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Study of Waterflooding Process in Naturally Fractured Reservoirs from Static and Dynamic Imbibition Experiments E. Putra, Y. Fidra and D.S. Schechter SCA9910

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Outline Introduction Static Imbibition Dynamic Imbibition Conclusions Objectives

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Static imbibition Dynamic imbibition Field dimension Determine rock wettability Upscaling Determine laboratory critical injection rate Fracture Capillary Number Scaling equations Capillary pressure curve Capillary pressure curve Introduction

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Objectives To investigate wettability of Spraberry Trend Area at reservoir conditions. To investigate the contribution of the capillary imbibition mechanism to waterflood recovery. To determine the critical water injection rate during dynamic imbibition.

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Experimental Set-up for Static Imbibition Tests at Ambient Conditions

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Experimental Set-up for Static Imbibition Tests at Reservoir Conditions

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Effect of Pressure and Temperature on Static Imbibition in Berea Sandstone

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Effect of Temperature on Static Imbibition with Spraberry Reservoir Rock

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Displacement A B Static imbibition Wettability index vs aging time for different experimental temperatures Spraberry cores

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C = 10.66 ; Scaling Equations for Static Imbibition

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Up-scaled Recovery Profile L s = 3.79 ft h = 10 ft 1U Upper Spraberry 1U Formation (Shackelford-1-38A)

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Effect of Matrix Permeability and Fracture Spacing on Oil Recovery

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Static Imbibition Modeling Brine Core plug Glass funnel Oil bubble Oil recovered Governing Equation No gravity effect Only Pc as driving force Fluid and rock are incompressible Assumptions

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Capillary Pressure Curves Obtained as a Result of Matching Experimental Data Static Imbibition Modeling Match between Laboratory Experiment and Numerical Solution for S or = 0.2

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Water Oil Invaded Zone Matrix Fracture Matrix Counter-current Exchange Mechanism Concept of Dynamic Imbibition Process

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Matrix Fracture Artificially fractured core Air Bath Core holder Brine tank Confining pressure gauge Graduated cylinder N 2 Tank (2000 psi) Ruska Pump Experimental Set-up for Dynamic Imbibition Tests at Reservoir Temperature

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Oil Recovery from Fractured Berea and Spraberry Cores during Water Injection using Different Injection Rates

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Comparison between Static and Dynamic imbibitions for Berea Core, Spraberry Brine and Crude Oil

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Dynamic Imbibition Modeling Rectangular grid block with grid size : 10 x 10 x 3 (Berea) ; z = 9 layers for Spraberry Single porosity, 2 phase and 3-D Fracture layer between the matrix layers Inject into the fracture layer Alter matrix capillary pressure only to match the experimental data zero P c for fracture straight line for k rw and k ro fracture use k rw and k ro matrix from the following equations (Berea core):

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Match Between Experiment al Data and Numerical Solution Berea Core Spraberry Core Cumulative water production vs. time Cumulative oil production vs. time Cumulative water production vs. time Cumulative oil production vs. time

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Capillary Pressure Curves Obtained by Matching Experimental Data (Berea and Spraberry Cores)

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Dimensionless Fracture Capillary Number Lab Units: Field Units: AmAm w dz AfAf Capillary force ( cos A m ) Viscous force (v w A f ) h

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Injection Rate versus Oil-cut

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Upscaling of Critical Injection Rate

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Conclusions The capillary pressure curve and wettability index obtained from spontaneous imbibition experiments indicate the Spraberry cores are weakly water-wet. Effect of pressure is much less important than the effect of temperature on imbibition rate and recovery. Performing the imbibition tests at higher temperature results in faster imbibition rate and higher recovery due to change in mobility of fluids.

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An effective capillary pressure curve can be derived from dynamic imbibition experiments as a result of matching between experimental data and numerical solution. Imbibition transfer is more effective for low injection rates due to lower viscous forces and longer time to contact the matrix. The capillary pressure curve obtained from dynamic imbibition experiments is higher that of the static imbibition experiments due to viscous forces during the dynamic process. Conclusions (Conted)