Disclosed are surface-modified nanoparticles and surfactants used in compositions and methods for enhancing hydro-carbon recovery from subterranean formations.

A surfactant of formula (I) ##STR00001## wherein each of R.sub.1 and R.sub.2 are independently a hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, or an optionally substituted arylalkyl, R.sub.3 and R.sub.4 are independently an optionally substituted alkyl, an optionally substituted cycloalkyl, or an optionally substituted arylalkyl, x is an integer in a range of 2-8, y is an integer in a range of 1-15, z is an integer in a range of 4-10, n is an integer in a range of 2-5, and A is one of a carboxybetaine group, a sulfobetaine group, or a hydroxy sulfobetaine group. An oil and gas well servicing fluid containing the surfactant and methods of servicing an oil and gas well are also described.

A surfactant of formula (I) ##STR00001## wherein each of R.sub.1 and R.sub.2 are independently a hydrogen, an optionally substituted alkyl, an optionally substituted cycloalkyl, or an optionally substituted arylalkyl, R.sub.3 and R.sub.4 are independently an optionally substituted alkyl, an optionally substituted cycloalkyl, or an optionally substituted arylalkyl, x is an integer in a range of 2-8, y is an integer in a range of 1-15, z is an integer in a range of 4-10, n is an integer in a range of 2-5, and A is one of a carboxybetaine group, a sulfobetaine group, or a hydroxy sulfobetaine group. An oil and gas well servicing fluid containing the surfactant and methods of servicing an oil and gas well are also described.

An aqueous suspension of polymer bodies is made by coalescing polymer from a flowing aqueous solution. These suspended bodies may be fibrous in appearance. However, the coalescence of the polymer bodies may be controlled to produce shapes. The coalesced polymer bodies are used for treating a downhole location within or accessed by a borehole. The bodies may be formed by coalescence at the surface and then pumped downhole or may be formed by coalescence downhole. Coalescence of polymer may result from crosslinking, complexing with material of opposite charge, or change in the polymer solution temperature, pH, solute concentration or solvent. The coalesced polymer bodies are maintained in aqueous solution after coalescence, and are not removed from solution for strengthening.

A method of treating a subterranean formation including suspending proppant particulates in a treatment fluid, wherein the proppant particles include a coating comprising a salt-tolerant, water-swellable polymer, and the treatment fluid includes at least one fluid consisting of fresh water, salt water, seawater, brine, an aqueous salt solution, and combinations thereof; and introducing the treatment fluid containing the settling retardant proppant particulates into the subterranean formation. A composite proppant particle includes a proppant substrate and a salt tolerant polymeric layer deposited on the proppant substrate.

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.

Rheology modifiers comprising cross-linked poly(amino acid) and methods of their use in aqueous compositions. The modifiers comprise cross-linked poly(amino acid) microparticles having a mean equivalent diameter when fully swollen in deionized water of up to 1000 μm, as measured by laser diffraction. In particular, the poly(amino acid) is D-, L- or D,L-Y-poly(glutamic acid). A method of preparing the modifier comprises cross-linking a poly(amino acid), drying the cross-linked poly(amino acid) and grinding the cross-linked poly(amino acid) to have the required diameter.

A method of extracting underground resources including a step of mixing hydrolysable particles and a proppant to an aqueous dispersion fluid, and introducing the fluid with pressure into an ore chute formed under the ground, wherein as the hydrolysable particles, use is made of spherical particles that include a hydrolysable resin of a weight average molecular weight (Mw) of not less than 5,000 and, specifically, not less than 10,000, and that have an average particle size (D.sub.50) in a range of 300 to 1,000 μm, and a circularity of a short diameter/long diameter ratio of not less than 0.8. The spherical particles have a hyrolysable capability, a circularity and a particle size adapted to the hydraulic fracturing.

The present disclosure relates to surfactants and methods used to increase hydrocarbon recovery from subterranean formations. Novel surfactant compositions are provided. In certain embodiments, the composition is a mixture of a sulfonated primary surfactant, water, and cosurfactants (anionic, zwitterionic/amphoteric or non-ionic surfactant). Methods to use these surfactant compositions to recover oil from formations using processes such as improved oil recovery (IOR) and flow-back processes are also provided.

The disclosure relates to a method of delaying viscosification of a well treatment fluid within a well or within a subterranean formation penetrated by a well by introducing into the well a hydratable viscosifying agent of particulates having a minimum of 40% retention on a 60 mesh screen and a minimum of 1% retention on a 20 mesh screen.