Christopher D. White, 2004. "Geostatistical and Flow Modeling of Intrareservoir Mudstones", Depositional Processes and Reservoir Characteristics of Siltstones, Mudstones and Shales, Erik D. Scott, Arnold H. Bouma
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Geoscientists and engineers have long appreciated that intrareservoir mudstones may affect oil and gas recovery significantly. Mudstones have particularly significant effects in reservoirs with low net-to-gross (e.g., overbank turbidites) or if reservoirs have highly continuous mudstone layers (e.g.., tide-influenced deltas).
Interdisciplinary outcrop and shallow analog studies formulated and tested models for the spatial distribution of mudstones in deltaic sandstones. At scales from decimeters to hundreds of meters, mudstone length distributions may be described using gamma distributions. This approach is data rich, computationally tractable, and provides direct links to covariance geostatistics commonly used in reservoir modeling. These outcrop observations have been related to and validated using shallow, high-resolution ground-penetrating radar surveys. Experimental design and flow simulations assessed the importance of the intrareservoir mudstones: in a tide-influenced delta the mudstones controlled flow, whereas the mudstones were nearly inconsequential in a marine-influenced distributary point bar.
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Siltstones, mudstones and shales have been studied mainly with regard to general transportdeposition processes and clay mineralogy. A small group of investigators, with differing backgrounds, have worked on these fine-grained deposits. Recent studies on deepwater deposits from cores and outcrops indicate that the presence of finer-grained deposits greatly affect the fluid flow properties of deepwater reservoirs. Characteristics and rock properties of these deposits, which resulted from a variety of depositional processes, are just beginning to be understood.