This is a simple production forecasting model for oil and gas wells, using the exponential decline curve. It uses the standard equation:

q = qie-at (3.3)

Where both the initial production rate, called IP (qi) and the decline rate (DECLINE) are treated as probabilistic distributions.

The model includes an additional parameter, t (time), which calculates the output through a timeline, and lets the user project how the volumetric reserves output will behave.

As the origin calculations for each time point are probabilistic, it is not necessary to have a distribution of numbers for each output. Instead, a distribution of forecasts or graphs is generated.
This example shows that prediction model using both a Trend and a Box-plot graphic, which bind several outputs together. The shaded region represents one standard deviation on each side of the mean. The dotted curves represent the 5-and 95 percentiles. Thus, between these dotted curves is a 90% confidence interval. Think of the band as being made up of numerous decline curves, each of which resulted from choices of Initial Production and Decline Rate.

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