Hydraulic Fracture Carter Leakoff Guide
A hydraulic-fracturing leakoff guide for Carter square-root-time fluid loss, spurt loss, exposed area, time basis, fluid balance, fracture efficiency, and model limitations.
linked formula references
verified source links
Practical workflow
- 1
Define whether area and injected volume represent one wing or both wings and one or both fracture faces.
- 2
Enter a leakoff coefficient, exposure time, and spurt-loss thickness on one consistent unit basis.
- 3
Calculate leakoff volume and reconcile it with injected volume and estimated fracture volume.
- 4
Test sensitivity to coefficient, time, and area, then use calibrated treatment data for design-critical decisions.
Fluid material balance
Injected fluid is partitioned between fracture volume and fluid lost to the formation. In the simplified Carter relationship, leakoff volume equals effective leakoff area multiplied by the sum of twice the leakoff coefficient times square root of exposure time and spurt-loss thickness.
Define the geometric basis before calculating. The cited University of Texas text notes that one-wing injected volume and rate may need a factor of two for a bi-wing fracture; a similar explicit convention is needed for leakoff faces and area.
Limits of square-root-time leakoff
Carter leakoff is a useful approximation, not a coupled fracture simulator. Real leakoff can change with pressure, filter cake, permeability, compressibility, fluid rheology, natural fractures, stress, and the continuously changing age of each newly created surface element.
Use measured treatment data, mini-frac or DFIT interpretation, pressure matching, and a calibrated fracture model when treatment design or post-job evaluation depends materially on leakoff behavior.
Start with these calculators
These links keep the guide close to the working calculator flow.