Method for controlling production of excessive water and aqueous fluids in oil and gas wells
Provided are methods for modifying the permeability of subterranean formations for the purposes of selectively reducing excessive production of water and aqueous fluids in oil and gas wells, wherein the methods utilize an emulsion containing a copolymer, which is typically prepared in an aqueous salt media.
1. A method for controlling aqueous fluids by treating a subterranean formation in a producing well, comprising the steps of:
(1) providing an emulsion comprising: (a) a copolymer in an amount of from 10 wt % to 30 wt %; (b) a water soluble salt in an amount of from 10 wt % to 50 wt %; and (c) optionally a polyol; weight percentages are based on the total weight of the emulsion;
(2) diluting said emulsion in water to form a treatment fluid;
(3) introducing said treatment fluid into the producing well,
wherein said emulsion is prepared by a process comprising the steps of:
(i) preparing an ionic charged polymeric dispersant from at least an ionic monomer, optionally in the presence of a radical polymerization control agent; and
(ii) charging said polymer dispersant into an aqueous solution comprising a nonionic monomer and an ionic monomer, the mixture is then subject to continuous polymerization, in presence of a water soluble salt, to obtain said copolymer.
2. The method according to claim 1 , wherein said emulsion comprises: (a) 15 wt % to 30 wt % of the copolymer; (b) 15 wt % to 50 wt % of the water soluble salt; (c) 0 to 5 wt % of the polyol; and (d) water; weight percentages are based on total weight of the emulsion.
3. The method according to claim 1 , wherein said emulsion comprises: (a) 15 wt % to 25 wt % of the copolymer; (b) 20 wt % to 50 wt % of the water soluble salt; (c) 0 to 5 wt % of the polyol; and (d) water; weight percentages are based on total weight of the emulsion.
4. The method according to claim 1 , wherein said water soluble salt is selected from the group consisting of: ammonium sulfate, ammonium chloride, potassium chloride, calcium chloride, sodium bromide, calcium bromide, sodium sulfate, magnesium sulfate, aluminum sulfate, sodium nitrate, magnesium nitrate, potassium nitrate, and combinations thereof.
5. The method according to claim 1 , wherein said ionic charged polymeric dispersant is prepared from at least an ionic monomer according to general formula (II):
wherein:
R 2 is a hydrogen or a C 1 to C 5 alkyl or hydroxyalkyl;
M is hydrogen, an alkali metal ion, or NR 4 + wherein R is a C 1 to C 5 alkyl or hydroxyalkyl.
6. The method according to claim 1 , wherein said nonionic monomer in the second step (ii) is according to the general formula (III):
wherein:
R 3 is a hydrogen or a C 1 to C 5 alkyl or hydroxyalkyl;
R 4 and R 5 , independently, is a hydrogen or a C 1 to C 5 alkyl or hydroxyalkyl; and
said ionic monomer in the second step (ii) is according to the general formula (II):
wherein:
R 2 is a hydrogen or a C 1 to C 5 alkyl or hydroxyalkyl;
M is hydrogen, an alkali metal ion or NR 4 + wherein R is a C 1 to C 5 alkyl or hydroxyalkyl.
7. The method according to claim 1 , wherein in first step (i) said ionic charged polymeric dispersant is prepared from said ionic monomer in the presence of a radical polymerization control agent.
8. The method according to claim 7 , wherein said radical polymerization control agent is according to general formula (I):
wherein Z represents:
a hydrogen atom,
a chlorine atom,
an optionally substituted alkyl or optionally substituted aryl radical,
an optionally substituted heterocycle,
an optionally substituted alkylthio radical,
an optionally substituted arylthio radical,
an optionally substituted alkoxy radical,
an optionally substituted aryloxy radical,
an optionally substituted amino radical,
an optionally substituted hydrazine radical,
an optionally substituted alkoxycarbonyl radical,
an optionally substituted aryloxycarbonyl radical,
an optionally substituted carboxyl or acyloxyl radical,
an optionally substituted aryloxy radical,
an optionally substituted carbamoyl radical,
a cyano radical,
a dialkyl- or diaryl-phosphonato radical,
a dialkyl-phosphinato or diaryl-phosphinato radical, or
a polymer chain,
and R 1 represents:
an optionally substituted alkyl, acyl, aryl, aralkyl, alkene or alkyne group,
a saturated or unsaturated, aromatic, optionally substituted carbocycle or heterocycle, or
a polymer chain.
9. The method according to claim 8 , wherein said radical polymerization control agent is a compound chosen from the group consisting of: xanthates, trithiocarbonates, dithiocarbamates and dithiocarbazates.
10. The method according to claim 7 , wherein said ionic charged polymeric dispersant is prepared from at least an ionic monomer according to general formula (II):
wherein:
R 2 is a hydrogen or a C 1 to C 5 alkyl or hydroxyalkyl;
M is hydrogen, an alkali metal ion, or NR 4 + wherein R is a C 1 to C 5 alkyl or hydroxyalkyl.
11. The method according to claim 7 , wherein said nonionic monomer in the second step (ii) is according to the general formula (III):
wherein:
R 3 is a hydrogen or a C 1 to C 5 alkyl or hydroxyalkyl;
R 4 and R 5 , independently, is a hydrogen or a C 1 to C 5 alkyl or hydroxyalkyl; and
said ionic monomer in the second step (ii) is according to the general formula (II):
wherein:
R 2 is a hydrogen or a C 1 to C 5 alkyl or hydroxyalkyl;
M is hydrogen, an alkali metal ion or NR 4 + wherein R is a C 1 to C 5 alkyl or hydroxyalkyl.
12. The method according to claim 1 , wherein said copolymer has an average weight molecular weight of from 750,000 to 10,000,000 Daltons.
13. The method according to claim 1 , wherein said emulsion is added in said treatment fluid in a concentration of from 500 ppm to 10,000 ppm.