High Resolution Sequence Stratigraphy of Scythian-Early Anisian Continental Deposits of East of Paris Basin; Applications to Gas Storage: ABSTRACT

Abstract

Continental facies of Scythian-early Anisian age (Buntsandstein) of East of the Paris Basin form the underground gas storage reservoir exploited by Gaz de France in the area of Nancy (east of France). An accurate sedimentological study and the application of Genetic Stratigraphy principles lead to the understanding of the deposition of fluvial, which form the reservoirs, and to the reconstruction of their geometries. The subsurface data are calibrated on outcrops. Three types of fluvial systems (braided, sinuous to straight and anastomosed) are defined. A special focus on anastomosed channels permits to differentiate a proximal and a distal facies. Study of laterally continuous outcrops induces recurrent cycles of thickness, velocity and time variations (few tens to hundred ka). These correspond to the highest frequence stratigraphic units, i.e. parasequences or genetic units. Maximum of channel and levee presentation occurs during base-level rise: base-level fall is characterised by amalgamation of sets, by-pass and erosion. This method is applied to subsurface data by an accurate calibration of well logs on cores. Thus the electric expression of genetic units corresponding to different environments is determined as well as the expression of base-level variations. The correlation of these units using stacking pattern method leads to amore » very fine subdivision of reservoir between timelines. Different orders of depositional sequences are pointed out, resulting in reservoir geometry characterization and permeability barrier distribution.« less