Sonic First-Arrival Time in a Borehole Formula
Sonic First-Arrival Time in a Borehole calculates sonic first-arrival time for rock properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (L_s, v_f, d_h, d_t, l_c, v_m) are known and the assumptions behind the cited rock properties relationship match the engineering case being checked.
Assumptions
- Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
- The declared units match the field-unit constants used in the formula.
- The cited formula applies to the selected petroleum engineering workflow.
Limitations
- The calculation does not replace a full engineering model or operating procedure.
- Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.
Common mistakes
- Mixing unit systems without converting the inputs.
- Using default example values as field recommendations.
- Applying the formula outside the source assumptions.
Default example
Using the default inputs, t_log equals 188.729833 us.
3
0.02
0.7
0.3
0.1
0.005
Inputs
L_s
ftTransmitter-Receiver Spacing
v_f
ft/usFormation Acoustic Velocity
d_h
ftBorehole Diameter
d_t
ftTool Diameter
l_c
ftMudcake Thickness
v_m
ft/usMud Acoustic Velocity
Outputs
t_log
Sonic First-Arrival Time
L_s
Transmitter-Receiver Spacing
d_h
Borehole Diameter
d_t
Tool Diameter
l_c
Mudcake Thickness
Source and review
reviewedTheory, Measurement, and Interpretation of Well Logs, Bassiouni, Z. (1994)
Bassiouni, Z. 1994. Theory, Measurement, and Interpretation of Well Logs. SPE Textbook Series Vol. 4, Chapter 10.