Reservoir characterisation of unconventional rock units in the middle jurassic Sargelu Formation, atrush field, zagros folded belt
File(s)
Accepted version
Author(s)
Zangana, Hawar A
Rashid, Fraidoon
Hussein, Devan
Lawrence, James
Type
Journal Article
Abstract
The heterogeneous lithological components of the Middle Jurassic Sargelu Formation in the Atrush field of the high folded zone were examined using rock samples, conventional wireline logs, mud logs and well test results throughout two wells. The Sargelu Formation is 45 m thick and has been divided into three units based on lithological characteristics and shale volume. The upper unit of the Sargelu Formation is composed of argillaceous limestone with intercalation of dolostone and anhydrite beds. The middle unit of the Sargelu Formation is composed of organic rich laminated shales, which contain residual bitumen, whilst the lower unit of the formation is dominated by argillaceous limestones. Lithological variation, mineralogy and organic matter contents are shown to be essential factors in controlling the reservoir matrix porosity and permeability. The maximum matrix porosity and permeability were observed within the dolomite plug samples (13.40%, 10.40 mD) and the lowest values were recorded in the anhydrite samples, both found in the upper unit of the Sargelu Formation. The fracture permeability is three orders of magnitude higher than the matrix permeability and the hydrocarbon production is predominately derived from the fractured intervals throughout the Sargelu Formation. The interconnected fracture pathways are influenced by the lithological variation and mineralogical components of the formation along with the tectonic position of the field. It was found that as the confining pressure increased the fracture permeability reduced. The different lithologies were also found to be sensitive to increases in the confining pressure. The clastic shale rich rocks are most sensitive to increases in confining pressure, whilst the more carbonate rich rocks showed the lowest variation as a function of confining pressure.
Date Issued
2022-12
Date Acceptance
2022-09-05
Citation
Journal of African Earth Sciences, 2022, 196, pp.1-11
ISSN
1464-343X
Publisher
Elsevier BV
Start Page
1
End Page
11
Journal / Book Title
Journal of African Earth Sciences
Volume
196
Copyright Statement
Copyright © 2022 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Identifier
https://www.sciencedirect.com/science/article/pii/S1464343X22002746?via%3Dihub
Subjects
0403 Geology
0404 Geophysics
Publication Status
Published
Article Number
104722
Date Publish Online
2022-09-16