Fluid viscosity control
A method of treating a subterranean formation penetrated by a wellbore includes introducing a treatment fluid comprised at least a crosslinkable component, and a metal crosslinker to the subterranean formation, forming a crosslinked treatment fluid, and de-crosslinking bonds of the crosslinked treatment fluid by manipulating a pH of the treatment fluid with a pH triggering agent, wherein the pH triggering agent is an amine-precursor compound or a derivative thereof.
1. A method of treating a subterranean formation penetrated by a wellbore, the method comprising:
introducing a treatment fluid comprised at least a crosslinkable component, and a metal crosslinker comprising a polyvalent metal ion to the subterranean formation;
forming a crosslinked treatment fluid, and
de-crosslinking bonds of the crosslinked treatment fluid by increasing a pH of the treatment fluid with a pH triggering agent,
wherein the pH triggering agent is an amine-precursor compound or a derivative thereof.
2. The method of claim 1 , wherein the pH triggering agent is present in the treatment fluid.
3. The method of claim 1 , wherein the pH triggering agent is present in the subterranean formation prior to the introduction of the treatment fluid.
4. The method of claim 1 , wherein the method further comprises a first pH triggering agent and a second pH triggering agent.
5. The method of claim 4 , wherein the second pH triggering agent re-crosslinks the de-crosslinked fluid.
6. The method of claim 5 , wherein the second pH triggering agent re-crosslinks the de-crosslinked fluid by decreasing the pH of the de-crosslinked fluid.
7. The method of claim 1 , wherein pH triggering agent is a solid suspended in the treatment fluid.
8. The method of claim 1 , wherein the pH triggering agent is encapsulated.
9. The method of claim 1 , wherein the pH triggering agent is selected from the group consisting of urea, thiourea, N,N-dimethylurea, N,N-diethylurea, N,N-diallylurea, tetramethylurea, hexamine and combinations thereof.
10. The method of claim 1 , wherein the treatment fluid further comprises a catalyst.
11. The method of claim 10 , wherein the catalyst is an oxide selected from the consisting of vanadium pentoxide, titanium dioxide, zirconia and silica.
12. The method of claim 10 , wherein the catalyst is a metal-organic complex of nickel (II) or palladium (II).
13. The method of claim 10 , wherein the catalyst is an enzyme.
14. The method of claim 1 , wherein the crosslinkable component is a natural polymer selected the group consisting of a guar gum, a locust bean gum, a tara gum, a honey locust gum, a tamarind gum, a karaya gum, an arabic gum, a ghatti gum, a tragacanth gum, a carrageenen, a succinoglycan, xanthan, diutan, alginate, hydroxylethylguar hydroxypropyl guar, carboxymethylhydroxyethyl guar, carboxymethylhydroxypropylguar (CMHPG), carboxymethyl cellulose (CMC), carboxyethyl cellulose, carboxymethyl guar (CMG) carboxymethylhydroxyethyl cellulose (CMHEC), and derivatives thereof.
15. The method of claim 1 , wherein the crosslinkable component is a synthetic polymer selected from the group consisting of polyacrylic acid, co-polymers of polyacrylamide and polyacrylic acid, partially hydrolyzed polyacrylamide (PHPA), polymethacrylic acid and derivatives thereof.
16. The method of claim 1 , wherein the metal crosslinker contains a metal ion selected from the group consisting of zirconium (IV), titanium (IV), aluminum (III), chromium (III) or any combination thereof.