Page 80 - Hydrocarbon

Drilling Engineering 67

stabilizer

rotor

universal
joint bypass
valve
stator

PDC bit

Figure 4.17 Mud turbine.

Maintaining angle
9.2m DC
long stabilizer
6.1m DC (drill collars)
Building angle

Dropping angle

= point of drillstring
support

Figure 4.18 Types of assemblies for directional drilling.

4.5.4. Horizontal drilling

Given the lateral distribution of reservoir rock or reservoir fluids, a horizontal well
may provide the optimum trajectory. Figure 4.19 shows the types of horizontal wells
being drilled. The build-up rate of angle is the main distinction from a drilling point
of view. Medium radius wells are preferred since they can be drilled, logged and
completed with fairly standard equipment. The horizontal drilling target can be
controlled within a vertical window of less than 2 m.