NGWA Conference on Characterization of Deep Groundwater: Alphabetical Content Listing
William Alley, Ph.D.
Andrew Manning, Ph.D.
Bill Arnold, Ph.D.
Hydrogeological characterization for deep borehole disposal should be focused on those aspects of the groundwater system most important to disposal safety, including the following. Saline groundwater residence time is an important indicator of long-term isolation of the deep hydrogeological system and can be interrogated using a number of natural isotopic tracers. Salinity stratification of deep fluids would oppose thermally driven circulation of fluids from waste heat. Overpressured conditions at depth would be unfavorable to waste isolation. Permeability of the host rock must be evaluated and is expected to have a low average value; although, individual fracture zones may have significantly higher permeability, even at great depth. Deep geochemical conditions have important implications for radionuclide mobility, with reducing conditions causing lower solubility and greater sorption for many radionuclides. Differential horizontal stress may impact borehole stability and the disturbed rock zone permeability in deep boreholes. Chemical and mineralogical interactions with borehole seals may affect long-term seals integrity.
Alexander Haluszka, M.Sc., P.Geol.
Deep Injection Wells Injection Capacity Evaluation for Disposal of RO Concentrate and Facility Process Wastewater
Richard Walther, P.G.
The injection zone is composed of moderately permeable limestone along with sequences of low permeability limestone and dolostone beneath a 1100-foot-thick anhydrite sequence. The injection zone has extremely high salinity, with total dissolved solids concentrations greater than 200,000 mg/L. The high salinity of the injection zone significantly increases the density of the formation fluids and presented unique challenges to performing pump tests, analyzing formation pressures resulting from injection testing, and assessing the portion of the open borehole available for injection.
A significant amount of data has been collected and analyzed within the injection zone from packer tests, coring, geophysics, and short-term step injection tests to acquire a better understanding of how the well and formations will respond to operational use. The short-term testing data indicates that the injectate is primarily utilizing the formation above 5000 feet below land surface; however, long-term operation will likely utilize all permeability in the borehole. Since this well will be receiving a combined waste stream, a plugging and precipitation study is being conducted to evaluate the risks and potential pretreatment to minimize geochemical issues.
Klaus Udo Weyer, Ph.D., PG, PHG
Contrary to widespread belief, aquitards are an integral part and also a reason for deep regional groundwater flow systems due to the thermodynamic principle that the total energy consumption in the groundwater force field and the dependent flow field is minimized. Accordingly, deep groundwater flow systems at the Athabasca oil sands (Birch Mountains), the Weyburn test site for CO2 sequestration (Moose Mountain, Missouri Coteau), and at the Manitoba escarpment (Riding Mountain and Turtle Mountain) penetrate many hundreds of meters of aquitard into the underlying aquifer systems as shown by a comparison of head values at the groundwater table and within various aquifers. The results confirm that the postulated long-range deep groundwater flow systems do not exist with groundwater flow from recharge areas in Montana to discharge areas more than a thousand kilometers away.
Saline Contamination Pathway Assessment Using Spatial Variations in Groundwater Salinity, Baton Rouge Fault, Southeast Louisiana
Frances Colleen Wendeborn, M.S., P. Geol.
A detailed study has been done of the spatial variations in salinity as calculated from wire line logs for wells on either side of the Baton Rouge fault. Most of the logs were run in the 1960s, and the information provides a snapshot of the salinity structure prior to significant groundwater contamination. The spatial variations in salinity across the fault are consistent with natural lateral interfingering of fresh waters derived from the north, and brackish waters from the south. A 2004-2005 study of chloride concentrations in the groundwater showed that the highest chloride concentrations occurred at mid-depth in the aquifer system rather than the base, as might be expected if salt transport were up the fault. The most likely source of the saline contamination lies to the south, where dissolution of salt domes has produced saline plumes which extend upward all the way to the ground surface. Conduits for upward transport of salty water appear to be faults associated with the domes rather than regional listric faults.
Andrew Manning, Ph.D.
Michael S. Johnson, PG
For 40 years only a few notices to drill into deep nonpotable aquifers were filed. From 2006 through 2010, 68 notices proposing 610 deep wells for the appropriation of over 1.7 million acre-feet were filed, in a veritable “gold rush” on New Mexico’s deep groundwater. In 2010, actual groundwater withdrawals in the state totaled about 1.8 million acre-feet. Most of these notices were filed for municipal and related uses in the Albuquerque area. To date (December 2013) 13 deep wells exist, and actual use of the resource has been small.
Amendments in 2009 allow the State Engineer to declare and administer deep basins. Appropriations from a declared deep basin for most uses would remain subject to the deep nonpotable aquifer statutes, except for drinking water uses, which would require a State Engineer permit. The amendments also specify that a deep aquifer contain only nonpotable water, limiting the potential for connection to freshwater sources and effects on senior users and interstate streams. New Mexico appears to be entering a new phase with respect to deep nonpotable groundwater, with active development to supply a proposed mining use in progress. Within this context the State Engineer is exploring management options for New Mexico’s deep groundwater, including developing an administrative framework that allows resource development while protecting existing water users.
David Jordan, PE
John Jansen, P.G., P.Gp., Ph.D.
Several electrical methods have been developed that can image the structure of an aquifer and estimate water quality. Many of the most common methods are limited to a few hundred feet of penetration. Two methods, Time Domain Electromagnetic Induction (TEM) and magnetotellurics (MT), can image aquifers to depths of several thousand feet. Case histories will be presented that demonstrate how these methods can be used to map aquifers, find faults and fractures, and map saline water to depths of 1000 to 3000 feet. The MT method can be used to even greater depths.
Seismic reflection can be used to image geologic strata to depths of tens of thousands of feet. The attributes of the reflections can also be used to estimate the lithology of the units and detect facies changes within the aquifer. A case history will be presented where seismic reflection was used to map a sandstone aquifer at a depth of about 3000 feet and identified a facies change where the sandstone graded into a shale unit.
Gravity methods can be used to map deep geologic structures and are often used to map the basement of a groundwater basin or the depth to dense aquifer units such as carbonates. A case history will be presented where gravity measurements were used to map a carbonate aquifer in a complex structural basin where the depth to the aquifer varied from less than 1000 feet to more than 8000 feet over distances of a few miles.
Geohydrology and Water Quality of Three Deep Test Holes in Fractured Bedrock, North-Central Pennsylvania
John H. Williams
A suite of geophysical logs was collected from the test holes including nuclear, electric, electromagnetic, and sonic; acoustic and optical televiewer and video; and fluid-resistivity, temperature, and flow under ambient and pumped conditions. Based on interpretation of the geophysical logs, water-quality samples were collected at specific depths with a wireline sampler for analysis of specific conductance, total dissolved solids, major cations and anions, trace metals, and gas isotopes. The specific conductance and flow rate of the air-lifted discharge was monitored during drilling of the Sullivan County test hole. A straddle-packer system was also used in this test hole to isolate selected fractured zones for hydraulic measurement of transmissivity and head and collection of water-quality samples.
The test holes penetrated multiple water-flow zones at bedding-related fractures and, in a few shallower zones, steeply dipping fractures related to regional jointing. Minimal fracture transmissivity was penetrated below 700 feet as indicated by the depth at which the temperature-log gradients approached the geothermal gradient. Fractured zones above 300 feet produced very fresh calcium-bicarbonate type water with no detectable methane. Fractured zones below 900 feet produced very small inflows of saline sodium-chloride type water with thermogenic methane concentrations that ranged up to 120 milligrams per liter. Intermediate-depth fractured zones produced water that was transitional between that produced by the shallow and deep zones.
The volumetric quantities involved in commercial CO2 capture and storage are quite large. The average emission from a power plant in the U.S. is approximately a million tons per year. Injecting such large quantities of CO2 from multiple sources for periods of decades can result in elevated subsurface pore pressures at distances exceeding several hundred miles. In order to simulate the induced pressures and predict the eventual fate of CO2, knowledge of the ambient groundwater flow field is essential for calibrating simulation models and specifying boundary conditions. However, due to the high cost of constructing deep observation wells, the potentiometric surface of deep aquifers is generally not known with certainty. As part of the (U.S. DOE sponsored) initiative to characterize the CO2 storage capacity in Kansas, drill stem test data was used to construct a potentiometric surface map of the Cambrian-Ordovician Arbuckle aquifer in Kansas, which is being evaluated for widespread commercial-scale CO2 storage. The results are highly encouraging, and have been verified with known hydraulic data, which validates the (incremental DST-pressure based) technical approach developed to construct region-wide potentiometric surfaces at multi-state scale. The findings are being used for constructing multiphase models to simulate the effect of commercial scale injection in Kansas.
William Alley, Ph.D.
Exploration and Groundwater Development from the DEEP Regional Carbonate Aquifer (RDCA) of Southeastern Nevada
Greg Bushner, RG
Other exploration techniques used included Natural Source Audio-Frequency Magnetotulluric (NSAMT) and Controlled Source Audio-Frequency Magnetotulluric (CSAMT) geophysical surveys that were used in combination with the down-hole geophysical data from each well to better understand the subsurface geology for siting new wells and understanding the RDCA in each basin. All of this information was used to develop a conceptual model and a numerical groundwater flow model in support of new groundwater appropriations from these basins. Efforts by Lincoln/Vidler to develop these water resources are entirely on federal lands with approvals for groundwater appropriations under the purview of the Nevada State Engineer.
Methodology for Characterizing Deep Groundwater Resources Using Studies from the Alberta and Williston Basins
The AER’s Alberta Geological Survey has a history of conducting hydrogeological mapping and continues to undertake regional scale projects in assessing both shallow and deep groundwater resources. This presentation will provide an overview of the methodologies that are currently being used to characterize deep aquifers. Moreover, an outline of the approach being taken to inventory our groundwater resources, construct regional groundwater flow models, and provide scientific results to regulators making decisions on water authorizations will be provided. Studies from the Alberta and Williston basins will be used to show methods and results in geological and hydrogeological modelling, mapping distributions of groundwater flow and chemistry, correcting for density-dependent flow, and also techniques to identify the effects of production/injection on data and pressure regimes.
William Alley, Ph.D., William Alley, Ph.D.
Andrew Manning, Ph.D.
Jennifer S. Stanton
The USGS Groundwater Resources Program recognizes the need for a better understanding of saline groundwater resources to support sustainable development of the resource and to provide reliable science for associated regulatory and policy issues as well as for advancing treatment technologies. To address this need, three pilot studies were conducted (2010-2012) to assess saline groundwater resources at regional scales. The goals of the pilot studies were to determine the availability of data for assessing the distribution and character of saline groundwater and test and develop methodologies for assessing the resource. The recently initiated (2012) National Brackish Groundwater Assessment, which is part of the USGS Water Census, will build upon knowledge gained from the three pilot studies and use a consistent approach across the nation to provide an updated national map of moderately saline, or brackish, groundwater resources less than 3000 feet below land surface, as well as critical information about the physical and chemical properties of the resource.
Jeffrey Henke, PG
A deep, fresh water well was completed in unconsolidated Eocene Jackson Group strata in northern Lavaca County, Texas to obtain fresh to slightly saline water for multi-stage hydraulic fracturing of multiple horizontal EFS oil wells. The well was installed as part of a water delivery and management system designed to supply make-up water over an approximated 25 square mile area. The well was designed using borehole geophysical logs and core samples from several adjacent oil well locations and installed using a combination of traditional water well and oil well completion technology. Testing of the well after installation and development indicated fresh to slightly saline water quality, substantial potential yield, and the presence of elevated dissolved methane in the produced groundwater. This presentation will describe aquifer evaluation; well design, installation, and development; well yield; and production issues surrounding use of the well for the intended purpose.
Steve Schneider, MGWC
Integrating Modern Suite of Geophysical Logs, Geochemistry, and Seismic Data for Characterizing Deep Aquifers
W. Lynn Watney, Ph.D.
Spectral Gamma Ray, Triple combo log suite, Magnetic Resonance Image (MRI), and Dipole Sonic were used to characterize pore volume, distribution, and connectedness, and also to identify potential sources of drinking water. The MRI data was used with a new (patent pending) Flow Zone Interval method to estimate permeabilities. The confining potential of the caprock was estimated using MRI based pore throat data to calculate entry pressure. The Extended Range Micro Imager log and Computed Tomography (CT) scan were used to characterize fractures.
The stratification and delineation of hydrostratigraphic units derived from geophysical logs was validated by formation geochemistry, and ionic and isotopic analyses. Geochemical logs and thin sections were analyzed for mineralogy and soil characterization to enable reaction kinetics modeling and determining potential for plugging pore space due to mineral precipitation.
Drill stem and injectivity tests were conducted to determine the relationship between laboratory, log, and field scale estimates of permeability. 3-D seismic data was collected to map formation structures and characterize the geologic fabric regionally. The entire set of data was finally integrated into a 3-D reservoir model using Schlumberger’s (geocellular) Petrel Geology/ Modeling software.
Michael Cardiff, Ph.D.
In this work, I discuss Multi-frequency Oscillatory Hydraulic Testing (M-OHT), in which pumping tests of various frequencies are performed, and the response of the aquifer to these oscillations is monitored. The ability to stress an aquifer at multiple frequencies is extremely useful, since the period of oscillation represents an additional testing parameter that can be changed in order to collect different information about the subsurface. In contrast, traditional testing strategies such as (constant rate) pumping tests and slug tests have only one parameter that can be changed—i.e., the rate of pumping, or the height of the slug test—and test response is often insensitive to changes in these testing parameters.
I discuss the theory behind M-OHT and first show some example numerical experiments demonstrating the added information content from multiple-frequency aquifer stimulations. I then present laboratory and field examples of this testing (along with analysis strategies), and discuss the practical implementation issues for carrying out such tests to characterize deep aquifers.
Ned A. Clayton
Deep Groundwater Monitoring Challenges and Best Practices After 30 Years of Westbay System Applications Worldwide
Given the significant investment in borehole drilling and completion there is significantly increased demand for reliable, modular instrumentation suitable for multi-level applications to deliver high-quality, verifiable, defensible measurements from all of the features intersected by the borehole. Nested monitoring wells, typically used in the environmental industry, are cost-prohibitive in such environments and cannot deliver on the requirements for ease of installation, modularity, verification and defensibility.
The Westbay System is a modular borehole completion technology that has been used worldwide on deep groundwater investigations for over 30 years. With a strong background in applications for geologic repository studies involving instrumentation to depths of 4000 ft or more the Westbay System has been accepted internationally as a reliable, high quality technology suitable to meet the performance and flexibility demanded by such high-visibility projects. Other deep groundwater applications include mining projects and hydrogeologic testing and monitoring of deep sub-permafrost environments in Canada's Arctic. From this breadth of experience comes an understanding of industry best practices and the challenges of operation in the deep groundwater environment. This paper describes the Westbay design, typical deep groundwater applications and limitations, and presents example data from several different sites to illustrate how the requirements for high-quality, defensible data are met, and how such data are used in implementation of data gathering and decision-making processes.
Since water chemistry can begin to change immediately upon exsolution of dissolved gases, prompt field chemistry is critical. Alkalinity, pH, and other project-specific parameters should be determined within minutes of depressurization.
Dissolved gas profiles can be very important for flow modeling, as gas exsolution can reduce the effective hydraulic conductivity by 30-50% or more around pumping wells.
Sampling dissolved gases at the surface raises a number of issues. In most cases, the sample has traveled through a significant length of plastic tubing to reach the surface. A flow-through gas separation system may preferentially collect some gases due to faster exsolution rates. In pumping a deep well, gases at the surface may have originated in water that has not yet left the borehole.
In-situ methods remove tubing from the equation, and are generally a better choice for control of pressure. However, some are not completely isolated from atmosphere, and most have small sample volumes.
An innovative sampler design allows a sample to be collected and maintained at reservoir pressures and isolated from the atmosphere until analyzed, minimizing the alteration in water chemistry associated with exsolution of gases. A large sample volume permits more analyses to be performed, and may entirely replace pumping for some applications. Discharge of the sample into an evacuated container allows capture of exsolving gases, which may then be decanted for analysis.