Well Profile and Directional Drilling Definitions
Mastering well profile and directional drilling terminology is the foundation for effective communication between the geosteering engineer and the directional driller. While geosteering provides the geological target, directional drilling provides the mechanical execution. Consequently, you must understand the language of wellbore architecture to ensure your steering recommendations are physically achievable.
Defining the Well Profile
A well profile describes the intended path of the well from the surface to the target. However, the profile must be chosen carefully based on the reservoir geometry.
- Vertical Well: A simple, straight hole. Although efficient for shallow targets, it offers very limited reservoir contact.
- Slant/Directional Well: A hole drilled at an angle. Therefore, this profile is used to reach targets located laterally away from the surface drilling pad.
- Horizontal Well: A well that “kicks off” and turns into a horizontal plane. As a result, this maximizes contact with a thin reservoir, which is critical for modern geosteering operations.
Essential Directional Drilling Terminology
Furthermore, you will encounter these mechanical terms daily in the field:
- Kick-Off Point (KOP): The exact depth where the directional driller begins to deviate the well from vertical.
- Build Section: The portion of the well where the inclination is actively increasing. If this is too aggressive, it can cause mechanical stress on the drill pipe.
- Landing Point: The specific point where the wellbore transitions from the build section into the target formation. Essentially, this is the “entry” to the geosteering phase.
- Tangent Section: A segment of the well drilled at a constant angle. For instance, many profiles include a long tangent to gain lateral distance before landing the well.
The Intersection of Geology and Engineering
In contrast to simple vertical drilling, directional drilling requires constant monitoring of “Dogleg Severity” (DLS). Because a high DLS can make it difficult to run casing or completion tools later, directional drillers must balance the need to steer with the need for a “smooth” hole. Therefore, when you provide a steering recommendation, you must always ensure it does not require a DLS that exceeds the mechanical limits of the drilling assembly.
Summary for Well Placement
- Know your profile: Understand if you are in the build, tangent, or horizontal section.
- Respect the limits: Always coordinate with the directional driller regarding the maximum allowed DLS.
- Plan the landing: The transition from the build section to the target zone is the most critical part of the well profile.