Aqueous petroleum sulfonate mixture and method of use in post-primary oil recovery

A method of preparing a viscous slug usable for displacing oil in an oil bearing subterranean formation, said steps including the steps of:

• (a) extracting from feed comprising a petroleum sulfonate containing a diluent oil and active petroleum sulfonate, at least a portion of the diluent oil, leaving active petroleum sulfonate and diluent oil in an amount of less than about 15 percent by weight of the total weight of diluent oil and active petroleum sulfonate;
• (b) adding a first oil having a distillation temperature of between about 600.degree. F. and about 1100.degree. F. to the active petroleum sulfonate whereby said first oil increases the tolerance of a mixture of the first oil, active petroleum sulfonate, water soluble polymer effective for increasing the viscosity of the mixture, water and monovalent metallic salt capable of forming an admixture with water and capable of reducing the interfacial tension between the mixture and oil contained in said formation to the inorganic salt than would be obtainable if the portion of the diluent oil had not been extracted, said first oil plus remaining diluent oil and active petroleum sulfonate being in a ratio of at least about 0.5:1 of the first oil plug remaining diluent oil to active petroleum sulfonate;
• and
• (c) mixing said first oil and active petroleum sulfonate with water, water soluble polymer, and monovalent metallic salt, said first oil, active petroleum sulfonate, water, water soluble polymer and inorganic salt are in relative proportions and said first oil being of a type to achieve a stable mixture with an interfacial tension of less than about 0.01 dynes per centimeter with oil contained in a formation, said water soluble polymer being present in an amount sufficient to increase the viscosity of the mixture above the viscosity which the mixture would have without the water soluble polymer, said diluent oil being characterized by causing instability upon mixing said feed, said water soluble polymer, water and said inorganic salt.

A method of displacing residual oil in an oil-bearing subterranean formation with an aqueous mixture containing a first oil and petroleum sulfonate, said method including the steps of:

• (a) adjusting the first oil-to-active petroleum sulfonate weight ratio to within a range of approximately 0.5:1 to approximately 2.0:1, said first oil having a distillation temperature of between about 600.degree. F. and about 1100.degree. F.;
• (b) forming a mixture of water, first oil, active petroleum sulfonate, water soluble polymer effective for increasing the viscosity of the mixture, and monovalent metallic salt capable of forming an admixture with water and capable of reducing the interfacial tension between the mixture and residual oil contained in the formation, said first oil being capable of and said inorganic salt and petroleum sulfonate being in amounts effective for producing a stable mixture having an interfacial tension of less than about 0.01 dynes per centimeter with residual oil in the formation, said water soluble polymer being present in an amount sufficient to increase the viscosity of the mixture above the viscosity which the mixture would have without the water soluble polymer;
• and
• (c) injecting said mixture into said oil-bearing subterranean formation.

A mixture usable in secondary oil recovery, said mixture including:

• (a) active petroleum sulfonate in an effective amount of up to approximately 10 percent by weight of the total mixture weight;
• (b) an oil having a distillation temperature of between about 600.degree. F. and about 1100.degree. F. and being in a weight ratio with active petroleum sulfonate in the range of about 0.5:1 to about 2.0:1, said oil being capable of producing a stable mixture having an interfacial tension with residual oil in an oil bearing porous medium of less than about 0.01 dyne per centimeter;
• (c) water soluble polymer effective for increasing the viscosity of the mixture in an effective amount of up to approximately 1 percent by weight of the total mixture weight;
• (d) monovalent metallic salt capable of forming an admixture with water and capable of reducing the interfacial tension between the mixture and the residual oil to less than about 0.01 dyne per centimeter in an effective amount of up to approximately 10 percent by weight of the total mixture weight;
• and
• (e) water in a quantity to make up the remainder of the mixture.

A method of displacing oil in an oil bearing subterranean formation, said method including the steps of:

• removing a diluent oil from feed comprising a petroleum sulfonate containing diluent oil and active petroleum sulfonate to form a substantially deoiled petroleum sulfonate with the remaining diluent oil being present in an amount of less than about 15 percent by weight of the total weight of the diluent oil and petroleum sulfonate;
• forming a mixture containing the deoiled petroleum sulfonate, water, inorganic salt capable of forming an admixture with water and capable of reducing the interfacial tension between the mixture and the oil contained in said formation, and a first oil, said first oil having a distillation temperature in the range from about 600.degree. F. to about 1100.degree. F. and being effective to increase the tolerance of the mixture of the inorganic salt and provide a stable mixture, said mixture having the components mixed in relative proportions to achieve an interfacial tension of less than about 0.01 dynes per centimeter with oil contained in the formation, said first oil plus remaining diluent oil, if any, and the active petroleum sulfonate being in a weight ratio of at least about 0.5:1 of first oil and diluent oil, if any, to active petroleum sulfonate, said diluent oil being characterized as causing instability upon mixing said feed, said water and said inorganic salt and upon mixing of the resulting mixture with a mobility buffer containing water and water soluble polymer effective for increasing the viscosity of the mobility buffer;
• and
• injecting said mixture into an oil bearing subterranean formation followed by said mobility buffer.

A method of displacing residual oil in an oil bearing subterranean formation with an aqueous mixture containing a first oil and petroleum sulfonate, said method including the steps of:

• adjusting the first oil-to-active petroleum sulfonate weight ratio to within a range of from about 0.5:1 to about 2.0:1, said first oil having a distillation temperature in the range from about 600.degree. F. to about 1100.degree. F.;
• forming a first mixture of water, first oil, active petroleum sulfonate, and monovalent metallic salt capable of forming an admixture with water and capable of reducing the interfacial tension between the first mixture and residual oil contained in the formation, said first oil being capable of and said monovalent metallic salt and active petroleum sulfonate being in amounts effective for producing a stable mixture having an interfacial tension of less than about 0.01 dynes per centimeter with residual oil in the formation;
• forming a second mixture of water and water soluble polymer, said water soluble polymer being present in an amount sufficient to increase the viscosity of said second mixture above the viscosity of said water in the absence of said water soluble polymer;
• and
• injecting into said oil bearing subterranean formation said first mixture immediately followed by said second mixture.

A mixture usable in post-primary oil recovery, said mixture including:

• active petroleum sulfonate in an effective amount of up to approximately 10 percent by weight of the total mixture weight;
• an oil having a distillation temperature in the range from about 600.degree. F. to about 1100.degree. F. and being in a weight ratio with active petroleum sulfonate in the range of from about 0.5:1 to about 2.0:1, said oil being capable of producing a stable mixture having an interfacial tension with residual oil in an oil bearing porous medium of less than about 0.01 dynes per centimeter;
• monovalent metallic salt capable of forming an admixture with water and capable of reducing the interfacial tension between the mixture and the residual oil to less than about 0.1 dynes per centimeter in an effective amount of up to approximately 10 percent by weight of the total mixture weight;
• and
• water in a quantity to make up the remainder of the mixture.