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Buenos Aires, 7 al 10 de agosto de 2012 OPTIMIZING DEFOAMER USAGE IN DRILLING & CEMENTING APPLICATIONS: TECHNOLOGY REVIEW & TESTING METHODOLOGIES Luciana Bava, Amir Mahmoudkhani, Robert Wilson, Leanne Levy, Patricia De Palma and Henry Masias Atlanta R&D Center, Atlanta, Georgia, USA

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Foam is a colloidal dispersion of gas in a liquid or a solid. Pure liquids do not foam Tap water, in spite of being aerated, does not foam Bubbles collapse immediately on the surface To generate foam, it is necessary to have a surface active component that stabilize the inclusion of dissolved and entrained gasses. 2 Foam Generation

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Water-based Drilling Muds Cement Slurries Foam Drillings / Cementing Aqueous Systems Oil & Gas Separators Oil-based Drilling Muds Non-aqueous Systems Examples of foaming/defoaming systems in upstream Oil & Gas industry under dynamic fluid conditions Foaming/Defoaming Systems

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Cement Well Completion

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Most common additives used to modify the behavior of drilling and cement systems are surface active molecules that cause the working fluid to foam during mixing Such additives include: Cement: retarders, dispersants, fluid loss control additives, gas migration control agents and ductility improvement additives. Water base drilling muds: salinity chemicals, dispersants, lost circulation materials and gelling agents and viscosifiers Drilling and Cementing Additives Cement G + Gas Migration Additive Blend, 1800 i kg/m 3 - without defoamer (left), with defoamer (right)

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Excessive slurry foaming can have several undesirable consequences: Loss of hydraulic pressure during pumping can occur owing to cavitation in the mixing system Air entrainment may cause higher than desired slurry densities Air entrainment also increases the risk of gas permeability and of improper wetting and mixing Liquid or Dry Defoamers are used Foam in Drilling and Cementing Operations

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Recirculating Centrifugal Pumps (max 4000 L /min) Slurry Tubs: 1000 8000 L Well Cementing Cement Mixing

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Cement Slurry Solids + Liquids Liquids Mix: Water + Water-Soluble Additives Solids Mix: Cement + Solid Additives Liquid Defoamers Dry Defoamers Foam Generation

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Performance Evaluation Methods

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A B Time Sparge Foam Test Blender Foam Test Simple & inexpensive Good for initial screening Measurements based on foam height May not accurately represent system under study (A vs. B) Single point data Single shear rates and fix mixing time Difficulty in replicating field conditions Non-Systematic Testing Methods Foam Height

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Modified Blender Test Mahmoudkhani et al., An Innovative Approach for Laboratory Evaluation of Defoamers for Oilfield Cementing Applications, SPE 143825, Brasil Offshore Conference and Exhibition, Brazil, June 2011

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P DFM Variable Rate Pump Density & Flow Meter Temp Controller Foam Cell Data Recording Drain Ancillary Gas 12 Foam and Entrained Air Test (FEAT)

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Data collected every 0.5 second At precision of 0.00005 g/mL Data collected every 0.5 second At precision of 0.00005 g/mL Fluid composition may be altered by addition of chemical components at any point during the test Foam and Entrained Air Test (FEAT)

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Cement Slurry Solids+Liquids Liquids Mix: Water + Water-Soluble Additives Solids Mix: Cement + Additives Defoamer performance FEAT Study Blender Test This comprehensive study approach (FEAT + Blender) is needed for proper laboratory validation and qualification under simulated field conditions (accounting for different dosage practices, additives, mixing regimes, etc.)

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Performance Evaluation: Defoamer Chemistry & Cement Additives

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Dispersant-Salt System FEAT analysis of silicone and non-silicone chemistries on 4% sodium polynaphthalenesulfonate + 30% salt solution.

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Dispersant-Salt System Blender foam test data in the dispersant-salt system, 4% sodium polynaphthalenesulfonate + 30% salt solution. All defoamers are dosed at 0.20% BWOC (by weight of cement)

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Latex System FEAT analysis of silicone and non-silicone chemistries on latex solution. Silicone A Blank Non-Silicone D

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Latex System Blender foam test data in latex system. All defoamers are dosed at 0.20% BWOC (by weight of cement)

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PVA (fluid loss additive) System Blender foam test data in latex system. All defoamers are dosed at 0.20% BWOC (by weight of cement)

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Dry vs. Liquid Defoamers Cement Slurry Solids + Liquids Mixing Liquids: Water + Water-Soluble Additives Mixing Solids: Cement + Additives Liquid Defoamers Dry Defoamers Dry Defoamers are prefer for better stability, ease of handling and storage Dry Defoamers are suitable for harsh climate areas Cannot be used as trimmer, a second (and liquid) defoamer is required

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Improved / Fast Release Dry Defoamers Conventional Dry Defoamers (silica) Improved / Fast Release Dry Defoamers High Surface Area Solids AdsorptionRelease High adsorptionSlow / incomplete release Substrate Defoamer

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Fast Release vs. Conventional Dry Defoamers Fast Release Dry Defoamers: Outperform conventional Dry Defoamers with a performance level comparable to Liquid Defoamers Reach maximum performance at lower dosages Fast Release Dry Defoamers: Outperform conventional Dry Defoamers with a performance level comparable to Liquid Defoamers Reach maximum performance at lower dosages FR Dry: fast release dry defoamer Dry: conventional dry defoamers Liq: liquid defoamer FR Dry: fast release dry defoamer Dry: conventional dry defoamers Liq: liquid defoamer

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1. What cause foaming? Additives: Dispersants, Salt, PVA, Latex, etc. 2. Where foaming is created? 3. Test Methods Blender (static, single point data) FEAT (dynamic / multipoint data) Summary 1: Foam Generation and Testing

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Summary 2: Choice of Defoaming Chemistry

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Summary 3: Form of Defoamer (Liquid, Conventional Dry or Fast Release)

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Thank you luciana.bava@kemira.com patricia.depalma@kemira.com