Well Treatment Fluids and Methods
A well treatment fluid includes an aqueous-based fluid, a crosslinked CMHEC polymer, and a crosslinker. The CMHEC polymer exhibits a DS of 0.2 to 0.6 and a MS of 2.0 to 2.5. The well treatment fluid exhibits a viscosity of at least about 100 cP. A well treatment method includes crosslinking a CMHEC polymer in an aqueous-based fluid at a pH of at least about 6. The crosslinking increases a viscosity of the well treatment fluid to at least about 100 cP. A well is treated with the well treatment fluid at a temperature of at least about 200° F. Another well treatment method includes forming a well treatment fluid from produced water that has a TDS content of at least about 150,000 ppm. The crosslinking increases a viscosity of the well treatment fluid to at least about 100 cP.
1 . A well treatment fluid comprising:
an aqueous-based fluid containing produced water, the well treatment fluid having a total dissolved solids (TDS) content of at least about 100,000 ppm;
a crosslinked carboxymethyl hydroxyethyl cellulose (CMHEC) polymer exhibiting a degree of substitution (DS) of 0.3 to 0.5 and a molar substitution (MS) of 2.0 to 2.5; and
a crosslinker configured to crosslink the CMHEC polymer in the aqueous-based fluid, the well treatment fluid exhibiting a property of stabilizing a sustained viscosity of greater than or equal to about 100 cP at a sheer rate of 100 sec −1 for a time of at least about 1 hour when at a temperature of at least about 200° F.
2 . The fluid of claim 1 wherein the well treatment fluid has a TDS content of at least about 150,000 ppm.
3 . The fluid of claim 1 wherein the well treatment fluid has a divalent cation content as CaCO 3 of at least about 10,000 ppm.
4 . The fluid of claim 1 wherein the well treatment fluid exhibits a property of stabilizing the sustained viscosity of greater than or equal to about 100 cP at a sheer rate of 100 sec −1 for a time of at least about 2 hours when at the temperature of at least about 200° F.
5 . The fluid of claim 1 wherein the well treatment fluid exhibits a pH of at least about 6.
6 . The fluid of claim 1 further comprising Mg(OH) 2 .
7 . The fluid of claim 1 wherein the well treatment fluid exhibits a property of stabilizing the sustained viscosity of greater than or equal to about 100 cP at a shear rate of 100 sec −1 for a time of at least about 2 hours when at a temperature of at least about 275° F.
8 . The fluid of claim 1 wherein the well treatment fluid exhibits a property of stabilizing the sustained viscosity of greater than or equal to about 100 cP at a shear rate of 100 sec −1 for a time of at least about 1 hour when at a temperature of at least about 300° F.
9 . The fluid of claim 5 wherein the pH is from greater than 7 to about 11.
10 . The fluid of claim 1 wherein the temperature is at least about 250° F.
11 . The fluid of claim 1 wherein the well treatment fluid has a divalent cation content as CaCO 3 of at least about 25,000 ppm.
12 . A well treatment fluid comprising:
an aqueous-based fluid formed from produced water, the well treatment fluid having a total dissolved solids (TDS) content of at least about 150,000 ppm and a divalent cation content as CaCO 3 of at least about 10,000 ppm and exhibiting a pH of at least about 6;
a crosslinked carboxymethyl hydroxyethyl cellulose (CMHEC) polymer exhibiting a degree of substitution (DS) of 0.3 to 0.5 and a molar substitution (MS) of 2.0 to 2.5; and
a crosslinker configured to crosslink the CMHEC polymer in the aqueous-based fluid, the well treatment fluid exhibiting a property of stabilizing a sustained viscosity of greater than or equal to about 100 cP at a sheer rate of 100 sec −1 for a time of at least about 1 hour when at a temperature of at least about 200° F.
13 . The fluid of claim 12 further comprising Mg(OH) 2 .
14 . The fluid of claim 12 wherein the temperature is at least about 250° F. and the divalent cation content as CaCO 3 is at least about 25,000 ppm.
15 . The fluid of claim 12 wherein the well treatment fluid exhibits a property of stabilizing the sustained viscosity of greater than or equal to about 100 cP at a shear rate of 100 sec −1 for a time of at least about 2 hours when at a temperature of at least about 275° F.
16 . The fluid of claim 12 wherein the well treatment fluid exhibits a property of stabilizing the sustained viscosity of greater than or equal to about 100 cP at a shear rate of 100 sec −1 for a time of at least about 1 hour when at a temperature of at least about 300° F.
17 . A well treatment fluid comprising:
an aqueous-based fluid formed from produced water, the well treatment fluid having a total dissolved solids (TDS) content of at least about 150,000 ppm and a divalent cation content as CaCO 3 of at least about 10,000 ppm;
Mg(OH) 2 , the well treatment fluid exhibiting a pH from greater than 7 to about 11;
a crosslinked carboxymethyl hydroxyethyl cellulose (CMHEC) polymer exhibiting a degree of substitution (DS) of 0.3 to 0.5 and a molar substitution (MS) of 2.0 to 2.5; and
a crosslinker configured to crosslink the CMHEC polymer in the aqueous-based fluid, the well treatment fluid exhibiting a property of stabilizing a sustained viscosity of greater than or equal to about 100 cP at a sheer rate of 100 sec −1 for a time of at least about 1 hour when at a temperature of at least about 200° F.
18 . The fluid of claim 17 wherein the temperature is at least about 250° F. and the divalent cation content as CaCO 3 is at least about 25,000 ppm.
19 . The fluid of claim 17 wherein the well treatment fluid exhibits a property of stabilizing the sustained viscosity of greater than or equal to about 100 cP at a shear rate of 100 sec −1 for a time of at least about 2 hours when at a temperature of at least about 275° F.
20 . The fluid of claim 17 wherein the well treatment fluid exhibits a property of stabilizing the sustained viscosity of greater than or equal to about 100 cP at a shear rate of 100 sec −1 for a time of at least about 1 hour when at a temperature of at least about 300° F.