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Graphic Correlation of Biostratigraphic Data as a Powerful Tool for Oil Exploration in Frontier Deepwater Areas: A Case Study in the Brazilian Equatorial Margin*

 

Jorge De Jesus Picanço De Figueiredo1, Emilson Fernandes Soares1, Ivo Trosdtorf, Jr.1, João Luiz Caldeira1, Paulus Hendrikus Van Der Ven1, and Elizabete Pedrão Ferreira1

 

Search and Discovery Article #50190 (2009)

Posted June 3, 2009

 

*Adapted from extended abstract prepared for AAPG International Conference and Exhibition, Cape Town, South Africa.

 

1 Petrobras S.A., Rio de Janeiro, RJ, Brazil ([email protected], [email protected])

 

Introduction

Exploration in offshore basins in the Brazilian Equatorial Margin faces a serious problem of lack of well data in deep waters. Despite the good quality of 3-D seismic over deepwater prospects, the response of seismic to the presence, distribution and quality of reservoirs is uncertain, thus precluding confident correlation between wells in the shallow platform with the deep offshore extensions.

The margin consists of six basins (from SE to NW: Potiguar, Ceará, Piauí-Camocim, Barreirinhas, Pará-Maranhão and Foz do Amazonas) straddling over 2000 km of coastline and only six deep water wells (Figure 1).

To mitigate exploration risk it is necessary to establish a reliable chronostratigraphic framework using the geological data to construct the highest possible frequency geological events charts. The recognition of variations in relative sea levels with geological time is a basic necessity, once these events can be correlated to Previous HitsequenceNext Hit boundaries in the seismic over deepwater prospects.

 

 

 

uIntroduction

uFigures

uMethodology

uBarreirinhas basin

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uIntroduction

uFigures

uMethodology

uBarreirinhas basin

uReferences

 

Figure Captions

Figure 1. Localization map of basins of the Brazilian Equatorial Margin.

Figure 2. Graphic correlation of biostratigraphic data of onshore and offshore wells from Barreirinhas Basin. Biostratigraphic hiatuses can be interpreted as Previous HitsequenceNext Hit boundaries.

Figure 3. Old and new stratigraphic chart (only drift Previous HitsequenceNext Hit) of the Barreirinhas Basin. Abbreviations: PER - Periá Formation, BON - Bonfim Formation, PRE – Preguiças Formation, ARE – Areinhas Formation, TRA – Travosas Formation, ISA – Ilha de Santana Formation, PIR – Pirabas Formation, BAR – Barreiras Formation. Modified from Feijó (1994) and Trosdtorf Jr. et al. (in press).

Methodology

The methodology consists of graphic correlations of biostratigraphic zonation of wells in the shallow areas (Wescott et al., 1988; Neal et al., 1998; Aubry et al., 1995; Figure 2). A crossplot of biostratigraphic data on the X-axis, plotted against depth on the Y-axis was built for each well taking into account: a) its position in the basin; b) the density of data; and c) the confidence of the data. These were integrated with the global eustatic sea level chart and available seismic data, resulting in the recognition of many unconformities that reflect the main Previous HitsequenceNext Hit boundaries of each basin.

Case Study – Barreirinhas Basin

A case study of the Barreirinhas basin is presented. Results revealed the power of this methodology in establishing the Previous HitsequenceNext Hit Previous HitstratigraphyNext Hit for shallow and deep waters, and in detecting Previous HitsequenceNext Hit boundaries correlative to significant sea level falls (reservoir prediction). Ten major events of fall-rise relative sea level were identified against only three events recognized in earlier works (Figure 3).

References

Aubry, M.P., 1995, From chronology to Previous HitstratigraphyNext Hit: interpreting the lower and middle Eocene stratigraphic record in the Atlantic Ocean, in Geochronology Time Scale and Global Stratigraphic Correlation: SEPM Special Publication 54, p. 213-274.

Feijó, F.J., 1994, Bacia de Barreirinhas: Boletim de Geociências da Petrobras, v. 8 (1), p. 103-105.

Neal, J.E., Stein, J.A., and Gamber, J.H., 1998, Nested stratigraphic cycles and depositional systems of the Paleogene Central North Sea, in Mesozoic and Cenozoic Previous HitSequenceNext Hit Previous HitStratigraphyNext Hit of European Basins: SEPM Special Publication 60, p. 261-288.

Trosdtorf, Jr., I.; Zalán, P.V., Figueiredo, J.J.P. de; Soares, E.F., in press, Bacia de Barreirinhas:. Boletim de Geociências da Petrobras.

Wescott, W.A., Krebs, W.N., Sikora, P.J., Boucher, P. J., and Stein, J. A., 1998, Modern application of Previous HitbiostratigraphyTop in exploration and production: The Leading Edge, v. 17, p. 1204-1210.

 

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