Applied Concepts in Naturally Fractured Reservoirs

INSTRUCTORS: John C. Lorenz PhD and Scott P. Cooper MS
DISCIPLINE: Geoscience, Engineering, Unconventional Reservoirs, Formation Evaluation
CEUS: 1.6
AVAILABILITY: Public & In-House

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WHO SHOULD ATTEND: Geologists who need to characterize and understand fracture systems and their effects on reservoir permeability from core and outcrops, who need to be able to differentiate between natural and induced fractures in cores, and who would like to be able to predict the effects of lithology, structure and stress on fracturing.

Engineers who want to understand fracture permeability in relationship to the in situ stress system, the interaction of natural fractures with hydraulic stimulation fractures, and the important differences between extension and shear fractures in controlling individual fracture permeability and fracture network interconnectedness. Petrophysicists who want an understanding of the significance of different fracture characteristics on image logs and the reliability of image logs in capturing the characteristics of fractures.

This is a hands-on class anchored with a 65-piece teaching collection of natural and induced fractures in core that students will work with during class exercises. In addition, and with pre-planning, in-house courses can utilize client core, image logs and CT scan data. The class provides insights into fracture mechanics and the origins of fractures, and uses those concepts in a very applied sense to instill an understanding of natural fractures and their potential effects on conventional and unconventional reservoirs.

Discussions and lectures include the use of and caveats for oriented cores, and the interactions between natural fractures, in situ stresses, and stimulation fractures. Course modules include discussions of image logs and their calibration with core, differentiating fractures by type and the effects of different types on reservoir permeability, and fracture types expected in different structural domains and different types of reservoirs. Students will learn to differentiate natural from induced fractures in cores.

Students will come away from the class with an appreciation of the wide range of structures that fall under the basket term “fracture”, and that the different types of fractures have different effects on permeability in hydrocarbon reservoirs.

Participants of this course will receive a copy of Applied Concepts in Fractured Reservoirs. This book covers the course subjects in depth, specifically the understanding, evaluation, and effects of fractures on reservoirs. It offers a comprehensive, practical discussion and description of natural fractures, their origins, characteristics, and effects on reservoir permeability. It introduces the reader to basic definitions and classifications of fractures, then provides a guide for fractured-reservoir characterization and analysis. It also includes discussions of the way fractures impact oilfield operational activities.

Well organized and clearly illustrated, the book starts with a section on understanding natural fractures, addressing different fracture types, their dimensions, and the mechanics of fracturing rock in extension and shear. The next section provides information on measuring and analyzing fractures in reservoirs. It covers logging core for fractures, assessing fractures in new core vs. old core, image logs, and more. The last part of the volume examines the effects of natural fractures on reservoirs including fracture volumetrics, the effects of fractures on drilling and coring, the interaction between natural and hydraulic fractures, and the permeability behavior of both individual fractures and fracture systems.

This book compiles various concepts and descriptions that have been scattered in the literature, and synthesizes them with unpublished oil-field data and the authors' experience. The book is a valuable reference for geologists and engineers who need to understand naturally fractured reservoirs in order to efficiently extract hydrocarbons, and helps bridge the gap between these disciplines. It is illustrated in full color throughout, and is a companion volume to the authors' Atlas of Natural and Induced Fractures in Core.



  • Shear and extension fractures have significantly different effects on reservoir interconnectivity, drainage anisotropy, and stimulation potential.
  • Fracture permeability can be dynamic, changing with changes in the in situ stresses during production. These dynamic effects are more prevalent in unconventional reservoirs.
  • Different lithologies (i.e. shales, sandstones, and carbonates) have different mechanical properties and are prone to different types of fractures with different permeability effects.
  • Fracture effects on a reservoir depend on the ratio between fracture and matrix permeability. Therefore, fractures have a much greater effect on permeability in unconventional reservoirs vs conventional reservoirs.
  • Image logs are important tools for fracture characterization that need to be calibrated.
  • Induced fractures in a core record the in situ stress conditions, but must not be mistaken for the natural fractures that control permeability.
  • Interaction of natural fractures and hydraulic stimulation fractures.


“The Importance of Natural-Fracture Type in Controlling Reservoir Permeability”