Seismic Geomorphology and Connectivity of Deepwater Reservoirs
- Gilberto M. Ragagnin (Petrobras) | Marco A.S. Moraes (Petrobras)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- August 2008
- Document Type
- Journal Paper
- 686 - 695
- 2008. Society of Petroleum Engineers
- 6.5.5 Oil and Chemical Spills, 1.2.3 Rock properties, 5.1.7 Seismic Processing and Interpretation, 1.2.7 Geosteering / reservoir navigation, 5.1.3 Sedimentology, 5.1.1 Exploration, Development, Structural Geology, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 5.1 Reservoir Characterisation, 4.3.4 Scale, 1.14 Casing and Cementing, 2.4.3 Sand/Solids Control
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Assessing reservoir connectivity and permeability heterogeneity is essential for predicting reservoir performance. Because reservoirs are 3D entities, there is little value in trying to predict reservoir connectivity on the basis of 2D data such as geological sections or maps. A new method for seismic volumetric visualization, complemented with outcrop analog data, was used for assessing reservoir connectivity and permeability heterogeneity of the deepwater reservoirs of Marlim Sul field, Campos basin, Brazil.
The seismic method consists of combining reflectivity and impedance seismic volumes. For the reservoir target zone, reflectivity was used as top drape covering the whole area, with color contrasts differentiating reservoirs from nonreservoirs. In the impedance volume, the anomalies represent the reservoirs. Such a volumetric visualization technique permits better identification of architectural elements and better understanding of the evolution of the depositional system. However, some limitations remain. Before building a reservoir model, it is necessary to assess the internal permeability heterogeneity of the different architectural elements and the petrophysical nature of the boundaries among the different elements. This was performed by comparing geometries and facies observed subsurface with geometries and facies documented in outcrop analogs. The main controls on connectivity and permeability heterogeneity in deepwater reservoirs are permeability barriers and baffles, such as hemipelagic shales and marls, turbiditic drapes, debris-flow deposits, shale-clast breccias, and cemented zones. Such features present a complex and varied distribution. Barrier and baffle 3D maps of the different architectural elements and of the limits among them obtained in representative outcrops were used to complement seismic information.
The integration of seismic volumetric visualization with outcrop analog data, calibrated by well information and tested against production data, proved to be useful for improving reservoir models.
The adequate assessment of reservoir connectivity and permeability heterogeneity in deepwater reservoirs requires a visualization of the 3D distribution of the sand bodies using seismic data and using analog data (mostly outcrops) to infer geological properties below seismic resolution. This paper presents an innovative method for visualizing reservoir seismic geomorphology, which, complemented with analog data, leads to a significant improvement of the reservoir characterization of Oligo-to-Miocene deepwater reservoirs of the Marlim Sul field. This field is one of many giant fields with similar geology that occur in the Brazilian continental margin, especially in the Campos basin. Thus, the method presented herein is applicable to several other hydrocarbon fields in Brazil and in other basins of the world where similar geological and seismic-quality conditions are found.
The Marlim Sul field (Fig. 1) is located approximately 170 km offshore Macaé, a town on the coast of the Rio de Janeiro state of Brazil. Water depth in the field varies from 600 m to 2000 m.
Marlim Sul is a giant field presenting a complex distribution of turbiditic reservoirs (Fig. 2). The main reservoirs include three units named herein: the upper, the middle, and the lower reservoirs. From these, the lower reservoir unit shows the most widespread distribution. The age of the reservoirs is Oligocene to Miocene. The field is divided into several areas, which correspond roughly to distinct depressions (minibasins) generated by salt tectonics.
|File Size||5 MB||Number of Pages||10|
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