In general, there can be following types of well profiles-
- L-Profile
- J-Profile
- S-Profile
- Horizontal Wells
- ERD Wells (Extended Reach Drilling)
L-Profile-
L-Profile wells have Building section and Holding (or Tangent) section.
Features:
- Shallow KOP.
- May have one or more than one Build-up rates.
Applications:
- Deep wells with large vertical sections.
J-Profile-
Features:
- Deep KOP.
- Build-up section
- Short tangent section (optional)
Applications:
- Appraisal wells to access the extent of a newly discovered reservoirs.
- Re-positioning the bottom part of the well or re-drilling.
- Salt dome drilling.
S-profile-
Features:
- Shallow KOP
- Building Section
- Tangent Section
- Dropping Section
There can be several variations such as,
-Build, Hold & Drop back to vertical
-Build, Hold & Drop & Hold (as shown)
-Build, Hold & Drop through reservoir.
Applications:
- Multiple pay zones
- Well spacing requirements
- Deep wells with small horizontal displacements
- Lease or target limitations
- Reduces final angle in reservoir
Disadvantages:
- Increased torque & drag
- Risk of key seating
- Logging problems due to inclination.
Horizontal Wells-
Features:
- Angle 90 deg or more is achieved.
- Can have one or more Building section.
Applications:
- Greater exposure to reservoir.
- Greater drainage capability.
- A single well can penetrate and produce from oil from multiple pockets.
Disadvantages:
- Increase in torque & drag.
- Increase in Equivalent Circulating Density.
- Hole cleaning problems.
Extended Reach Drilling Wells (ERD)-
Features:
- Generally, vertical sections of length > 5000 m.
- In many cases, they are referred as well having vertical section to TVD ratio of 2:1 or more.
- Similar sets of problems can be associated with ERD wells as with Horizontal wells.
When planning a directional well, a number of technical issues & constraints will have to be considered and accordingly well plan are prepared or approved.
These includes:
- Target location
- Target shape & size
- Surface location (Rig)
- Sub surface obstacles (faults, salt dome, etc.)
- Adjacent Wells
- Casing Programs
- Mud Programs
- Geological Sections
