Page 20 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

Overview of Formation Damage During Improved and Enhanced Oil Recovery 3

1.2 SUMMARY OF FORMATION DAMAGE DURING EOR

In the most general sense, formation damage can be defined as the
various damage mechanisms affecting the properties of reservoir forma-
tions (matrix, pore space and fractures) through which the transport
efficiency of multi-phase fluids (oil, gas, water, particles, droplet, foam
and emulsion) is determined. It is usually diagnosed as the changes of
well performance in terms of well injectivity/productivity and oil
recovery factor. The major damage mechanisms can be categorized as
four types, i.e., mechanically, chemically, thermally and biologically
induced formation damage. Among these categories, the types of chemi-
cal damage mechanisms can be further classified as (Civan, 2015): (1)
fluid-fluid incompatibility (such as, inorganic scale deposit, organic
asphaltene deposit, foam/emulsion blockage, hydrate formation etc.); (2)
rock-fluid incompatibility (such as, clay swelling/deflocculation, wettabil-
ity alteration, and ionic/surfactant/polymer adsorption). The mechani-
cally induced damage mechanisms mainly include fines/sands or any
other types of particle migration, phase trapping caused by high capillary
force in multiphase flow, and rock compaction or dilatation caused by
changes of pressure. Changes of temperature (thermally-induced mechan-
isms) also lead to the dissolution and or deposition of minerals, transfor-
mation of minerals, and temperature-dependent wettability alternation. In
addition, the biological activities of bacteria in reservoirs can cause the
souring of crude oil, erosion of minerals, and blockage of pore-throats.
For the different approaches of IOR to be successful, various changes to
the physical, chemical, thermal-electrical, mechanical and/or biological
environment of the reservoir must be initiated. The following sections
group the mechanisms of formation damage associated with diverse
techniques of IOR, and also provide a special focus on the potential
formation damage in the development of deepwater, geothermal, and
unconventional reservoirs, including shales and coal-bed methane.

1.3 LOW-SALINITY WATER FLOODING (LSWF)

LSWF has been justified as an effective EOR method by numerous
experimental studies and field trials for both tertiary (residual oil) and