3 Straight hole Well deviates < 3 deg. per 100 ft (30m) Cone with a maximum angle of 5 deg
4 A well with an excessive angle in it that has not been drilled on purpose that way is call a crooked hole.If the bit hits a subsurface rock layer with a dip greater than 45 deg., the bit tends to be deflected down dip. If rock layer dip less than 45 deg., the bit tends to be deflected updip.
5 Directional Drilling or Deviation Drilling Modern rotary rigs can be controlled so that the well is drilled out at a pre-determined angle during directional or deviation drilling and ends up in a pre-determined location called target.
6 Directional Drilling (Patterns) Directionally drilled wells will usually be drilled according to one of three basic hole patterns.
7 Directional Drilling (Patterns) After making an initial deflection from vertical, the well may be drilled to the target, or deflected once more to allowed the bottom of thehole to be drilledvertically(“double dogleg”).
12 Directional DrillingThe deviation begins when the hole is deflected using one of several techniques:(1) downhole hydraulic motors with a“bent sub” (井底馬達 與 彎曲接頭)(2) jet bits (沖鑽頭)(3) whipstocks (導斜具)