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Expressions

The variables needed in the energy functions for the variable consumers, may not always be directly found in the reservoir inputs. For example, there may be two group rates that should be added to be consistent with the net rate through a compressor system. Or, it may be that a pressure defined in a network node is not equal to the pressure at the inlet/outlet of a compressor system and some delta pressure must be added.

To avoid forcing the users to define new variables in the simulation files/CSV data and also keep the data in the consumer’s energy function consistent, the calculator supports expressions to define variables (and conditions in the CONDITIONS.

warning

When creating new variables from CSV files make sure to choose the right interpolation type! See INTERPOLATION_TYPE for more information.

Available operators​

As reservoir simulation vectors (and also CSV headers) may include mathematical operators like +, - in their names, the operators must be surrounded by curly brackets, {}, in the expressions. Logical operators (>, >=, <, <=, ==, !=) evaluates to 0 or 1.

The following operators are supported:

OperatorDescriptionExample
{+}Addition2 {+} 1
{-}SubtractionSIM;GAS {-} 10
{*}MultiplicationSIM;GAS {*} 2
{/}DivisionSIM;GAS {/} 2
{^}PowerSIM;GAS {^} 2
( )Parentheses( SIM;GAS {+} 2 ) {/} 2
<Less thanSIM;GAS {+} (SIM1;OIL < 150) {*} 1000000
<=Less than or equalSIM;GAS {+} (SIM1;OIL <= 150) {*} 1000000
>Greater thanSIM;GAS {+} (SIM1;OIL > 150) {*} 1000000
>=Greater than or equalSIM;GAS {+} (SIM1;OIL >= 150) {*} 1000000
==EqualSIM;GAS {+} (SIM;FLAG == 1) {*} 1000000
!=Not equalSIM;GAS {-} (SIM;FLAG != 1) {*} 1000000

Examples​

Combining data from different reservoir inputs​

The rate through a gas injection compressor is the sum of injection rate for the field plus some additional injection rate for a tie-in (whose data is specified in a CSV file with key SIM2):

VARIABLES:
  total_rate_through_compressor:
    VALUE: SIM1;GAS_INJ {+} SIM2;GAS_INJ

Model of additional rate​

The rate through a compressor is the produced rate plus some additional term. This term Q is a function of pressures P1P_{1} and P2P_{2},

Q=25000⋅P1⋅(P2−P1)Q = 25000 \cdot \sqrt{P_{1} \cdot \left( P_{2} - P_{1} \right)}

The addition is only added when the reservoir gas rate is positive.

VARIABLES:
  rate:
    VALUE: SIM;GAS_PROD {+} ( SIM;GAS_PROD > 0 ) {*} 25000 {*} ( SIM;P1 {*} ( SIM;P2 {-} SIM;P1 ) ) {^} 0.5