In accordance with one or more embodiments, this disclosure describes a viscoelastic fluid for a subterranean formation comprising: viscoelastic surfactant comprising the general formula:

##STR00001##

where R.sub.1 is a saturated or unsaturated hydrocarbon group of from 17 to 29 carbon atoms, R.sub.2 and R.sub.3, are each independently selected from a straight chain or branched alkyl or hydroxyalkyl group of from 1 to 6 carbon atoms; R.sub.4 is selected from H, hydroxyl, alkyl or hydroxyalkyl groups of from 1 to 4 carbon atoms; k is an integer of from 2-20; m is an integer of from 1-20; and n is an integer of from 0-20; brine solution; and at least one nanoparticle viscosity modifier comprising a particle size of 0.1 to 500 nanometers, or 0.1 to 100 nanometers.

A method of treating a bottom hole region of a formation (BRF) with an estimated frequency for performing the stages, wherein the second and each stage is carried out when the factor and/or the daily crude oil flow rate of a well has decreased by 25% or more over the preceding 6 months of well operation. In the first and second stages, the BRF is treated with an emulsion system containing silicon dioxide nanoparticles, an acid composition, and an aqueous solution of potassium or calcium chloride. In the third stages, the BRF is treated with an emulsion system containing silicon dioxide nanoparticles, a composition of surfactants and alcohols, and an aqueous solution of potassium chloride or calcium chloride. The thermal stability of the emulsion system, increase the rate of development of an oil and gas bearing layer, increase the duration of a positive effect and enhance oil production.

The methods of suspending at least one weighting agent in a drilling fluid include synthesizing carbon nanotubes via chemical vapor deposition on iron oxide catalyst nanoparticles to form a quantity of nanoparticles. Individual nanoparticles of the iron oxide catalyst nanoparticles include a transition metal disposed on iron oxide. The embodiments further include adding a quantity of nanoparticles to the drilling fluid which results in an amount of carbon nanotubes dispersed within the drilling fluid. The dispersion of the quantity of nanoparticles increases the value of at least one of a Newtonian viscosity, a yield point, a plastic viscosity, and a density of the drilling fluid with the dispersed nanoparticles versus a similar or equivalent drilling fluid without the nanoparticle dispersion. The method may further include adding at least one weighting agent which will become suspended in the drilling fluid.

A method of preparing a polymer-sand nanocomposite for water shutoff. The method includes applying a surface polymerization to sand particles. The surfaced polymerization formed by combining a polymerization initiator dissolved in a solvent with the sand particles to form a precursor sand mixture, combining a co-monomer and additional polymerization initiator in the presence of graphene, where the graphene is not functionalized, to form a precursor polymer mixture, and combining the precursor sand mixture and the precursor polymer mixture to form a sand-copolymer-graphene nanocomposite. The method further includes drying the sand-copolymer-graphene nanocomposite, preparing a polymer hydrogel, and combining the polymer hydrogel and the sand-copolymer-graphene nanocomposite to crosslink the components and form the polymer-sand nanocomposite. The associated method of forming a barrier to shut off or reduce unwanted production of water in a subterranean formation utilizing the polymer-sand nanocomposite is also provided.

A silicon oxide Janus nanosheets relatively permeability modifier (RPM) for carbonate and sandstone formations. The silicon oxide Janus nanosheets RPM may be used to treat a water and hydrocarbon producing carbonate or sandstone formation to reduce water permeability in the formation and increase the production of hydrocarbons. The silicon oxide Janus nanosheets RPM for carbonate formations includes a first side having negatively charged functional groups and a second side having alkyl groups. The silicon oxide Janus nanosheets RPM for sandstone formations includes a first side having positively charged functional groups and a second side having alkyl groups. The negatively charged functional groups may include a negatively charged oxygen group groups and hydroxyl groups. The positively charged functional groups may include amino groups and an amine. Methods of reducing water permeability using the silicon oxide Janus nanosheets RPM and methods of manufacturing the silicon oxide Janus nanosheets RPM are also provided.

Disclosed herein is a nanoparticle modified fluid that includes nanoparticles that are surface modified to increase a viscosity of the nanoparticle modified fluid and that have at least one dimension that is less than or equal to about 50 nanometers; nanoparticles that are surface modified to increase a viscosity of the nanoparticle modified fluid and that have at least one dimension that is less than or equal to about 70 nanometers; and a liquid carrier; wherein the nanoparticle modified fluid exhibits a viscosity above that of a comparative nanoparticle modified fluid that contains the same nanoparticles but whose surfaces are not modified, when both nanoparticle modified fluids are tested at the same shear rate and temperature.

Aqueous well treatment fluids especially suited for use in far field diversion in low viscosity carrier fluids comprise water, a friction reducer, and a diverter. The diverter comprises dissolvable particulates and proppants. The dissolvable particulates have a specific gravity of from about 0.9 to about 1.6 and a particle size of about 50 mesh or less. The proppants have a specific gravity of from about 0.9 to about 1.4 and a particle size of from about 20 to about 100 mesh. The dissolvable particulates have a higher specific gravity and a smaller particle size than the proppant.

A method includes placing a treatment fluid including a crosslinked gel in a wellbore penetrating a subterranean formation, the crosslinked gel including a gelling agent and a borate crosslinking agent, de-crosslinking a portion of the crosslinked gel, the de-crosslinking induced by a sufficient change in operating pressure, the de-crosslinking providing a release of active sites on the borate crosslinking agent and reducing the viscosity of the treatment fluid, and providing a borate-affinity agent to capture the released active sites on the borate crosslinking agent. A fracturing fluid includes a gelling agent, a borate crosslinking agent, a latent borate-affinity agent, and a proppant.

An oil-based drilling fluid composition, includes a base fluid and a treating agent. The base fluid comprises a base oil and an inhibitor; the treating agent comprises an organic soil, a main emulsifier, an auxiliary emulsifier, a plugging agent, a weighting agent, a humectant, an alkaline regulator and a filtrate reducer. 5-25 parts by weight of the inhibitor, 5-12 parts by weight of the organic soil, 1-6 parts by weight of the main emulsifier, 2-8 parts by weight of the auxiliary emulsifier, 3-18 parts by weight of the plugging agent, 5-30 parts by weight of the weighting agent, 2-6 parts by weight of the humectant, 2-7 parts by weight of the alkaline regulator and 2-10 parts by weight of the filtrate reducer are used, based on 100 parts by weight of base oil.

Embodiments disclosed relate to a composition and a method of treating a formation. The method includes introducing a loss circulation material system through a wellbore into a formation, where the loss circulation material system is comprised of an esterified derivative of an epoxidized organic material and a curing agent. The esterified derivative of an epoxidized organic material has a formula of: ##STR00001##
where R′ comprises H, a substituted or an unsubstituted (C1-C12) hydrocarbyl group; and where R″ comprises a substituted or an unsubstituted (C2-C30) hydrocarbyl group, including where at least one oxygen atom is attached to two different adjacent carbon atoms of the (C2-C30) hydrocarbyl group. The method also includes maintaining wellbore conditions such that the loss circulation material system cures into a loss circulation material in the formation. The cured loss circulation material may withstand a pressure differential up to about 20,000 psid.