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A New Approach to Drilling Directional Wells with Coile

by Matt Varhaug, Oilfield Review editor
Tue, Mar 20, 2007 23:57 GMT

THE WOODLANDS, Texas - Field testing is opening the way for coiled tubing in directional wells drilled in the San Juan Basin of Colorado and New Mexico, USA.

Speaking here at the Intervention & Coiled Tubing Association's (ICoTA) 2007 Coiled Tubing and Well Intervention conference and exhibition, Tony Pink, Drilling Engineering Manager with Schlumberger, described how the San Juan Coiled Tubing Project was launched by BP America to evaluate directional drilling systems used in coiled tubing applications.

Working with Schlumberger directional drilling coordinators, BP drilled a series of wells using coiled tubing, with each well progressively more challenging than the previous. In the process, they demonstrated the feasibility of using rotary steerable systems (RSS) in combination with positive displacement motors (PDM) to drill directional holes.

Drilling with coiled tubing requires a downhole motor to turn the bit, as opposed to the conventional rotary-drilling method. Over the years, coiled tubing drilling (CTD) has gained a reputation for efficient pressure control, quick trips out of the hole and small footprint. Pink noted that "CTD has also recorded great success in small-diameter re-entry projects," while using electric or hydraulic orienters and PDMs to drill directionally.

Pink pointed out that the San Juan Basin project recorded another success with "the world's first downhole-powered rotary steerable system on 3 ?inch coiled tubing," drilling 6 ? and 8 ?inch holes. Using a PowerDrive vorteX* powered rotary steerable system, in combination with a positive displacement motor, the coiled tubing drilling operation was able to meet all directional requirements. This combination permitted drilling operations without the downtime formerly required to set direction using the orienter and PDM combination.

Pink stated that BP and Schlumberger directional drilling teams thoroughly planned the project in advance of its execution, counting on experience gained on each well to improve performance on the next. "The engineering we did up front is what made it so successful," he said. The plan called for greater complexity with each well. The first two wells were drilled vertically, using a PDM. The next well was also drilled vertically, but used a combination of PDM and RSS. The fourth well was S-shaped, incorporating a 150?azimuthal turn with a build in inclination before dropping back to vertical. The fifth and sixth wells were both drilled on the same surface pad, alongside an existing well. Both wells required a directional surface hole in order to reduce the potential for wellbore collision. These two wells used a build-and-drop architecture to achieve an S-shaped wellpath, with maximum inclinations of 24?and 36? respectively.

This project demonstrated that coiled tubing, in combination with a rotary steerable system and a positive displacement motor provides significant advantages over conventional directional drilling methods. Major benefits include increased rates of penetration due to the elimination of standard drillstring connections, and ease of directional steering while drilling different well profiles.

The Society of Petroleum Engineers (SPE) and the Intervention and Coiled Tubing Association (ICoTA) jointly sponsor the Coiled Tubing Conference and Exhibition.

Pink T, Neves M, Seyler C, Watkins J, Allcorn M, O扡eary J, Noynaert S and Hartensteiner F: " Drilling with a Positive Displacement Motor and a Rotary Steerable System on 3 1/2" Coiled Tubing in the San Juan Basin," paper SPE 107115, presented at the SPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition in The Woodlands, Texas, U.S.A., March 20?1, 2007.

*Mark of Schlumberger

Additional information on SPE/ICoTA is available at:

@2007 Schlumberger Limited.

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