Allshorn, SL, Dawe, RA and Grattoni, CA orcid.org/0000-0003-4418-2435 (2019) Implication of heterogeneities on core porosity measurements. Journal of Petroleum Science and Engineering, 174. pp. 486-494. ISSN 0920-4105
Abstract
Heterogeneities within core samples affect the accuracy of the laboratory measured core plug interconnected porosity. The laboratory measures the volume averaged porosity of the interconnected pores, <ϕm>. For homogeneous cores this is the correct porosity ± any experimental error. However for heterogeneous cores when any embedded material (unknown or ignored) has a differing porosity, ϕi, to that of the containing outer shell, ϕo, there will be increased uncertainty. We show that the difference between the measured volume averaged porosity, <ϕm>, and the porosity of the outer shell of the core, ϕo can be quantified by our Heterogeneity Factor, H. H is defined as (<ϕm> - ϕo)/ϕo and given by H = F(R-1), where F is the ratio of the bulk volume of the embedded material to the total core bulk volume (measured), VBi/VBm, and R is the ratio of the embedded and the host outer porosity, ϕi/ϕo. The core plug homogeneous model can create increased error bounds in porosity for heterogeneous plugs.
When H is zero there is no error in the porosity measurement due to heterogeneity, but when H≠ 0 then the differences can be significant and increases the experimental error bound. We present graphs for relevant industry scenarios to demonstrate the effect of any inclusions in the measured porosity. We find that when F is ∼0.1 i.e., inner included porosity is 10% of bulk volume, the relative error between <ϕm> and ϕo can reach ∼30% and even larger differences when F > 0.1. We then give a real example from a faulted vuggy outcrop carbonate which demonstrates extra porosity uncertainties, even for a very small vug. Finally we discuss the possible effect of embedded clay intrusions emitting adsorbed gas on grain/pore volume determinations of porosity using gas expansion, a common laboratory method of porosity determination.
Appreciation of core heterogeneity on the precision of the laboratory porosity measurements is essential to improve the confidence in the error bounds for the quality control of laboratory core porosity measurements, and of the porosity distribution frequency for inputs to statistical methods such as Monte Carlo analysis for oil-in-place estimations, STOIIP.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018 Elsevier B.V. All rights reserved. This is an author produced version of a paper published in Journal of Petroleum Science and Engineering. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Porosity; Heterogeneity; Core plugs; Inclusions; Vugs; Clay; CT scanning |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 30 Nov 2018 11:34 |
Last Modified: | 20 Nov 2019 01:38 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.petrol.2018.11.045 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:139373 |
Commentary/Response Threads
- Allshorn, SL, Dawe, RA and Grattoni, CA Implication of heterogeneities on core porosity measurements. (deposited 30 Nov 2018 11:34) [Currently Displayed]
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