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The purpose of this article is to explain the options under the DCA Wrangler Decline Parameters menu.

Decline Parameters Menu

The Parameters menu is used to adjust the parameters and thresholds of the decline algorithm.

Option	Description
Decline	Pressing the Decline button will generate declines for the wells that are currently marked.
Reset	Reset will reset all parameter in the submenus to the DCA Wrangler defaults.
Submenus	Submenus are drop-down menus that allow for user adjustment of each parameter. Oil, Gas, Water, GOR, Yield, WOR, Forecast, Normalize, Fluid Limits, and Type Curve submenus are more fully described below. Important Note: To have GOR calculated by MCF/BBL in Linear Piecewise , set the gas stream to none, then go to the GOR parameter menu and set a new parameter.

Stream Submenus

The Oil, Gas, Water, GOR, Yield, and WOR submenus are used to select the decline algorithm for the streams. The algorithm's parameter thresholds are also set in these submenus.

IMPORTANT NOTE: The submenus for Oil, Gas, and Water are the same. The submenus for GOR, Yield, and WOR are the same.

Option	Description
Dropdown	The drop-down will select the decline algorithm for the stream. See below for the options: None No decline for this stream will be produced. Modified Arps (Auto) A Modified Arps Hyperbolic decline algorithm will produce the stream's decline. This option will allow the user to select a range of parameters (defined below). This option is normally used for declining multiple wells with the same range of parameters. Only available with Oil, Gas, Water Modified Arps A Modified Arps Hyperbolic decline algorithm will produce the stream's decline. This option will allow the user to select specific parameters (defined below). This option is used for declining a single well. Only available with Oil, Gas, Water Linear Piecewise (Auto) A Linear Piecewise decline algorithm will produce the stream's decline. This option will allow the user to select a range of parameters (defined below). This option is normally used for declining multiple wells with the same range of parameters. Available for all streams. Linear Piecewise  A Linear Piecewise decline algorithm will produce the stream's decline. This option will allow the user to select specific parameters (defined below). This option is used for declining a single well. Available for all streams.
Modified Arps (Auto)	Qi Range for Qi (Initial Rate) value. If less than or equal to 2, takes the percent of global maximum rate, else takes the absolute rate values. De Range for initial decline parameter, De. B Range for constraining the B1 value. Low B2 - High B2 The Range for constraining the B2 values (Multi-Segment Decline) Low Time 2 - High Time 2 (Days) The Range in days for the B2 Factor (Multi-Segment Decline) Low B3 - High B3 The Range for constraining the B3 values  (Multi-Segment Decline) Low Time 3 - High Time 3 (Days) The Range in days for the B3 Factor  (Multi-Segment Decline) Dmin Range for limiting decline rate Dmin (D lim). Set as both numbers to same to enforce a hard limit.
Modified Arps	Qi Qi (Initial Rate) value. If less than or equal to 2, takes the percent of global maximum rate, else takes the absolute rate values. De Initial decline parameter, De. B B factor value. Dmin Limiting decline rate Dmin (D lim). B2 (1/month) B2 Factor value  (Multi-Segment Decline) Time 2 (Days) The range in days for B2 factor (Multi-Segment Decline) B3 (1/month) B3 Factor value  (Multi-Segment Decline) Time 3 (Days) The range in days for B3 factor (Multi-Segment Decline)
Linear Piecewise (Auto)	Scale Linear or Log10. No. Segments Number of segments to be used in the continuous Linear Piecewise model. Initial Rate Range for Initial Rate. If less than or equal to 2, takes the percent of the average rate for the initial period, else takes the absolute rate values. For GOR - The initial rate is the GOR (MCF/BBL) boundary range for the initial GOR. It will try to fit a GOR between these values. Segment Time (days) Range for guessing the length of the linear segment in days. (Segment range) Segment Change (%) Range for guessing the change in slope of the model when switching. The segment change will be defined as the change in slope for each of the different segments. Outlier SD Standard deviation (from mean data fit) for declaring data points as outliers. Initial Period (Days) Defines the initial period starting from the peak production rate for primary fluid. Example - Input 90 - will skip 90 days of production then start the Linear Piecewise segments. Final Decline Limiting decline rate Dmin (D lim). The Final Decline will fit the last segment for the life of the well.
Linear Piecewise	Scale Linear or Log10. No. Segments Number of segments to be used in the continuous Linear Piecewise Time (days) Absolute days from start as Comma Separated Values. This defines the length of each segment. Value (units) Rate for the stream at each end of the segment as Comma Separated Values. This defines the rate of each segment's end. This will be aligned with the rate values on the y-axis.  Final Decline Limiting decline rate Dmin (D lim). The Final Decline will fit the last segment for the life of the well.

Forecast Submenu

Forecast parameters determine the length of the decline and if the decline will use a previous output to anchor against.

The DCA Wrangler uses declines stored in the database to “anchor” the autocasting engine.  Using anchoring, the engine will attempt to “update” the previously stored forecast using new data since the model was saved.  In updating, the engine will employ the Eliot Tie method, which:

• Ties the updated forecast to the most recent data (changing Qi and start date)
• Adjusts effective decline to handle the latest data
• Does not change b-factor

If the change in data is too great (5%), the engine will honor the previous forecast decline rather than the data.

Option	Description
Years	Number of years the decline algorithm will forecast past the last date of production.
Anchor	Determines if the decline to be run will be anchored on previous results if they exist in the project. To Anchor, previous results must be saved as Official (using Save) to the Petro.ai Engine and then pulled back into the DCA Wrangler via the Sync Button. Options: Latest Official, Models, or None Latest Official Anchor on Latest Official declines that have been synced with the project from Petro.ai. Models If other models have been brought into the project using the Sync button, the user can anchor on those models. None Do not Anchor on previous forecasts.
Minimum Production History Data Points	Set a minimum production history data points. Example: If the minimum is set to 3, any wells that have less than 3 production data points, the screen below will show.

Normalize Submenu

When creating and comparing type wells, it is important to normalize the production data against a common differing property associated with the well or its location. DCA Wrangler can normalize by linearly scaling individual well history based on a normalization column and value.

Fluid Limits Submenu

Fluid Limits are economic thresholds that will end a decline if the decline curve forecast moves outside of the specified range. 

IMPORTANT NOTE: TTD is Total To Date.

Type Curve Submenu

A type well is a pseudo-well that is usually created by averaging the production rate from many wells. Its intended use is to determine the production rate that can be expected from a new well(s) based on the performance of analogous wells. It may also be used as a benchmark to provide confidence in individual well forecasts for a group of similar wells. These use cases make Type Wells necessary for portfolio management, play inventory ranking, budgeting and forecasting processes, and business case analyses.

DCA Wrangler offers a Type Curve mode to create an average, P10, P50 and P90 type wells for a given group of wells. We use the following formula to create the average Type well for a given group of wells.

For additional information on RAI DCA Wrangler documentation, click here