WATER RESOURCES RESEARCH GRANT PROPOSAL
Project ID: 2005OK42B
Title: Estimating the orientation and intensity of fractures in sedimentary rocks using multi-component 3-D ground-penetrating radar (GPR)
Project Type: Research
Focus Categories: Methods
Keywords: hydrogeology, fractures, GPR
Start Date: 03/01/2005
End Date: 02/28/2006
Federal Funds: $24,982
Non-Federal Matching Funds: $50,506
Congressional District: 3rd
Oklahoma State University
Ground water in Oklahoma is a vital resource for the well being of its citizens. In some parts of the state, the ground water aquifer(s) supply a large portion of the drinking water. These aquifers are in a range of unconsolidated and consolidated materials. The major source of recharge of Oklahoma aquifers is precipitation. The amount of recharge and the flow of water through aquifer rock units depend on their porosity and permeability. Although much of the porosity/permeability of sandstones is matrix dominated, the other fractured rock aquifers are greatly affected by solution cavities and fractures. Therefore, an understanding of the fracture orientation and intensity is crucial for realistic modeling of recharge and discharge of a fractured rock aquifer. One common method of mapping fractures is from outcrop studies. However, outcrop mapping is insufficient to describe fractures in the subsurface.
We propose a feasibility study to determine if multicomponent 3-D ground-penetrating radar (GPR) technique can be used effectively to map the fracture orientation and intensity in fractured rocks. The multicomponent GPR method involves acquiring the data with the electric-field oriented parallel and perpendicular to a fracture and measuring the phase difference between the two orientations. We will select a field location where fractures of different aperture, open or filled, and of varying intensity are present. The PulseEkko 100 GPR system owned by Oklahoma State University will be used for the study. Antenna frequencies of 100 MHz and 200 MHz, and different acquisition parameters will be tried to determine the best approach to acquire GPR data for fracture mapping. The GPR data will be analyzed with the software available at the University of Oklahoma and Oklahoma State University. The fracture orientation and intensity mapped by GPR will be verified by hydraulic tests in the field.
The results of this study could be used to refine hydrologic modeling in fractured rock aquifers. Specifically, the Oklahoma Water Resources Board (OWRB) has on-going studies on the Arbuckle-Simpson aquifer in south-central Oklahoma. The United States Geological Survey (USGS) has done modeling studies in conjunction with this work. Therefore, the feasibility study proposed here could have significant impact on the work of both the OWRB and the USGS.