Wellbore Sidetracking Guidelines

Wellbore Sidetracking Guidelines The following guidelines are used to aid in understanding and in establishing some protocol in the event of  having to sidetrack while drilling. Although this may not cover all circumstances, it gives useful information for   both the desk and field engineer. engineer.

General Principles

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Sidetracking a Harder Target Formation - a diamond sidetrack bit should be employed. aution needs to  be e!ercised when using a diamond sidetrack bit as, it can produce very high doglegs. "otor settings typically used with sidetrack bits should be between #-#.$. Sidetrack bits are used only to establish the %ledge&. 'enerally only $-(m is cut with a sidetrack bit, as this is the distance that the ledge will be the same width as the bit face )typically*the actual amount drilled will vary+. nce the entire bit face is off, and is cutting new hole, the bit will generally stop drilling, and typically an increase in S will be seen. These two signs indicate that a good ledge is started, and the assembly should be pulled out in favour of  a traditional irectional rilling assembly. Sidetracking from a ement lug - a new bit of the same type used to drill the original wellbore should be used. The ideal situation is the cement plug is harder  )drills slower+ than the formation, for the natural tendency is drilling in the path of least resistance. Should the formation be harder, than the cement plug, a higher motor setting, and a less aggressive )slower+ time drilling program should be considered. The type of " ideally to use is a medium speed configuration, as higher bit speeds typically result in easier sidetracking. /it and formation types need to be considered when making this decision. Sidetracking Hori0ontals - it is important not to begin drilling out of the bottom of the wellbore )123 toolface+, as is the natural tendency. A setting of appro!imately 1#$4 either left or right toolface will work. 5sing gravity somewhat and a sharp directional change in either direction will aid in the process. This scenario allows a greater ability to return to either wellbore. 6!ercise e!treme caution when e!iting out of casing. Sidetracking should not be commenced less than 1$-#3m 1$-#3m out of the H0 casing shoe. This This ensures there is no magnetic magnetic interference interference and to eliminate any damage to the casing. "aintain "aintain a distance distance of 1$-#3m separation between multi-lateral multi-lateral 78s, 78s, This distance allows an easier  determination of which sidetrack you are re-entering. rior to beginning your sidetrack and when re entering, always re-strap, and check pipe tally to be assured of bit depth. ouble checking measurements will ensure confidence that the sidetrack is being initiated in the proper place. nce a sidetrack ledge is established, it is very important not to drill ahead aggressively, for the ledge may break off and one would have to re start the entire process again. Higher than normal doglegs are typically e!perienced when sidetracking, so e!ercise caution when sidetracking.

Sidetracking off Cement Plugs

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A minimum of 133m of cement should be used. 7eep a minimum of $3m above and $3m below the estimated sidetrack point. To begin drilling )polishing+ the cement plug, a %slick& assembly can be used or to begin faster a " can be employed to drill up the cement. cement. 9f using a slick assembly to polish the plug, follow the rule of  $8s for drilling a hard cement plug : with $333da;