Computerized geochemical modeling of burial diagenesis of the Eocene turbidite reservoir elements: Urucutuca Formation, Esp\xedrito Santo Basin, southeastern Brazil passive margin

Marcos Antonio Klunk,Rommulo Vieira Conceição,Sudipta Dasgupta

doi:10.1186/s42501-018-0009-z

Marcos Antonio Klunk, Rommulo Vieira Conceição + Show 1 more

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https://doi.org/10.1186/s42501-018-0009-z

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Abstract

The computerized geochemical modeling, a useful tool to understand the diagenetic processes influencing the quality of hydrocarbon reservoirs, is performed by using different modules of computer codes based on the thermodynamic and chemical kinetic principles and their associated parameters. As observed in the reservoir lithofacies deposited from the marine sediment-gravity flows, a case study of diagenesis is presented here from the Espírito Santo Basin in southeastern Brazil. The study uses the Geochemist’s Workbench (GWB™), PHREEQC™ and TOUGHREACT™ computation packages. The comparison of performances of these packages demonstrates the convergence of results from the software-based geochemical modeling with the petrographic observation of dissolution, albitization, kaolinization, and the precipitation of calcite and dolomite. Moreover, with limited data points, e.g., the sedimentary petrographic data acquired from limited number of boreholes, the computer simulation establishes itself to be a powerful quantitative method estimating the degree and type of diagenetic alteration of turbidite reservoir bodies in contact with a source of saline-water influx associated with salt tectonics. Therefore, using the limited petrographic data points, the geochemical computer-simulation method can even be utilized and extrapolated for areas where similar geological context is interpreted but no borehole data are available. Hence, porosity of turbidite reservoir lithofacies can be predicted in relation to the spatial distribution of dissolution, kaolinization, and albitization of feldspars and authigenic carbonate precipitation.

Highlights

1.1 Computerized geochemical modeling Over the last few decades, investigators in the hydrocarbon exploration, development, and production-related sector have been trying to address the increasing complexity of reservoir formations and the consequent uncertainty which include post-depositional diagenetic changes taking place within the reservoir architectural elements
An important prerequisite to be considered before constructing a geochemical model is that the results must be calibrated after simulation with a reference set of data derived from, for example, at least a borehole or from an analog outcrop that represents the geological context of the computer model
3.1 Diagenesis of the Eocene turbidite reservoirs of the Cangoá field The detailed petrographic analysis and petrological interpretation of the reservoir suggest a diagenetic history divided into 4 stages: (1) The marine eodiagenesis, (2) The meteoric eodiagenesis, (3) The compactional mesodiagenesis, and (4) The thermobaric mesodiagenesis. (Fig. 3a-h; sensu Galloway 1984; Worden and Burley 2003; de Oliveira et al 2018)

Summary

Introduction

An important prerequisite to be considered before constructing a geochemical model is that the results must be calibrated after simulation with a reference set of data derived from, for example, at least a borehole (i.e., from sedimentological and formation-water data analyzed from conventional cores, cuttings, and sidewall cores) or from an analog outcrop that represents the geological context of the computer model. This allows testing the validity and reliability of the codes and increases confidence in employing an individual geochemical computer-modeling module elsewhere in the same geological context where well data are lacking. Once a numerical method is defined and calibrated for a specific sedimentological and stratigraphic context, it is possible to carry out simulations by modifying variables or parameters to test the sensitivity of the model by considering various geological scenarios which arise from different seismic-stratigraphic interpretations (with or without additional borehole calibration points)

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