Naturally Fractured Reservoir Characterization

Naturally Fractured Reservoir Characterization

By
Wayne Narr
Wayne Narr
Chevron Energy Technology Co.

Wayne Narr is a Structural Geologist at Chevron Energy Technology Company in San Ramon, CA, where he works on both technology development and consulting projects involving naturally fractured reservoirs. His earlier industry experience includes a variety of structural-geology interpretation work, mainly involving complexly deformed fold-thrust belts. Wayne’s previous positions at Chevron include leader of the Structural Geology Team, and exploration geologist, with focus on Colombia. Prior to this, he held both exploration and research positions at Gulf Oil Corporation. Wayne earned a Ph.D. in geology from Princeton University (1990), an M.Sc. from the University of Toronto (1978), and a B.S. from Pennsylvania State University (1976).

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David S. Schechter
David S. Schechter
Texas A&M U.

David S. Schechter is currently an Associate Professor of Petroleum Engineering at Texas A&M U. He also is an author and Principal Investigator for a Dept. of Energy/Natl. Petroleum Technology Class III Field Demonstration project in the naturally fractured Spraberry Trend Area, although his interests extend to all facets of characterization, reservoir engineering, and enhanced oil recovery in naturally fractured reservoirs. Previously, Schechter was a senior scientist and an adjunct professor in chemical engineering at the Petroleum Recovery Research Center at New Mexico Tech and a postdoctoral research associate and acting assistant professor at Stanford U. He holds a BS degree in chemical engineering from the U. of Texas at Austin and a PhD degree in physical chemistry from Bristol U., England.

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Laird B. Thompson
Laird B. Thompson
Utah State U.

Laird B. Thompson has spent 30 years in the oil and gas industry, most of it with Mobil Oil. He was responsible for Mobil’s R&D program on characterizing fractured reservoirs in the mid- to late 1990s. Thompson currently serves as an adjunct professor of geology at Utah State U., is continuing his research on predicting flow characteristics of faults and fractures, and consults on fractured reservoirs around the world.

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Society of Petroleum Engineers
DOI:
https://doi.org/10.2118/9781613999615
ISBN electronic:
978-1-61399-961-5
Publication date:
2006
Preface  
Considered physically or metaphorically, fracture systems form a labyrinth.  
Reservoir characterization involves describing the nature of both the static (geologic)  
and dynamic (fluid-flow) nature of a rock. Naturally fractured reservoirs (NFRs) are par-  
ticularly challenging to characterize because of the extreme heterogeneity of both their  
static and dynamic natures. Furthermore, few geologists or engineers have a high level of  
skill or familiarity with natural fracture systems. They constitute a niche specialization.  
However, the trend toward exploitation of lower-quality reservoir rocks and toward ever-  
increasing enhanced-oil-recovery efforts brings increasing numbers of petroleum-industry  
professionals face to face with naturally fractured reservoirs.  
Fractures can make primary production from a low-quality reservoir economically feasi-  
ble. On the other hand, fractures can compromise an enhanced-recovery project through  
channeling of injected fluids. Whether dealing with primary production or enhanced re-  
covery, reservoir management decisions can be improved through better understanding of  
the natural fractures in a reservoir.  
“Classic” NFR behavior is often a myth. Fracture systems do not behave according to  
“conventional” geostatistical methods (or at least we think they don’t). Seismic methods for  
fracture system analysis are still in their infancy—or, at best, in their adolescence. Numer-  
ical simulation is challenged by extreme contrast of juxtaposed permeability systems.  
There is no standard, generally agreed-upon workflow for characterizing naturally frac-  
tured reservoirs. This is due in part to the challenges posed by the flow heterogeneity in-  
duced by natural fractures and in part to the variability in character that fractures present.  
However, there are methods that may be employed to better understand and describe NFRs,  
and in this book we have compiled basic information about fracture systems, NFR behav-  
ior, and practical methods for exploiting NFRs.  
Every NFR seems to be a learning experience from the standpoint of science, engineer-  
ing, and economics. The surprises teach the lesson of humility when eventualities depart  
from expectations. From a more tangible perspective, some surprises come with dire eco-  
nomic consequences. This is a prime reason for seeking a broad understanding of the frac-  
ture labyrinth.