--> An Approach for a 3D Fracture and Geomechanical Modeling in the Exploratory Phase, Queiroz, Claudia L.; Lima, Claudio C.; Trzaskos, Barbara; Oliver, Flavio, #90100 (2009)
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An Approach for a 3D Fracture and Geomechanical Modeling in the Exploratory Phase

Queiroz, Claudia L.1
 Lima, Claudio C.2
 Trzaskos, Barbara1
 Oliver, Previous HitFlavioTop3

1E&P-Exploration, Petrobras, Rio de Janeiro, Brazil.
2
CENPES, Petrobras,
Rio de Janeiro, Brazil.
3
Schlumberger,
Rio de Janeiro, Brazil.

Fracture modeling consists in the generation of a 3D model that can be populated with fracture surfaces, thus allowing the calculation of fracture contribution to reservoir porosity/permeability. During exploratory phase, this quantitative evaluation is barely possible, because there are only a few wells, little porosity/permeability precise data, and no production curves. In the same way, geomechanical models (determination of the present day in situ stress and the rock response to it) are generally used for well stability calculation or reservoir compartmentalization studies. Although the geomechanical analysis is very time consuming, it can bring essential information regarding the stress state of the fractures. However, a question may be posed: is this approach worthwhile during the early exploratory phases, when the main interest is to add value to the petroleum delimitation process? We tested an exploratory workflow to address the question above in a case where only one well was available. Firstly, we interpreted conductive and resistive fractures, breakouts and tensile induced fractures on the image log. Those structures were used to build the geomechanical model and apply it to the conductive fractures. This work flow allowed the discrimination of conductive-critically stressed fractures, those that reached the failure envelope of the Mohr circle and are believed to be presently open. Then, the conductive-critically stressed fractures were used to generate a fracture intensity log. Following, a 3D model was built with a mesh of 100x100m using two seismic horizons converted to depth. The fracture intensity log was scaled up to the 3D model and two different seismic attributes (based on traces dissimilarities) were also re-sampled into the model. After that, an unsupervised neural network was run using fracture intensity and the seismic attributes as properties. The resulting model was called a Combined Intensity Distribution Model (CIDM), classified into five classes. The fracture intensity range of the well was split into five sub-ranges; and the upper limit of each was used as a discrete number of intensity and applied to the CIDM classes. The final 3D model was called the Composite Intensity Grid (CIG), which seems to be more appropriate to exploratory conditions than the Discrete Fracture Networks (DFN).

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil