Study of fluid flow through porous rocks is vital to studies of groundwater hydrology and contaminant protection. Previous work has shown that fluid flow is controlled by factors such as porosity, sedimentary grain size, interparticle cement and interstitial mud. Such factors can be measured easily and are widely used in modelling porous media. This project aims to assess the impact of another parameter, CRYSTAL SIZE, on fluid flow in dolostone aquifers. An emerging application of computer-technology, image analysis will be developed and the results shall expand its utility within engineering and geosciences. In addition, the project deals with fundamental questions of the controls of fluid flow in natural materials and the effects that these controls have upon paleohydrology and diagenesis. The results will help satisfy the nation's needs for water and petroleum. In siliclastic rocks, fluids flow between sedimentary particles that are packed together, commonly leaving large, well-connected, interparticle pore spaces. Cements may be precipitated into these pore spaces, but the basic control of the fabric is depositional. In dolostones, fluids flow between crystals that are fitted together in a mosaic; the pore network consists of narrow, sheetlike spaces. Fluid flow in dolostones thus depends on the tortuosity and pore width of the intercrystalline pore system, which are themselves closely related to crystal size. Crystal size is commonly controlled by diagenetic rather than depositional processes. Dolomite aquifers are commonly very finely crystalline, difficult to analyze with a standard dissecting microscope. Image analysis, using core material and a dissecting microscope with slightly enhanced magnification, makes it possible to carry out statistical analyses of crystal size ranges and size distributions. These can be correlated with other textural parameters, and with core analysis data. The project will use around 30 lower San Andres cores in a detailed study of crystal size versus permeability and transmissibility.
