Modeling functions

The list shows the modeling functions that you can use in expressions.

Note: To add and edit the Arps modeling functions in expressions, you must have the Spotfire Industry Pro license (the Arps decline curve license feature).

See also Arps decline curve on the Curve fit models page for more information.


Function	Description
`Arps(Arg1, Arg2, Arg3, Arg4, (Arg5))`	Calculates production using the Arps model, given t, q_i, b, D_i, and optionally, D_lim. If D_lim is provided, the Modified Arps equation is used, otherwise the Standard Arps equation is used. If b is an empty value (null), it is treated as 0.0, which corresponds to an Exponential decline. Example: `Arps([x] - [x_min], [q_i], [b], [D_i])`
`ArpsCumulative(Arg1, Arg2, Arg3, Arg4, (Arg5))`	Calculates the cumulative production for the Arps model given t, q_i, b, D_i, and optionally, D_lim. If D_lim is provided, the Modified Arps equation is used, otherwise the Standard Arps equation is used. If b is an empty value (null), it is treated as 0.0, which corresponds to an Exponential decline. The cumulative production is the integral of the production from time zero to the given time t. It can be evaluated using the formulas: Example: `ArpsCumulative([x] - [x_min], [q_i], [b], [D_i], [D_lim])`
`ArpsEffectiveToNominalDecline(Arg1, Arg2)`	Converts the secant effective initial decline rate to the nominal initial decline rate Dᵢ, given the Arps exponent b. Example: `ArpsEffectiveToNominalDecline([D_esi], [b])`
`ArpsNominalToEffectiveDecline(Arg1, Arg2)`	Converts the nominal decline rate D_i to the effective decline rate D_esi, given the Arps exponent b. Example: `ArpsNominalToEffectiveDecline([D_i], [b])`
`ArpsNominalToTangentEffectiveDecline(Arg1)`	Converts the nominal decline rate D_i to the tangent effective decline rate. Example: `ArpsNominalToTangentEffectiveDecline([D_i])`
`ArpsTangentEffectiveToNominalDecline(Arg1)`	Converts the tangent effective decline rate to the nominal decline rate D_i. Example: `ArpsTangentEffectiveToNominalDecline([D_e])`
`ArpsTimeAtDecline(Arg1, Arg2, Arg3)`	Calculates the time for an Arps decline curve to reach a target nominal decline rate D_lim, that is, the point where the curve switches over to become exponential. The arguments are b, D_i, and D_lim. Example: `ArpsTimeAtDecline([b], [D_i], [D_lim])`
`ArpsTimeAtRate(Arg1, Arg2, Arg3, Arg4, Arg5)`	Calculates the time for an Arps decline curve to reach a certain production. The arguments are q_i, b, D_i, D_lim, and q_lim. If D_lim is not an empty value (null), the Modified Arps equation is used, otherwise the Standard Arps equation is used. If b is an empty value (null), it is treated as 0.0, which corresponds to an Exponential decline. The time is given by: The q_lim value is also known as the Economic limit. Example: `ArpsTimeAtRate([q_i], [b], [D_i], [D_lim], [q_lim])`