AQUEOUS DRILLING FLUID FOR REDUCING BITUMEN ACCRETION
Some embodiments of the present disclosure relate to drilling fluids that comprise an aqueous solvent and an ampholytic semi-hydrophobic polymer that is readily hydratable under field mixing conditions. The ampholytic semi-hydrophobic polymer comprises semi-hydrophobic monomer units comprising a C 1 -C 7 hydrocarbyl substituent, a hydrogen substituent, or a combination thereof. Some embodiments of the present disclosure relate to use of a drilling fluid as defined herein to reduce bitumen accretion to a wellbore drilling component. Some embodiments of the present disclosure relate to methods for reducing bitumen accretion to a wellbore drilling component, the method comprising introducing a drilling fluid as defined herein into a wellbore containing the wellbore drilling component.
1 . A drilling fluid comprising:
an aqueous solvent; and
an ampholytic semi-hydrophobic polymer that is hydratable under field mixing conditions,
wherein the ampholytic semi-hydrophobic polymer comprises a semi-hydrophobic monomer unit that comprises a C 1 -C 7 hydrocarbyl substituent, a hydrogen substituent, or a combination thereof.
2 . The drilling fluid of claim 1 , wherein the semi-hydrophobic monomer units are present in the ampholytic hydrophobic polymer in an amount of less than about 10% (w/w).
3 . The drilling fluid of claim 1 , wherein the C 1 -C 7 hydrocarbyl substituent is one of a C 4 -C 7 alkyl substituent, a C 4 -C 7 alkenyl substituent, a C 4 -C 7 alkynyl substituent, and a combination thereof.
4 . The drilling fluid of claim 1 , wherein the semi-hydrophobic monomer unit comprises a cationic semi-hydrophobic monomer units.
5 . The drilling fluid of claim 4 , wherein the cationic semi-hydrophobic monomer unit comprises a quaternary ammonium substituent.
6 . The drilling fluid of claim 4 , wherein the cationic semi-hydrophobic monomer units are as shown in formula (I) or formula (II):
wherein n is an integer between 1 and about 300,000, and wherein R, R′, R″, and R′″ are each independently a C 1 -C 7 alkyl substituent, a C 2 -C 7 alkenyl substituent, a C 2 -C 7 alkynyl substituent, and a hydrogen substituent.
7 . The drilling fluid of claim 6 , wherein R, R′, R″, and R′″ are each independently a C 4 -C 7 alkyl substituent, a C 4 -C 7 alkenyl substituent, and a C 4 -C 7 alkynyl substituent.
8 . The drilling fluid of claim 1 , wherein the ampholytic semi-hydrophobic polymer further comprises anionic monomer units and non-ionic monomer units.
9 . The drilling fluid of claim 8 , wherein the anionic monomer units are acrylate monomer units.
10 . The drilling fluid of claim 8 , wherein the non-ionic monomer units are acrylamide monomer units.
11 . The drilling fluid of claim 1 , wherein between about 2% and about 4% (w/w) of the ampholytic semi-hydrophobic polymer is comprised of a cationic semi-hydrophobic monomer unit.
12 . The drilling fluid of claim 1 , wherein between about 10% and about 20% (w/w) of the ampholytic semi-hydrophobic polymer is comprised of an anionic monomer unit.
13 . The drilling fluid of claim 1 , wherein between about 75% and about 95% (w/w) of the ampholytic semi-hydrophobic polymer is comprised of a non-ionic monomer unit.
14 . The drilling fluid of claim 1 , wherein the semi-hydrophobic monomer units are each an anionic semi-hydrophobic monomer unit.
15 . The drilling fluid of claim 1 , wherein the semi-hydrophobic monomer unit is a non-ionic semi-hydrophobic monomer unit.
16 . A method for reducing bitumen accretion on a wellbore drilling component, the method comprising introducing a drilling fluid into a wellbore containing the wellbore drilling component, wherein the drilling fluid comprises:
an aqueous solvent; and
an ampholytic semi-hydrophobic polymer that is hydratable under field mixing conditions, wherein the ampholytic semi-hydrophobic polymer comprises semi-hydrophobic monomer units comprising a C 1 -C 7 hydrocarbyl substituent, a hydrogen substituent, or a combination thereof.
17 . A method for reducing bitumen accretion on a wellbore drilling component, the method comprising introducing the drilling fluid defined in claim 1 into a wellbore containing the wellbore drilling component.
18 . The method of claim 16 , wherein the drilling fluid is circulated through the wellbore.
19 . The method of claim 17 , wherein the drilling fluid is circulated through the wellbore.
20 . The method of claim 18 , further comprising separating drill cuttings from the drilling fluid.