Application of Glauconite Morphology in Geosteering and for on-Site Reservoir Quality Assessment in Very Fine-Grained Sandstones: Carnarvon Basin, Australia

  1. Richard H. Worden5 and
  2. Sadoon Morad6
  1. J. P. Schulz-Rojahn,
  2. D. A. Seeburger and
  3. G. J. Beacher§

Published Online: 17 MAR 2009

DOI: 10.1002/9781444304336.ch21

Clay Mineral Cements in Sandstones

Clay Mineral Cements in Sandstones

How to Cite

Schulz-Rojahn, J. P., Seeburger, D. A. and Beacher, G. J. (1999) Application of Glauconite Morphology in Geosteering and for on-Site Reservoir Quality Assessment in Very Fine-Grained Sandstones: Carnarvon Basin, Australia, in Clay Mineral Cements in Sandstones (eds R. H. Worden and S. Morad), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304336.ch21

Editor Information

  1. 5

    Department of Earth Sciences, University of Liverpool, Brownlow Street, Liverpool L69 3GP, UK

  2. 6

    Department of Earth Sciences, Uppsala University, Villa vägen 16, S-752 36 Uppsala, Sweden

Author Information

  1. West Australian Petroleum Pty Ltd. (WAPET), Box S1580 GPO, Perth, Western Australia 6001, Australia

  1. Shell International Exploration and Production B.V. (SIEP), c/o Brunei Shell Petroleum, EPE/21, KB 3534, Seria, Brunei Darussalam

  2. Chevron Petroleum Technology Company (CPTC), 6001 Bollinger Canyon Road, San Ramon, CA 94583, USA

  3. §

    Kalaro Pty Ltd., 40 Campbell Drive, Hillarys, Western Australia 6025, Australia

Publication History

  1. Published Online: 17 MAR 2009
  2. Published Print: 7 OCT 1999

ISBN Information

Print ISBN: 9781405105873

Online ISBN: 9781444304336

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Keywords:

  • glauconite case study;
  • application of glauconite morphology in geosteering, Carnarvon Basin;
  • oil based mud (OBM);
  • West Australian Petroleum Pty Ltd. (WAPET);
  • lower Cretaceous Mardie Greens and Member of the Muderong Shale;
  • Saladin Field - eastern end of Thevenard Island in TL/4, Western Australia;
  • well-site observations;
  • dinoflagellate zones and approximate ages for Early Cretaceous sediments of Australia's North West Shelf

Summary

This paper describes the innovative application of drill cuttings during the drilling of a horizontal development well in the Mardie Greensand of Early Cretaceous age, Saladin Field, Australian North West Shelf (Carnarvon Basin). Well results show that the morphology of glauconite pellets, as observed in drill cuttings under the binocular microscope, can be useful for making a first-pass assessment of reservoir quality when drilling with oil-based mud (OBM) in this very fine to fine-grained sandstone. The shape of the glauconite pellets is controlled by the degree of rock compaction, which, in turn, is controlled by the degree of framework grain support that drives reservoir quality. At Saladin, good-quality Mardie reservoir rock (up to 100mD at least) capable of producing initial oil rates of up to 4000 BOPD (barrels of oil per day) from individual horizontal wells is dominated by more or less well-rounded (‘marshmallow-shaped’) glauconite pellets with gently curved flat tops and bottoms, consistent with very minor compaction owing to abundant framework grain support. In contrast, relatively poor-quality Mardie Greensand reservoir (≤10mD) is dominated by thin glauconite pellets with long flat tops and bottoms, and non-reservoir Mardie Greensand lithologies contain disk- or plate-shaped glauconite pellets that are estimated to have compacted by as much as 80% or more. The description of the clay pellet style rather than just a conventional description of cuttings is the key to a reliable lithology indicator because the bulk of the very fine to fine sand grains tends to be lost at the shakers, whereas the larger glauconite pellets are retained preferentially. This simple recognition could have important implications for pay detection in low-resistivity (greensand) exploration settings, although unproven for non-OBM borehole conditions. Further, despite lag time, the simple but effective method can complement measurement-while-drilling (MWD) controlled geosteering, as exemplified by the Saladin Field, where along-hole variations in the shape of glauconite pellets provided key stratigraphical clues. In the event that exclusively disk- or plate-shaped glauconite pellets are encountered along supposed reservoir target sections, an early well-site warning system is provided that could accelerate the decision to plug and abandon. Finally, in horizontal or high-angle deviated wells the technique has potential applications for static reservoir modelling because it may allow the reservoir geologist to gain an improved understanding of lateral facies transitions and sand geometries in subtle greensand lithologies.