Mechanistic models of biofilm growth in porous media

Abstract

Nondestructive acoustics methods can be used to monitor in situ biofilm growth in porous media. In practice, however, acoustic methods remain underutilized due to the lack of models that can translate acoustic data into rock properties in the context of biofilm. In this paper we present mechanistic models of biofilm growth in porous media. The models are used to quantitatively interpret arrival times and amplitudes recorded in the 29 day long Davis et al. (2010) physical scale biostimulation experiment in terms of biofilm morphologies and saturation. The model pivots on addressing the sediment elastic behavior using the lower Hashin-Shtrikman bounds for grain mixing and Gassmann substitution for fluid saturation. The time-lapse P wave velocity (V P ; a function of arrival times) is explained by a combination of two rock models (morphologies); "load bearing" which assumes the biofilm as an additional mineral in the rock matrix and "pore filling" which assumes the biofilm as an additional fluid phase in the pores. The time-lapse attenuation (Q P À1; a function of amplitudes), on the other hand, can be explained adequately in two ways; first, through squirt flow where energy is lost from relative motion between rock matrix and pore fluid, and second, through an empirical function of porosity (ϕ), permeability (κ), and grain size. The squirt flow model-fitting results in higher internal ϕ (7% versus 5%) and more oblate pores (0.33 versus 0.67 aspect ratio) for the load-bearing morphology versus the pore-filling morphology. The empirical model-fitting results in up to 10% increase in κ at the initial stages of the load-bearing morphology. The two morphologies which exhibit distinct mechanical and hydraulic behavior could be a function of pore throat size. The biofilm mechanistic models developed in this study can be used for the interpretation of seismic data critical for the evaluation of biobarriers in bioremediation, microbial enhanced oil recovery, and CO 2 sequestration.

Effects of bacterial dextran on soil geophysical properties

“…The observed constant P-wave velocity and the slight decrease in S-wave velocity can be explained using the two biofilm growth style models: load-bearing and pore-filling models presented by Jaiswal et al (2014). The biofilm growth first originates on the surface of the mineral grains and then grows into the pore spaces and expands along the surface, which results in the interconnection of the biofilm at the grain contacts.…”

“…Davis et al (2010) and Kwon and Ajo-Franklin (2013) also observed that the decrease in P-wave amplitude ceased around 80% of the original, which is similar to the near constant value of Q −1 p observed after 20 d in this study. This phenomenon was explained by Jaiswal et al (2014) as follows: when the system porosity and permeability fall below a minimum threshold, attenuation depends only on the constant parameters of the dry soil matrix. Since the pore fluid has no effect on the shear wave propagation, the increase in S-wave attenuation can be attributed to the energy loss from the interaction between dextran and grains or among dextran molecules.…”

Stabilizing Effects of Bacterial Biofilms: EPS Penetration and Redistribution of Bed Stability Down the Sediment Profile

“…Depending on biotic and abiotic conditions, natural biofilms can be complex, varying with factors such as the availability of nutrients (Wang et al, ), intensity and wavelength of light (Paterson et al, ), hydrodynamic conditions (Celmer et al, ; Chao et al, ; Kim et al, ; Stoodley et al, ), and grazing pressure (Sommer, ; Wey et al, ). Moreover, while natural sediments provide an excellent substratum for biofilm growth (large surface to volume ratio, rich in nutrients, and porous structure) (Fagherazzi et al, ), colonization is very different from impermeable surfaces (such as biofilms growing on glass slides) since EPS may be distributed throughout the porous medium (Davis et al, ; Gerbersdorf et al, ; Jaiswal et al, ; Van Colen et al, ; Volk et al, ).…”

Influence of drill mud on the microbial communities of sandstone rocks and well fluids at the Ketzin pilot site for CO2 storage

“…Organic constituents of the drill fluids may promote bacterial growth by acting as energy and carbon sources Struchtemeyer et al 2011). Consequently, proliferation of microorganisms can damage the rock formation or the filter screens of the well and lower injection rates by blocking the pores through production of biofilms or promoting mineral precipitation (Rosnes et al 1991;Lappan & Fogler 1992;Spark 2000;Schwartz et al 2009;Zettlitzer et al 2010;Jaiswal at al. 2014).…”