# arps: Arps decline classes and S3 methods In aRpsDCA: Arps Decline Curve Analysis in R

## Description

Create Arps decline curve objects and compute rates, cumulative production, and nominal declines.

## Usage

 ```1 2 3 4 5 6 7``` ```arps.decline(qi, Di, b=NA, Df=NA) ## S3 method for class 'arps' arps.q(decl, t) ## S3 method for class 'arps' arps.Np(decl, t) ## S3 method for class 'arps' arps.D(decl, t) ```

## Arguments

 `qi` initial rate [volume / time], i.e. q(t = 0). `Di` nominal Arps decline exponent [1 / time]. `b` Arps hyperbolic exponent. `Df` nominal Arps decline exponent [1 / time]. `t` time at which to evaluate rate, cumulative, or nominal decline [time]. `decl` an Arps decline object as returned by `arps.decline`.

## Details

Depending on whether arguments `b` and `Df` are supplied, `arps.decline` will select an exponential, hyperbolic, or hyperbolic-to-exponential decline and return an object appropriately. The returned object will have class `"exponential"`, `"hyperbolic"`, or `"hyp2exp"` in addition to class `"arps"`.

Assumes consistent units of time between `qi`, `Di`, `Df`, and `t`. To convert, see the decline-rate conversion functions referenced below.

## Value

`arps.decline` returns an object having class `"arps"`, suitable for use as an argument to S3 methods discussed here.

`q.arps` returns the rate for each element of `t` applying decline `decl`, in the same units as the value of `qi` for `decl`.

`Np.arps` returns the cumulative production for each element of `t` applying decline `decl`, in the same units as the value of `qi * t` for `decl`.

`D.arps` returns the nominal decline for each element of `t` applying decline `decl`, in the same units as the value of `Di` for `decl`.

`print.arps`, `exponential`, `hyperbolic`, `hyp2exp`, `as.effective`, `as.nominal`, `rescale.by.time`.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14``` ```## exponential decline with ## qi = 1000 Mscf/d, Di = 95% effective / year ## rate for t from 0 to 25 days decline <- arps.decline(1000, as.nominal(0.95, from.period="year", to.period="day")) arps.q(decline, seq(0, 25)) ## hyperbolic decline with ## qi = 500 bopd, Di = 3.91 nominal / year, b = 1.5, ## cumulative production at t = 5 years decline <- arps.decline( rescale.by.time(500, from="day", to="year", method="rate"), 3.91, 1.5) arps.Np(decline, 5) ```

### Example output

``` [1] 1000.0000  991.8317  983.7301  975.6946  967.7249  959.8202  951.9800
[8]  944.2040  936.4914  928.8418  921.2547  913.7296  906.2660  898.8633
[15]  891.5211  884.2389  877.0161  869.8524  862.7471  855.6999  848.7103
[22]  841.7778  834.9019  828.0821  821.3181  814.6093
[1] 197890.1
```

aRpsDCA documentation built on July 24, 2017, 1:03 a.m.