Anisotropic permeability and bimodal pore-size distributions of fine-grained marine sediments

Author(s): Bolton, Alistair J.; Maltman, Alex J.; Fisher, Quentin
Author Affiliation(s): Primary:
University of Wales, Institute of Geography and Earth Sciences, Aberystwyth, United Kingdom
University of Leeds, United Kingdom
Volume Title: Marine and Petroleum Geology
Source: Marine and Petroleum Geology, 17(6), p.657-672. Publisher: Elsevier, Oxford, United Kingdom. ISSN: 0264-8172
Note: In English. 58 refs.; illus., incl. 1 table
Summary: We present preliminary results illustrating that overconsolidated fine-grained sediments without a compactional fabric but favourably aligned microfractures can show significant anisotropic permeability. At much reduced effective stress, substantial flow can occur parallel to the fabric such that anisotropy indices--calculated by dividing horizontal permeability by vertical permeability--increase by factors above 10. SEM observations show no intense particle alignments in the materials, but the presence of parallel oriented microfractures; mercury-intrusion porosimetry data indicate that this enhanced flow is due to microfractures opening when favourably oriented. Such an effect is displayed as a distinctly bimodal pore-size distribution when intruded by mercury parallel to the fabric; identical samples with the fabric oriented perpendicular to intrusion direction show only unimodal pore-size distributions. While the results, at present, are only directly applicable to the shallow subsurface, it is proposed that directional bimodal pore-size distribution needs further investigation for deeper, more consolidated sediments in light of the potential ramifications highlighted by the results. For example, in some instances shales may not be as efficient hydrocarbon seals as traditionally thought. Abstract Copyright (2000) Elsevier, B.V.
Year of Publication: 2000
Research Program: ODP Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; 29 Economic Geology, Energy Sources; Anisotropy; Australasia; Clastic rocks; Distribution; Fabric; Grain size; Leg 180; Marine sediments; Microstructure; ODP Site 1108; Ocean Drilling Program; Offshore; Papua New Guinea; Permeability; Petroleum; Petroleum engineering; Petroleum exploration; Physical properties; Pressure; Reservoir properties; SEM data; Sampling; Saturation; Sedimentary rocks; Sediments; Shale; Stress; Woodlark Basin
Coordinates: S094443 S094443 E1513732 E1513732
Record ID: 2001069931
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands