Systematic diagenetic changes in the grain-scale morphology and permeability of a quartz-cemented quartz arenite
The material properties of sedimentary rocks are controlled by a range of parameters, including grain size, sorting, and modification of the original sediment through the diagenetic processes of compaction and cementation. To isolate the effects of diagenesis and explore how they modify permeability, we quantified changes in grain and pore morphology accompanying progressive diagenesis of a simple system: a well-sorted, variably quartz-cemented quartz arenite of relatively uniform grain size. The most common type of authigenic cement in sandstones, quartz overgrowths, is responsible for significant porosity and permeability reduction. The distribution of overgrowths is controlled by available pore space and the crystallographic orientations of individual quartz grains. We show that progressive quartz cementation modifies the grain framework in consistent, predictable ways. Detailed microstructural characterization and multiple regression analyses demonstrate that both the number and length of grain contacts increase as the number of pores increases and the number of large well-connected pores decreases with progressive diagenesis. The aforementioned changes progressively alter pore shape and reduce pore-size variability and bulk permeability. These systematic variations in the pore network correlate with changes in permeability, such that we can use our data to calibrate the Kozeny-Carmen relation, demonstrating that it is possible to refine predictions of permeability based on knowledge of the sedimentary system. Jennie Cook completed her Ph.D. in 2010 at the University of Wisconsin-Madison on the structural and mechanical effects of diagenesis in sandstone. She presently works for BP as a geologist. Laurel Goodwin has been a professor at the University of Wisconsin–Madison since 2004, after working at New Mexico Tech. Her research interests include the mechanics of fracture and faulting and fluid-fault interactions in granular porous media. She received a B.A. degree from the University of Maine-Orono and an M.A. degree and Ph.D. from the University of California-Berkeley. David F. Boutt is an assistant professor of geosciences at the University of Massachusetts–Amherst. He received his Ph.D. from New Mexico Tech in 2004 with a specialization in hydrology. His research is focused on understanding the coupling between fluid flow and deformation in permeable media, with the goal of improving the characterization and conceptualization of hydrogeologic systems.
David L. Boutt, Jennie E. Cook, and Laurel B. Goodwin. "Systematic diagenetic changes in the grain-scale morphology and permeability of a quartz-cemented quartz arenite" AAPG Bulletin 95 (2011): 1067-1088.
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