Bilinear Time

Bilinear time or quad root time, is used to analyze bilinear fracture flow data. Bilinear fracture flow occurs in long fractures with finite conductivity.

The constant rate solution for bilinear fracture flow data is:

For oil and water:

For gas:

Based on these definitions, bilinear fracture flow data appears as a straight line on a plot of pressure versus quad root time (p vs. Dt0.25). For a complex sequence of flow rates, the superposition bilinear time function is used instead.

For buildup data, bilinear equivalent time is used as defined below: