Abstract: A well treatment method includes forming a well treatment fluid by combining ingredients including a polymer, a crosslinker, an acidifying substance, and a base fluid. Crosslinking increases viscosity of the fluid during a development time. A pH decrease is controlled during the development time using the acidifying substance. The method also includes delaying the development time of the viscosity increase by controlling the pH decrease. A well treatment method includes forming a well treatment fluid by combining ingredients including a hydratable polymer, a crosslinker, an acidifying substance, and a base fluid. The method includes delaying development time of a viscosity increase by controlling a pH decrease without adding further acidifying substance after combining the polymer, crosslinker, acidifying substance, and base fluid. A well treatment fluid formulated with ingredients include a base fluid, a polymer, a crosslinker, and an acidifying substance.

Abstract: 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.

Abstract: A well treatment method includes forming a well treatment fluid by combining ingredients including a polymer, a crosslinker, an acidifying substance, and a base fluid. Crosslinking increases viscosity of the fluid during a development time. A pH decrease is controlled during the development time using the acidifying substance. The method also includes delaying the development time of the viscosity increase by controlling the pH decrease. A well treatment method includes forming a well treatment fluid by combining ingredients including a hydratable polymer, a crosslinker, an acidifying substance, and a base fluid. The method includes delaying development time of a viscosity increase by controlling a pH decrease without adding further acidifying substance after combining the polymer, crosslinker, acidifying substance, and base fluid. A well treatment fluid formulated with ingredients include a base fluid, a polymer, a crosslinker, and an acidifying substance.

Abstract: A well treatment method includes forming a well treatment fluid by combining ingredients including a polymer, a crosslinker, an acidifying substance, and a base fluid. Crosslinking increases viscosity of the fluid during a development time. A pH decrease is controlled during the development time using the acidifying substance. The method also includes delaying the development time of the viscosity increase by controlling the pH decrease. A well treatment method includes forming a well treatment fluid by combining ingredients including a hydratable polymer, a crosslinker, an acidifying substance, and a base fluid. The method includes delaying development time of a viscosity increase by controlling a pH decrease without adding further acidifying substance after combining the polymer, crosslinker, acidifying substance, and base fluid. A well treatment fluid formulated with ingredients include a base fluid, a polymer, a crosslinker, and an acidifying substance.

Abstract: 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.