ComboCurve: Operations

ComboCurve: Operations


See the Scenario Tooltip Overview Article for all assumptions and modeling concepts

In v42, we have introduced a new economic assumption: Operations. In this assumption we have added Curtailment (new functionality) and moved Shut-In from Risking to the new Operations assumption.  Curtailment allows users to model reductions in forecasted volumes and may extend the life of a forecast depending on economic cutoff selection. Technical EUR is preserved while modeling reservoir deliverability via mathematical adjustment of Arps inputs. 

How it works: Curtailment is applied using rate-versus-cumulative interpolation over the forecast.  1. Initialize the cumulative curtailed volume at zero.  2. At each time step, use the previous month’s cumulative curtailed volume to interpolate the original rate that corresponds to that cumulative point.  3. Check constraints. If the interpolated rate exceeds the user-defined curtailment limit, apply the constraint; otherwise, keep the original rate.  4. Add the resulting rate to the curtailed cumulative and proceed to the next time step.  5. With this methodology, the result will be a “curtailed” array of rates that sum to equal the original array of rates. (i.e. original cumulative = curtailed cumulative)
  1. Curtailment (Top Table)
    1. Ratio Stream Behavior (top of curtailment) - Curtailment will only be applied to "parent" rate streams but what happens to ratio streams while the parent stream is reduced?  Note: Only rate-based, forecasted volumes are directly curtailed. Dependent phases (e.g., NGL, drip condensate, and any ratio-forecasted phases) are recalculated from the curtailed parent phase volumes
      1. Default - Attempts so conserve ratio phase EUR by interpolating the ratio parameter at each cumulative volume (ie, partially or fully pauses the ratio time-series while the parent is manipulated)
      2. Legacy - Does not conserve ratio phase EUR; uses defined ratios and extrapolates to forecast end (ie, the time-series variable ratio runs as normal as if the parent were not manipulated)
        1. We recommend using this method for tie-out purposes with legacy software, or if the ratio forecast was constructed to honor time, regardless of base phase forecast volumes (i.e. at this date, my ratio parameter should always be X).  
    2. Key - Similar to other assumptions, this is the phase that is being affected by the Category. Users have the following options:
      1. Oil
      2. Gas
      3. Water
      4. Company Custom Streams
      5. Project Custom Streams
    3. Category - This is the action that is being performed on the Key. Currently, only Curtailment is allowed in the top table of Operations. However, it is very likely other functionalities will be added to the Category dropdown in the future.
    4. Criteria and Period - Like other assumptions, Criteria and Period allows users to determine how the model affects economics through time. Depending on the Key/Category used, the Criteria options might differ. Additionally, depending on the Criteria selection, the entry Syntax for Period will change. Users have the following selections for all: Key/Category pairs:
      1. Flat
      2. FPD
      3. As Of
      4. Dates
      5. Seasonal
      6. Unit - Across all the economic assumptions, unit allows for a variety of things. In the case of the top table of Operations, it allows users to specify the subcategory of the action performed by the Category. In the case of Curtailment, it allows users to specify either a max rate based curtailment or a percentage-based curtailment (remaining percent of total capacity). 
        1. BBL/D, MCF/D, or Unit/D
        2. %
    5. Stream Type - This is the difference between the Operations assumption and the other ComboCurve economic assumptions. By default, the “Stream Type” column will be unviewable on the top Operations table. Users can enable it by selecting “Columns” on the side menu and checking it on. This column allows the user to designate the type of stream (key) that you are applying the Category to. However, since this will be auto populated based on Key selection, most of the time users will not need to worry about this column. Users might want to enable this column if they are copying and pasting from Excel.
Note for ARIES imports/exports: Currently, specifying a “TO LIFE” keyword for CUR in ARIES, will curtail the phase to the end of the original forecast end date. In ComboCurve, “Flat” or the last line of time series, always occurs until ECL. Additionally, ARIES help file recommends using 100 YRS to model to ECL in the CUR line obviate the truncation. If using the legacy method, it is recommended to directly specify the end date of curtailment until updates are made to account for this difference in behavior.  Imports and exports to ARIES will take this behavior into account for the 2 methods.

Percentage Curtailment (Pipeline Capacity Scenario)
This example is modeling a 50% curtailment from 1/1/2023 to 12/31/2023. It follows the general shape of the original curve but at a lower rate and then shifts to 100% on 1/1/2024. At the shift, it is now interpolating at a higher rate because the cumulative volume is lower compared to the original curve at the same point in time. As a result, the curtailed volumes are effectively added onto the whole curve mathematically for each and every time period onward.

Max Rate Curtailment (Facilities Maximum Constraint)

This example is modeling a flat 20 BBL/D curtailment on oil. As we curtail the volumes, the curve is “shifted” forward in time (later in time). In July 2024, we see the curve drops below the constrained rate and begins an interpolated decline generated from the cum-capacity array. 

SHUT-IN - Bottom Section
In general, shut-ins can be thought of as 0% curtailments over the user specified time period. If there are no curtailments applied, shut-in will work as it always has. However, if both a shut-in and curtailment is used, there are some important behaviors that must be noted.  See the v42.0 release notes for a detailed explanation.
  1. Insert Shut-in Period - Scenario method to SI a well temporarily for adjustment.  This is in addition to any SI Period used in the forecasting module.
    1. Shut-in periods can be scheduled for one or all product phases in a well to account for known upcoming or averaged unknown events.  Scheduling a shut-in will cause production to cease for a period and return to the next scheduled production rate after that period expires.
      1. As Of: Starting # days from the As Of date to # days from the As Of date. (ie, As Of plus 100 days to 200 days)
      2. Dates: Begin date of shut-in to end date of shut-in.
    2. Scale Post Shut-in can be used to return the well at a reduced or enhanced production rate and percentage of remaining reserves from that point. (ie, for a well making 1 MMcf/d with remaining reserves of 1 bcf, a scale factor of 0.5 applied would return the well at 0.5 MMcf/d and 0.5 Bcf reserves.  However, economic cutoff might then further reduce reserves.)
      1. Scale Post Shut-In End Criteria - The point at which to stop reflecting that scalar and return to the default: 1
      2. Fixed Expenses and CAPEX defaults are “Yes” and allow scheduled charges to occur during the shut-in period.  Per unit production charges such as variable expenses and production tax (%) will not be applied during the shut-in period.
    3. Note: NO LONGER RECOMMENDED since robust curtailment is modeled above but historically: Shut-in Period can be used to model curtailment.  If you enter one day SI per month and repeat, this works similarly to preserve EUR by truncating the forecast at that point and picking up at the next scheduled production point at the end of the SI period.  So this would be a quanta of 1/30.4375 (3.29% Curtailment) for each repeated day per month (on average as it would change by the number of days in each month).  Increase the number of days each month to scale the curtailment.  Note that using this method will sometimes slow economic calculation speed.  Full curtailment support is planned for a future release.
    4. Note: Interaction with any cutoff method selected in the dates tab may affect total remaining reserves.
    5. Note: Care should be taken not to cross months/years using the repeater in such a way as to create an illogical or inconsistent condition.  Some validation exists to avoid this.  For example: having a SI from 1/1 to 3/1 and repeating monthly is illogical as is a SI from 2/20 to 3/4 and repeating monthly.
Considerations:
- Has Advanced View (no Standard View)
 - Does not yet support custom streams on SI Period (except for "All" which covers Custom ALL streams including custom streams).

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