Repeated injection of hydrothermal fluids into downdip carbonates: a diagenetic and stratigraphic mechanism for localization of reservoir porosity, Indian Basin Field, New Mexico, USA

Abstract

AbstractA detailed study of the Pennsylvanian Indian Basin Field of New Mexico, USA is used to develop a conceptual model that predicts reservoir porosity in clean down-depositional-dip marine carbonate, where repeated fracturing allows for hydrothermal fluid flow. Strata updip probably experienced repeated events of subaerial exposure, resulting in mineralogical stabilization and extensive calcite cementation that prevented extensive hydrothermal alteration. Clean, carbonate sediment deposited downdip was more prone to alteration by hydrothermal fluids. In the reservoir, cement stratigraphy shows regionally persistent zones closely associated with fracturing. Fluid inclusion data show high temperatures and repeated rises and falls, indicating tectonic valving in a hydrothermal system. Salinity data support this and indicate a late event of meteoric influx. Sr- and O-isotope data indicate higher temperature and less rock–water interaction in fault damage zones, evidence for intensified fluid flow in such areas. Formation of vugs and molds was associated with the hydrothermal fluid flow, which was driven by convection, probably initiated during 40–30 Ma intrusive activity and continuing after the onset of Basin and Range uplift and unroofing.