Coiled tubing drilling (CTD) is coming into the mainstream in a number of locations and applications, and the availability of improved BHA elements is a significant contributor in this regard. This paper describes BHA elements including a hydraulic orienter and MWD system recently employed by ARCO in CTD operations, examines their capabilities, and provides a series of examples in which these tools were successfully employed. The BHA elements formerly utilized in coiled tubing drilling have often not performed as well or as reliably as the industry has become accustomed to in conventional drilling operations. 1 Principle concerns here include the overall ROP, attainment of timely survey and steering data, and directional control of the BHA. The BHA elements utilized in the recent operations represent an improvement in these critical functions. The BHA orienter is a newly engineered, simple, hydraulically actuated device. Its performance attributes affecting overall ROP and directional control of the BHA are examined, including its speed of actuation, and its ability to change the BHA orientation while in a medium radius curve. The MWD system really represents a new application of an existing reliable system, with attributes that are especially important in the CTD environment. Modifications related to downsizing are examined, as well as relevant performance attributes including: steering data update rate; real time gamma log quality; mud pulse detection capability on coil in a range of drilling fluids; and reliability. The BHA is also looked at from an overall system perspective, including its integration with the coiled tubing and other equipment associated with the CTD operation. As of this writing, ARCO Alaska, Inc. and THUMS Long Beach Co. (a wholly owned subsidiary of ARCO) have completed 16 CTD reentry sidetrack jobs utilizing these BHA elements in Alaska and Long Beach, California. Overall performance and reliability from these jobs are summarized. Additionally, specific cases are examined in greater detail, with these BHA elements contributing towards successful CTD window milling, medium radius curves, and laterals.

Coiled-tubing drilling (CTD) is coming into the mainstream in a number of locations and applications, and the availability of improved bottomhole assembly (BHA) elements is a significant contributor in this regard. This paper describes BHA elements, including a hydraulic orienter and measurement-while-drilling (MWD) system, recently used by Arco in CTD operations; examines their capabilities; and provides examples in which these tools were used successfully.The BHA orienter is a newly engineered, simple, hydraulically actuated device. This paper examines its performance attributes affecting overall rate of penetration (ROP) and directional control of the BHA, including its actuation speed and its ability to change the BHA orientation while in a medium-radius curve. The MWD system represents a new application of an existing reliable system, with attributes that are especially important in the CTD environment. Modifications related to downsizing are examined, as well as relevant performance attributes including steering-data-update rate; real-time gamma log quality; mud-pulse-detection capability on coil in a range of drilling fluids; and reliability. The BHA is also looked at from an overall system perspective, including its integration with the coiled tubing (CT) and other equipment associated with the CTD operation.As of the writing of Ref. 1, Arco Alaska Inc. and THUMS Long Beach Co. (a wholly owned subsidiary of Arco) had completed 16 CTD re-entry sidetrack jobs in Alaska and Long Beach, California, with these BHA elements. This paper summarizes overall performance and reliability from these jobs. Additionally, specific cases are examined in greater detail, with these BHA elements contributing to successful CTD window milling, medium-radius curves, and laterals. (As of this publication, Arco companies have performed 47 such jobs with these BHA elements; however, this paper focuses on the first 16 jobs.)

Coiled tubing (CT) has been used at Prudhoe Bay since the early 1980’s, saving hundreds of millions of dollars in well servicing costs for such operations as cement squeezing, well cleanouts, stimulation, inflatable packers and plug placements, fishing, and temporary artificial lift applications previously performed by drilling/workover rigs. The majority of these CT jobs are currently conducted with 1-3/4″ OD CT which has proven to have excellent strength, capacity, and durability for typical field operations. With the recent availability of 2.0″, 2-3/8″, 2-7/8″ and 3-1/2″ OD CT, additional drilling and production applications once thought improbable to impossible have been achieved.

The paper describes the recompletion of an oil well in the Prudhoe Bay field using coiled tubing (CT) in the first use of two inch outside diameter (OD) CT. The CT and currently available auxiliary equipment were installed inside of the existing production tubing to improve flowing tubing hydraulics. The feasibility of relatively large CT for production tubing is demonstrated. In the example well, installation of coiled tubing enabled a "dead" well to be restored to production at a rate of several hundred barrels per day without an expensive rig workover or modifications to existing wellhead or downhole equipment.

Summary The paper describes the successful sidetrack of an oil well in the Slaughter Field in West Texas using coiled tubing (CT). Several first-time CT operations performed during this workover include: Setting a whipstock in casing on CT Cutting a window with CT Using measurement-while-drilling (MWD) with CT in a "real" well Use of a fluid-operated orientation tool for in-hole tool face changes Successful use of an "autodriller" to maintain weight on bit while drilling Directional control of the sidetracked hole proved to be ineffective due to a surface software problem. The resultant wellbore was not horizontal as planned, but instead closely paralleled the original well for much of its length. However, the previously non-productive well flowed 1000 barrels of fluid per day (BFPD) from the sidetrack following the workover. Introduction The Slaughter Field is located in Cochran County, Texas, approximately 50 n-tiles southwest of Lubbock (Figure 1). Production is from the San Andres formation (dolomite and anhydrite) at true vertical depths (TVD) of 5000 - 5200 ft. Most producing wells are on rod pump. The subject well, H.T. Boyd 59X, had been drilled to a total depth of 5245 ft MD (measured depth) in 1989 as the center well (producer) in a five-spot waterflood pattern. The well failed to produce significant fluid volumes during initial completion attempts. Stimulation with acid and a subsequent fracture treatment failed to significantly open the well up. It tested 64 BFPD with 6% oil cut following stimulation (producers in the area generally produce in the 400 BFPD range) and was shut in until initiation of sidetrack operations in July, 1992. PLANNED ACTION Using CT, it was planned to sidetrack the well to a bottom hole location (BHL) approximately 700 ft. to 900 ft. NNW of the original BHL. A build rate of 15/100 ft. would be required to yield 500 ft. of horizontal section in the pay zone. Planned TD was 5850 ft. MD (5052 ft. TVD) (Figure 2). The 3.75 inch hole was to be left uncased and the well produced on rod pump, as required by most wells in the reservoir. DESCRIPTION OF THE CASE HISTORY WELL Prior to the workover, the Boyd 59X well was cased with 5-1/2 inch outside diameter (OD), 15.5 pounds per foot (ppf), J-55 casing set at 5245 ft. A cast iron bridge plug had been set at 5030 ft. with +90 ft. of cement on top of it following unsatisfactory completion attempts in the interval 5082 ft. - 5165 ft. MD. The well had an inclination of approximately 14 at the projected window depth of 4845 ft. MD. Direction of the wellbore at this depth was 3461 (Figure 3) DISCUSSION OF FIELD OPERATIONS Rigup A detailed CT drilling plan for the sidetrack was prepared by the coiled tubing service company and the operator.