A Field-scale Examination of Fault Controls on Subsurface Fluid Flow
Abstract
Geologic faults are features that can substantially alter fluid flow in the subsurface. Intrinsic permeability of a fault body is constrained by the feature's structure and architecture. These permeability differences can create a flow conduit, barrier, or combination thereof. Despite the important role that faults play in subsurface flow regimes, many flow models represent faults as straight vertical features with uniform permeability. Applications including groundwater supply, carbon sequestration, and petroleum reservoir analysis could each benefit from a more sophisticated understanding of how faults affect fluid flow.
The Loma Blanca fault, located in central New Mexico, U.S.A., is an ideal site for examining controls of faults on fluid flow at the field-scale. The Loma Blanca is a normal fault dipping approximately 70°E. Abundant carbonate cement is visible in fault surface outcrops; geological and geophysical studies suggest that the cement continues in the subsurface. Field measurements taken at cemented portions of the fault outcrop reveal permeabilities substantially lower than the host sediments, which are expected to hinder fluid flow across the fault. We installed 21 wells along the Loma Blanca fault, screened in a shallow unconfined aquifer. Wells were completed in two fault-normal transects: one across a section of inferred continuous low permeability cement (south transect), and a second in an area of infrequent, discontinuous cement (north transect). Here, we present and discuss a series of pumping tests planned for Fall 2018. Aquifer test results will be processed via traditional time-drawdown analyses and pressure derivative diagnostics. A concurrent study of the local sediment stratigraphy will also assist with designation of hydrostratigraphic units. We posit that extracting water from different fault blocks and transects will produce distinct drawdown profiles induced by variations in the local fault architecture and permeability.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H41J2196S
- Keywords:
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- 1829 Groundwater hydrology;
- HYDROLOGYDE: 1835 Hydrogeophysics;
- HYDROLOGY