A salt-tolerant polymer microsphere plugging agent and a preparation method thereof, the agent being made of white oil, fumed silica, acrylamide monomer, acrylic acid, sorbitan fatty acid ester, N,N′-methylene bisacrylamide, ammonium persulfate, sodium bisulfite, hydrophilic surfactant and water. The present general inventive concept synthesizes salt-tolerant polymer microspheres with ultra-low interfacial tension by adopting inverse phase emulsion polymerization. The prepared polymer microsphere plugging agent is a new type of polymer microspheres with ultra-low interfacial tension, such that the tension can reach 4.3×10.sup.−3 mN/m, and the salt tolerance can reach 50000 mg/L salinity, which improves the problem of low interfacial tension and poor salt tolerance in existing polymer microspheres.

The present disclosure to a cementitious plugging wall solidifier for water-based drilling fluid and a preparation method thereof and a water-based 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 method of forming a barrier to overcome lost circulation in a subterranean formation. The method includes injecting a polymer-sand nanocomposite into one or more lost circulation zones in the subterranean formation where the polymer-sand nanocomposite is formed from sand mixed with a polymer hydrogel. Further, the polymer hydrogel includes a hydrogel polymer, an organic cross-linker, and a salt. The sand additionally comprises a surface modification. The associated method of preparing a polymer-sand nanocomposite lost circulation material for utilization in forming the barrier is provided.

Methods and compositions for introducing a treatment fluid into a wellbore penetrating a subterranean formation wherein the treatment fluid comprises: a base fluid; and composite diverting particulates, wherein the composite diverting particulates each comprise a degradable polymer and an oil-soluble material, wherein the composite diverting particulate 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.

A mixture of at least two shapes of a dissolvable diverter material. The shapes range from a flake having a high surface area to mass ratio to beads having a low surface area to mass ratio. The density of the various shapes may be manipulated by including voids or low-density materials within the shape. The density manipulation allows matching the transport properties of the at least two shapes to the transport fluid so that both shapes may arrive at the desired location at the desired time.

A mixture of at least two shapes of a dissolvable diverter material. The shapes range from a flake having a high surface area to mass ratio to beads having a low surface area to mass ratio. The density of the various shapes may be manipulated by including voids or low-density materials within the shape. The density manipulation allows matching the transport properties of the at least two shapes to the transport fluid so that both shapes may arrive at the desired location at the desired time.

Sealant compositions that may be used for creating fluid flow preventing barriers in a subterranean formation. A method may comprise reacting components comprising an oxazoline functionalized polymer and a crosslinking agent in a subterranean formation to create a barrier in the subterranean formation.

A two-component lost circulation material (LCM) is provided having a polymer component and a sodium hydroxide component. The polymer component may include a carrier fluid such as water, a particulate material such as fly ash, a fibrous material such as polypropylene fibers, and an acrylic polymer. The sodium hydroxide component may include water and sodium hydroxide. The sodium hydroxide component is introduced to contact the polymer component to form the two-component LCM. Methods of lost circulation control and manufacture of a two-component LCM are also provided.

The present disclosure relates to fluid loss control agents for use in a water-based wellbore fluid. The fluid loss control agents generally include non-crosslinked copolymers of non-carboxylated monomers. The present disclosure also relates to water-based wellbore fluids containing the above fluid loss control agents and to methods of servicing a wellbore in a subterranean formation by placing the water-based wellbore fluids in the wellbore.