IPTC 17668

Installation of Long Interval Conductor String Across Challenging Offshore Drilling Environment K. Won, Weatherford; K. Muir, C. Chanpen, PTTEP Myanmar; W. Thet, F. Noble, Oil States; I.B. Budi Utama, Weatherford

Copyright 2014, International Petroleum Technology Conference This paper was prepared for presentation at the International Petroleum Technology Conference held in Doha, Qatar, 2022 January 2014. This paper was selected for presentation by an IPTC Programme 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 Petroleum Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the International Petroleum Technology Conference, its officers, or members. Papers presented at IPTC are subject to publication review by Sponsor Society Committees of IPTC. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the International Petroleum Technology Conference 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, IPTC, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax +1-972-952-9435.

Abstract Conductor string installation has always proven to be key element process for a successful well construction in offshore project. However, challenging drilling environment such as rough current presents a huge resistance for the conductor string installation with conventional drilling technique. Previous offshore exploration activities have seen many case studies with failure on conductor installation causing significant delay on drilling operation consequently impacted with higher project cost. Non-retrievable casing drilling technology, has gained wide reception from operators in Asia Pacific region for drilling top hole sections in offshore project recent years. The high value realized in reduction on well construction costs and efficient installation process across challenging drilling environment has contributed to the high popularity of this innovative drilling technique in the regions offshore work. A non-retrievable casing drilling bit has been successful in previous casing drilling application across Myanmar shallow water. The previous success has raised interest for an attempt in pushing deeper conductor string setting depth to simplify well design and determining the ultimate capability of this system in drilling a 549 m conductor string, the deepest 20-Inch string set with casing drilling technique in Asia Pacific region. A new Leopard SD casing connector with higher torque capacity was first time utilized on a casing drilling application in this project. This paper introduces the planning and implementation process of the long interval 20 casing drilling through challenging drilling environment in this project. In the paper it also discusses the detail running procedure, drilling parameters involved, operational results of the casing drilling bit, casing connectors performance and lesson learnt from the project.

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Introduction Conductor casing string installation is one of the most important processes in the construction of an offshore casing program. The conductor string serves as the foundation for subsequent casing strings, and can be a predominant factor in the overall success of the drilling and completion of each well. Casing while Drilling technology has been developed and used by many operators since its inception in 1907. Recent successes across offshore Asia Pacific (most notably in Australia, Malaysia, Vietnam, and Myanmar) have spurred this technologys tremendous growth within the drilling industry. The non-retrievable CwD system uses the casing string as a drill string, with a simple cement-in-place bottom hole assembly (BHA) comprised of a casing drill bit and a float collar. Specialized design features on the casing drill bit allow it to subsequently be drilled-out with any conventional roller cone or PDC bit. This system provides a means for drilling, running casing, and cementing in single trip. CwD has proven to be a cost effective solution for getting casing to bottom and mitigating hazards such as wellbore instability and lost circulation. Growing numbers of operators have been choosing this simple and effective drilling technique for installation of top hole casing strings on their exploration and appraisal wells. This single-trip operation helps reduce flat time from the drilling curve, hence increasing the drilling efficiency and providing significant cost savings, especially for offshore projects (Galloway, 2004). Strong subsea currents and seasonal tides in offshore Myanmar have presented a major challenge for the operators when attempting to trip conductor casing into pre-drilled holes. This can be especially problematic when operating from a jack-up rig, since the rig position cannot easily be moved to compensate for the effects of sea current on the casing string. In numerous previous offshore operations in the area, it has required the assistance of a subsea casing guide and subsea monitoring devices. A significant benefit of Casing while Drilling is that drilling and running casing are combined into a single operation. This eliminates many of the difficulties associated with conventional techniques when running casing in strong sea currents. PTTEP planned to drill four exploration wells on a jack-up drilling rig in offshore Myanmar. The ASK-4 well is located in Block M3 and is owned by PTTP Myanmar. The 20 inch conductor casing was planned to be set at a new record depth of 600 m below mud line, using CwD techniques. According to offset well data and past drilling experience in a similar block, the lithology throughout this interval was expected to be comprised of sandstone, clay stone, and shale. Furthermore, a new type of casing connector with increased torque capacity was utilized to help ensure the successful implementation of the project. Previous CwD Job Offshore Myanmar Prior to the ASK-4 well, CwD was successfully implemented by PTTEP in offshore Southern Yangon waters in 2010 and 2011. On these previous CwD applications, a smaller 13-3/8 inch conductor was installed. Several different casing bit designs available on the market were utilized on these projects. All of the casing bits evaluated reached the target depth successfully. The previous longest drilled interval by non-retrievable Casing while Drilling techniques within this region was approximately 390 m. Longer drilling intervals had not been attempted because of uncertainties about the limitations of the casing bits cutting structure and formation compatibility.

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Offshore Myanmar Drilling Challenges The Myanmar region experiences a South-West monsoon season from May to early October, which brings heavy rain to the country and causes high tides along the offshore portions of Myanmar beach. The winds associated with this monsoon cause strong currents which are a major challenge for Myanmar offshore drilling operations. In many instances, the offshore drilling work has been delayed for extensive periods due to the high tides. The top hole conductor string is the foundation for the overall construction of each exploration well. The successful installation of this string can directly increase the probability for success of each lower well section and ultimately the pay zone. Hence, the correct conductor string installation technique is critical in every well designers planning package. With conventional drilling techniques, the drill string and BHA must be retrieved prior tripping-in the conductor casing. During the high tide season in Myanmar offshore waters, there have been several cases in the past where the conductor string could not be tripped into its predrilled hole. This has caused extensive delays on the top hole conductor installation process. These costly delays can potentially increase the risk of open hole formation collapse which would require an additional hole cleaning trip prior re-running the casing string. Casing while Drilling Technique One of the mitigation technologies proposed to overcome the high tide problem during conductor installation was the Casing while Drilling technique, which has been widely used around the region for top hole casing installation. The CwD system is a relatively simple technology which utilizes a casing drive tool to grip the casing string at surface and transmit the rotary torque and weight to the BHA. (See Fig. 1) The BHA is comprised of a non-retrievable casing bit and a one way float valve system which are attached to the bottom of the casing string. The BHA remains in the hole with the casing string after reaching target depth. At the target depth, the BHA is cemented in place through a conventional float valve system without requiring an additional trip. The drilling, running casing, and cementing are completed in single trip. After cementing, the shoe track and drillable casing bit can be subsequently drilled out with any conventional PDC or roller cone bit selected for the next hole section. The PDC cutting structure on the drillable casing bit is supported with an aluminum core and a minimal quantity of steel on the blades to facilitate drill-out without causing damage to the drill-out bit. This system allows the conductor string to be run in strong sea currents, and once spudded the casing always remains inside the borehole. This eliminates the conventional drilling technique concern of failure to re-enter the hole with casing string. Furthermore, the combination of simultaneous drilling and casing has been proven to reduce flat time, providing additional savings to the operator.

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Fig. 1: Non-Retrievable Drilling with Casing Technology System.

Float Collar

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Well Aung Sinkha-4 (ASK-4) Overview The well ASK-4 was planned as a vertical well to penetrate a single target of the Miocene carbonate reservoir at the crest of the M3W-C4 structure in the Myanmar Sea (see Fig. 2). The water depth at well location was 12 m and rig elevation was 50.6 m (RKB-ML).

Fig. 2: Location of ASK-4 well The ASK-4 well was originally designed to a total depth of 2,696 m MD which was comprised of 20 inch conductor used for casing off the uppermost section of the formation. Following that, 13-3/8 inch casing was planned to be installed, and finally 9-5/8 inch casing (see Fig. 3). From 2,296 m MD 2,696 m MD, the formation is left uncased to allow for installation of tubing to complete the well where the expected location of the pay zone is situated. Installation of the 600 m length of 20 inch conductor section was identified as a good candidate for CwD. The upper section formation was expected to have high potential for total losses during drilling operations. However, it was anticipated that the smear effect mechanism associated with the CwD technique might be able to mitigate lost circulation issue (Watts et al, 2010).

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Fig. 3: Well schematic of ASK-4 well

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The entire well geological stratigraphy includes different types of formations. The formation M4 lies at the top, followed by formation M3, and then M2 where the payzone exists (see Fig. 4). The Casing while Drilling system was selected to drill the M4 formation which comprises a thick sequence of claystones, sandstones, and siltstones that have been deposited by the Paleo Ayeyarwady River and Deltaic system. Claystone is commonly light grey to medium grey and soft to firm hardness. Sandstone is predominantly clear, transparent to transculent, very fine to fine grained, with traces of carbonaceous material and shell fragments.

Fig. 4: Formation lithology of ASK-4 well

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Casing while Drilling Challenges A major challenge in non-retrievable Casing while Drilling applications is the selection of the proper casing bit. The casing bits cutting structure must be durable enough to safely drill the entire interval to target depth at an acceptable ROP. Conversely, the casing bits cutting structure must also be easily drilled-out by a subsequent bit for advancing the next hole section. The cutting structure must be sufficient to reach TD, without unduly hindering drill-out for the next hole section. These considerations made it a challenge to select the optimum cutting structure for the record length 600 m, 20 inch conductor CwD application in offshore Myanmar. There was no past job history drilling data for the entire 600 m interval, so a conservative decision was made to use an eight-bladed, 19mm PDC cutting structure. This would help ensure that the casing bit could reliably reach target depth. Additionally, hole cleaning is another important consideration for large diameter CwD applications. This is due in part to the large volume of drilled cuttings that must be circulated up through the relatively narrow annulus between the casing OD and the drilled borehole. Proper circulation rates are required to keep cutting loading below 6% so as to maintain adequate hole cleaning throughout the casing drilling operation to prevent pack-off problems. Detailed hydraulic analyses are conducted to optimize the nozzle sizes in the casing bit to provide good bit face cleaning and hydraulic horsepower while pumping at the pre-determined flow rates. Additionally, the packer cup rating of the casing drive tool must be taken into account when sizing the casing bit nozzles. Pre-Job Engineering Pre-job engineering planning is one of the core practices for the applications engineering team. This preliminary work is performed to ensure that the most suitable style of casing bit is selected, based on comprehensive analysis of the interval to be drilled. The objective is to ensure that the casing bits cutting structure is capable of drilling to the desired target depth. A drillability analysis study was performed based on offset wells comprised of Aung Sinkha-1, Shwe Pyi Tan-1, Janka-1 and Janka-2. The four-bladed 13-3/8 x 17 inch CWD bit with 6 mm TSD cutters had been used successfully on the nearest offset wells which are Aung Sinkha-1 and Shwe Pyi Tan-1 wells in early 2011. The D-Exponent chart (see Fig. 5) of these two wells further suggests that the area is comprised of low compressive strength rocks where the D-exponent values are generally lower than 1.0 with an overall average of 0.5. There are some short intervals of firm formations seen on the Shwe Pyi Tan-1 well, but these were not seen as detrimental to the four-bladed TSD casing bit. Generally, the formation in this area above 450 m was deemed drillable using the four-bladed CwD bit with 6 mm TSD cutters. Well Janaka-1 and well Janaka-2 are also in close proximity to the proposed ASK-4 well. Both the Janaka-1 and Janaka-2 wells used CwD techniques to drill in the 13-3/8-Inch conductor string. However, these sections were drilled using casing bits with a more durable PDC cutting structure. From the mud loggers data, minimum drilling parameters were used throughout the run with WOB average of 3-10 klbs and 30-70 RPM which indicates the formation was mainly comprised of soft clay stone and sandstone. However, there were some more competent formations noted between 320 m 335 m which required higher weight on bit applied to penetrate through the formation. This is a strong indication of hard and firm stringers in the drilling interval. Considering the long interval setting depth of 600 m for the planned 20 inch conductor string, a more durable eight-bladed, 20 x 24 inch casing bit with PDC cutters was recommended for this job. The heavier set PDC cutting structure was selected to ensure the casing bit would be capable of reaching the targeted setting depth. This casing bit is designed to drill medium to medium hard formations with 19 mm PDC cutters mounted on special steel alloy blades (see Fig. 6). High-velocity oxy fuel (HVOF) hardfacing on the aluminum surfaces helps limit erosion from fluids and abrasive cuttings, as well as enhances retention of the cutting structure. Hydraulic energy plays a significant role in bit face cleaning and enhances the penetration rate. Proper nozzle configuration is very important in order to minimize erosion without affecting the casing bit drilling performance. A pre-job hydraulic analysis suggested installation of eight each size 12/32 inch and six each size 14/32 inch drillable nozzles to provide a total flow area of 1.786 inch2 across the bit face. Furthermore, the high jet velocity (216 feet/sec) of this proposed nozzle configuration will ensure effective cleaning across the cutting blades and evacuation of cuttings from the bit face. A new type of high torque casing connector was firstly utilized for casing drilling operation. The Leopard connector (see Fig. 7) combines the advantages of a pre-loaded, thread-type connector with the rapid make-up desired for offshore operations has strength characteristics equivalent to those of the conductor. The Leopard connector has a high cone angle and is available

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in a twin or four start thread. When stabbed, the box swallows approximately 90% of the pin length. The stabbing guide prevents cross-threading. Full make-up is achieved in less than half a turn with a four start thread and less than one turn for a two start thread. To prevent back-off during casing drilling and to permit the connection to transmit torque, integral antirotation tabs are engaged using a hand-held Hilti gun or manual shear tool. Utilization of the anti-rotation tabs increases connectors breakout torque. The connector is fully made up in less than 1 turn with a required torque figure of 20 to 26 kips-ft providing a fully preloaded connection. These connectors features are important criterias for withstanding the high casing drilling torque expected to encounter while drilling through the medium soft formation.

Connector Capacities 20" x 0.625" Leopard SD 65ksi (SD/044/3/3A) Connector OD 21.190 " 0.538 m Connector ID 18.000 " 0.457 m Drift Size 17.813 " 0.452 m Plain End Weight 133.0 PPF 197.9 kg/m Tension 2,310 KIPS 10.28 MN Compression 1,810 KIPS 8.05 MN Bending 900 KIPS/FT 1.22 MNm Internal Pressure 3,500 PSI 24.12 MPa Collapse Pressure 3,500 PSI 24.12 MPa Material Yield Strength 65,000 PSI 448.16 MPa Make-Up Torque 20 to 26 KIPS-ft 27.12 - 35.25 KNm

Pipe Capacity, 20" x 0.625"Wt, API 5L, X56 Tension 2,130 KIPS 9.47 MN Bending 830 KIPS/FT 1.13 MNm Internal Pressure 3,063 PSI 21.11 MPa Collapse Pressure 1449.1 PSI 9.99 MPa Material Yield Strength 56,000 PSI 386.11 MPa

The Leopard SD connector has an integral 4 point anti-rotation feature, where sheer tabs located on the box connector can be engaged into a profile on the pin connector, effectively locking pin and box together. The sheer tabs are activated by means of Hilti Tool (which uses cartridges) or a manual sheer tool, both of which have a profiled chisel head designed to ensure that a full and precise engagement of the tab achieved (see Fig: 8 & 9). The connector is capable of accommodating up to 40 kips-ft of torque, however with all 4 of the anti-rotation tabs engaged this figure can rise to 50 kips-ft. This considerably above what is required when DwC, making this connector the correct selection for this application.

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Fig. 5: D-exponent chart of offset wells.

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Fig. 6: Aluminium nose PDC cutters casing bit.

Fig. 7: 20-Inch Leopard Casing Connector.

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Fig. 8: 20-Inch Leopard Casing Connector.

Fig. 9: 20-Inch Leopard Casing Connector Anti Rotation Tab.

Drilling with Casing Actual Operation The eight-bladed 20 x 24 inch PDC casing bit and float collar with high-torque premium connectors were assembled onshore and sent out to the rig. Thread locking compound was applied to all shoe track connections to enhance the connections strength for withstanding high drilling and drill-out torque. Prior to commencing CwD operations, a Job Safety Analysis (JSA) was performed among the rig crew and all parties involved in the operation. Before tripping the shoe joint in through rotary table, the shoe track was visually inspected and a flow check was performed on the float collar valve. The casing drive tool assembly was rigged up and connected directly to the rigs top drive system. The drive tool was function tested before tripping-in the shoe track and first casing joint. Upon tagging seabed at 52 m, the well was spudded with low drilling parameters: 1,1501,900 lpm, 1 klbs WOB and 10-30 RPM to wash-in the casing string to a depth of 80 m. This is a critical process required for maintaining the vertical integrity of the conductor string. Initial up string weight was recorded at 70 klbs and down string weight was 70 klbs. The drilling parameters were increased gradually during the operation in order to maximize the rate of penetration (ROP). General drilling parameters used were: 30-50 rpm, 1,1503,000 lpm flow, 0-6 klbs WOB, 80-380 psi SPP and 0-7 kft-lbs torque to drill through the top hole formations.

Anti-Rotation Tab fully engaged

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At 138 m, the Top Drive Systems brake was found to be slipping. While attempting to stop drilling, the casing string became stuck. A total of 350 klbs overpull force was required to successfully free the casing string. The wellbore was continuously circulated with sea water through the casing drive tool throughout the 13.5 hour delay to repair the Top Drive System. The drilling operation was then continued from 138 m until 392 m with parameters indicated below. Rotation : 50 80 rpm Flow Rate : 3,350 4,200 lpm Pressure : 380 630 psi WOB : 3 10 klbs Torque : 3 18 kft-lbs A 20 bbl hi-viscosity mud sweep was pumped at every casing connection. The drilling operation was halted for a second time at 392 m, due to a similar Top Drive System brake slipping problem. One joint of casing was pulled, leaving the casing bit off bottom at a depth of 380 m to allow continuous circulation while troubleshooting the problem with the Top Drive System. The casing drive tool was re-engaged into the string after 22.5 hours. Initial pick up weight was 220 klbs with no indications of stuck casing. The casing string was then reamed down to bottom at 392 m and the drilling operation was resumed. An increase in drilling torque was observed on the casing string, prompting the operator to increase the volume of hi-viscosity sweeps to 40 bbl after drilling down each casing joint. Drilling operations were paused at 488 m for another hour to replace the air supply hose between the rig floor and main deck. A circulation rate of 2,850 lpm and rotation of 20 RPM was maintained on the casing string to ensure the annulus remained clear of cuttings and limit the possibility of pack-off. After drilling to 582 m, one joint of drill pipe was made up onto the top of the casing drive tool assembly. The 20 inch casing bushing insert was removed from the rotary. CwD operations resumed to continue drilling the casing string down below rotary table until the targeted depth of 600 m was reached. A 1,000 bbl hi-viscosity sweep was pumped at target depth to clean the hole. The final pick up string weight was recorded at 280 klbs, rotary string weight at 270 klbs, and slack off weight at 280 klbs. The casing spear assembly was retrieved to allow the installation of the casing hanger assembly and proceeds with the cementation process as per designed procedure. However, it was noted that at the end of the casing drilling operation when the casing spear was rigged down, one of the casing drilling spear drag blocks segment had come free and hanging on the housing. The driller immediately stopped picking up the casing spear to inspect the tool and later it was laid down on pipe deck for investigation. It came to field personnel knowledge that two screws to lock the retainer sleeve and drag blocks housing via a locking block were found missing. Further investigation in town discovered that the drag block was believed to be dropped out due to losing the holding mechanism by the retainer sleeve after it was allowed to be rotated freely without the locking block in proper place as the locking screws backed out. Drilling with Casing Performance Results The non-retrievable CwD technology was successfully implemented to drill in a long 20 inch conductor string in Offshore Myanmar, notably known for its strong sea currents. A total of 49 joints of 20 inch conductor were successfully drilled down to the planned depth of 600 m MDRT, which is the longest interval drilled to date for this size conductor. Average ROP was very high at 51.72 m/hr over10.72 on-bottom drilling hours. The drilling operation was performed in a safe manner with no recordable incidents or accidents. The expected lost circulation problem while drilling was mitigated, as no major losses were encountered during the entire Casing while Drilling operation. This suggests that the CwD technology added value with the smear effect mechanism for limiting lost circulation.

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Throughout the 20-Inch conductor string casing drilling process, there are a total of 119 hours downtime to repair the Drawworks which the casing remained stationery in hole with only circulation. After each repair and maintenance process, the casing string was still able to be rotated and resumed with drilling oiperation, none indication of hole packoff problem. Excellent verticality of the well was maintained throughout the operation with inclination measuring less than one degree. These combined results demonstrate that the non-retrievable CwD system offers a simple BHA configuration and cost effective means of top hole casing installation. After a careful pre-job analysis of the formation lithology and offset wells, the proposed eight-bladed 20 x 24 inch PDC casing bit performed as designed. Coupled with the new premium casing connectors which allowed higher drilling torque, the bit aggressively drilled down through the medium soft formation until reaching the planned depth in a single run. The charts (see Fig. 10) show the performance parameter of the casing bit drilling through the formation. The 20 x 24 casing bit was drilled out with a subsequent section 17.5 PDC bit. However, the PDC bit was return with a unfavorable condition, suspecting could be due to drilling out the fallen bolt inside the string from the casing spears drag block during the rig down incident.

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Fig. 10: 20-Inch conductor DwC operation parameters chart

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Lesson Learnt and Future Job Recommendation A few lessons can be taken from ASK-4 20-Inch casing drilling operation. While retrieving the casing spear from the casing, one of the eight casing drilling spear drag blocks came free from the drag block housing. On investigation, it was found that the two retaining sleeve bolts had rattled free and were lost which consequently allowed the retaining sleeve to rotate free.

Upon investigation in town, a prompt action was taken where an alert pertinent to the incident was distributed globally. Immediate remedial action was emphasized to be taken to prevent occurrence of similar issue. Based on the findings from investigation, recommendations were raised to be implemented as below: The screws should be applied with removable thread lock compound before installation to firmly attach on the

locking block. Washers have to be used along with screws to enhance the locking mechanism. Field personnel are advised to frequently check for loose screws during drilling operation.

A 50 bbl hi-viscosity sweep was pumped every three joints on this Casing while Drilling operation. It is highly recommended to pump 20-40 bbl of hi-viscosity sweep on every joint of conductor to promote good hole cleaning and cuttings removal throughout the CwD operation. Compared to conventional drilling techniques, CwD provides smaller annular clearance between the formation and the pipe. Excessive cuttings accumulation in the annulus could potentially lead to stuck casing or casing string pack-off problems. Therefore, it is recommended to pump hi-viscosity sweeps on every joint drilled to limit the potential for such problems. On the subsequent well utilization casing drilling technology on the same top hole 20 section with similar casing bit in the nearby area, the casing bit was drilled out with roller cone bit and return with a favorable condition. A roller cone bit can be considered for drilling out the casing bit in the near future.

Conclusions Casing while Drilling techniques mitigated difficulties associated with the conventional methods of stabbing the

conductor casing into a pre-drilled hole in strong subsea currents.

The 20 inch conductor was efficiently drilled and set at a depth of 600 m a record for the longest top hole section in offshore Myanmar.

Pre-job analyses of the lithology and offset wells guided the applications team to select a 20 x 24 inch PDC casing bit with a cutting structure capable of drilling the entire interval at high ROP in a single trip.

The high probability of lost circulation was mitigated with the smear effect mechanism as seen in many other CwD applications.

Acknowledgements We would like to take this opportunity to express appreciation to PTTEP, Weatherford and Oil States for allowing this paper to be published and to IPTC for hosting this conference to highlight this project.

References

1. Galloway, G. 2003. Rotary Drilling with CasingA field proven method of reducing wellbore construction cost. Paper WOCD-0306-02 presented at the World Oil Casing Drilling Technical Conference, Houston, Texas, USA, 67 March.

2. Galloway, G. 2004. Cement in Place Drilling with Casing System Provides Safe, Reliable Method for Improving Drilling Efficiency. Paper OTC 16565 presented at the Offshore Technology Conference, Houston, Texas, 36 May.

3. Watts, R.D., Greener, M.R., McKeever, S., Scott, P.D., and Beardmore, D. 2010. Particle Size Distribution Improves Casing-While-Drilling WellboreStrengthening Results. Paper IADC/SPE 128913 presented at the IADC/SPE Drilling Conference and Exhibition, New Orleans, Louisiana, USA, 24 February.

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Nomenclature

BHA Bottom Hole Assembly

CwD Casing while Drilling

HVOF High Velocity Oxy-Fuel

JSA Job Safety Analysis

lpm liters per minute

MD Measured Depth

MDRT Measured Depth from Rotary Table

OD Outside Diameter

PDC Polycrystalline Diamond Compact

PSI Pounds force per Square Inch

RKB-ML Rotary Kelly Bushing to Mud Line

ROP Rate of Penetration

RPM Revolutions per Minute

SPP Stand Pipe Pressure

TD Target Depth or Total Depth

TSD Thermally Stable Diamond (also called TSP)

WOB Weight on Bit