SwRI: Integrated Structural Geologic and Hydrologic Investigations of Faulting in Carbonate Strata

A Southwest Research Institute^® (SwRI) Project

Project Motivation and Scope

The permeability architecture of faults in carbonate rocks is of fundamental importance to hydrocarbon reservoir performance, but the architecture remains poorly understood. We will characterize the deformation features that dceevelop in faulted carbonate rocks and integrate structural analysis with lithologic and hydrologic characterization.

The project will generate a quantitative data set of normal fault characteristics in carbonate strata and their effects on permeability.

This low-altitude aerial photograph of Canyon Lake Gorge shows traces of faults and locations of springs, pools, and infiltration points in a channel. View is to the east northeast, along the strike of the Hidden Valley fault.

Project Location

Detailed work will be conducted on the recently exhumed Hidden Valley fault, which cuts the Cretaceous Glen Rose formation of south-central Texas. Additional work on faults within the Cretaceous strata of south-central and west Texas will provide a context for the interpretation and application of the detailed work. The Hidden Valley fault is representative of structures that are common in carbonate oil reservoirs and the unique site permits us to study the interplay between structure, rock type, and fault-zone hydraulic properties.

	This profile view of Hidden Valley fault zone at waterfall looking west southwest shows a  synthetic dip in the footwall damage zone, and conjugate normal faulting in both footwall and hanging wall.

Specific Project Tasks

Stratigraphic and Lithologic Characterization

• Develop detailed measured sections of hanging wall and footwall

• Measure natural gamma ray log

• Characterize textures and quantify clay content of host lithologies

Structural Analysis

• Analyze mechanical stratigraphy

• Produce detailed maps of outcrop scale structural elements

• Perform microstructural analysis

• Develop a digital geologic framework model from field mapping and borehole data

Well Infrastructure

• Drill, core, log, and complete wells as multi-level piezometers in the hanging wall and footwall of Hidden Valley fault

Hydrologic Characterization

• Assemble water-level data for Canyon Lake and local water wells

• Monitor springs, seeps, and influent/effluent surface water bodies

• Measure water flow rates within Canyon Lake Gorge

• Monitor water pressures at multiple intervals in monitoring wells

Photomicrographs of fault rock in Cretaceous limestone, from a fault in the the Balcones fault system in Central Texas, illustrates stylolites, vein fill, and twinning of vein calcite.

For more information about  investigations of faulting in carbonate fault techniques at SwRI or how you can contract with SwRI, please contact Dr. David A. Ferrill at dferrill@swri.org or (210) 522-6082, or Dr. Alan P. Morris at amorris@swri.org or (210) 522-6743.