Clay minerals in Enhanced Oil Recovery; Implications for
fines migration as a redox controlled process during Low
Salinity Water Flooding

Abstract

In oil and gas exploration and production, the chemical and physical properties of reservoir clay
minerals can have an effect on drilling operations, reservoir quality and oil recovery rates. Various
methods have been used to optimize the recovery of oil from reservoirs, through technologies
that are more economical, easier to apply and environmentally friendly, culminating in the
development of low salinity water flooding (LSWF). LSWF is a chemical method whereby the
concentration of cations, especially multivalent cations, in the injected water is carefully reduced
and controlled. LSWF is used in secondary and tertiary enhanced oil recovery (EOR) operations. In
this present study, we explore a new frontier in EOR research by examining the wettability and
swelling capacity of reservoir clay minerals as a function of reduction extent. We investigate how
changes in the redox state during a LSWF impact on the wettability of iron rich clay minerals. We
make an attempt to map the roughness profile of the clay minerals, to be used as baseline for
wettability and contact angle studies. For that, we introduce a novel approach to measuring the
roughness with the use of Confocal Microscopy in combination with Atomic Force Microscopy
(AFM) and White Light Interferometry (CCI). To further elucidate the behavior of clay minerals, we
test the hydration of model clays, including swelling and non – swelling types, using infrared
spectroscopy. Additionally we investigate how reduction extent impacts the surface hydration and
water sorption by nitrogen BET and water vapor volumetry methods. We couple these studies
with controlled humidity XRD scans of the clay minerals and measuring of the interlayer cation
budget by means of the ICP-OES method. Building on the basic understanding of redox active clay
mineral at the mineral level derived from the above studies, a polymer – coated silicon wafer is
used as proxy to a sandstone, and anoxic – reduced conditions simulated by means of an
experimental apparatus. This setup will allow direct visualization and modelling of the effects of
reduction and re – oxidation within the context of low salinity water flooding, creating a better
tool for understanding fines migration in EOR applications that could lead to optimizing the
operations.