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

Abstract

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 0.50-0.90). Emulsions were generated with comb polymer surfactants with a polydimethylsiloxane (PDMS) backbone and pendant linear alkyl chains. The C alkyl chains are CO-insoluble but oil soluble (oleophilic), whereas PDMS with more than 50 repeat units is CO-philic but only partially oleophilic. The adsorbed surfactants sterically stabilized CO droplets against Ostwald ripening and coalescence. The optimum surfactant adsorption was obtained with a PDMS degree of polymerization of ∼88 and seven C side chains. The emulsion apparent viscosity reached 18 cP at a ϕ of 0.70, several orders of magnitude higher than the viscosity of pure CO, with CO droplets in the 10-150 µm range. These environmentally benign waterless emulsions are of interest for hydraulic fracturing, especially in water-sensitive formations.

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

“…Furthermore, Ca 2+ bridging between Si–O – groups was small for 1 wt % NPs indicating that the concentration of the uncapped Si–O – was relatively small. Apparently, the small CH 3 groups of ED ligand, which are more hydrophilic than CH 2 groups, , do not reduce the hydration enough to prevent the colloidal stability of the NPs at 90 °C in API brine. The higher stability at lower pH may be attributed to protonation of Si–O – to weaken Ca 2+ bridging, but changes in other interactions involving hydrogen bonding and changes in partial charges on the various O groups are likely to be present.…”

“…Bulk foams were generated from 2 mL NP brine solutions with pH adjusted to 6.5 in small vials (10 mL) by shearing at 20 000 rpm with an Ultra-Turrax homogenizer (T25, IKA Works Inc.) for 30 s. For the N/W foams in porous media, the system used to characterize μ app and bubble size at 3000 psia has been shown previously. ,,− The NP solution was mixed with N 2 and flowed through a 22 darcy beadpack (0.38 cm internal diameter and 11.3 cm length) to generate the foam. The beadpack was filled with 180 μm glass beads with a 0.44 mL pore volume and 0.34 porosity.…”

“…The system was equilibrated for 15–30 min (100–200 beadpack pore volumes) to allow steady-state foam generation. It was also connected to an in situ cell in a microscope for bulk foam texture observation versus time. ,, The Sauter mean diameter D sm and the dimensionless polydispersity U poly of foam bubbles are given by in which D i is the diameter of the i th foam bubble and D med is the median diameter of bubbles in one microscopic photo.…”

“…It was also connected to an in situ cell in a microscope for bulk foam texture observation versus time. 26,63,66 The Sauter mean diameter D sm and the dimensionless polydispersity U poly of foam bubbles are given by…”

Design of facile technology for the efficient removal of hydroxypropyl guar gum from fracturing fluid

“…The total amount of fracturing flowback fluid generated by the operations has increased sharply with the large-scale development of oilfields and the frequent industrial fracturing construction operations [18,19]. More seriously, the fracturing technology always requires copious amounts of water resources, which is still a potential waste for precious resource [20,21]. Presently, oxidation and flocculation processes are mostly adopted to the treatment of fracturing fluid throughout the world.…”