Preserved eolian bedforms control reservoir heterogeneity: Characterization and modeling workflow for the Avilé Member, Neuquén Basin, Argentina

Abstract

Under certain conditions, most commonly abrupt flooding events, entire eolian bedforms can be incorporated into the geological record. Sediment that was essentially ‘in transport’ within these bedforms at the time of preservation has a distinct sedimentary architecture compared to that of sensu stricto accumulated intervals. Despite this, while the preservation of bedforms has been readily documented from outcrop and subsurface eolian successions, stratigraphic intervals corresponding to these bedforms have rarely been identified and separated from accumulated intervals. The impact of capturing and representing bedform intervals in reservoir models has therefore not been explored. The Avilé Member (Neuquén Basin, Argentina) is a prolific oil reservoir of eolian origin in which both bedforms and accumulated intervals are documented. The aim of this study is to use the Avilé Member record at the Puesto Hernández oilfield to develop a workflow to identify, characterize, map and model discrete eolian bedform and accumulated intervals in a subsurface scenario. Characterization of the unit's geometry, sedimentary facies, and petrophysics was carried out from seismic, wireline log and core analysis. The development of a conceptual model of the accumulation system and its evolution allowed the identification of bedform and accumulated intervals. Precise mapping of these intervals required the development of a geometrical method, based on correlating interdune lows and using a datum surface to provide for an approximation to the ancient accumulation surface. A zoning scheme conditioned by the intervals was tested against a simple, ‘one-zone’ model, to determine its effectivity in separating discrete heterogeneity zones. The model was also tested in a dynamic simulator to history match the field production and analyze its impact in dynamic reservoir simulation. This example serves as a valuable reference to illustrate how eolian bedforms and accumulated intervals may be identified, characterized, and modelled in subsurface scenarios around the world.