ABSTRACT

As the importance of self-sourcing reservoirs continues to increase, it is more important than ever to evaluate rock properties that contribute to productive wells. It has become increasingly evident that in order to maximize potential returns, an integrated approach to shale play characterization is necessary to identify productive areas. Numerous criteria exist to characterize ultra-low permeability shale reservoirs and their associated resource potential; these include measures of organic richness, thermal maturity, lithologic heterogeneity, and formation brittleness. The latter, a descriptor of the geomechanical rock properties, can play a significant role in overall well performance and is commonly a key productivity driver. Thus, an understanding of the mechanical properties of the target section is fundamental for high-grading prospective areas, well placement design, and hydraulic stimulation effectiveness.

Observation of geomechanical attributes extracted from seismic data in the Eagle Ford Shale captures changing mechanical properties indicative of strike-oriented lithologic facies changes. Using acoustic logs, core, and three-dimensional seismic data, we assess the mechanical contrast between Eagle Ford facies units and their effect on well performance. We use three-dimensional seismic data to map the structure and facies distribution in an area where identification of reservoir facies is a major challenge to development drilling. In this study, we demonstrate how Young’s modulus and density, inverted from three-dimensional seismic data, prove as effective discriminators for the purpose of identifying and mapping facies changes and establishing the hydraulically fracturable limits in areas where effective stimulation and proppant embedment in the formation during pressure drawdown is a concern. The result is an interpretation that identifies and uses the mechanical changes from three-dimensional seismic data attributes associated with the brittle carbonate-rich Eagle Ford facies to predict both the reservoirs hydraulically fracturable limits as well as the variability in well performance associated with proppant embedment. The changes in mechanical properties of the Eagle Ford facies are important in high-grading productive intervals in these ultra-low permeability rocks. We believe we can apply this method to other shale reservoirs where rock mechanics may play an important role.

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