US 4,066,124 A · Salinity tolerant surfactant oil recovery process

Abstract

Primary anionic surfactants such as organic sulfonates are effective for recovering oil from subterranean formations only if the salinity and/or hardness of the formation water is relatively low. In petroleum formations containing high salinity, or hard water, either the high salinity water must be displaced by a preflush or the primary anionic surfactant must be used in conjunction with an effective solubilizing co-surfactant, such as ethoxylated alcohols or alkyl phenols, or alkyl or alkylaryl thiols, as well as sulfated or sulfonated, ethoxylated alcohols or alkyl phenols. Optimum performance is achieved if two or more samples of petroleum sulfonate having different equivalent weight ranges and distributions are blended in a ratio which requires the minimum amount of solubilizing cosurfactant to achieve a condition of borderline solubility in the particular formation water in which the surfactants are to be employed. This ratio may be identified by preparing a number of blended petroleum sulfonate samples in the formation water using different ratios of total primary surfactant concentration to solubilizing co-surfactant concentration, and determining whether borderline solubility is achieved, by direct observation or by identifying the sample which produced the minimum electrical conductivity, or at which point the conductivity vs. concentration ratio curve exhibits an inflection point.

Claims23

Dependent claims

In a method of recovering petroleum from a subterranean, petroleum-containing, permeable formation said formation also containing water of known or determinable salinity greater than 5000 parts per million total dissolved solids, said formation being penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with the petroleum formation, comprising injecting an aqueous, saline surfactant-containing fluid into the formation via the injection well to displace and drive petroleum toward the production well from which it is recovered to the surface of the earth, said surfactant fluid comprising an aqueous fluid whose salinity is about equal to the salinity of the formation water and having dissolved therein surfactants comprising a mixture of at least two organic sulfonate primary anionic surfactants and at least one solubilizing co-surfactant, wherein the improvement comprises:

blending at least two anionic organic sulfonate surfactants at least one of which is predominantly water soluble and at least one which is at least partially oil soluble to form a blend which requires a minimum amount of solubilizing co-surfactant to achieve a condition of borderline solubility

A method of recovering petroleum from a subterranean, petroleum-containing permeable formation, said formation containing water of known or determinable salinity and divalent ion concentration, said formation being penetrated by at least one injection well and one production well, both wells in fluid communication with the formation, comprising:

a. preparing a first series of at least three samples comprising a first blend of two organic sulfonates in different weight ratios, one of the organic sulfonates being at least partially water soluble and one other of the organic sulfonates being at least partially oil soluble, the organic sulfonates having average equivalent weights which differ by at least 50;
b. determining the minimum weight ratio of a preselected solubilizing co-surfactant selected from the group consisting of ethoxylated alkyl or alkylaryl compounds, alkyl or alkylarylpolyethoxy sulfates alkyl or alkylarylpolyethoxyalkyl sulfonates and mixtures thereof, required to solubilize each sample of the first series of blends of organic sulfonates in an aqueous fluid having a salinity about equal to the salinity of the formation water;
c. preparing a second series of at least three samples of two organic sulfonates in different weight ratios, one of the organic sulfonates being at least partly water soluble and one other of the organic sulfonates being at least partly oil soluble, the average equivalent weights of the organic sulfonates differing by at least 50, at least one of the organic sulfonates of the second series having an average equivalent weight which differs from the corresponding organic sulfonate in the first series by at least 25;
d. determining the minimum weight ratio of the same solubilizng co-surfactant as used in step (b) required to solubilize each sample of the second series of blends of organic sulfonates in an aqueous fluid having about the same salinity as was used in step (b);
e. determining which series of blends of organic sulfonates require the lesser weight ratio of solubilizing co-surfactant for solubility in aqueous fluid having about the same salinity as the formation water;
f. determining the concentration and weight ratio of the series of blended organic sulfonates identified in step (e) when used with the minimum weight ratio of solubilizing co-surfactant required for solubility at the salinity of the formation water which result in optimum oil recovery;
g. preparing an aqueous saline surfactant-containing fluid comprising the preselected solubilizing co-surfactant and the organic sulfonate blend identified in step (e) above in the concentration and weight ratio determined in step (f) above having a salinity about equal to the salinity of the formation water;
h. injecting the aqueous saline surfactant-containing fluid of step (f) into the petroleum containing formation via the injection well to displace the formation petroleum toward the production well;
and
i. recovering petroleum displaced by the surfactant-containing fluid from the formation via the production well.

7 more elements

Dependencies are inferred from the claim text.

Salinity tolerant surfactant oil recovery process

Life of this patent

Salinity tolerant surfactant oil recovery process

Life of this patent

Abstract

Claims23