Mini thief zones

subcentimeter sedimentary features enhance fracture connectivity in shales

Alistair T. McCay, Zoe K. Shipton, Rebecca J. Lunn, Julia F. Gale

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

This study examines the influences on fluid flow within a shale outcrop where the networks of two distinct paleoflow episodes have been recorded by calcite-filled veins and green alteration halos. Such direct visualization of flow networks is relatively rare and provides valuable information of fluid-flow behavior between core and seismic scale. Detailed field mapping, fracture data, and sedimentary logging were used over a 270 m 2 (2910 ft 2) area to characterize the paleo–fluid-flow networks in the shale. Distal remnants of turbidite flow deposits are present within the shale as very thin (1–10 mm [0.04–0.4 in.]) fine-grained sandstone bands. The shale is cut by a series of conjugate faults and an associated fracture network, all at a scale smaller than seismic detection thresholds. The flow episodes used fluid-flow networks consisting of subgroups of both the fractures and the thin turbidites. The first fluid-flow episode network was mainly comprised of thin turbidites and shear fractures, whereas the network of the second fluid-flow episode was primarily small joints (opening mode fractures) connecting the turbidites. The distribution of turbidite thicknesses follows a negative exponential trend. which reflects the distribution of thicker turbidites recorded in previous studies. Fracture density varies on either side of faults and is highest in an area between closely spaced faults. Better predictions of hydraulic properties of sedimentary-structural networks for resource evaluation can be informed from such outcrop subseismic scale characterization. These relationships between the subseismic features could be applied when populating discrete fracture networks models, for example, to investigate such sedimentary-structural flow networks in exploration settings.

Original languageEnglish
Pages (from-to)951-971
Number of pages21
JournalAmerican Association of Petroleum Geologists Bulletin
Volume103
Issue number4
DOIs
Publication statusPublished - 30 Apr 2019

Fingerprint

sedimentary feature
fluid flow
connectivity
shale
Flow of fluids
Shale
fracture network
turbidite
outcrop
hydraulic property
visualization
Calcium Carbonate
Calcite
calcite
Sandstone
sandstone
Deposits
Visualization
resource
Hydraulics

Keywords

  • fluid flow
  • fracture data
  • flow deposits

Cite this

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abstract = "This study examines the influences on fluid flow within a shale outcrop where the networks of two distinct paleoflow episodes have been recorded by calcite-filled veins and green alteration halos. Such direct visualization of flow networks is relatively rare and provides valuable information of fluid-flow behavior between core and seismic scale. Detailed field mapping, fracture data, and sedimentary logging were used over a 270 m 2 (2910 ft 2) area to characterize the paleo–fluid-flow networks in the shale. Distal remnants of turbidite flow deposits are present within the shale as very thin (1–10 mm [0.04–0.4 in.]) fine-grained sandstone bands. The shale is cut by a series of conjugate faults and an associated fracture network, all at a scale smaller than seismic detection thresholds. The flow episodes used fluid-flow networks consisting of subgroups of both the fractures and the thin turbidites. The first fluid-flow episode network was mainly comprised of thin turbidites and shear fractures, whereas the network of the second fluid-flow episode was primarily small joints (opening mode fractures) connecting the turbidites. The distribution of turbidite thicknesses follows a negative exponential trend. which reflects the distribution of thicker turbidites recorded in previous studies. Fracture density varies on either side of faults and is highest in an area between closely spaced faults. Better predictions of hydraulic properties of sedimentary-structural networks for resource evaluation can be informed from such outcrop subseismic scale characterization. These relationships between the subseismic features could be applied when populating discrete fracture networks models, for example, to investigate such sedimentary-structural flow networks in exploration settings.",
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Mini thief zones : subcentimeter sedimentary features enhance fracture connectivity in shales. / McCay, Alistair T.; Shipton, Zoe K.; Lunn, Rebecca J.; Gale, Julia F.

In: American Association of Petroleum Geologists Bulletin, Vol. 103, No. 4, 30.04.2019, p. 951-971.

Research output: Contribution to journalArticle

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AU - Lunn, Rebecca J.

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