This module performs a DCA autofit on all streams (oil, gas and water) of all wells in a given project. There are three steps: 1. Initialize, 2. Autofit and 3. Summary.
How does the autofit algorithm work?
The autofit algorithm finds the timestep with the maximum production data and performs a single-segment best from that timestep and rest of historical time.
This is where the autofit is initialized with both fit ranges and other relevant assumptions.
1.1. b-factor switch
The switch at the top of the screen dictates what should happen if the b-factor min or max is the converged solution during the autofit.
- When switch is ON: if the best fit solution hits the upper, or lower, b-factor bound, do a best fit with the default b-factor is done instead.
- When switch is OFF: if best fit solution hits the upper, or lower, b-factor bound, that is what is used.
1.2 Autofit ranges
- Default: starting point for autofit.
- Min: lower bounds of best-fit solution for \(q_i\), b and \(a_i\).
- Max: upper bound of best-fit solution for \(q_i\), b and \(a_i\).
- Total Production Period: sum of historical time and forecasted time.
- Oil Cut-off rate: the rate at which to stop the forecast.
- Limiting Effective Decline Rate: specifies when the hyperbolic decline curve transitions into an exponential decline curve at a specified limiting effective decline rate.
This is where you get an overview of your autofit. In this view you can filter and manually update the individual fits.
2.1 Autofit all wells
Click "Autofit all wells" to the upper left to best-fit all the wells in a given project.
2.2 Sort, Filter and Change Streams.
- Sort: Click the header parameter to sort the well list by that parameter.
- Search: Use the search bar to search for a specific well.
- Change stream: click OIL | GAS | WATER tabs to change between the streams.
2.3 Manually Edit
By clicking the row with the well name, you can edit that individual fit. In this view, you can click the right, or left arrow, and move to the next well.
2.4 Save Fit
Click SAVE up to the right to save all the autofits (for all the streams). These forecasts can be appended to the historical data in the type well feature.
Click EXPORT up to the right to export to third-party software (for all streams).
- To quality check that the overall fits are ok, a simple "roll-up" exercise can be performed on all the data.
- That is done by adding up all the rates from all the wells producing at a given time step and plotting that over time in both rate and cumulative space.
- Here you like to visually ensure that there are no strange discontinuities when the data goes from the historical data to the forecasted part of the data.