HISTORY_DATA

HISTORY_DATA is used to do history matching analysis. History matching is the process of adjusting a reservoir model to closely match the behaviour of the reservoir with the observed historical data. Pressure and production need to be reproduced, as well as possible, by the reservoir model.

During the sensitivity analysis, it is important to be able to easily compare historical data against model predictions. For example, the user may control the injection rate of a well and check if its pressure profile matches the historical data.

The HISTORY_DATA block is used to set up historical values of production or injection wells in the model. It is the native set of keywords to do history matching in PFLOTRAN-OGS (Note that it can also be done through ESCHED -WCONINJH and WCONHIST- , although only one of the two history matching approaches can be used per simulation).

In HISTORY_DATA, the data is introduced using tables with two headers, a mnemonic and the corresponding unit. In this way, a prior ordering of the table is not required by the user and the introduced data is automatically converted to internal units. HISTORY_DATA can be used to impose a well target (one target only). In the output, new fields ending with “H” will be added accounting for the historical values (for example, from WBHP we would now have also WBHPH). All the input data in the tables is output in the summary file so the user can cross-compare with the results obtained by the current simulation and the historical data introduced. Below there is an example of a HISTORY_DATA block and setting up a historical target for a well:

WELL_DATA well1
  WELL_TYPE PRODUCER
  CIJK 10 10 1 1
  USE_HIST_TARG OSV
END

This could reference a well history table of the form:

HISTORY_DATA
  WELL_NAME well1
  STEP_MATCH
    DATE            BHP     WOPR    WWPR    WGPT
    dd/mmm/yyyy     bar     m^3/d   bbl/d   Mcf
    01/Jan/2000     68.9476 3179.7  100     0
    01/Feb/2000     100     5000.5  120     3100
    01/Mar/2000     100     5000.5  120     6290
  END
END

or equally using TIME:

HISTORY_DATA
  WELL_NAME well1
  STEP_MATCH
    TIME            BHP     WOPR    WWPR    WGPT
    day             bar     m^3/d   bbl/d   Mcf
    0               68.9476 3179.7  100     0
    31              100     5000.5  120     3100
    60              100     5000.5  120     6290
  END
END

The input data describes the following:

  • The well well1 is of type producer, with a target defined by the historical data of the oil column.

  • STEP_MATCH: This keyword, ensures that the simulator has to honour the time-periods defined in the table.

  • DATE: Times in the format of days/month/year (using abbreviation of the month), when historical data change value.

  • TIME: Times in days, from the start of the simulation time, when historical data change value.

Regarding the table data, WOPR is the well historical oil production rate imposed as a target with USE_HIST_TARG OSV, while WWPR, WGPT and BHP are the water rate, total gas production and the bottom hole pressure historical data to match. Also, since oil and water rates are provided, the Liquid rate will be computed internally and can be used as a target. Finally, note that different unit systems have been used for the different rates/totals.

The options and characteristics supported by HISTORY_DATA are listed below:

WELL_NAME

This keyword has to be included before any tabulated data and must be followed by the name of the well the historical data refers to. Example:

WELL_NAME prod1

STEP_MATCH

By default the simulator time steps will not necessarily match the times defined in the history data. If the user wants an exact match with the times provided in the table, the keyword STEP_MATCH should be used.

Mnemonics header

Each mnemonic defines the data that its column is going to have. Accepted mnemonics and structure is as follows:

  • TIME or DATE: times can be described either using time from the start of the simulation using the keyword TIME or using a date with the keyword DATE.

    • TIME (time units): times can be introduced as elapsed time from the beginning of the simulation.

    • DATE: The format of the date has to be consistent with units defined in the header.

      • dd/mm/yyyy: days, months and years are introduced using numerical values.

      • dd/mmm/yyyy: days and years are introduced using numerical values, while the month is introduced using an abbreviation of the name of the month, e.g. JAN, FEB, MAR, …

    The separators need to be consistent but can be anything that is one single character width (excluding spaces). For example “/”, “.” or “-”. A row is active until the next DATE or TIME is reached by the simulator time.

  • BHP (pressure units): history data for the bottom hole pressure.

  • Rates ([volume or mass]/time) and Total (volume or mass): production and injection history data can be introduced using the following mnemonics:

WOPR

Oil production volume rate at surface conditions

WOPT

Oil production volume total at surface conditions

WGPR

Gas production volume rate at surface conditions

WGPT

Gas production volume total at surface conditions

WWPR

Water production volume rate at surface conditions

WWPT

Water production volume total at surface conditions

WLPR

Liquid production volume rate at surface conditions

WLPT

Liquid production volume total at surface conditions

WSPR

Solvent production volume rate at surface conditions

WSPT

Solvent production volume total at surface conditions

WOPRM

Oil production mass rate

WOPTM

Oil production mass total

WWPRM

Water production mass rate

WWPTM

Water production mass total

WGPRM

Gas production mass rate

WGPTM

Gas production mass total

WSPRM

Solvent production mass rate

WSPTM

lvent production mass total

WWIR

Water injection volume rate at surface conditions

WWIT

Water injection volume total at surface conditions

WGIR

Gas injection volume rate at surface conditions

WGIT

Gas injection volume total at surface conditions

WSIR

Solvent injection volume rate at surface conditions

WSIT

Solvent injection volume total at surface conditions

WWIRM

Water injection mass rate

WWITM

Water injection mass total

WGIRM

Gas injection mass rate

WGITM

Gas injection mass total

WSIRM

Solvent injection mass rate

WSITM

Solvent injection mass total

Rates and totals differences

For a given entry, either a total or a rate can be introduced. If both are introduced, although consistent, the simulator will throw an error. The main differences between using rates and totals are:

  • Rates are active from the start of the time/date provided.

  • If rates of oil and water are provided the liquid rate is calculated internally and can be used as a target.

  • Totals are considered until the time/date provided.

For example, the input below is equivalent to the example provided at the top of this section (final time is 01/Mar/2000 and 2000 is a leap year):

HISTORY_DATA
  WELL_NAME well1
  STEP_MATCH
    DATE            BHP     WOPR    WWPR    WGPR
    dd/mmm/yyyy     bar     m^3/d   bbl/d   Mcf/day
    01/Jan/2000     68.9476 3179.7  100     100
    01/Feb/2000     100     5000.5  120     110
  END
END

In this case we have provided historical gas production using WGPR instead of totals, and therefore, we do not need to provide the final total.

Input units

Both metric and field unit systems can be used to introduce data into HISTORY_DATA (See Units and Conventions for accepted units). The units need to be defined per column, so defining in the same table a rate of gas using m^3/d and a rate of water using bbl/y is accepted.

USE_HIST_TARG

Historical data can be used to specify the target for a well. When using historical data as well target, only one target can be specified for the well. The target is selected in the section WELL_DATA using the keyword USE_HIST_TARG. Below an example of using a historical BHP as target for an injector well:

WELL_DATA well1
  WELL_TYPE INJECTOR
  CIJK 1 1 1 1
  USE_HIST_TARG BHP
END