A method of drilling in a subterranean formation. A method may include providing a direct emulsion drilling fluid comprising an aqueous fluid, an oil, and a polysorbate emulsifier; circulating the direct emulsion drilling fluid from a surface, through a wellbore, and back to the surface; and extending the wellbore in the subterranean formation while circulating the direct emulsion drilling fluid.

A method of drilling in a subterranean formation. A method may include providing a direct emulsion drilling fluid comprising an aqueous fluid, an oil, and a polysorbate emulsifier; circulating the direct emulsion drilling fluid from a surface, through a wellbore, and back to the surface; and extending the wellbore in the subterranean formation while circulating the direct emulsion drilling fluid.

The invention relates to the technical field of oil and gas drilling, and discloses an amphiphilic block polymer ultralow-permeability agent and an intelligent temporary plugging type water-based drilling fluid. The ultralow-permeability agent contains a structural unit provided by styryl hydrophobic monomer, maleic anhydride and acrylamide; the drilling fluid contains two or more of water, sodium bentonite, Pac-Lv, the ultralow-permeability agent, calcium carbonate, one-way plugging agent, white asphalt and barite which are stored in a mixed manner or independently stored. When the amphiphilic block polymer provided by the invention is used as the ultralow-permeability agent of the intelligent temporary plugging type water-based drilling fluid, the self-adaptive characteristic is realized; according to the amphiphilic block polymer, temporary plugging layer gaps formed in pore and throats by plugging materials in drilling fluid can be fully filled under the condition that the sizes and the distribution of the pore and throats of reservoirs are not required to be clear, so that the permeability of temporary plugging layer is greatly reduced, ultralow-permeability is realized, and the amphiphilic block polymer is weak in tackifying effect, has gel-improving effect and can improve the rheological property of the drilling fluid.

A crosslinked polymer comprising reactants of a first repeating unit, a second repeating unit, and a crosslinker that react to form the crosslinked polymer, wherein the first repeating unit is a sulfonic acid-containing monomer present from 50% to 99% by weight of the reactants, wherein the second repeating unit is selected from the group consisting of an N-vinyl amide-containing monomer, a terminal double bond-containing monomer, and any combination thereof, and is present from 1% to 50% by weight of the reactants, and wherein the crosslinker comprises at least two olefinic bonds, and is present in the range of about 9% to about 25% by weight of the reactants.

A crosslinked polymer comprising reactants of a first repeating unit, a second repeating unit, and a crosslinker that react to form the crosslinked polymer, wherein the first repeating unit is a sulfonic acid-containing monomer present from 50% to 99% by weight of the reactants, wherein the second repeating unit is selected from the group consisting of an N-vinyl amide-containing monomer, a terminal double bond-containing monomer, and any combination thereof, and is present from 1% to 50% by weight of the reactants, and wherein the crosslinker comprises at least two olefinic bonds, and is present in the range of about 9% to about 25% by weight of the reactants.

Invert emulsions may be used in downhole operations to delay the swelling of water-swellable polymers. For example, a treatment fluid may be introduced into a wellbore penetrating a subterranean formation, the treatment fluid comprising an emulsion with an continuous oil phase and a discontinuous aqueous phase, an emulsifier, and a water-swellable polymer suspended in the continuous oil phase, wherein the aqueous discontinuous phase has a pH of about 0 to about 11; the emulsion may be broken while the treatment fluid in a portion of the subterranean formation; and the water-swellable polymer may be swollen into a swollen polymer, thereby reducing fluid flow through the portion of the subterranean formation. In some instances, for carbonate subterranean formation, the aqueous discontinuous phase may have a pH of about 7 to about 11.

Invert emulsions may be used in downhole operations to delay the swelling of water-swellable polymers. For example, a treatment fluid may be introduced into a wellbore penetrating a subterranean formation, the treatment fluid comprising an emulsion with an continuous oil phase and a discontinuous aqueous phase, an emulsifier, and a water-swellable polymer suspended in the continuous oil phase, wherein the aqueous discontinuous phase has a pH of about 0 to about 11; the emulsion may be broken while the treatment fluid in a portion of the subterranean formation; and the water-swellable polymer may be swollen into a swollen polymer, thereby reducing fluid flow through the portion of the subterranean formation. In some instances, for carbonate subterranean formation, the aqueous discontinuous phase may have a pH of about 7 to about 11.

A method of treating a well comprising introducing a well treatment fluid into the well, and a well treatment fluid, are provided. The well treatment fluid comprises an aqueous base fluid, sepiolite clay, and a polymer component selected from the group of an acryloylmorpholine polymer, a polyvinylpyrrolidone polymer, and mixtures thereof. In one embodiment, for example, the method is a method of drilling a well. In this embodiment, the well treatment fluid is a drilling fluid.

Provided herein are drilling muds, including water-based drilling muds. The components of the drilling muds are a degradable fluid loss additive, for example, synthetic degradable nanoparticles, a clay mineral, for example, a smectite, and a base fluid, for example, water. Also provide are methods for preventing leak-off during a drilling operation and for automatically cleaning-up filter cake after completion of a drilling process both of which utilize the drilling muds and water-based drilling muds.

Provided herein are drilling muds, including water-based drilling muds. The components of the drilling muds are a degradable fluid loss additive, for example, synthetic degradable nanoparticles, a clay mineral, for example, a smectite, and a base fluid, for example, water. Also provide are methods for preventing leak-off during a drilling operation and for automatically cleaning-up filter cake after completion of a drilling process both of which utilize the drilling muds and water-based drilling muds.