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

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.

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 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.

A method may include: providing a cleanout fluid comprising a single anionic surfactant, a single nonionic surfactant, and a solvent; preparing a cleanout pill by mixing the cleanout fluid with a brine; and displacing a fluid in a wellbore using the cleanout pill.

A method may include: providing a cleanout fluid comprising a single anionic surfactant, a single nonionic surfactant, and a solvent; preparing a cleanout pill by mixing the cleanout fluid with a brine; and displacing a fluid in a wellbore using the cleanout pill.

A process for recovering oil from an oil-bearing formation is disclosed comprising providing a first oil recovery formulation comprising a first surfactant able to create low interfacial tension with reservoir crude oil; injecting the first oil recovery formulation into the oil-bearing formation via an injection well (201); providing a second oil recovery formulation having a second surfactant with a higher solubility in water than the first formulation; injecting the second oil recovery formulation into the oil-bearing formation via the injection well; and producing oil to a production well (203).

A process for recovering oil from an oil-bearing formation is disclosed comprising providing a first oil recovery formulation comprising a first surfactant able to create low interfacial tension with reservoir crude oil; injecting the first oil recovery formulation into the oil-bearing formation via an injection well (201); providing a second oil recovery formulation having a second surfactant with a higher solubility in water than the first formulation; injecting the second oil recovery formulation into the oil-bearing formation via the injection well; and producing oil to a production well (203).

A method includes injecting an aqueous-based injection fluid into a wellbore at a first temperature, where the aqueous-based injection fluid includes phase-changing nanodroplets having a liquid core and a shell. The method also includes exposing the phase-changing nanodroplets to a second temperature in the wellbore that is greater than or equal to a boiling point of the liquid core to change a liquid in the liquid core to a vapor phase and expand the phase-changing nanodroplets, thus removing debris from the wellbore and surrounding area.