Oil & Natural Gas Projects
Exploration and Production Technologies
Characterization of Heterogeneities at the Reservoir Scale: Spatial Distribution and Influence on Fluid Flow
This project was selected under DOE's Historically Black Colleges and Universities
The project goal was to characterize heterogeneities in sedimentary rocks that
influence fluid flow at the reservoir/aquifer scale using innovative geographic
information systems (GIS)-based analyses. Heterogeneities of interest include
fractures, faults and solution cavities.
Florida International University
U.S. Geological Survey
Occidental of Elk Hills, Inc.
The project developed new techniques to characterize the spatial distribution
of fractures and solution cavities in sedimentary rocks. Fractures mapped from
bedrock exposures can be analyzed in terms of fracture type (joints or faults),
intensity, orientation and dimensions within the framework of a GIS database.
In addition, a new method was developed to quantify porosity in karst limestones
from borehole image logs. As a consequence, zones of high porosity are correlated
to subsurface conduits that localize fluid flow.
One outcome of the geospatial analysis of fracture networks is the capability
to identify through-going fracture zones as linear trends of high fracture intensity.
These fracture zones often serve as preferential pathways for fluid flow in
the subsurface and therefore are of great interest to the oil and gas industry
because they provide hydraulic connectivity among populations of smaller fractures.
Quantifying the distribution and dimensions of these multi-layer, through-going
fractures may lead to a better understanding of fractured reservoirs.
Freshwater supplies for many municipalities in the United States are derived
from karst limestone aquifers. The high productivity of these aquifers is a
direct consequence of the numerous solution cavities in the limestone bedrock.
This study provides new methods to quantify the distribution and dimensions
of solution cavities in karst aquifers using high-resolution borehole imagery.
Despite their impact on aquifer-scale fluid flow, large solution cavities and
conduits have been difficult to quantify in the past. Results from this study
may help municipalities and regulatory agencies monitor and protect these valuable
resources through more accurate characterization of the aquifer medium.
Many important oil and gas reservoirs are naturally fractured, deriving the
bulk of their production from a network of highly permeable fractures of various
dimensions. However, direct observation of fractures (and solution cavities
for the case of karst limestone) in the subsurface is inherently limited by
the dimensions of the wellbore and the resolution of available borehole and
seismic techniques. This project addresses the fundamental scaling problem faced
by petroleum geoscientists and water resource hydrologists: how to characterize
the reservoir/aquifer scale heterogeneities that impact fluid flow.
Project researchers have developed:
- Geospatial analyses to characterize the distribution of fractures in layered
rocks, focusing on fracture zones and fracture type.
- A new GIS-based method to identify solution conduits in karst limestone from
borehole image logs.
- A new GIS-based method to estimate the representative elementary volume (REV)
for porosity in karst limestone aquifers.
Fracture zones are geologic structures consisting of numerous, closely spaced
fractures, localized within narrow linear zones. They serve as major pathways
for fluid flow, especially in rocks with low matrix permeability, and hence
represent zones of enhanced weathering and preferential pathways for contaminant
migration. Using outcrop surveys, air photos, and published maps, reseaerchers
developed a method to identify fracture zones based on the spatial distribution
of fracture intensity.
The project resulted in the development of a method to estimate the 2-D porosity
of karst limestone using a combination of remote sensing and GIS techniques.
When applied to high-resolution borehole imagery, the method can yield an
estimate of the medium's REV, thus providing the means to quantify the heterogeneity
of these complex aquifers.
Current Status (August 2005)
The project is nearly completed, with two months remaining in the no-cost
Finn, M.D., Gross, M.R., Eyal, Y., and Draper, G., Kinematics of through-going
fractures in jointed rock: Tectonophysics, V. 376, 2003, pp. 151-166.
Manda, A.K., and Gross, M. R., Estimating aquifer-scale porosity (the representative
elementary volume, REV) for karst limestones using geospatial (GIS) analysis:
in Harmon and Wicks, eds., Geological Society of America Special Paper on
Advances in Karst Research honoring Derek Ford and William White (in press).
Manda, A.K., and Gross, M.R., Identifying and characterizing solution conduits
in karst aquifers through geospatial (GIS) analysis of porosity from borehole
imagery: an example from the Biscayne aquifer, south Florida (U.S.A.): Advances
in Water Resources (in press).
Project Start: September 30, 2001
Project End: September 29, 2005
Anticipated DOE Contribution: $199,004
Performer Contribution: In-kind support (matching) equivalent to ~$50,000
(~25% of total)
Other Government Organizations Involved: U.S. Geological Survey, U.S.
Army Research Office
NETL - Purna Halder (firstname.lastname@example.org or 918-699-2083)
Florida International U. - Michael Gross (email@example.com or 305-348-3932)