Are stylolites fluid-flow efficient features?

Abstract

It sounds counter-intuitive to consider contraction features such as stylolites as potential conduits for flow. However, this idea has grown since 1980, with geoscientists finding many examples principally in carbonate reservoirs where stylolites can be considered as fluid-efficient features. Among others, these features can be reactivated stylolites, can generate positive porosity and permeability anomalies, can drive corrosive fluids or can remain open in an overpressured system. Conversely, stylolites can also be closed forever. These impermeable stylolites can generate permeability anisotropy that may impact fluid movements. Stylolites require particular attention to evaluate whether they act as drains or as barriers to flow (compartmentalisation). We review some of the key studies of the past thirty years with a special attention to the most recent ones. We end-up considering their mechanical origin, their nucleation and growth, their past and present impact on reservoir properties and performances as key factors influencing the flow efficiency differentiation of these features. This short review presents the latest theories and observations about stylolites with respect to the key factors aforementioned. The authors support herein that a distinction should be made between processes occurring in the past and the present-day impact the stylolite had on reservoir properties.