10,372
edits
Changes
Jump to navigation
Jump to search
Line 37:
Line 37: − file:wellbore-trajectory_fig4.png|{{figure number|4}}Using an open hole whipstock for sidetracking+ − file:wellbore-trajectory_fig2.png|{{figure number|2}}Right-hand walk and lead angle.+ − file:wellbore-trajectory_fig3.png|{{figure number|3}}Directional well design example: build and hold.+ + + + Line 59:
Line 62: − − [[file:wellbore-trajectory_fig5.png|left|thumb|{{figure number|5}}Kicking off with a jet bit.]] − − [[file:wellbore-trajectory_fig6.png|thumb|{{figure number|6}}(a) Steerable bottom hole assembly, (b) Kicking off with a bent sub and straight mud motor.]] Line 84:
Line 83: − − [[file:wellbore-trajectory_fig7.png|left|thumb|{{figure number|7}}(a) Packed bottom hole assembly, (b) Fulcrum effect for build angle.]]
→Directional wellbore
==Directional wellbore==
==Directional wellbore==
<gallery mode=packed heights=200px widths=200px>
<gallery mode=packed heights=200px widths=200px>
wellbore-trajectory_fig2.png|{{figure number|2}}Right-hand walk and lead angle.
wellbore-trajectory_fig3.png|{{figure number|3}}Directional well design example: build and hold.
wellbore-trajectory_fig4.png|{{figure number|4}}Using an open hole whipstock for sidetracking
wellbore-trajectory_fig5.png|{{figure number|5}}Kicking off with a jet bit.]]
wellbore-trajectory_fig6.png|{{figure number|6}}(a) Steerable bottom hole assembly, (b) Kicking off with a bent sub and straight mud motor.]]
wellbore-trajectory_fig7.png|{{figure number|7}}(a) Packed bottom hole assembly, (b) Fulcrum effect for build angle.]]
</gallery>
</gallery>
The oldest method of kicking off or deviating a wellbore uses an open hole ''whipstock'' ([[:file:wellbore-trajectory_fig4.png|Figure 4]]), which is a casing joint with an upward-tapering wedge cut out of one side. Although this operation is time consuming, it is still occasionally used to sidetrack around fish or abandoned open holes. Whipstocks are also used to sidetrack out of casing by milling a “window” and deflecting the wellbore using a mud motor.
The oldest method of kicking off or deviating a wellbore uses an open hole ''whipstock'' ([[:file:wellbore-trajectory_fig4.png|Figure 4]]), which is a casing joint with an upward-tapering wedge cut out of one side. Although this operation is time consuming, it is still occasionally used to sidetrack around fish or abandoned open holes. Whipstocks are also used to sidetrack out of casing by milling a “window” and deflecting the wellbore using a mud motor.
====Jet bit====
====Jet bit====
Another kicking-off method uses a ''jet bit''. The bit has one large nozzle that erodes a pocket from the hole bottom in the desired trajectory ([[:file:wellbore-trajectory_fig5.png|Figure 5]]). Weight is applied to the bit while it is rotated into the pocket. This procedure is repeated until the desired trajectory is achieved. The disadvantage of jetting is that it is highly dependent on formation hardness. Some formations are too hard to be hydraulically eroded, and some soft formations erode too quickly, making it difficult to jet in the desired trajectory.
Another kicking-off method uses a ''jet bit''. The bit has one large nozzle that erodes a pocket from the hole bottom in the desired trajectory ([[:file:wellbore-trajectory_fig5.png|Figure 5]]). Weight is applied to the bit while it is rotated into the pocket. This procedure is repeated until the desired trajectory is achieved. The disadvantage of jetting is that it is highly dependent on formation hardness. Some formations are too hard to be hydraulically eroded, and some soft formations erode too quickly, making it difficult to jet in the desired trajectory.
====Bottom hole assemblages used to kick off wells====
====Bottom hole assemblages used to kick off wells====
Current technology has simplified directional drilling based on improvements in the following:
Current technology has simplified directional drilling based on improvements in the following:
* Polycrystalline diamond compact (PDC) bits.
* Polycrystalline diamond compact (PDC) bits.