1、Dynamic Gridding in STARSWhy Use Dynamic Gridding?Dynamic gridding allows you to model processes which require small grid blocks in limited, time dependent, regions in an optimal waySmall grid blocks are used when and where needed, and large blocks are used elsewhereThis can significantly reduce run

2、 timeRun times up to 10 x faster depending on processHow Does It Work?The user will set up the associated grid block size and what property will cause the dynamic changeThe simulator will then refine or amalgamate the grid based on this property changeAmalgamation or Derefinement?There are 2 Dynamic

3、 grid optionsDerefinement: Removes static refinement dynamicallyAmalgamation: Combines fundamental grid blocksDynamic Gridding ThresholdsThe user must give STARS a guideline of when to adjust the grid or notThis value can be one or two of the following:TemperatureSaturationPressure (for dilation)Glo

4、bal Mole FractionPhase Mole Fraction (Oil, Gas, Water)Fluid EnthalpyThis value is the maximum difference allowed within a group of blocks in order that they can amalgamate or derefine into a single blockThreshold Checking CommandsBesides the threshold you select you can choose the direction and freq

5、uency of checkingBy checking less frequently and only in selected directions you can speed up the simulation even more!Averaging TechniqueCombining grid blocks requires that the new block contains some representation of the properties of the fundamental blocksSTARS uses geometric averaging to combin

6、e block propertiesWARNING: It is important to pay attention to permeability averaging because no-flow barriers can be averaged into flowing blocks!Example*DYNAGRID AMALGAMATE *TEMPER 10 *INTO 5 1 3 *1:260 1:140 1:3*DYNAGIRD-TSINT 20 *DYNAGRID-IGN-DIR JDIRTuningIt is mended that tuning the dynamic gr

7、idding be done on a sub-model or cross-section so that sensitivity testing can be done quicklyAdjusting the threshold type & value, as well as the checking parameters and amalgamated block size, can drastically change the model speed and accuracy SAGD mendationsModeling SAGD effectively requires qui

8、te small grid blocks to model the steam front, while large blocks will suffice in the cold bitumen and inside the steam chamber It is important to adequately monitor the movement of the front while not spending too much simulation time doing so SAGD mendationsThreshold parameter TemperatureStart wit

9、h a value of 5-15 CTune to a value which does not deamalgamate too soon but does not accept too much energy before deamalgamatingChecking interval Start with every 10-20 time stepsIf time steps are large, decrease this; if small, increase thisUsually you can ignore the direction along the well as th

10、e heat transfer is mostly in the cross-section (gridding artifact?)Our 2-D SAGD CaseOriginal CaseRuntime: 64 minutesCase 1Temper 10, Tsint 10, Into 5,1,2Poor results (vertical flow boundaries are lost)Runtime: 39 minutesOur 2-D SAGD CaseCase 2Temper 10, Tsint 20, Into 8,1,1Near Identical ResultsRuntime 31 MinutesCase 3Temper 15, Tsint 40, Into 8,1,1Near Identical results to Case 2 but better speed upRuntime 24 Mi