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.

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.

The subject invention relates to methods for post-primary oil recovery that utilize multiple mechanisms of action, wherein biochemical-producing microbes are injected into an oil well in a certain predetermined order, based on, for example, the metabolites and by-products they are capable of producing. Preferably, gas-, acid- and/or solvent-producing microbe such as a Clostridium bacterium, is injected into the well first, followed by a biosurfactant and/or biopolymer-producing microbe, such as Bacillus subtilis, Bacillus licheniformis and/or a combination thereof.

A method includes providing an expandable metal slurry downhole in a wellbore. The expandable metal slurry includes granules of an expandable metal material suspended or dispersed in a fluid. Further, the method includes positioning the expandable metal slurry within the wellbore such that the granules of the expandable metal material in the expandable metal slurry are activatable to expand and form a seal within the wellbore.

A chemical gel system having a polymer and a silicon oxide Janus nanosheets crosslinker for treating thief zones in carbonate formations. The polymer and silicon oxide Janus nanosheets crosslinker may form a crosslinked polymer gel to reduce or prevent water production via thief zones during hydrocarbon production. The silicon oxide Janus nanosheets crosslinker includes a first side having negatively charged functional groups and a second side having amines. The negatively charged functional groups may include negatively charged oxygen groups and hydroxyl groups. Methods of reducing water production in a thief zone using the silicon oxide Janus nanosheets crosslinker and methods of manufacturing the silicon oxide Janus nanosheets crosslinker are also provided.

Disclosed are a high-temperature-resistant tertiary amine-grafted silica nano-plugging agent and water-based drilling fluids, relating to oil-gas field drilling. The nano-plugging agent is prepared from a hydrazine compound, a diallyl compound, an enamine compound, silica particle, and an amino-containing silane coupling agent by stepwise reaction. The nano-plugging agent has a grain size of 58-280 nm.

In one aspect, a method for plugging a bore includes pumping a slurry composition comprising a swellable phyllosilicate clay in an amount of 70 wt % or less into the bore, and permitting compaction of the phyllosilicate clay in the slurry to plug the bore.

In accordance with one or more embodiments of the present disclosure, a drilling fluid may include a base fluid and one or more formaldehyde-based resins. The drilling fluid may further comprise one or more water-soluble acid catalyst precursors or the reaction products of such water-soluble acid catalyst precursors. The base fluid may include an aqueous or non-aqueous solution. 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.

The present invention describes a hydraulic cement composition, its obtaining process and its use. More precisely, the hydraulic cement composition comprises increased resistance to CO.sub.2 for application in subsurface fluid reservoirs.