Geostatistics applied to cross-well reflection seismic for imaging carbonate aquifers
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2013-05Metadata
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Parra, Jorge
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Geostatistics applied to cross-well reflection seismic for imaging carbonate aquifers
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Abstract
Cross-well seismic reflection data, acquired from a carbonate aquifer at Port Mayaca test site near the eastern
boundary of Lake Okeechobee in Martin County, Florida, are used to delineate flow units in the region
intercepted by two wells. The interwell impedance determined by inversion from the seismic reflection
data allows us to visualize the major boundaries between the hydraulic units. The hydraulic (flow) unit properties
are based on the integration of well logs and the carbonate structure, which consists of isolated vuggy
carbonate units and interconnected vug systems within the carbonate matrix. The vuggy and matrix porosity
logs based on Formation Micro-Imager (FMI) data provide information about highly permeable conduits at
well locations. The integration of the inverted impedance and well logs using geostatistics helps us to assess
the resolution of the cross-well seismic method for detecting conduits and to determine whether these conduits
are continuous or discontinuous between wells. A productive water zone of the aquifer outlined by the
well logs was selected for analysis and interpretation. The ELAN (Elemental Log Analysis) porosity from two
wells was selected as primary data and the reflection seismic-based impedance as secondary data. The direct
and cross variograms along the vertical wells capture nested structures associated with periodic carbonate
units, which correspond to connected flow units between the wells. Alternatively, the horizontal variogram
of impedance (secondary data) provides scale lengths that correspond to irregular boundary shapes of
flow units. The ELAN porosity image obtained by cokriging exhibits three similar flow units at different
depths. These units are thin conduits developed in the first well and, at about the middle of the interwell
separation region, these conduits connect to thicker flow units that are intercepted by the second well. In
addition, a high impedance zone (low porosity) at a depth of about 275 m, after being converted to ELAN
porosity, is characterized as a more confined low porosity structure. This continuous zone corresponds to a
permeability barrier in the carbonate aquifer that separates the three connected conduits observed in the
cokriging image. In the zones above and below this permeability barrier, the water production is very high,
which agrees with water well observations at the Port Mayaca aquifer.
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Artículo de publicación ISI.
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URI: https://repositorio.uchile.cl/handle/2250/126310
DOI: DOI: 10.1016/j.jappgeo.2013.02.010
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JOURNAL OF APPLIED GEOPHYSICS Volume: 92 Pages: 68-75
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