Petrophysical Properties of Twenty Drill Cores from the Los Azufres, Mexico, Geothermal Field

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For this study we selected 20 drill cores covering a wide range of depths (400-3000 m), from 15 wells, that provide a reasonable coverage of the field. Only andesite, the largely predominant rock type in the field, was included in this sample. We measured bulk density, grain (solids) density, effective porosity and (matrix) permeability on a considerable number of specimens taken from the cores; and inferred the corresponding total porosity and fraction of interconnected total porosity. We characterized the statistical distributions of the measured and inferred variables. The distributions of bulk density and grain density resulted approximately normal; the distributions ... continued below

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Iglesias, E.R.; Contreras L., E.; Garcia G., A. & Dominquez A., Bernardo January 20, 1987.

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For this study we selected 20 drill cores covering a wide range of depths (400-3000 m), from 15 wells, that provide a reasonable coverage of the field. Only andesite, the largely predominant rock type in the field, was included in this sample. We measured bulk density, grain (solids) density, effective porosity and (matrix) permeability on a considerable number of specimens taken from the cores; and inferred the corresponding total porosity and fraction of interconnected total porosity. We characterized the statistical distributions of the measured and inferred variables. The distributions of bulk density and grain density resulted approximately normal; the distributions of effective porosity, total porosity and fraction of total porosity turned out to be bimodal; the permeability distribution resulted highly skewed towards very small (1 mdarcy) values, though values as high as 400 mdarcies were measured. We also characterized the internal inhomogeneity of the cores by means of the ratio (standard deviation/mean) corresponding to the bulk density in each core (in average there are 9 specimens per core). The cores were found to present clearly discernible inhomogeneity; this quantitative characterization will help design new experimental work and interpret currently available and forthcoming results. We also found statistically significant linear correlations between total density and density of solids, effective porosity and total density, total porosity and total density, fraction of interconnected total porosity and the inverse of the effective porosity, total porosity and effective porosity; bulk density and total porosity also correlate with elevation. These results provide the first sizable and statistically detailed database available on petrophysical properties of the Los Azufres andesites. 1 tab., 16 figs., 4 refs.

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  • Proceedings, Twelfth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, Calif., January 20-22, 1987

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  • Report No.: SGP-TR-109-28
  • Grant Number: AT03-80SF11459
  • Grant Number: AS07-84ID12529
  • Office of Scientific & Technical Information Report Number: 888534
  • Archival Resource Key: ark:/67531/metadc885403

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  • January 20, 1987

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  • Sept. 21, 2016, 2:29 a.m.

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  • Dec. 6, 2016, 3:39 p.m.

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Iglesias, E.R.; Contreras L., E.; Garcia G., A. & Dominquez A., Bernardo. Petrophysical Properties of Twenty Drill Cores from the Los Azufres, Mexico, Geothermal Field, article, January 20, 1987; United States. (digital.library.unt.edu/ark:/67531/metadc885403/: accessed August 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.