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Day 2: Acidizing placement and diversion techniques Diversion, Pumping Schedule & Placement defini9ons Engineering a good matrix acid job the treatment effectiveness depends on getting the fluids where they’re supposed to go ! Diversion ‐ methods and materials to appropriately distribute fluids across the treatment interval ! Pumping Schedule ‐ injection method and rates to efficiently place fluids ! Placement ‐ calculated end effect of combining fluid stages, diversion and pumping on formation interval Placement and diversion ! Placement refers to the way the stimulation fluids are introduced in the well ! Diversion is about the ways to distribute the fluids across the target zone. Diversion, Pumping Schedule & Placement Purpose of Diversion ! Achieve uniform damage removal ! Distribute flow across the treated interval ! Alter flow path to prevent treatment fluids from being disproportionately injected into high‐ perm zones Placement and Diversion Diversion and placement philosophy ! The length of the interval to be treated. ! Whether it is more or less homogeneous. ! Do we want to steer away from water bearing intervals? ! What is the completion type; i.e.open hole, perforated casing, slotted liner, etc? ! Bottom hole temperature ! Wellbore deviation and ! Reservoir type and fluid Maximum Pump Rate Without Fracturing Diversion, Pumping Schedule & Placement 10000 Injectivity (m3/d/m) 1000 100 10 1 10 10 mD 100 mD dP (Bar) 100 1000 mD 10,000 mD Acid Placement in Heterogeneous Forma9ons High Skin Thief Zone Low Skin High Skin Thief Zone Low Skin Plain HCl < cp Emulsified HCl > 20 cp Example case for placement & Diversion zones of different permeability Example Well Bottom Hole Static Temperature: Drainage Radius: Kvertical/Khorizontal: Reservoir Pressure Gradient: Pressure at .: Calcite/Total Carbonate Ratio: HCl Solubility: Top Measured Depth: Bottom Measured Depth: Average Deviation: Average Pressure: Average Skin: Average Permeability: Effective Zone Height: Effective Top MD: Effective Bottom MD: 91 °C 1000.0 m 0.10 0.0705 bar/m 0.0 bar 41.18 % 85.00 % 3726.0 m 3765.0 m 65.5 ° 188.7 bar 16.32 87.2 md 28.5 m 3729.0 m 3764.0 m Emulsified acids Diversion, Pumping Schedule & Placement Types of Diverter ! Ball Sealers ! Particulates ! Gels and Gelled Acids ! Cross‐linked Gel Slugs ! Foams Foams ! Foam spacers between treatment stages (multi‐ stage process) or, ! Part or all of the treating acid as foam (one‐stage process) ! Foamed acids are more complex to use than polymer viscosified acids ! extra equipment and ! liquid nitrogen supply Diversion, Pumping Schedule & Placement Foam Diversion ! Viscosity for zonal coverage and fines recovery ! Energy for flowback in low pressure reservoirs ! When used for staged diversion, carrier fluid is typically not acid ! When used for continuous diversion, fluid is usually acid ! Note – dissolving power for the foam stages is dependent on the acid volume, not the total fluid volume Diversion, Pumping Schedule & Placement Foam Diversion (cont.) ! Can be used in both sands and carbonates ! Recently use in carbonate reservoirs has increased ! Initially used in gravel pack completions ! Can be used for most completions including gravel pack and slotted liner ! Significant advantages over particulates and balls in horizontal applications Diversion, Pumping Schedule & Placement Foam Diversion Design Considera9ons ! Permeability contrast ! Foam slug volume ! Tubing size ! Foam quality ! Injection rates ! Foaming agents Foamed acid high viscosity in water viscosity break after mixing with oil OilSeeker (Schlumberger) Divert acid away from water zone, into oil zone Some good case histories published Unspent acid Mixing with oil Spent acid Viscosity develops as acid spends spents Diversion with visco‐elas9c surfactants acid + visco-elastic surfactants plain acid wormholes in high k zone stage plain acid viscosity block stage stage next acid stage into low k zone ¥ acid is pumped through a jetting nozzle, improving acid-rock contact and wormhole initiation ¥ while acid is pumped through the CT, an inert fluid is pumped simultaneously through tubing-CT annulus, with the purpose to improve diversion and placement ¥ Patented tool is run on coiled tubing ¥ Unique design of the tool causes the tool to oscillate as fluid is pumped through the tool Ð Fluid can be acid, water, diesel, nitrified fluids, etc ¥ Near wellbore mud removal, screen cleaning Combines coiled tubing efficiency with fluidic oscillator technology Decision tree ... Placement ‐ calculated end effect of combining fluid stages, diversion and pumping on formation interval Placement and diversion ! Placement refers to the way the stimulation fluids are introduced in the well ! Diversion is about the ways to distribute the ... 85.00 % 3 726 .0 m 3765.0 m 65.5 ° 188.7 bar 16. 32 87 .2 md 28 .5 m 3 729 .0 m 3764.0 m Interval Reservoir Data Name! zone 1 zone 2 zone 3 zone 4 Top Bottom Meas. Meas. Depth Depth (m)! (m)! 3 726 .0... Alter flow path to prevent treatment fluids from being disproportionately injected into high‐ perm zones Placement and Diversion Diversion and placement philosophy ! The length of the interval to be treated. ! Whether it is more or less homogeneous.