Polyelectrolyte complex (PEC) nanoparticles with a diameter of less than a micrometer can be formed spontaneously by mixing together dilute solutions of polyanion and polycation.
The resulting charged nanoparticles have been used in medicine to entrap and deliver drugs and DNA, with the characteristics of the nanoparticles being tuned to allow gradual or delayed release of the entrapped material.
There are many applications in the oil and gas industry that would benefit from this kind of control over delivery and release of chemicals, and TORP is actively developing the technology in several areas.
In-depth profile modification
- Polymer gels have been used extensively to improve sweep efficiency by blocking high conductivity channels during enhanced oil recovery operations
- Cr(III) crosslinks with partially hydrolyzed polyacrylamide polymer (HPAM) to form a strong gel which cannot propagate in formation rock
- Gelation time too short (< 30 min.) to place gel deep into formation rock
- Delayed gelation time (weeks to months) is needed for in-depth profile modification
By entrapping chromium in PEC, gelation can be delayed, allowing in-depth placement.
Fracturing fluid cleanup
Gelation and Degradation of Guar
- Guar and its derivatives are often used in hydraulic fracturing fluids to increase the viscosity in order to increase pumping pressure and carry proppants. Guar can be gelled with borate ions complexing the hydroxyl groups on the galactose.
- Hydrolysis (destruction) of the ether bonds on the backbone of polymer can be catalyzed by enzymes, e.g. pectinase.
- Existing breaker packages suffer from premature/incomplete/heterogenous breaking.
- Entrap breaker with nanoparticles and pump with fracturing fluid.
- Electrostatic repulsion between like-charged nanoparticles insure suspension and even distribution in fracturing fluid.
- Evenly distributed breaker insures effective breakdown of fracturing fluid when released.
- Breaker release can be controlled until desired elapsed time (e,g., 1 day)
PECs Protect Enzymes from High pH and Temperature
- Enzymes are proteins and their activity is highly dependent on pH and temperature.
- Outside of optimal range, activity is reduced.
- Optimum conditions are enzyme-specific.
- At “extreme” pH and Temp, proteins are denatured.
- Entrapping enzymes in PECs confers some protection from environmental conditions.