Constant Pressure, Variable Pressure, & Superposition Time

The procedure for the variable pressure and superposition time option is the same as constant pressure. Selecting the Variable Pressure or Superposition Time option when creating the worksheet changes the y-axis of the Square-root Time plot from reciprocal rate to normalized pressure. This accounts for changing flowing pressures when interpreting the slope of the Square-root Time plot. Note that the production forecast still uses a sandface forecast pressure (pwff) that you enter.

There are two superposition time functions available: linear superposition time and material balance time. These functions were developed for different flow regimes, but they should yield consistent analyses. The superposition time function defaults to linear superposition time, as linear flow is the dominant flow regime in unconventional reservoirs.