Polymeric gel system and methods for making and using same in hydrocarbon recovery
View Patent ↗Coacervate gels having excellent shear viscosities and other properties are made with anionic or cationic polymers, a smaller amount of a surfactant having a charge opposite that of the polymer, and a hydrophobic alcohol and an effective amount of a phosphorus-containing compound sufficient to increase the viscosity of coacervate gels up to 3 times as compared to the gels in the absence of the phosphorus-containing compound. The Zeta Potential of the gel is maintained at an absolute value of at least 20. Optional gel promoting additives include betaines and amine oxides. A preferred gel comprises poly diallyl dimethyl ammonium chloride, a lesser amount of sodium lauryl sulfonate, and lauryl alcohol. The gels are particularly useful in well drilling fluids and well fracturing fluids.
1. An aqueous gel comprising:
a water-soluble cationic polymer in an amount no greater than 1% by weight,
an anionic surfactant in an amount less than that of the polymer, and
a phosphorus-containing compound in an effective amount between about 0.001 wt % and about 10 wt. %,
where the phosphorous-containing compound is selected from the group consisting of mono-alkali metal phosphate (PO(OH)(OM), where M is Li, Na, K, Rd, or Cs, di-alkali metal phosphate (PO(OH)(OM) 2 , where each M is the same or different and is Li, Na, K, Rd, or Cs, tri-alkali metal phosphate (PO(OM) 3 , where each M is the same or different and is Li, Na, K, Rd, or Cs, carbyl phosphate (PO(OR)(OM) 2 , where R is a carbyl group and each M is H, Li, Na, K, Rd, or Cs, dicarbyl phosphate (PO(OR 1 )(OR 2 )(OM), where R 1 and R 2 are the same or different carbyl groups and M is H, Li, Na, K, Rd, or Cs, tricarbyl phosphate (PO(OR 1 )(OR 2 )(OR 3 ), where R 1 , R 2 , and R 3 are the same or different carbyl groups, or mixtures or combinations thereof,
where the polymer and the anionic surfactant form a coacervate gel and where the effective amount is sufficient to increase a gel viscosity of the composition, increase a viscosity build up of the composition, and increase gel stability of the composition and where the composition is characterized in that the composition has
a zero shear viscosity of at least 45,000 or
a settling rate of no more than 8 millimeters measured by adding 10 mL of 20/40proppant to 100 mL of a 1.1 wt. % gel maintained at 80° C. in a 100 mL graduated cylinder and measuring a depth in millimeters of the gel from a top of the graduated cylinder.
2. The gel of claim 1 , wherein the water-soluble polymer is present in the gel in an amount no greater than 0.7%.
3. A well treatment fluid comprising a proppant and a gel of claim 2 .
4. The gel of claim 1 , further a hydrophobic alcohol.
5. The gel of claim 4 , further comprising:
a gel promoter comprising one or more of an amphoteric surfactant and/or an amine oxide surfactant, while maintaining a Zeta Potential value greater than or equal to 20 millivolts or less than or equal to -20 millivolts.
6. The gel of claim 1 , wherein the phosphorus-containing compound in an amount between about 0.05 wt. % and about 3 wt. %.
7. The gel of claim 1 , wherein the effective amount of the phosphorus-containing compound is between about 0.05 wt. % and about 1 wt. %.
8. The gel of claim 1 , further comprising:
a gel promoter comprising one or more of an amphoteric surfactant and/or an amine oxide surfactant, while maintaining a Zeta Potential value greater than or equal to 20 millivolts or less than or equal to -20 millivolts.
9. The gel of claim 1 , wherein the phosphorous-containing compound comprises tricarbyl phosphate (PO(OR 1 )(OR 2 )(OR 3 ), where R 1 , R 2 , and R 3 are the same or different carbyl groups, or a mixture of tricarbyl phosphates.
10. The gel of claim 1 , wherein the R 1 , R 2 , and R 3 groups are the same or different the alkyl groups having from about 4 to about 12 carbon atoms.