1. What is the Seismic Fresnel Zone?

The Fresnel zone is the area of a reflector that contributes to the reflected wave energy at a given time. In seismic interpretation, it represents the minimum horizontal resolution needed to distinguish two features.

2. How Does the Calculator Work?

The calculator uses the Fresnel Zone formula:

Where:

• \( r \) — Fresnel zone radius (m)
• \( v \) — Seismic wave velocity (m/s)
• \( t \) — Two-way travel time (s)
• \( \lambda \) — Wavelength (m)

Explanation: The formula calculates the radius of the first Fresnel zone, which is the area that contributes most significantly to the reflected energy.

3. Importance of Fresnel Zone Calculation

Details: Understanding the Fresnel zone helps in interpreting seismic resolution limits and determining the minimum size of detectable features in seismic data.

4. Using the Calculator

Tips: Enter velocity in m/s, time in seconds, and wavelength in meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is the Fresnel zone important in seismic interpretation?
A: It determines the horizontal resolution of seismic data and helps interpreters understand what size features can be reliably detected.

Q2: How does frequency affect the Fresnel zone?
A: Higher frequencies (shorter wavelengths) result in smaller Fresnel zones, providing better resolution.

Q3: What's the difference between first and nth Fresnel zone?
A: The first Fresnel zone contributes most to the reflection energy. Subsequent zones alternate between constructive and destructive interference.

Q4: How does depth affect the Fresnel zone?
A: Fresnel zone radius increases with depth due to increasing travel time and typically decreasing frequency content.

Q5: Can we reduce the Fresnel zone size?
A: Yes, by using higher frequency sources or through migration processing which effectively collapses the Fresnel zone.