Article
Geologic characterization of nonconformities using outcrop and core analogs
Solid Earth
(2020)
Abstract
The occurrence of induced earthquakes in crystalline
rocks kilometers from deep wastewater injection wells
poses questions about the influence nonconformity contacts
have on the downward and lateral transmission of pore-fluid
pressure and poroelastic stresses. We hypothesize that structural
and mineralogical heterogeneities at the sedimentary–
crystalline rock nonconformity control the degree to which
fluids, fluid pressure, and associated poroelastic stresses are
transmitted over long distances across and along the nonconformity
boundary. We examined the spatial distribution of
physical and chemical heterogeneities in outcrops and core
samples of the Great Unconformity in the midcontinent of
the United States, capturing a range of tectonic settings and
rock properties that we use to characterize the degree of past
fluid communication and the potential for future communication.
We identify three end-member nonconformity types
that represent a range of properties that will influence direct
fluid pressure transmission and poroelastic responses far
from the injection site. These nonconformity types vary depending
on whether the contact is sharp and minimally altered
(Type 0), dominated by phyllosilicates (Type I), or secondary
non-phyllosilicate mineralization (Type II). Our observations
provide geologic constraints for modeling fluid
migration and the associated pressure communication and
poroelastic effects at large-scale disposal projects by providing
relevant subsurface properties and much needed data regarding
common alteration minerals that may interact readily
with brines or reactive fluids.
Keywords
- nonconformity,
- permeability,
- subsurface
Disciplines
Publication Date
Fall November 12, 2020
DOI
https://doi.org/10.5194/se-11-1803-2020
Citation Information
Elizabeth S Petrie, Kelly K. Bradbury, Laura Cuccio, Kayla Smith, et al.. "Geologic characterization of nonconformities using outcrop and core analogs" Solid Earth Vol. 11 Iss. 3 (2020) p. 1803 - 1821 ISSN: 1869-9510 Available at: http://works.bepress.com/james_evans/99/
Creative Commons license
This work is licensed under a Creative Commons CC_BY-SA International License.