PSDM for Unconventional Reservoirs? A Niobrara Shale Case Study

Summary As of this writing, unconventional resource plays absorb a significant proportion of onshore U.S. E&P budgets. The perceived simplicity and homogeneity of unconventional reservoirs explained their initial appeal to firms seeking to reduce “dry hole risk”. However, as inconsistent drilling results from many resource plays highlight, shale reservoirs are neither simple nor homogeneous. Used infrequently 510 years ago, drillers today commonly employ 3D seismic to improve horizontal well “geosteering”. Explorers also increasingly rely on 3D seismic to delineate productive “sweet spots”. In particular, differential horizontal stress (from azimuthal anisotropy analysis) and elastic inversion for “brittleness” are paired to find optimal drill locations and wellbore orientation (Sena et al., 2011). While prestack depth migration (PSDM) is commonly applied in “complex” plays such as the sub-salt Gulf of Mexico, it has been adopted in resource plays at a slow (but accelerating) pace. PSDM promises two major “structural” benefits over conventional time imaging: