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Simulation of Polymer Gel Injection Well Treatments Chuck Norman Tiorco, Inc. Tiorco de Argentina
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Agenda ► Flood-Out Waterflood Model Input Model Process Information Generated by the Waterflood Model ► Flood-Out Polymer Gel model Dykstra-Parsons Theory Information generated by the Gel Model Forecasts with the Gel Model (Examples)
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ABILITY TO CONTROL LAYER PROPERTIES ACCORDING TO IN-SITU CHEMICAL CONCENTRATIONS: 1.RESERVOIR (TOTAL) 2.ADSORBED (IMMOBILE) 3.MOBILE (PRODUCIBLE)
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What data entry is required? MANDATORY – PVT & reservoir data
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What data entry is required? MANDATORY – model layers NOTE: MORE LAYERS RESULT IN IMPROVED FORECASTING RESOLUTION AS EACH LAYER CONTRIBUTES ONE “POINT” IN THE TYPE-CURVE
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What data entry is required? MANDATORY – production profiles
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What data entry is required? OPTIONAL – log layers
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The flood-out Process 01 Import fine resolution log data and define coarse model layers - 02 Create coarse model layers -
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The flood-out Process 03 Generate forward model pseudo-relative permeability - 04 Generate forward model fractional flow -
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The flood-out Process 05 Generate the forward model production type-curve - 06 View the first-pass water-cut history match (match needs improvement) - First-pass: Poor history match!
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The flood-out Process 07 Generate reverse model fractional flow - 08 Generate reverse model pseudo-relative permeability -
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The flood-out Process 09 Generate the reverse model “Eglew” layers -
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The flood-out Process 11 Generate a new forward model fractional flow - 12 Generate a new forward model production type-curve - 10 Generate a new forward model pseudo-relative permeability -
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The flood-out Process 13 An improved water-cut history match results from importation of the reverse model into the forward model - 14 An optimised production and injection forecast can now be generated within system’s constraints -
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The flood-out Process 15 Create a flood-out slide show and generate synthetic logs - 16 forecast production and injection by multi-cell material balance -
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Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modeling DYKSTRA-PARSONS’ THEORY: (a) is applicable for all mobility ratios (b) assumes layers flood-out in flow- velocity order (c) layer cross-flow does not occur
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Polymer Flood Model: How does it work? Dykstra-Parsons’ theory is employed to accomplish the following (at each time step) for a user-specified set of Model Layers: 1. Determine relative flood-frontal advancement for each layer 2. Generate a type-curve (Oil Recovery Factor versus Water-cut), which is interpolated by the forecasting optimiser 3. Once polymer is introduced, layer permeability is altered according to resistance factor expressed as a function of in-situ (i.e. reservoir) polymer concentration (ppm) 4. Highly-permeable layers accept larger water injection volumes, and consequently polymer concentration builds-up preferentially in these layers. This stabilises the flood, or invokes profile conformance.
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Dykstra-Parsons’ Water Flood Theory adapted to Chemical Flood Modelling A spreadsheet employing non-linear regression automatically finds a cubic polynomial of best- fit to tabulated data HOW DOES IT WORK? High K Layers build-up the highest polymer concentration, which alters layer flow-velocity order and invokes profile conformance. Note: THIS CURVE APPLIES FOR A FIXED INJECTION RATE IN-SITU POLYMER CONCENTRAION RESISTANCE FACTOR
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Polymer Gel Model Output and Forecasts
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In this example, polymer is injected over a three month period: Month1 – 500 ppm Month2 – 1000 ppm Month3 – 1500 ppm in-situ or reservoir polymer concentration produced polymer concentration Re-commence “pure” water injection adsorbed polymer concentration
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Produced polymer concentration – high permeability layers are produced preferentially in-situ or reservoir polymer concentration Polymer injection “flag” adsorbed polymer concentration Zoomed view of “production side” NOTE that the adsorbed polymer concentration dilutes once “pure” water injection re- commences
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Produced water rate decreases due to polymer injection Oil rate increases due to polymer injection Production response to the polymer flood Actual Water Injection Rate (AWIR) is optional User input
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Once polymer injection ceases, displaced by “pure” water injection, the resistance factor decreases. Adsorbed polymer is entrapped in order to model residual resistance. Resistance Factor > Re-commence “pure” water injection
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Average Permeability changes with in-situ polymer concentration Re-commence “pure” water injection
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Maximum permeability of all model layers Average permeability and standard deviation of model layer permeability NOTE: standard deviation of K is a measure of profile conformance, enhanced by the injection of polymer (i.e. Std Dev. decreases once polymer is introduced)
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Commence polymer injection Mobility Ratio “M” decreases as the flood front stabilises Mobility Ratio “M” increases as the in-situ polymer concentration dilutes (i.e. post-polymer flood)
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WOR: water flood (base case – left) versus polymer flood (right) “BEFORE” AND “AFTER” PRODUCTION PERFORMANCE - Reduced WOR due to polymer injection Base Case Water-flood
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Oil Rate: water flood (base case – left) versus polymer flood (right) “BEFORE” AND “AFTER” PRODUCTION PERFORMANCE - Oil rate uplift due to polymer injection Base Case Water-flood
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The Polymer Flood Model allows the User to track the performance of any Model Layer – here and in the following slides layer # 20 performance is shown. Dykstra-Parsons relative layer water flood penetration distance (versus time) for layer # 20 Layer # 20 100% flooded
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Produced polymer concentration in-situ or reservoir polymer concentration Polymer injection “flag” adsorbed polymer concentration Polymer production (at the producing well) only commences once the layer has 100% flooded (according to Dykstra- Parsons’ Theory) – prior to layer-by-layer water breakthrough each layer produces clean oil into the producing well.
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Layer # 20 Oil Rate increases as the model allocates more Water Injection to layer # 20 (i.e. following the commencement of polymer injection) Layer # 20 100% flooded Water breakthrough at producer for layer # 20
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Once polymer injection ceases, displaced by “pure” water injection, the resistance factor decreases. Adsorbed polymer is entrapped in order to model residual resistance. Layer # 20 Resistance Factor > Re-commence “pure” water injection
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Layer # 20 Permeability changes with in-situ polymer concentration Re-commence “pure” water injection
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Simulation of Polymer Gel Injection Well Treatments Chuck Norman Tiorco, Inc. Tiorco de Argentina
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