HR: 1340h
AN: H23A-1112    [Abstracts]
TI: Quantification of Meso-Scale Porosity From Borehole Wall Images. Example From the ALIANCE Campos Experimental Site, Mallorca, Spain.
AU: Pezard, P
EM: ppezard@gulliver.fr
AF: Tectonophysique, ISTEEM, Universit‚ de Montpellier 2,49 Place EugŠne Bataillon, Montpellier, 34095 France
AU: * Gaillot, P
EM: philippe.gaillot@univ-pau.fr
AF: FRE 2639-Imagerie G‚ophysique, UPPA, Av. Universite, Pau, 64013 France
AU: Maria-Sube, Y
EM: yves.maria-sube@dstu.univ-montp2.fr
AF: Tectonophysique, ISTEEM, Universit‚ de Montpellier 2,49 Place EugŠne Bataillon, Montpellier, 34095 France
AU: Gouze, P
EM: Philippe.Gouze@msem.univ-montp2.fr
AF: Tectonophysique, ISTEEM, Universit‚ de Montpellier 2,49 Place EugŠne Bataillon, Montpellier, 34095 France
AU: Lotz, G
EM: Gerard.Lotz@ msem.univ-montp2.fr
AF: Tectonophysique, ISTEEM, Universit‚ de Montpellier 2,49 Place EugŠne Bataillon, Montpellier, 34095 France
AB: The porosity distribution in carbonates from reefal origin is controlled both by primary and diagenetic processes (fracturing, dolomitisation and dissolution). The study and characterisation of porosity in reservoirs therefore requires a multi-scale and multidisciplinary approach. The analysis of mm-scale digital borehole wall images provides a reliable and practical method to identify mesoscale (vuggy to karstic) porosity and/or fracture porosity, and a new method providing a quantitative analysis of such images is presented here. This new method is based on the analysis of borehole acoustic and optical images. These images have been collected from the MC2 corehole that penetrates the Miocene reefal carbonates of the Campos Coastal site (Mallorca, Baleares, Spain). These sites were drilled in the framework of the Advance Logging Investigations of Aquifers iN Coastal Environment (ALIANCE) European Community Program aimed at developing new techniques to investigate salt-water intrusion in coastal regions. This new method (i) is insensitive to potential eccentering bias of the borehole image logging tools, (ii) analyses vugs and background based on the greyscale colour of each digital images and (iii) calculates the percentage of vuggy/fracture porosity and its attributes in terms of pores size, shape and orientation distributions. Experimentation and comparison with classical porosity determinations (triple weight and Mercury (Hg) porosity) on core, image analysis of slabbed-core samples and thin sections showed that a simple greyscale threshold would not realistically differentiate between greyscale contrast of vugs and background. A moving average calculated around the circumference of the borehole and expressed as the background greyscale intensity is identified as a baseline from which to identify a local greyscale threshold for vugs. Once identified, the characterization of the pores intersected by the borehole as a function of depth and azimuth allow (i) to correlate porosity with lithology (natural gamma ray, velocity and electrical conductivity) as well as hydrological profiles (fluid temperature, pH, dissolved 02), (ii) to characterize lithological units, (iii) to identify the diagenetic processes leading to the present transport properties of the structure and (iv) to evaluate the impact of present brine intrusion several km into the island.
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
DE: 1832 Groundwater transport
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting