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Using Seismic, Core and Numerical Modelling for Natural Fracture Network Prediction Around the Bray Fault, Paris Basin, France

Abstract

Identifying areas of enhanced natural fracturing can be crucial when evaluating low permeability reservoirs. This study addresses a Mesozoic carbonate reservoir in the central Paris Basin, France. The area contains a segment of the regional-scale Bray fault that formed in the Carboniferous and was reactivated in subsequent tectonic events (the Pyrenean through Alpine). We use 2D seismic, well tops, gravity/magnetic data and publications to construct a fault-horizon framework around the Bray fault system. The fault framework is then subjected to paleostress states and analyzed using a numerical elastic dislocation approach. The resulting computed stresses are compared to fracture intensities observed in cores from wells around the block. Multiple regional stress scenarios were tested to identify areas of likely natural fracture formation around the Bray fault at the reservoir level during distinct tectonic episodes. The Pyrenean regional stress state was found to best fit the calibration against core-fracture intensities. The study identifies areas of higher potential fracture intensity, compared to background levels, and also the preferred orientations of potential fractures in these areas. The analysis is also used to make recommendations for future well locations.