Porosity and permeability are notoriously difficult to predict in carbonates, especially prior to drilling when there is a lack of direct petrophysical data. The aim of this paper is to document the initial results of an integrated outcrop and laboratory study designed to investigate the relationships between pore systems and acoustic velocities in faulted Oligo-Miocene carbonates on the Mediterranean islands of Malta and Gozo. Depositional facies is shown to have a significant effect, with velocities in grain-dominated carbonates up to 1000 m s−1 higher than those in micrite-dominated carbonates. Based on outcrop structural data, the fault zones can be separated into three architectural components: a fault core; an intensely damaged zone; and a weakly damaged zone, with the last passing into undamaged protolith. Our data suggest that only the fault core component can be identified using porosity–velocity data, with P-wave velocity (Vp) values of 5000–6500 m s−1 at helium porosities of less than 5%. Our study is novel in that the prediction of elastic properties and acoustic velocities across fault zones is anticipated by linking laboratory-scale measurements with seismic-scale predictions through quantitative rock physics modelling.
|Number of pages
|Special Publication - Geological Society of London
|Geological Society of London
|Published - 7 Jul 2014
Bibliographical noteWe thank C. Taylor, W. Ritchie and G. Cunha for technical assistance at the University of Aberdeen, and I. Alsop for field photographs. S. Boon (University College, London) provided invaluable advice on ultrasonic velocity equipment and measurements. We also thank Total E & P, the BG Group, and the Industry Technology Facilitator (Aberdeen) for project funding and ongoing support. The Aberdeen Formation Evaluation Society (AFES) helped with significant additional funding for equipment and thin sections. Lastly, we thank the Hedberg conference organizers for a stimulating and intellectually challenging
From: Agar, S. M. & Geiger, S. (eds) Fundamental Controls on Fluid Flow in Carbonates.