Methods and compositions for performing a sealing operation in a wellbore. An example method introduces a sealant composition into the wellbore while the sealant composition is under shear. The sealant composition comprises a thixotropic material, a conformance gel system, and an aqueous base fluid. The sealant composition is placed into a target location, and applied shear is reduced to the sealant composition when in the target location thereby allowing the sealant composition to thicken in the target location. Fluid flow across the target location is reduced by a fluid seal formed by the thickened sealant composition.

In accordance with one or more embodiments of the present disclosure, a drilling fluid may include a base fluid, one or more formaldehyde-based resins, and one or more water-soluble acid catalysts. The base fluid may include an aqueous or non-aqueous solution. The one or more water-soluble acid catalysts may be present in an amount sufficient to reduce the pH of the drilling fluid to less than or equal to 6. The present disclosure also describes sealed subterranean petroleum formations that include such drilling fluids and methods for sealing subterranean wellbores by utilizing such drilling fluids.

Methods and compositions for the use of thermally responsive lost circulation materials in subterranean formations are provided. In one embodiment, the methods include introducing a treatment fluid including a base fluid and a thermally responsive lost circulation material including a thermally responsive hydrogel that includes at least one thermoresponsive polymer into a wellbore penetrating at least a portion of a subterranean formation including a loss zone; allowing the thermally responsive lost circulation material to reach a thickening transition temperature; and allowing the treatment fluid to at least partially set in the subterranean formation.

Accordingly, this disclosure describes systems, compositions, and methods that may use pelletized diverting agent particulates for diversion, fluid loss control, and/or other subterranean treatments for controlling fluid flow in subterranean formations. In an embodiment, a method comprising: introducing a treatment fluid into a wellbore penetrating a subterranean formation wherein the treatment fluid comprises: a base fluid; a pelletized diverting agent comprising a degradable polymer, wherein the pelletized diverting agent at least partially plugs a zone in the subterranean formation; and diverting at least a portion of the treatment fluid and/or a subsequently introduced fluid away from the zone. In an embodiment, a treatment fluid comprising: a base fluid; and a pelletized diverting agent comprising a degradable polymer.

A treatment fluid can include: a base fluid, wherein the base fluid comprises water; and a lost-circulation material, wherein the lost-circulation material comprises a polymer network having at least one branching point formed with a monomer and a cross-linking agent that comprises at least three active functional groups. The treatment fluid can maintain a pressure differential of at least 1 psi when tested with a cylindrical void that has a diameter of 0.02 inches. The monomer can be a vinyl ester-based monomer that is polymerized with the cross-linking agent to form the polymer network. The treatment fluid can be used in an oil and gas operation.

The present disclosure provides elastomer blends comprising mixtures of partially fluorinated elastomers, such as tetrafluoroethylene propylene elastomers (FEPM or TFEP) and fluorocarbon rubbers, such as vinylidene fluoride-based elastomers (FKM or FEP). The elastomer blends can be prepared using two-roll mills, internal mixers, or other mixing technique and can be molded into seals, gaskets, o-rings or other articles using extrusion, injection molding, compression molding or the like. The resultant elastomeric articles can provide good sealing performance, including at moderate or low temperatures, and exhibit good chemical compatibility and resistance when exposed to common wellbore environments. In some cases, the elastomer blends can provide performance characteristics previously only available from perfluorinated elastomers (FFKM), but without requiring the complex processing conditions associated with preparing perfluorinated elastomers.

A device for forming one or more wellbore sealants in a wellbore can include a wellbore barrier and a cured polymer. The wellbore barrier can be positioned in the wellbore. The cured polymer can be positioned with respect to the wellbore barrier for swelling the device from a compressed configuration to a swelled configuration for forming one or more wellbore sealants in the wellbore.

Described are methods and compositions for treating a subterranean formation. The method comprising introducing into the subterranean formation via a well-bore a diverter composition, the diverter composition comprising a combination of at least one deformable particle and at least one non-deformable particle; and allowing the diverter composition to block the flow of at least a portion of a treatment fluid from a first location within the well-bore to a second location.

The present disclosure provides a temperature-responsive self-degradable temporary plugging agent and a preparation method thereof as well as its application in plugging the wellbore, which relates to the technical field of oilfield exploitation. The temporary plugging agent provided in the present disclosure includes preparation raw materials of the following mass percentages: monomer 4-6%, crosslinker 0.2-1%, initiator 0.02-0.06%, degradation catalyst 0.05-0.1%, chain transfer agent 0.01-0.05%, and the balance water. The temporary plugging agent of the present disclosure is liquid before gelling, with a low viscosity and a good fluidity, and easy to be pumped. When being pumped into the wellbore, the temporary plugging agent may crosslink at the temperature of the reservoir section, with good gelling properties. At the end of the operations, it can be degraded by itself, without drilling tools, with no need for gel breaking, and with no need for additional degradation promoters.

A reversible gel composition including nanosilica and polyethylene oxide, the nanosilica and polyethylene oxide present at concentrations operable to allow for the reversible gel composition to be a flowable liquid at pH greater than about 8 and operable to allow for the reversible gel composition to be a substantially solid gel at pH less than about 8.