In U.S. Patent 7,644,764, University of Kansas (KU) (Lawrence, KS) researchers divulge a process to manufacture nanoparticle polyelectrolyte complexes for use as delayed gelling agents in oil and gas drilling operations. The term "polyelectrolyte" refers to a macromolecule, usually a polymer, possessing more than one charge. The term "polyelectrolyte" includes polycations and polyanions.
KU researchers Cory Berkland, Mary Cordova, Jenn-Tai Liang and G. Paul Willhite developed gel-forming compositions for reducing the permeability of a subterranean formation or zone. The nano-composition is comprised of a water soluble polymer (e.g., Alcoflood™. 935) and a polyelectrolyte gelling agent comprising a polycation (e.g., polyalkylene imine) and a polyanion (e.g., dextran sulfate). The gel-forming composition is used to delay gelation in the subterranean formation.
This compositions and processes for oil and gas field applications useful for controlling and/or delaying the gelation of an aqueous composition in a subterranean zone. Various techniques for injecting liquids and slurries into such wells are known in the art and can be utilized for injection of the compositions.
The polyelectrolytes form a complex that is characterized as a nanoparticle. In some instances, it is theorized that the nanoparticles comprise a polymeric core and a polymeric shell that are opposite in charge. For example, a polyanionic core may be covered by a polycationic shell or corona. The nanoparticle may alternatively comprise a polycationic core and a polyanionic shell or corona.
FIG. 2 is a transmission electron microscopy image of dextran sulfate (DS) to chitosan (CS) DS/CS nanoparticles for use in delayed gelling agents for oil and gas drilling applications.
FIG. 2 is a transmission electron microscopy image of dextran sulfate (DS) to chitosan (CS) DS/CS nanoparticles for use in delayed gelling agents for oil and gas drilling applications.
