Empirical Factors Leading to a Good Fractured Reservoir Early recognition of fractures High fracture intensity & good connections Good interaction between fracture & matrix High reservoir energy Low water influx If deep or fine grained, partial mineralization along fractures

Exploration & Development Drilling Score Card Picking optimum well locations - Good Picking optimum drilling directions - Great Assigning reservoir properties –Rates - Good –Volumes - Poor –Cross flow - Poor

E & D Drilling Score Card (cont.) Determining drainage area - Fair Predicting well & reservoir response –Recovery - Poor –Longevity - Poor –Well history - Fair Assigning risk & economic success rate - Poor to Fair

Modern Approaches are Based On: New quantitative techniques in fracture characterization Multidisciplinary & integrated analyses More available reservoir simulation Better use of directional & horizontal drilling techniques More in-depth use of Risk Analysis

General Outline 1.Introduction 2.Fracture Origin 3.Fracture Morphology 4.Fracture Porosity 5.Fracture Permeability 6.F/M Interaction 7.Fracture Intensity 8.Intensity Prediction 9. Orientations 10. Reservoir Types 11. Well Directions 12. Simulation 13. Fracture Reservoir Production 14. Reservoir Screening 15. Summary (Field Examples)

Summary 6 phase approach to study of fractured reservoirs. Build from rock data first. Geophysical and rock mech. data can be used to highlight sweet spots. Reservoir prop. in fractures are different than matrix. Res. Mgmt. Strategies are very important.

Summary (cont.) Future advances will include upscaling fracture descriptions for reservoir simulation and defining connectedness in natural fracture systems. Because we can better quantify fractured reservoirs and predict their properties we should no longer fear or avoid them.

Apply Screening Tools Gather Fracture Distribution Data (Static Data) Interpret Fracture System Origin & Apply Distribution Models (Static Data) Gather Reservoir Property Data for Matrix & Fractures (Static Data) Gather Fluid & Pressure Data (Dynamic Data) Determine Fracture/ Matrix Interaction Measure or Infer In Situ Stress Field Create Dynamic Conceptual Model Create Static Conceptual Model Determine Fractured Reservoir Type Estimate Resources, Reserves, Rates Define Inhomogeneity, Anisotropy & Shape Factor Develop Integrated Static & Dynamic Reservoir Description for Simulation History Match to Wells & Tests and Iterate Select Optimum Well Locations & Well Paths Develop Depletion Scheme and Reservoir Management Strategies Monitor Field Performance and Adjust Obtain Subsurface Flow & Test Data (Dynamic Data) Economic? Restudy? Sanction? Is this a Fractured Reservoir? R.A. Nelson 9/00 Decision Steps, Critical Modeling Steps