Influence of Biofilms on Porous Media Hydrodynamics - Porous Media: Applications in Biological Systems and Biotechnology - page 208

use of injection wells has resulted in a flurry of research and development
efforts that contribute toward the continued development of such permeable
reactive subsurface biofilm barriers.
5.6.2 Deep Subsurface Biofilms for Enhanced
Oil Recovery and Carbon Sequestration
The initial recovery of oil from deep subsurface reservoirs is typically esti-
mated to reach between 10% and 35% of a reservoir's oil. Secondary recovery,
which most often involves waterflooding, can increase recovery by 20% or
more. Tertiary recovery, often also called secondary enhanced oil recovery,
further increases the recovery of oil from these reservoirs. Thermal recov-
ery, chemical flooding, miscible displacement (such as gas injection), and
microbially enhanced oil recovery (MEOR) have been explored as tertiary
techniques.
Microbially enhanced oil recovery is proposed to be applicable in a number
of different ways, such as production of biosurfactants or gases to enhance oil
mobility, selective plugging of high-permeability channels in reservoir rock
to increase sweep eciency, and in situ biocracking, during which microbes
break down long alkane chains to produce higher solubility shorter alkane
chains.
A flurry of research and development efforts in the 1980s and 1990s investi-
gated the use of microorganisms to enhance oil recovery from deep subsurface
oil-bearing formations, and detailed information can be found in a number of
topics and reviews (Zajic and Donaldson 1985; Kosaric et al . 1987; Donaldson
et al . 1989; Yen 1990).
Biofilms are thought to be effective in selectively plugging water-filled high-
permeability areas, also called thief zones. Selectively reducing the permeabil-
ity of such high-permeability areas would allow fluids used for enhanced sec-
ondary or tertiary oil recovery, such as water or supercritical CO 2 (scCO 2 ),
to more effectively mobilize residual oil in low-permeability areas of the for-
mation. Significant research and development efforts have been conducted
to develop this technology (e.g., Shaw et al . 1985; MacLeod et al . 1988;
Lappin-Scott et al . 1988a,b; Cusack et al . 1992; Lappin-Scott and Costerton
1992) yet widespread reports of successful implementation of this technology
are lacking. This may be due to diculties in evaluating the economics of
using biofilm-mediated plugging of high-permeability areas in the deep sub-
surface. Determining the location of biofilms in the deep subsurface is even
more challenging than the imaging of biofilms in laboratory-scale reactors
as described earlier. Hence, MEOR is continuing to be proposed for appli-
cation in the oilfield but has yet to gain widespread acceptance, and thus
application.
The potential of using biofilms to enhance the deep subsurface sequestra-
tion of carbon dioxide has been proposed as well (Davis et al . 2006; Mitchell
et al . 2008a; Mitchell et al . 2009). Recent work by Mitchell et al . (2008, 2009)