Abstract
Heterogeneous permeability, porosity, capillary pressure, and strength are key characteristics of sedimentary and volcanic rocks in geologic reservoirs. In many cases, the heterogeneity is due to nested geological features like the mm-scale coarse-fine intercalations of cross-bedded sandstones, or the km-scale channel, levy, and overbank facies associations in a fluvial environment of deposition.
Where such rocks have experienced an overprint by deformation or reactive fluid flow, initial heterogeneities might be amplified even further: fracturing can impart long-range spatial correlations on the permeability structure, strongly amplifying permeability anisotropy, even in the absence of a noticeable increase of porosity.
This presentation examines the impact of nested heterogeneities on flow, (reactive) transport, and multiphase fluid displacement in natural heterogeneous porous media. The emphasis will be on intermediate-scale features (~0.1 - 500-m in size), difficult to investigate in the lab or below the earth’s surface because flow patterns can only partly be resolved by geophysical imaging techniques. The investigative methods used here are field-data-based numeric simulations, solving elliptic-parabolic equations (fluid pressure, temperature, chemical diffusion) with finite element, and hyperbolic ones (multiphase flow and tracer transport) with finite volume methods.
The behavior of the heterogeneous systems will be explored, proceeding from tracer transport to gas injection and water flooding of naturally fractured reservoirs to maximize hydrocarbon recovery. The presentation will conclude with a general discussion of the impact of heterogeneity, addressing questions such as: Given the nested nature of geologic heterogeneity, is the spreading of injection plumes ergodic? – or – in view of the impact of heterogeneity on sweep, how can CO2 geosequestration or hydrocarbon recovery be optimized?
Brief Biography
Stephan Matthai is Professor and Chair of Reservoir Engineering at the University of Melbourne, Australia, and an internationally recognised expert on subsurface (multiphase) fluid-flow processes and their computer simulation. His research interests include coupled flow, geomechanics, and reactive transport processes facilitated by rock fractures and faults with applications to hydrocarbon extraction, gas storage/geological CO 2 sequestration, enhanced geothermal systems, nuclear waste repository safety, and hydrothermal ore deposits. On the subjects, he has taught graduate students, consulted to the industry, and has acted as advisor to government agencies and professional societies.
During his career, Matthai held positions like a Governors’ Lectureship at Imperial College London, a professor and directorship of the (Petroleum) Reservoir Engineering Institute at Leoben, and postdoctoral positions at Cornell University, Stanford University, and a research fellowship at the ETH Zurich, Switzerland. Matthai earned his PhD from the Research School of Earth Sciences at the Australian National University, Canberra.
