Based on the provided reference, the term "core angle" refers specifically to the beta angle, which is a crucial measurement used in geological drilling to help orient features found within the core.
The beta angle is measured clockwise around the circumference of the core to determine the position of a specific point (an apex) relative to a reference line.
Understanding the Beta Angle Measurement
The beta angle provides a circular measurement around the core axis. It's essential for orienting planar features like bedding, veins, or faults observed in the core relative to the original orientation in the ground.
Key Steps for Measuring the Beta Angle
Measuring the beta angle involves a specific procedure to ensure consistency and accuracy:
- Establish a Reference Line (A): A starting line is marked along the length of the core. This line is typically placed at the top-of-core or bottom-of-core, serving as the 0-degree mark for the measurement.
- Determine Drilling Direction: The direction in which the hole was drilled is critical for applying the correct perspective.
- Adopt the Correct Perspective: The measurement is taken while looking in the direction of drilling. The right-hand thumb rule is used to confirm that clockwise rotation is correctly identified from this perspective.
- Identify the Apex (B or B'): Locate the apex of the feature you are measuring on the core's surface. This is the point where the trace of the feature (like a vein) is either furthest from (B) or nearest to (B') the drill collar end of that section of core.
- Measure Clockwise: Starting from the established reference line (A), measure the angle clockwise around the circumference of the core to reach the identified apex (B or B').
This clockwise angle, measured from the reference line to the apex while looking down-hole, is the beta angle. It provides the radial position of the apex on the core surface.
