Russell T. Johns (rjohns@mail.utexas.edu) is the Program Manager of the Environmental Engineering research program.
The primary purpose of the Environmental Engineering Program is to provide short-term and long-term cost-effective solutions to challenging subsurface environmental problems faced by industrial and governmental groups. Research in subsurface environmental engineering is directed toward both the characterization and remediation of contaminated aquifers. These research projects range from the fundamental investigation of the transport of chemicals and microbes in permeable media using advanced techniques such as magnetic resonance imaging to applied projects up to and including pilot field tests of several technologies.
The environmental engineering program of the Center is supervised by eight faculty members. Current and recent projects include characterization and surfactant-enhanced remediation of aquifers contaminated by organic wastes known as non-aqueous phase liquids (NAPL), soil heating for cleanup of aquifers contaminated with organic liquids or metals, development of a three-dimensional NAPL fate and transport model and parallel algorithms for flow in permeable media with ground water applications, development of an interwell-partitioning tracer test to detect and measure the volume of NAPLs, investigation of surfactant-enhanced remediation of aquifers contaminated by dense nonaqueous-phase of liquids (DNAPL), development of laboratory and field-scale test methodology for solidified/stabilized hazardous wastes, characterization of multiphase flow and transport of VOC in unsaturated aquifers, multiphase transport characterization and scale-up in tight rocks and seals, and the development of a three-dimensional streamline model for tracer test analysis. Several field tests of these technologies are planned or have been completed in cooperation with environmental engineering companies such as INTERA, TerraTherm, Radian, and other governmental agencies.
Research Projects
Three-Phase Flow (Experiments and Simulation) - David DiCarlo
Understanding the dynamics of three-phase flow is essential for optimizing enhanced oil recovery and vadose zone remediation processes. The ultimate recovery of oil and other non-aqueous phase liquids (NAPLs) depends on the residual saturations and relative permeabilites of each of the phases. In particular, the wettability of the porous media affects the placement of the fluids in the porous media and the relative permeabilities. Previously we have shown experimentally how the oil relative permeability scales with oil saturation at low oil saturations for different wettabilities. These results imply very low residual oil saturations are obtainable under three-phase gravity. Currently, we are measuring three-phase relative permeabilities throughout the entire saturation range for a range of wettabilities. These results will lead to experimentally based relative permeability models which can be directly input into simulations of gas injection.
Flow Transport Modeling - Gary A. Pope, Mojdeh Delshad (more info)
In Situ Thermal Desorption for Aquifer Remediation - Gary A. Pope, Russell T. Johns
In-Situ Thermal Desorption (ISTD) is a soil heating remediation technology currently applied primarily to remove organic contaminants from the vadose zone. It has been shown to be effective in the clean up of a wide range of contaminants from volatile organics to heavy oils. A removal on the order of 99.99% of the contaminants has been documented in several field tests. This is a very robust technology that could prove invaluable in the remediation of saturated zone contamination. To date, however, there has been little research into the feasibility of its application when contaminants are located in the saturated zone. To this end, two-dimensional numerical simulations using a commercial reservoir simulator were performed. The preliminary results are published in SPE 81204, and they show that it is possible to use ISTD in the saturated zone and that the remediation time is dependent upon these factors.Reductive Dehalogenation - Larry N. Britton
Widespread use of degreasing solvents like tetrachloroethene (PCE) and trichloroethene (TCE) has left a legacy of subsurface contamination. One of the strategies for remediation of contaminated sites is biological reductive dehalogenation whereby soil microorganisms sequentially remove chlorine atoms from the compounds in a reductive pathway under anaerobic conditions. However, in heavily contaminated source zones the rates of biological dehalogenation often are nil because of inhibitory effects. We are developing a chemical approach that borrows on biological mechanisms that include use of transition metal-containing, oxidation/reduction (redox) catalysts and reductants. Straight-forward, rapid dehalogenation of chlorinated solvents can be achieved with select redox catalysts and reductants, and this chemical approach can be used in source zones where the solvents exists as dense non-aqueous phase liquids (DNAPL). The research seeks to discover highly effective, environmentally-acceptable catalysts and other chemicals that can be injected into the contaminated sites to achieve cleanup. It is important to understand the mechanisms and issues related to the flow and transport of the remediation fluids to the subsurface sites such that the entire remedial process can be reliably engineered.Feasibility of High-Resolution Site Characterization and Remediation Monitoring Using Tracers - Steven L. Bryant (more info)
The fundamental question being addressed in this project is: how can we extract more information from partitioning interwell tracer tests? The answer depends in part on the answer to the following question: can the influence of spatial distribution of NAPL on partitioning tracer histories be distinguished from the influences of unrelated phenomena such as mass transfer kinetics, dispersion, etc.?The forward simulations of tracer transport through a complex, realistic contaminated site have continued and now offer a more comprehensive picture of the feasibility of spatial resolution of NAPL location. Many geostatistical realizations of the permeability field have been generated to test the influence of permeability heterogeneity, the primary control on NAPL distribution during contamination. The methodology for conducting these simulations and analyzing the results was detailed in the previous research report.
Influence of Grain-scale Geometry on Colloid Transport - Steven L. Bryant (see the Environmental Engineering page for more information)
Mechanisms for Permanent CO2 Trapping in Sedimentary Rocks - Steven L. Bryant, Gary A. Pope
Funding source: Advanced Technology Program (State of Texas)Funding amount: $150,000 for the period of January 2004 - December 2006
Geological sequestration is one way greenhouse gases can be mitigated in sufficient volumes. This project focuses on obtaining quantitative assessments of the potential for permanent geological sequestration of carbon dioxide in aquifers. Current schemes for sequestering CO2 depend on storage in the gas phase and assume the gas will flow upward in the aquifer until a geological seal is reached. These schemes require seal integrity over long periods of time and do not assure integrity. CO2 can escape through abandoned wellbores, faults and fractures. Three ways the CO2 can be sequestered that avoids these concerns include: 1) CO2 can dissolve in brine, 2) CO2 can chemically react to form an immobile solid phase, and 3) CO2 can form a CO2-rich gas phase that is not mobile due to trapping by capillary forces for saturations below the residual gas saturation. How can these three highly desirable forms of sequestration be maximized so that very large volumes of CO2 are permanently stored in aquifers without a mobile gas phase? Flow and transport models are available to quantitatively answer this question under realistic aquifer conditions. We will simulate CO2 injection into large aquifers for time scales of several years, simulating the gravity driven flow of the CO2-rich gas and CO2-saturated brine for 1000 years or more.
Related Research
Injection Water Management - Mukul M. Sharma
Injectivity decline in water injection wells can have a large impact on the economics of offshore and onshore water disposal and waterflooding operations. Most mature oil and gas producing regions of the world currently have a ratio ofproduced water to oil in excess of 25 to 1. The disposal of produced water is, therefore, becoming an increasingly important issue in the management of produced fluids. In offshore operations, the injection of sea water and produced water for pressure maintenance, disposal or for waterflooding is becoming more common. It is, therefore, imperative to have reliable models to predict the behavior of water injection wells.
The objective of this Joint Industry Partnership is to develop a computational tool that will allow us to determine water quality specifications and help in the design of surface facilities for water injection projects. To achieve this goal, the proposal aims at obtaining relevant laboratory data, collecting and compiling field data and incorporating this information into a comprehensive water management simulator.
Surfactant Enhanced Aquifer Remediation - Gary A. Pope
Please see the SEAR Technology Alliance page for information.
Research Initiatives
Subsurface Contaminant Remediation (single or two-phase)
Foam for Aquifer Remediation (more info)
Fractured Media - Characterization and Remediation (more info)
New Tools for Risk Management - Soil Physics
Anomalous Rapid Transport Processes (more info)
Slug/Pumping Tests in Low-Conductivity Aquifers
Other Research
Free-Product Recovery Using Skimmer and Dual-Pump Wells - Russell T. Johns, Larry W. Lake
Accidental release of petroleum hydrocarbons to the subsurface may occur through spills around refineries, leaking pipelines, storage tanks or other sources. If the spill is large, the hydrocarbon liquids may eventually reach a water table and spread laterally in a pancake-like lens. Hydrocarbons in the aquifer that exist as a separate phase are termed free product or light nonaqueous phase liquids (LNAPL). This project presents new analytical solutions for the effective design of long-term free-product recovery from aquifers with skimmer-, single- and dual-pump wells. The solutions are derived for steady-state flow based on the assumption of vertical equilibrium, and include the effect of coning of LNAPL, air, and water on flow.
The results show how to estimate the maximum rate of inflow of LNAPL for skimmer wells, i.e. wells in which LNAPL is recovered with little or no water production. The paper also shows how to calculate the increase in LNAPL recovery when water is pumped by single or dual-pump wells. A simple equation is given that can be used to adjust the water rate to avoid smearing of the LNAPL below the water table.
Surfactant Enhanced Aquifer Remediation - Gary A. Pope, Mojdeh Delshad (more info)
Geologic Disposal of Immobilized Plutonium in Very Deep Boreholes - Mukul M. Sharma, Russell T. Johns
The Role of Rate-Limited Mass Transfer in Surfactant-Enhanced Aquifer Remediation - Mojdeh Delshad, Gary A. Pope (more info)