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Abstract


 
Chapter from: SG 42:  Applications of 3-D Seismic Data to Exploration and Production

Edited by: 
Paul Weimer and Thomas L. David

Authors:
Mario Gutierrez, Eduardo Lozano, and Michael Sroczynski



Published 1996 as part of Studies in Geology 42
Copyright © 1996 The American Association of Petroleum Geologists.  All Rights Reserved.

*Editorial Note: Page numbers in this digital version (HTML and PDF) do not correspond to those of the hardcopy.
Otherwise, the two are the same.
 

CHAPTER 6

Chapter 6: Impact of 3-D Seismic Interpretation on Reservoir Management in the Apiay-Ariari Oil Fields, Llanos Basin, Colombia

Mario Gutierrez*, Eduardo LozanoÝ, and Michael Sroczynskiý
 

 

 Gutierrez, M., E. Lozano, and M. Sroczynski, Impact of 3-D seismic interpretation on reservoir management in the Apiay-Ariari oil fields, Llanos Basin, Colombia, in P. Weimer and T. L. Davis, eds., AAPG Studies in Geology No. 42 and SEG Geophysical Developments Series 
No. 5, AAPG/SEG, Tulsa, p. 57-68.
SEISMIC OVERVIEW

ECOPETROL contracted Western Geophysical to acquire and process 125 km2 (78 mi2) of 3-D seismic data covering the Apiay-Ariari area. The data were jointly interpreted by an interdisciplinary team of ECOPETROL and Western Geophysical personnel.

The overall topography of this region is gently rolling farmlands. The acquisition of data was slightly hampered by pre-existing production facilities around the Apiay and Suria fields. Table 1 lists a summary of the main parameters used for the seismic acquisition (Figure 3).

Standard 3-D seismic processing was done in Bogotá. In addition, random noise attenuation, instrument phase correction, and time variant spectral whitening were performed in Houston to achieve a dataset suitable for stratigraphic interpretation.

STRATIGRAPHIC FRAMEWORK

The stratigraphy of the Llanos Basin, Colombia, is typically described with standard lithostratigraphic nomenclature (Reyes, 1992). Nomenclature used in this study is consistent with the operational units of the Llanos Basin as defined by ECOPETROL. These units are bounded by unconformities and/or lithology changes (Figure 4).

PALEOZOIC-MESOZOIC STRATA

Paleozoic strata lie unconformably upon Precambrian rocks. The lower units consist of Cambro-Ordovician strata overlying phyllites. The seismic reflection for this boundary is of poor quality. The Mesozoic section in the Apiay area consists of Upper Cretaceous strata, which are Cenomanian-Maastrichtian in age (Castro-Arévalo et al., 1991). ECOPETROL recognizes two operational units in this formation. The older K-2 reservoir is the most economically significant. Core analysis of this unit indicated quartzose, medium- to coarse-grained sandstones, varying locally to conglomeratic. This unit has been interpreted as braided stream channel deposits. Overlying the K-2 is the K-1 unit, which consists of shales with interebedded fine- to 
ABSTRACT

The Apiay-Ariari oil field of the Llanos Basin, Colombia, is located within a structurally complex area. A 3-D seismic survey was necessary to understand the structural factors controlling the distribution of hydrocarbons within the field. The results of the interpretation were used in conjunction with core, production, and log data to complete an integrated reservoir evaluation. Time structure maps were converted to depth using geostatistical techniques which resulted in a more detailed realization of strike-slip, normal, and reverse faults, consistent with a right lateral shear system. The 3-D interpretation is also much more simplified than the 2-D interpretation. This integrated study realized an increase of field reserves of greater than 60.7 million bbl over those originally calculated. The study also identified several exploration plays, such as that successfully tested by the Gavan-1 well. The ability to fully integrate the new 3-D seismic information with all available data resulted in a more accurate understanding of structural components responsible for the trapping of hydrocarbons within the Apiay-Ariari fields. This knowledge has proven to be essential for proper management of the field development.

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