Method and materials for manipulating hydraulic fracture geometry
A method for manipulating hydraulic fracture geometry. In one embodiment, the method comprises injecting a fracturing fluid into a well to generate one or more hydraulic fractures in a subsurface rock formation and then substantially draining any fluids from the one or more hydraulic fractures. The method may further comprise injecting a hydrophilic polymer and one or more crosslinking agents into the well to subsequently form low-density hydrogels which may then screen out only each tip of the one or more hydraulic fractures. A working fluid may then be injected into the well to increase fracture width of the one or more hydraulic fractures without substantially increasing fracture length. In an alternative embodiment, the hydrophilic polymer may be fully crosslinked by the one or more crosslinking agents and injected as pre-formed particle gels (PPGs) which may also screen out only each tip of the one or more hydraulic fractures.
1. A method for bridging one or more hydraulic fractures of a well, comprising:
(A) injecting a tip screen-out mixture into the well, wherein the tip screen-out mixture comprises:
a hydrophilic polymer of anionic polyacrylamide which is hydrolyzed at least in part; and
one or more crosslinking agents selected from a group of compounds consisting of polyvalent metal cations,
wherein the concentration of the hydrophilic polymer and the one or more crosslinking agents is between about 0.01 wt. % and about 10 wt. % in water,
(B) mixing the hydrophilic polymer and the one or more crosslinking agents to form hydrogels in-situ;
(C) bridging each tip of the one or more hydraulic fractures by transporting the hydrogels along the one or more hydraulic fractures as a result of the injecting;
wherein the group of compounds consisting of polyvalent metal cations comprises Calcium (II), Chromium (II), Chromium (III), Titanium (IV), a Chromium (III) complex with one or more carboxylic acid, a Chromium (III) complex with acetic acid, or combinations thereof.
2. The method of claim 1 , further comprising injecting lost circulation materials to augment bridging of each tip with the hydrogels.
3. The method of claim 2 , wherein the lost circulation materials comprise bentonite clay.
4. The method of claim 1 , wherein concentrations of both the hydrophilic polymer and the one or more crosslinking agents selected from the group of compounds consisting of polyvalent metal cations are selected to form the hydrogels as rigid hydrogel.
5. The method of claim 1 , wherein the polyvalent metal cations are organic polyamines.
6. The method of claim 5 , wherein the organic polyamines are amine terminated polymers of ethylene oxide.
7. The method of claim 5 , wherein concentration of the organic polyamines is between about 0.01 wt. % and about 1 wt. % in water.
8. The method of claim 1 , wherein the concentrations of both the hydrophilic polymer and the one or more crosslinking agents selected from the group of compounds consisting of polyvalent metal cations are selected to form the hydrogels as viscous hydrogels.
9. The method of claim 1 , wherein the concentrations of both the hydrophilic polymer and the one or more crosslinking agents selected from the group of compounds consisting of polyvalent metal cations are selected to form the hydrogels over a time period, wherein the time period is greater than one hour and less than or equal to one week.
10. The method of claim 1 , wherein the concentrations of both the hydrophilic polymer and the one or more crosslinking agents selected from the group of compounds consisting of polyvalent metal cations are selected to form the hydrogels over a time period, wherein the time period is greater than one week.