Gas Development Planning

Gas Plateau Fall off

Load an unconstrained gas deliverability forecast, choose a plateau rate, and see how long the development holds plateau before depletion pulls it off. Fall off is computed from cumulative production, not from a calendar crossing, so a lower plateau correctly delays the fall off.

Input must be unconstrained potential. The uploaded rate is treated as the maximum deliverability the asset can flow at each depletion state. Do not upload sales constrained or facility constrained actuals, the deliverability curve would be wrong.

Forecast input

Map uploaded CSV

Choose the time column, rate column, and time format before loading the forecast.

Expected CSV format

After you choose a file, the app asks what each column contains before it runs the calculation.

  • Time columnUse calendar dates such as 2026-01 or 2026-01-01, or elapsed values such as 0, 1, 2.
  • Time basisFor elapsed values, choose days, months, quarters, or years during the upload mapping step.
  • Rate columnUse gas rate in MMscf/d. Values must be non-negative.
  • Forecast typeUse unconstrained deliverability potential, not sales constrained or facility constrained actuals.

Header rows are allowed. Rows are sorted by time automatically. Blank or invalid rows are removed. Comma, tab, and semicolon delimiters are accepted.

Calendar example:
time,rate
2026-01-01,220
2026-02-01,208
2026-03-01,197
Elapsed months example:
month,rate
0,220
1,208
2,197

Plateau rate

0MMscf/d
minmax

Output

Calendar dates are available when the loaded time column contains dates.

Data preview

TimeRateGp

Validation

    Production rate versus time

    Constrained plateau case against the deliverability potential at each depletion state. Potential sits above during plateau and merges with actual through decline.

    Constrained actual Deliverability potential Selected plateau Fall off plateau

    Deliverability versus cumulative production

    The depletion relationship q potential as a function of Gp. Fall off occurs where the plateau line meets this curve.

    Deliverability, q = f(Gp) Selected plateau Fall off point

    How the constrained case is calculated

    Cumulative production Gp is integrated from the uploaded rate and time curve by the trapezoidal rule, with increment in Bcf = rate in MMscf/d times days divided by 1000. Because cumulative production rises monotonically, every value of Gp maps to a single deliverability, giving the backend relationship q deliverability = f(Gp).

    The constrained case is then stepped through cumulative production, not calendar time. At each state the rate is actual = min(plateau, q deliverability at current Gp). While deliverability sits above the plateau the asset holds flat and depletes slowly. When cumulative production reaches the point where deliverability has fallen to the plateau, the asset falls off plateau and follows the deliverability curve down.

    This is why a lower plateau pushes the fall off later. The fall off always happens at the same cumulative production, but a lower plateau takes longer in calendar time to reach it. Modelling fall off as a simple crossing of the plateau against the original calendar time curve would place it too early and is not used here.

    The dashed deliverability potential is plotted along this same constrained timeline, as q deliverability at the current Gp. It is the maximum the asset could flow given how depleted it is in this case, so the actual rate, being min(plateau, potential), is never above it. During plateau the potential sits above the flat actual and declines slowly. At fall off the two meet, and through decline they are identical. Because the depletion pace depends on the plateau, both curves stretch in time together as the slider moves.