Vivek Muralidharan Simulation and imaging experiments of fluid flow through a fracture surface: a new perspective

Log Analysis Fracture Characterization Aperture distribution Fracture Model Fractured Reservoirs Poor recovery Laboratory Experiments Simulation X-ray CT scanner

Presentation Outline Historical PerspectiveHistorical Perspective Objectives and ApproachObjectives and Approach ApplicationsApplications Conclusions

Fracture Model Historical perspective w Constant fracture aperture

Historical perspective Cubic Law Aperture Size

Parallel Plate Assumption w Single Fracture Aperture

Fracture Aperture Fracture roughness Better History Match Realistic simulation model

Fracture Aperture Distribution Fracture aperture distribution Pyrak-Nolte et al., (1987) Tsang et al., 1987 Gale, 1987 Keller, (1996) Lognormal distribution for natural fractures

Log-Normal Mean Log-Normal Deviation Variable ( Aperture ) Apertures distributed log-normally Lognormal Function

Generation of apertures

Smooth fracture surface Aperture Distribution

Slightly rough fracture surface

Highly rough surface fracture Aperture Distribution Larger Aperture Size

Problems Aperture distribution is proved for fractures without experiencing any stress. Aperture distribution has not yet been investigated under different stress condition. Single fracture aperture does not represent the actual flow through fracture

Presentation Outline Historical PerspectiveHistorical Perspective Objectives and ApproachObjectives and Approach ApplicationsApplications Conclusions

Objectives X-ray CT scanner Stress Aperture distribution? Aperture distribution has not yet been investigated under different stress condition. Problem:

Objectives X-ray CT scanner Gravity drainage experiment Single fracture aperture does not represent the actual flow through fracture Problem:

Aperture distribution under stress using X-ray CT scanner

Experiments in X- ray CT scannerApproach Scan Scans at multiple locations Calibration Aperture Distribution

X-ray CT Scanner CT scanner analyzes density differences between objects Matrix and fracture identification Density of rock Density of fluid in fracture

Pixel number CT number X-ray CT Scans Matrix Fracture CT numbers are different from actual aperture size Calibration Technique to correlate CT to obtain fracture aperture size No direct measurement of fracture aperture

Scanned the core between feeler gauges Calibration Procedure Smooth surface Feeler gauge of known size

Calibration Procedure Fracture Matrix

Min rock CT Calibration Procedure Integrated CT area

Calibration Curve Feeler gauge size

Calibration curve Integrated CT area Scans of fractured core of unknown apertures Fracture aperture

Calibration Curve Determination of fracture aperture

Aperture Distribution

Scans taken along the length of the core

Animation Apertures along the length of the core No stress 500 psi 1000 psi 1500 psi

Apertures 90 sections 70 locations Around 6000 sections Four different stress conditions apertures Apertures are calculated from calibration curve

Aperture Distribution without stress Lognormal distribution Mean = σ =

Aperture Distribution with stress Mean = , σ = Mean = , σ =

Aperture Distribution with stress Mean = , σ = Mean = , σ = Mean = , σ =

Aperture Distribution with stress Mean = , σ = Mean = , σ = Mean = , σ = Mean = , σ =

Aperture Distribution with stress Aperture distribution follows Lognormal distribution at all conditions

Highly rough surface fracture Larger Aperture Size Fracture apertures have to be distributed Lognormal Distribution

Presentation Outline Historical PerspectiveHistorical Perspective Objectives and ApproachObjectives and Approach ApplicationsApplications Conclusions

Experimental Procedure Unfractured Core pp Pressure Drop K m  q inj /  p Matrix Permeability q inj Injection rate 5 cc/min 500,1000, 1500

matrix fracture l Experimental Procedure Fractured Core  p avg Average Pressure Drop K avg  q inj /  p avg Average Permeability q inj Injection rate 5 cc/min

Analytical Equations

Fracture Permeability Area of fracture Matrix Permeability Area of matrix Average Permeability Total area of core

Analytical Equations Combining above equations to determine w w A d matrix fracture Fracture Permeability Cubic Law

Fracture Aperture

Fracture Permeability

Fracture Flowrate 500 Psi 1000 Psi 1500 Psi

Flow through fracture and matrix Flow through fracture

Flow through fracture and matrix Flow through fracture Flow through matrix

Modeling Laboratory Experiment Simulation model using aperture distribution

Simulation Model Model Description 10x10x15 grids Fracture in 8 th block in K dirn i j k

Injector Water Injection Producer - matrix Matrix Production rate Producer - fracture Fracture Production rate Water prod

Aperture distribution in fracture region Aperture distribution maps Lognormal Mean eff aperture variance 500 psi 1000 psi 1500 psi

Example flow on the distributed fracture surface

Flow Through Matrix and Fracture Flow through fracture Flow through matrix

Pressure drop

Objectives X-ray CT scanner Gravity drainage experiment

Approach Gravity Drainage Experiment

X-Ray Detector X-Ray Source Brine X-ray CT scan

Fluid flow pattern 0 min 12 min

Parallel Plate Experiment Simulation

Flow on a smooth fracture surface

Lognormal distribution Fluid flow using aperture distribution

Saturation Experiment Simulation

Presentation Outline Historical PerspectiveHistorical Perspective Objectives and ApproachObjectives and Approach ApplicationApplication Conclusions

Fluid flow experiments under stress Recap

Gravity drainage experiment

Conclusions Fracture Aperture Lognormal distribution Parallel plate assumption valid Distributed apertures Realistic flow behavior Better History Match

Acknowledgement Dr. D. S. Schechter, Texas A&M University Dr. Erwin Putra, Texas A&M University Mr. Dicman Alfred, Schlumberger Department of Energy (D.O.E) for sponsoring the project.

Thank You