Some carbonate strata contain vugs or cavities about the size of a few centimeters. This project unites the expertise of geologists, geo-engineers, and mathematicians to study experimentally and computationally the flow and transport of solutes in vuggy rocks over distances of 0.1 to 100 meters. Experimental studies of the Pipe Creek Reef outcrop in Central Texas will be made: (1) in the laboratory on samples at the sub 10-20 cm scale to determine rock and vug properties and micro-scale tracer transport characteristics; (2) in the field over 1-10 m scales to determine effective permeabilities and tracer injection response; and (3) in the field using ground penetrating radar to map the large scale geology over 1-100 m scales. The data will be used to construct a micro-scale model of the transport process at the detailed sub-cm scale and a macro-scale model to represent the system, including its topological vug interconnectivity, time-scales, and macro-dispersion on scales of at least 1-100 m. Efficient and accurate computational implementation will allow testing and verification. Statistical analysis will quantify uncertainty in the data for use at full field scales. The project is expected to result in substantially improved modeling of flow and transport in vuggy media over the macro-scale, with a solid empirical basis for the selection of the effective parameters in the macro-scale model, and the handling of parameter uncertainty. It should illuminate modeling of similar porous media, such as karsts and fractured systems, and, more generally, related multi-scale systems. The project will impact three Ph.D. students and enhance two outreaches to the industrial community, the the Reservoir Characterization Research Laboratory (RCRL) and the Center for Subsurface Modeling (CSM). Finally, since carbonate rocks comprise many of the world's aquifers and oil reservoirs, society will benefit as progress allows more effective protection of groundwater supplies and production of petroleum.
Some carbonate rock strata contain cavities, called vugs, about the size of a few centimeters. Fluid can flow much more easily in these vugs than within the rock itself (i.e., between the rock grains). The transport of chemical species, such as groundwater contaminants, is strongly influenced by the nature of these vugs. Within an inter-connected vug path, the contaminant can flow quite rapidly, but it must slow considerably when it re-enters the rock. However, little is currently known about how fluid flows in such vuggy rocks over long distances. This project unites the expertise of geologists, geo-engineers, and mathematicians to address the problem. Experimental studies will be made to determine the behavior of fluid flow in small vugs over 10-20 centimeters, and within vug channels up to 10 meters long. Ground penetrating radar will be used to map the large scale geology over 1-100 meter scales. Using this data, two models, or computer simulation codes, will be constructed. The first model will describe the flow at the detailed sub-cm scale. The second will describe the flow only in an average sense, so that it can be used meaningfully at the field scale of an entire aquifer or petroleum reservoir. Moreover, statistical analysis will allow for the quantification of uncertainty in the data. The project is expected to result in substantially improved modeling of flow and transport in vuggy media over large scales. The project will impact the education of three Ph.D. students, who will be trained in an interdisciplinary environment. Since carbonate rocks comprise many of the world's aquifers and oil reservoirs, society will benefit indirectly. Subsurface simulation is an important engineering tool. Groundwater contamination can be remediated or prevented through the engineering design of valid, predictable, and cost effective remediation or containment strategies. Engineering analysis based on simulation studies is also used to quantify, manage, and reduce risks related to oil reservoir management.
