Diutan biopolymer has recently been introduced for drilling with coiled tubing on the North Slope of Alaska. Diutan biopolymer has replaced a xanthan biopolymer based mud system when drilling new sidetrack laterals from existing wells and also in well servicing with non-rig coiled tubing operations. This change in fluid systems was made by replacing the existing xanthan biopolymer used in the solids free mud system with a diutan biopolymer. The new diutan based solids free mud has shown improvements in several areas thus providing a significant performance advantage. Coiled tubing drilling (CTD) has been conducted in Alaska since 1994 with over 600 sidetrack laterals drilled to date. For the majority of these wells a solids-free mud system was used to drill in either an overbalanced or managed- pressure drilling mode. The solids-free mud used was based on a xanthan biopolymer. In 2009 planning for more difficult well candidates suggested that the existing xanthan drilling fluid systems would be inadequate for drilling certain wells without exceeding acceptable working pressures in the coiled tubing or surface equipment. The higher pump pressures expected, along with acceptable coiled tubing design parameters associated with this higher pressure demonstrated the need to modify the drilling fluid. The standard solids-free mud was modified by replacing the xanthan biopolymer with diutan biopolymer. This new system demonstrated a 20% reduction in pump pressure, better hole cleaning, a higher tolerance to the pH changes related to cementing operations and longer fluid system life. This paper will document the development of the diutan reservoir drilling fluid (RDF) system, including laboratory testing, field testing, a comparison to the xanthan based RDF, and the results of drilling actual wells. This new drilling fluid system has been in use now since July of 2009 and is the preferred drilling fluid used for coiled tubing drilling and well servicing in Alaska.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Kuparuk Coiled Tubing Drilling (CTD) program began with the development of dynamically overbalanced CTD techniques 1 in 1998. Although many of the first wells were technical successes, the economic and productive results were less than expected.Starting with a step change in 2002, improvements in the economic results of the CTD program have materialized over the past 3 years fueling excitement about CTD in the Kuparuk River Unit (KRU). Results from the 11 well 2005 CTD program suggests that the successful application of CTD technology will continue in the Greater Kuparuk Area (Fig. 1).Technological advances, changes in target focus, improved well designs, improved CT drilling techniques, and persistence all paid off. The 2004 & 2005 CTD programs delivered wells yielding rates beyond expectations and, in the case of 2005, were achieved "at or below" the authorized expenditure budget. In addition to the overall CTD program success story, what the authors believe as 3 new world records were set on one particular well: Deepest 3" CTD sidetrack -18,350' MD; deepest CTD openhole sidetrack -17,935' MD; and deepest CTD liner run -18,320' MD. All drilling objectives were achieved and the well completed under the AFE (Authorization for Expenditure).

A new system for running and cementing liners using Electric line coiled tubing has been proven on the North Slope of Alaska. The SELRT, the Side Exhaust Liner Running Tool, gives the functionality to run and release a liner while utilizing a liner wiper plug system to ensure good cement quality. A jointed pipe liner is conveyed and cemented with the coiled tubing containing an electric umbilical.This innovative equipment has proven to be a substantial HSE benefit and savings in rig time when compared to a more conventional liner running system. Older systems used in Alaska required switching to an electric line free coiled tubing reel prior to running and cementing liner. Jointed pipe liners up to 3,700' long have been successfully run and cemented with electric line coil using the SELRT system, saving an average of 19 hours of rig time per well. This paper will describe the system development including pumping test slurries of cement through electric line coiled tubing, confirming that dropping balls is possible through electric line coiled tubing and the development and use of the new liner running equipment. Several successful liner running and cementing jobs will be reviewed. This is now the standard liner running equipment used for wells drilled with coiled tubing in the Prudhoe Bay field. IntroductionThere has been a continuous coiled tubing drilling campaign on the North Slope of Alaska since 1994. This program reenters existing vertical wells and drills horizontal sidetracks in the Prudhoe Bay, Kuparuk, Endicott and Milne Point fields. These sidetracks are typically drilled thru 4-1/2" production tubing without pulling the tubing or removing the existing production tree. (See Figure #1). Over 575 new sidetrack wells have been drilled in these fields since 1994. Prior to 2001 conventional 2-3/8" OD coiled tubing (electric line umbilical free) was in use. When a well reached TD the typical completion was a solid/cemented liner followed by coiled tubing conveyed perforating guns. The liner running tool used a ball drop system to release the liner and a coil dart/liner wiper plug system to ensure that uncontaminated cement was accurately placed behind the liner. This system proved quite reliable and robust and accounted for the majority of wells drilled up to 2001. In 2001 a new MWD BHA was tested. This BHA required an electrical umbilical inside the coiled tubing to operate. There were significant advantages to this drilling system. It provided higher data telemetry rates, more real time downhole information and better directional control using an electrical downhole orienter instead of a mechanical orienter. This system proved to be especially beneficial in managed pressure and under balanced drilling applications. The electric orienter minimized shale damage by eliminating the pump cycles needed to operate a mechanical orienter. This new equipment provided enough time savings to enable a 30% increase in effective ROP.Unfortunately, some of the productivity gains realized from using the e-line coil BHA wer...

TX 75083-3836 U.S.A., fax 1.972.952.9435. AbstractIn 2005, BP Alaska began evaluating the application of Underbalance Drilling (UBD) Technology as a method for drilling multilateral wells in the Lisburne Field. The evaluation process was enacted as a response to three key challenges at Lisburne: