Systems and methods for controlling subcritical fracturing via chemical complexation reactions at the crack tip
View Patent ↗The choice of anion in aqueous fluid composition therefore enables enhancing or arresting subcritical crack growth in crystalline and amorphous solids. The fluid composition selected based on anion's ability to form complexes with cation in the fracturing solid can be injected around wellbores, or into subsurface formations to stabilize them (decrease subcritical crack growth), or to enhance fracturing (hydrofracking). Applications include the development of chemical methods for both sealing and enhancing cracks in the subsurface and other environments where aqueous chemistry can be varied in a controlled manner.
1 . A system for controlling crack propagation, comprising consisting essentially of:
a fluid source that consists essentially of an aqueous fluid consisting essentially of water and anions; and
a system for contacting the aqueous fluid from the fluid source into within a crystalline material;
wherein the anions are selected from the group consisting essentially of a sulfate, anions to arrest tip crack growth to promote crack growth by forming a chemical complex with the crystalline material.
2 . The system of claim 1 , wherein the crystalline material contains a cation selected from the group consisting of Li′, Na 1 , K, Rb 1 , Cs′, Ca 21 , Sr 21 , Mg 2 , and Ba 2+ .
3 . The system of claim 2 , wherein the cation is in a functional group selected from the group consisting of oxides and hydroxides of these cations.
4 . The system of claim 1 , wherein the crystalline material is a rock or an individual component of rock in a subterranean formation.
5 . The system of claim 1 , wherein the crystalline material is calcite.
6 . The system of claim 1 , wherein the crystalline material is portland cement.
7 . The system of claim 1 , wherein the first aqueous fluid anion is sulfate.
8 . The system of claim 1 , wherein the sulfate anions are at a concentration of greater than 0.1 M and less than the saturation concentration in the aqueous fluid.
9 . The system of claim 1 , wherein the sulfate, phosphate, oxalate, chloride, bromide and fluoride anions are at a concentration of greater than 1 M and less than the saturation concentration in the aqueous fluid.