Process for enhanced recovery of oil from a subsurface reservoir for surfactant flooding

摘要

A process for enhanced oil recovery from a subsurface reservoir by surfactant flooding useful for surfactant flooding in reservoirs with great temperature fluctuations or a temperature gradient where surfactants soluble in themselves and effective for oil mobilization do not retain such properties over wide temperature ranges of, e.g., 10. degree. to 100° C. The new process now provides good surfactant effectiveness even at such extreme temporary and/or local temperature fluctuations as between 10° and 100° C. In the process, a mixture of a more readily soluble and a slightly soluble sulfonate is used. The solubilities may be defined in terms of the amount of a cosurfactant necessary for production of a 4% by weight sulfonate solution in synthetic seawater. Such sulfonates include, respectively, PP(a) a sulfonate of higher solubility, a 4% by weight solution of which can be produced by addition of, by weight, 3-11% of butylglycol or 2-8% of butyldiglycol at room temperature in synthetic seawater; andPP(b) a sulfonate of lesser solubility, a 4% by weight solution of which can be produced by addition of a minimum of, by weight, 20-60% of butylglycol, or 16-40% of butyl diglycol at room temperature in synthetic seawater.