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Improving the Compartmentalization Definition of Prospective Areas in the Paleo-Flattened Space – An Eagle Ford Case Study


Unconventional plays, such as Eagle Ford, require a high definition fault interpretation to understand its compartmentalization. These faults are revealed through the application of both advanced seismic methods (e.g. diffraction imaging) and traditional methods (e.g. volumetric coherence and curvature) that emphasize geometric discontinuities in the seismic volume. These faults can also have a controlling influence of the presence of natural fractures in shale formations which, in turn, can provide a pathway for higher permeability. Conventional discontinuity attributes can carry both geometric and positional fault uncertainty where data quality is poor or the fault framework is complex. To map the structural fault network with higher accuracy, a new approach based on a UVT Transform is proposed where U and V represent the paleo-coordinates or coordinates at the time of sediment deposition (T), when the sediments have been deposited horizontally and sedimentary horizons were not tectonically deformed. This method allows flattening the original seismic data according to the relative geologic time represented by T and relatively to the fault planes, to minimize the deformations. Then, geometrical attributes are generated directly in the paleo-space. By applying this method, faults lineaments appear more continuous in the paleo-flattened space than in the X, Y and Z space. The combination of paleo-flattened seismic volumes in UVT space is ideal for characterizing the reservoir continuity, especially in areas with faults and poor signal/noise ratio, where reflectors can be discontinuous from place to place, and where conventional flattening techniques might not be able to appropriately track sedimentary layers and faults. Additionally, the search for prospective areas (or sweet spots) can be improved by transforming reservoir properties attributes such as total organic carbon (TOC) and brittleness to paleo-space to gain extra insight into the reservoir quality for an effective placement of horizontal wells. As brittleness is derived from seismic inversion methods, it benefits from building a background geologic model from well data using geostatistics carried out in paleo-space. This paper describes the technology and illustrates its benefits by application to an Eagle Ford shale dataset, leading to an accurate, high-resolution, and high-certainty seismic interpretation for risk-managed field development.