Cox, P.A. and Wood, R.A. and Dickson, J. A. D. and Al Rougha, H.B. and Shebl, H. and Corbett, P.W.M. (2010) Dynamics of cementation in response to oil charge: Evidence from a Cretaceous carbonate field, U.A.E. Sedimentary Geology, 228 (3-4). pp. 246-254. DOI https://doi.org/10.1016/j.sedgeo.2010.04.016
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Abstract
Oil charge is thought to inhibit the growth of cements within subsurface pore systems. We explore this phenomenon in a giant Cretaceous carbonate field from U.A.E., where the oil-filled crest porosity ranges from 10 to 50% and permeability from 0.08 to 830 mD but coeval water leg porosity is reduced to 10 to 23% and permeability to 0.1 to 4 mD. Only 5% of primary interparticle pores (> 30 [mu]m diameter) in the crest are fully cemented, compared to 99% of pores in the water leg.<br/>Syntaxial calcite burial cements (> 10 [mu]m diameter) in the oil leg show 12 cathodoluminescence zones with oil inclusions (n = 27) occurring in four of the five final zones. Mean in-situ ion microprobe [delta]18OVPDB data from the oil leg cements range from -1.2[per mille sign] in the oldest zone decreasing to -10.3[per mille sign] in zone 11, returning to -7.7[per mille sign] in the final zone. The oldest distinguishable cement zone in the water leg shows highly variable [delta]18O from -3.6[per mille sign] to -9.3[per mille sign] with a mean of -7.3[per mille sign], and with subsequent zones decreasing to a mean value of -9.4[per mille sign] for the youngest cement zone. Decreasing [delta]18O values are interpreted as indicating increasing temperature reflecting burial and the evolution of pore water composition: broadly similar trends in the oil and water legs suggest precipitation under the same general conditions.<br/>Unlike the oil leg cements, the final zone in the water leg occludes nearly all remaining pore space. The [delta]18OVPDB of bulk micrite from the water leg shows an average of -7.4[per mille sign] (n = 9) compared to -6.2[per mille sign] (n = 10) from the oil leg, suggesting the precipitation of further micrite cement at greater burial depths. We infer that burial cementation slowed in the presence of oil due to a reduction of potential nucleation sites as well as porewater and solute movement within weakly oil-wet pores, whereas continued flow and solute movement through all pores including the micropores (< 10 [mu]m diameter) enabled extensive cementation in the water leg.
Item Type: | Article |
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Additional Information: | cm:ZADCO (http://www.zadco.ae/) |
Uncontrolled Keywords: | 2010AREP; IA59; cml |
Subjects: | 02 - Geodynamics, Geophysics and Tectonics |
Divisions: | 02 - Geodynamics, Geophysics and Tectonics |
Journal or Publication Title: | Sedimentary Geology |
Volume: | 228 |
Page Range: | pp. 246-254 |
Identification Number: | https://doi.org/10.1016/j.sedgeo.2010.04.016 |
Depositing User: | Sarah Humbert |
Date Deposited: | 25 Aug 2011 11:04 |
Last Modified: | 23 Jul 2013 10:02 |
URI: | http://eprints.esc.cam.ac.uk/id/eprint/2170 |
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