Geologic Analysis of Naturally Geologic Analysis of Naturally Fractured ReservoirsFractured Reservoirs

22ndnd Edition, R.A. Nelson (2001) Edition, R.A. Nelson (2001)

Gulf Professional Publishing

a subsidiary of

Butterworth-Heinemann, Boston, MA

Geologic Analysis of Naturally Geologic Analysis of Naturally Fractured ReservoirsFractured Reservoirs

22ndnd Edition, R.A. Nelson (2001) Edition, R.A. Nelson (2001)

• The following contains renditions of the figures included within the book as well as additional figures used by the author to teach industry courses on the subject.

• Also included is Appendix D of the book.

Ronald A. Nelson

Discipline Structural Geology & Rock Mechanics

Location BP Amoco, Upstream Technology, Geology Team, Houston

History 26 years with BP Amoco as

Specialist & Manager

Education BS (Northern Illinois), MS, PhD

(Texas A&M) all in Geology

Skills Fractured Reservoirs, Technology

Management, Peer Assists,

Recruiting, Structural Interpretation

in Thrust Belts and Rifts

Publications 75 citations; including a textbook

“Geologic Analysis of Naturally

Fractured Reservoirs” eds. 1&2.

Liesegang Liesegang Banding in Banding in Aztec Ss,Aztec Ss, NevadaNevada

Work Builds On:Work Builds On:

• Nelson, R. A., 1985, Geological Analysis of Naturally Fractured Reservoirs: Contributions in Petroleum Geology & Engineering, Gulf Publishing Co., Houston, TX, 320 p.

• Material presented in the AAPG Fractured Reservoir Analysis School, 1984-1996.

Courtesy of Gulf Professional Publishing, Boston

General OutlineGeneral Outline1. 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)

Reasons Why We Look at Reasons Why We Look at Natural FracturesNatural Fractures

• Delineate Structure• Determine Mode & Path of Deformation• Define Mechanics of Fracture• Determine Paleo-stress Directions• Determine Velocity Anisotropy• Determine Mechanical Anisotropy• Predict Reservoir Properties & Potential

Total Integration Includes:Total Integration Includes:

• Fracture system characterization

• Stratigraphic interpretation & modeling

• Structural geology

• Petrophysics

• Seismic mapping & attribute analysis

• Well testing, inc. production logs

• Production history matching

• Reservoir engineering, inc. dual porosity flow behavior

• Fracture scaling and reservoir simulation

• Drilling and completion technology

Static Conceptual Model

Dynamic Conceptual Model

Simulation Model

Static Description Dynamic Description

Upscaling

SubsurfaceOutcropWellboreGeophysics

PressureTemperatureFluid TypesEnergy

Full Static &Dynamic Simulation

Sanction, Recovery Planning, Flood Design, etc.

Statistical & GeomechanicalRepresentation

Well Test Data & Well Histories

Modeling in Fractured Reservoirs SPE Forum, Sept. 2000

Oil

Water

bedding contained joints -type, orientations, spacing non bedding contained joints -type + orientation + forelimb/ backlimb joint zones -type + orientation + forelimb/ backlimb faults -type +orientation + forelimb/ backlimb

•normal•reverse•strike slip•thrusts

Data considered: Outcrops

no increase of fractures at hingefaults near hinge?dominant fracture direction

Hansen

Peng

Peng

Rawnsley

Pressure

PressureDerivative

Experience & Analogs

Discrete Model Continuous Model

Nelson

Fundamental ApproachFundamental Approachafter Nelson (1985)

• Determine fracture system origin(s) in 3-d– Allows for predictability away from wellbore

Tectonic, regional, cleat, diagenetic, sequence

• Determine reservoir properties & var. in 3-d– Quantifies porosity, permeability, etc.

Morphology, width, spacing/intensity, stress affects

• Fracture/matrix communication– Linkage in dual porosity system

Cross flow, connectivity, recovery

Fundamental Approach (cont.)Fundamental Approach (cont.)• Determine reservoir type

– Defines relative contribution of fractures and problems

Simulation, production character, management

• Locate optimum drill locations & well paths– Quantifies “sweet spots” & maximizes wellbore

surface Intensity, azimuth, directional drilling, seismic attributes

• Develop reservoir management strategies– Control the reservoir to efficiently balance rate &

recovery and reduce well costsFracture closure, well patterns, sweep

Recent Advancement AreasRecent Advancement Areas

• Log Characterization

• Spacing Estimates

• Fracture Zone Identification

• Reservoir Simulation

• Azimuth Predictions

• Reservoir Analogs

• Effects of Fracture and Diagenetic History

Simplified E&P Process in Fractured Reservoirs

Business Model& Decision

Experience Input Data(Static & Dynamic)

Models(Static & Dynamic)

Learnings fromBP, Amoco, &Industry

OutcropLab Subsurface

Improved Model-ing Tools & Procedures

Cross ProjectIssues

Base-case learnings from other fields and analogues that give guidanceto current evaluations and planning

Obtaining appropriatequality input data to characterize fracturedreservoirs

Obtaining fast & accurate modeling routines & proceduresto predict fractured reservoir performance

Appropriate & cost-effectivedrilling & completion techniques infractured reservoirs

Impacts on Fractured Reservoir StudiesImpacts on Fractured Reservoir Studies

FractureFracture

• A macroscopic planar discontinuity in rock which is interpreted to be due to deformation or physical diagenesis

• It may be due to compactive or dilatent processes, thus having either a positive or negative effect on fluid flow

• Its characteristics may have been modified by subsequent deformation or diagenesis

Fractured ReservoirFractured Reservoir

• Any reservoir in which naturally occurring fractures have, or are predicted to have, a significant effect of flow rates, anisotropy, recovery, or storage.

AvoidAvoid

“Fracture Denial”“Fracture Denial”

““Fracture Denial”Fracture Denial” Keeps Us From:

• Gathering important static data early

• Optimizing our well locations & paths

• Designing our secondary recovery patterns correctly

• Accurately predicting field rates & recovery

• Economically depleting our field