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The Leading Edge; November 2003; v. 22; no. 11; p. 1135-1141; DOI: 10.1190/1.1634919
© 2003 Society of Exploration Geophysicists
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Porosity and lithology prediction at Caballos Formation in the Puerto Colón Oil Field in Putumayo (Colombia)

Horacio Acevedo

Ecopetrol, Bogotá, Colombia

Wayne D. Pennington

Michigan Technological University, Houghton, Michigan, U.S.

Corresponding author: horacio.acevedo@ecopetrol.com.co

The first 20% of the full text of this article appears below.

At a given pressure and temperature, differences in the velocities of propagation of P- and S-waves in rocks can indicate differences in various properties of the rocks, including porosity, lithological composition, and the fluids occupying the pore space. In the absence of direct S-wave observations, we study the response of interfaces between rock units to wavefronts with different angles of incidence to infer changes in S-wave velocities. We have used modern techniques of seismic inversion that involve P- and S-impedance estimation from various angle stacks to estimate the rock properties.

This study presents the results of a seismic inversion analysis and interpretation of the Acae-3D seismic volume. The main target is the higher-quality areas of Caballos Formation at Puerto Colón oil field in the foreland of Columbia's Putumayo Basin (Figure 1). The oil field is a faulted anticline or monocline with regional dip (Figure 2). The study was based on 3D angle-dependent seismic data and well-log information, which were used to obtain P-impedance (PI) and S-impedance (SI) response. The log data available was of mixed quality due to poor borehole conditions. As a result, this study used existing rock physics models and extreme well-log editing to create suites of highly corrected logs, including modeled VS logs, for inversion and interpretation.


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  		Figure 1. Location of the Acae 3D seismic volume. (Modified from Higley, 2001.)

 

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  		Figure 2. Geologic model along a dip section at Puerto Colon Oil Field and the interpreted horizons.

 
Caballos Formation (Aptian-Albian) is mostly a sequence of sandstones, interbedded with dark gray shales with thin coal laminations. The mean thickness is 250 ft and average porosity in the sands is 12%. This sequence represents the initiation of the Cretaceous sedimentation in a transgressive deltaic environment over Jurassic volcano-sediments. Figure 3 shows more details of the stratigraphic sequence.


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  		Figure 3. Generalized stratigraphic . . . [Full Text of this Article]

 





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