Origins of pressure dependent permeability in unconventional hydrocarbon reservoirs.

Unconventional hydrocarbon assets represent a rapidly expanding proportion of North American oil and gas production. Similar to the incipient phase of conventional oil production at the turn of the twentieth century, there are ample opportunities to improve production efficiency. In this work we demonstrate that pressure dependent permeability degradation exhibited by unconventional reservoir materials is due to the mechanical response of a few commonly encountered microstructural constituents.

Elastic gas/water interface for highly stable foams with modified anionic silica nanoparticles and a like-charged surfactant.

Hypothesis: Surface active anionic nanoparticles (NPs) with strategically designed covalent ligands may be combined with a liked-charged surfactant to form a highly elastic gas-water interface leading to highly stable gas/water foams.

Experiments: The colloidal stability of the NPs was determined by dynamic light scattering, and the surface elastic dilational modulus E' of the interface by sinusoidal oscillation of a pendant droplet at 0.1 Hz, which was superimposed on large-amplitude compression-expansion cycles.

Tuning Surface Chemistry and Ionic Strength to Control Nanoparticle Adsorption and Elastic Dilational Modulus at Air-Brine Interface.

The relationship between the interfacial rheology of nanoparticle (NP) laden air-brine interfaces and NP adsorption and interparticle interactions is not well understood, particularly as a function of the surface chemistry and salinity. Herein, a nonionic ether diol on the surface of silica NPs provides steric stabilization in bulk brine and at the air-brine interface, whereas a second smaller underlying hydrophobic ligand raises the hydrophobicity to promote NP adsorption. The level of NPs adsorption at steady state is sufficient to produce an interface with a relatively strong elastic dilational modulus ' = dγ/d ln .

Tuning Nanoparticle Surface Chemistry and Interfacial Properties for Highly Stable Nitrogen-In-Brine Foams.

The design of surface chemistries on nanoparticles (NPs) to stabilize gas/brine foams with concentrated electrolytes, especially with divalent ions, has been elusive. Herein, we tune the surface of 20 nm silica NPs by grafting a hydrophilic and a hydrophobic ligand to achieve two seemingly contradictory goals of colloidal stability in brine and high NP adsorption to yield a viscoelastic gas-brine interface. Highly stable nitrogen/water (N/brine) foams are formed with CaCl concentrations up to 2% from 25 to 90 °C.

Effect of surface chemistry of silica nanoparticles on contact angle of oil on calcite surfaces in concentrated brine with divalent ions.

Hypothesis: For an oil droplet on calcite with an intervening brine film, the water contact angle θ may be reduced markedly (greater water wetness) with surface modified silica nanoparticles (NP). Modification with cationic, anionic, and nonionic ligands may be used to control the nanoparticle adsorption and interactions at the oil-brine and brine-calcite interfaces to influence the rate and degree of reduction in θ.

Experiments: The colloidal stability at 25 °C was determined in concentrated divalent brine (8 wt% NaCl and 2 wt% CaCl) with dynamic light scattering, and the NP adsorption was determined on calcite.

Carbon dioxide-in-oil emulsions stabilized with silicone-alkyl surfactants for waterless hydraulic fracturing.

The design of surfactants for CO/oil emulsions has been elusive given the low CO-oil interfacial tension, and consequently, low driving force for surfactant adsorption. Our hypothesis is that waterless, high pressure CO/oil emulsions can be stabilized by hydrophobic comb polymer surfactants that adsorb at the interface and sterically stabilize the CO droplets. The emulsions were formed by mixing with an impeller or by co-injecting CO and oil through a beadpack (CO volume fractions (ϕ) of 0.

Viscoelastic diamine surfactant for stable carbon dioxide/water foams over a wide range in salinity and temperature.

Hypothesis: The viscosity and stability of CO/water foams at elevated temperature can be increased significantly with highly viscoelastic aqueous lamellae. The slow thinning of these viscoelastic lamellae leads to greater foam stability upon slowing down Ostwald ripening and coalescence. In the aqueous phase, the viscoelasticity may be increased by increasing the surfactant tail length to form more entangled micelles even at high temperatures and salinity.

Self-Association of Rafoxanide in Aqueous Media and Its Application in Preparing Amorphous Solid Dispersions.

Our primary objective is to characterize the self-association of rafoxanide in alkaline media. The second objective is to illustrate the feasibility of using rafoxanide micellar solution as the feed solution to prepare amorphous solid dispersion via spray drying. Rafoxanide is a poorly water-soluble drug.

High temperature ultralow water content carbon dioxide-in-water foam stabilized with viscoelastic zwitterionic surfactants.

Ultralow water content carbon dioxide-in-water (C/W) foams with gas phase volume fractions (ϕ) above 0.95 (that is <0.05 water) tend to be inherently unstable given that the large capillary pressures that cause the lamellar films to thin.

Ultradry Carbon Dioxide-in-Water Foams with Viscoelastic Aqueous Phases.

For foams with ultra low water contents, the capillary pressure is very large and induces rapid drainage that destabilizes the aqueous lamellae between the gas bubbles. However, we show that high-pressure CO2-in-water foams can be stabilized with a viscoelastic aqueous phase composed of entangled wormlike micelles, even for extremely high CO2 volume fractions ϕ of 0.95 to 0.