvo Z-3 with 10,675 m TD. Field Results Figure 12 summarizes the drilling torque vs. the measured depth for all 8-1/2-in. hole sections drilled to date. The following observations related to the applied torque reduction tools can be made:

1. Mechanical torque-reduction tools showed the largest

torque reductions. 2. The integral subs showed a smaller torque reduction

than the clamp-on tools. Because of this (and the high associated cost), their use was discontinued.

3. The two lubricants gave torque reductions in the 5-15% range.

4. A larger lubricant concentration (beyond the threshold of approximately 6 %) did not yield a measurable torque decrease.

5. Torque fluctuations became smaller with use of the lubricants

6. On some wells, the rate of torque increase with depth was reduced.

7. Lubricants had to be added continually to keep torque at an acceptable level.

Observations related to other operational and equipment related changes include:

1. Sudden drops in torque appeared after reaming or bit trips where the hole was thoroughly circulated and cleaned.

2. Torque also was influenced by bit design (using a less aggressive cutting structure or gage protection).

3. The two gas wells ZG-1 and ZG-2 (with different trajectories) showed a considerably lower torque level than the oil wells.

It is believed that the different directional profile of the gas wells (which do not have the second build section to horizontal) had a large impact on the observed lower torque. While the design build rate (BUR) for the second build used in the Chayvo oil wells is only 0.5 deg/100ft, it contributes to the cumulative dogleg which influences the torque. Both gas wells have the lowest cumulative dogleg, as shown in Figure 13.

Other Mechanical Torque Considerations Drill pipe Hardbanding Wear. From the onset of drilling Chayvo ERD wells, excessive hardbanding wear was noticed on the DP tool joints. This led to the need to install a hardbanding unit at this remote location. The rig's pipe barn and maintenance tent facilities provide for enough working space for the unit and eliminate costly shipping back and forth of the pipe. About 50% of the DP has to be re-hardbanded after drilling long sections. As the CoF of hardbanding is lower than that of steel (0.15 vs. 0.21), a considerable effect of worn hardbanding on the overall torque was observed. Range III DP. An additional source of torque may be caused by the use of range III drill pipe. Range III drill pipe has a length of 13.5-14.8 m (41-45 ft), while the more common range II drill pipe has a length of 9.2-10.2 m (28-31 ft). The additional length of each range III joint creates a large contact area in the middle of each joint caused by gravity-based sag in a highly inclined borehole. Calculations indicated a ~7-m contact length on a 15-m joint. Additional evidence that this drill pipe-casing/borehole contact might be contributing to torque was provided when regularly scheduled drill pipe inspections detected increased rejection rates due to excessive tube body wear after approximately 4-5 million revolutions. As a trial, 4,500 m of range II drill pipe were used as part of the drill string in several Chayvo wells. The torque using the range II drill pipe appeared to be less than when a string was made up using only range III drill pipe. While new drill pipe orders could go back to the more conventional range II length, it is desirable to find ways to use the existing stock of range III drill pipe. For this purpose, a drill pipe mid-joint stand-off band is being evaluated. This treatment is applied in a thermal heat-spray process. During the application process, an alloy-based material (similar to that used in hardbanding) is liquefied in a twin-wire electric arc and then sprayed on the carrier material. While the technology is proven and has been used extensively in military applications, it represents a first for the drilling industry and had to be pilot tested. Laboratory tests on the large-scale testing apparatus showed an early significant reduction of the CoF which can be explained by the polishing of the initial material surface. Once the material is polished, the CoF stays at a constant and very low level (Figure 14). Ten joints of range III drill pipe were prepared with the midjoint standoff band and shipped to Sakhalin and field tested in casing and open hole drilling. Figure 15 shows the 0.6-m (2-ft) long -in. thick upset.

During the field test, 10 joints were run in the 12-1/4-in. and 8-1/2-in. open hole sections. After ~7,000 m were drilled, an average OD loss of only 0.02 in. was noted; the tools were in good condition. This wear loss was much less than the wear loss experienced on the hardbanded tool joints.

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Conclusions

At the time of this writing, eight Chayvo ERD wells have been successfully drilled into the reservoir. After the initial pilot wells, six 8-1/2-in. hole sections were drilled using liquid lubricants or integral torque-reduction subs. All products used were the result of a focused research effort to reduce the CoF in a NAF. The following findings and conclusions can be drawn from the laboratory results and the field testing:

The two wells with mechanical torque reduction

tools (clamp-on tools and integral subs) showed the largest reduction in torque.

Wear and tear on the integrated drill string subs stayed at an acceptable level, but clamp-on tools could not withstand the downhole conditions.

In general, the laboratory lubricant testing indicated that, under ideal conditions, certain lubricants added to the NAF could reduce the CoF by up to 50%. But unfortunately this was not found in the field trials.

Liquid lubricants added at concentrations from 2 % to 6% showed field torque reductions of 5-15%, but the lubricants needed to be added continuously to maintain the torque reduction benefit.

Higher lubricant concentrations (e.g., >6% by volume) did not yield additional torque reductions.

The two gas wells that had a different directional profile and a shorter 8-1/2-in. hole section showed significantly lower torque.

Cumulative dogleg in each well has an important effect on the overall torque range.

Other factors like bit torque and BHA design (stabilizer set-up, motors) influence the level of drilling torque.

The additional length of range III drill pipe joints compared to range II drill pipe joints appears to contribute to both torque and tube body wear in the Chayvo ERD wells.

Next Steps The remaining wells to be drilled from the Chayvo land pad are similar in measured depth and horizontal displacement to the wells already drilled. The authors believe that the existing lubricants and available tools will enable all of the currently planned wells to be drilled to TD. Better protection of the drill pipe will be necessary to reduce both costly hardbanding requirements and drill pipe replacement. This will hopefully come with the added benefit of a CoF reduction.

Future ERD wells with up to 11-15 km reach are currently under consideration. To accomplish this world-record reach, the following drilling technologies may need to be applied:

Higher-torque top drive, Drill pipe with high-torque connections,

Advanced RSSs to minimize cumulative dogleg, and

Optimized BHAs that support steerability and drillability.

Most likely, these wells also will require additional CoF reduction measures to reach the distant reservoir targets. Acknowledgements The authors wish to thank ExxonMobil for permission to publish these results. Furthermore the support of the following companies was greatly appreciated during the research work: Westport Technology Center (mixing of test muds), Halliburton-Baroid Fluids (base oil, lubricants and EP tester measurements), Southwest Research Laboratories (Falex tester measurements), and Mohr Engineering (full-scale testing). References 1. McDermott, J.R. et al.: "Extended Reach Drilling (ERD)

Technology Enables Economical Development of Remote Offshore Field in Russia" paper SPE 92387 presented at the SPE/IADC Drilling Conference, Amsterdam, 23-25 February 2005

2. Meader, T. et al.: "To the Limit and Beyond - The Secret of

World-Class Extended Reach Drilling Performance at Wytch Farm", paper SPE 59204 presented at the 2000 IADC/SPE Drilling Conference, New Orleans, Louisiana, February 23-25.

3. Cameron, C. Drilling Fluids Design and Management for

Extended Reach Drilling, paper IADC/SPE 72290 presented at the 2001 IADC/SPE Middle East Drilling Technology Conference, Bahrain, October 22-24

4. Payne, M. L.: "Advanced Torque-and-Drag Considerations in

Extended-Reach Wells", SPE Drilling & Completion, March 1997, 55-63.

5. Payne, M.L. et al.: "Critical Technologies for Success in

Extended Reach Drilling," paper SPE 28293 presented at the SPE 69th Annual Technical Conference and Exhibition held in New Orleans, LA, U.S.A., 2528 September 1994.

6. Rodman, D.W. et al. "Extended Reach Drilling Limitations: A

Shared Solution", paper SPE 3846 presented at the 1997 Offshore Europe Conference held in Aberdeen, Scotland, 9-12 September 1997.

7. Moore, N.B. et al.: "Reduction of Drill String Torque and

Casing Wear in Extended Reach Wells Using Non-Rotating Drill Pipe Protectors", paper SPE 35666 presented at the SPE Western Regional Meeting, 22-24 May, Anchorage, Alaska, 1996

8. "Extending the Limits" Hart's E&P, December 1999, pp 66-68. SI Metric Conversion Factors ft x 3.048* E-01=m in. x 2.54* E+00=cm lbf x 4.448 222 E+00=N Psi x 6.894 757 E+00=kPa

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Figure 1: Aerial View of Chayvo Wellsite

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Figure 9: Full-scale Testing Device

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6% Lubricant-51% Torque

12% Lubricant-51% Torque

Fig. 11: Full-scale Lubricity Testing Example

30,000

35,000

40,000

45,000

50,000

55,000

60,000

7,500 8,000 8,500 9,000 9,500 10,000 10,500 11,000 11,500Depth (m MD)

Torq

ue (f

t-lbs

)

Z-4Added into NAF :alphaltenic lubricantsInstalled :Non-Rotating Drill Pipe Protectors on 3000m of drill pipe; drilled 7998-9303m MD.

Z-6Added into NAF : solid fibruous lubricants (coarse & medium), asphalten lubricants.

TDS Torque Limit @ 110 rpm

Z-1Added into NAF :5% lubricant HInstalled :151 torque reduction subs

TDS Torque Limit @ 120 rpm

Z-2Added into NAF :6% lubricant K

ZG-2Added into NAF :6% lubricant H

ZG-1Added into NAF 6% lubricsant H

Z-5Added into NAF :2% lubricant H

1

7

66

5

4

3

2

n : Section Drilling Sequence

Z-3Added into NAF :16% Lubricant H

8

Figure 12: 8-1/2 in. Hole Section Drilling Torque vs. Depth for all Chayvo Wells

Tool Joint CasingTool JointTool JointTool Joint CasingCasingCasing

IADC/SPE 98969 9

Cumulative Dogleg

ZD-1

Z-4

Z-6

Z-1 Z-2

ZG-1ZG-2

Z-5

Z-3

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

11,000

12,0000 50 100 150 200 250 300

Cumulative Dogleg [deg]

Dep

th [m

, MD

]

ZD-1Z-4Z-6Z-1Z-2ZG-1ZG-2Z-5Z-7Z-23Z-3

Figure 13: Cumulative Dogleg of Chayvo Wells

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60Minutes

Torq

ue (f

t-lb)

Bare TJ, No SandMid-Joint Upset, No Sand

Figure 14 : Torque Reduction Through Mid-Joint Upset

Figure 15: Mid-Joint Upset (with heat spray application)