Secondary recovery of petroleum
Oil recovery using a surfactant waterflood can be improved by injecting a weak salt solution before and after the surfactant slug. Fresh water can then be used as the drive flood. If the concentration and nature of the salts in the original connate water are within about 0.5% to about 10% (preferably 4 to 6%) by weight salt and consist of chloride, citrate, sulfate, phosphate, carbonate, silicate, or borate salts (preferably sodium chloride), the weak saline flood preceding the surfactant slug may be omitted. If the reservoir was previously flooded with such a saline waterflood for secondary oil recovery, the weak saline preflood may also be omitted. The weak saline flood following the surfactant slug should be of 0.5 to 2.5% (preferably 1 to 1.5%) concentration. This flood can also be used in place of the fresh waterflood. The surfactant slug consists of 1 to 10% by weight of Promor SS-20 and Tween 85 or just Promor SS-20 dissolved in either water or oil. Consolidated sandstone cores filled with Hawes crude oil from the Hardinsburg sand, Butler County, Kentucky yielded between 10 and 20% PV of additional oil over a conventional waterflood, which consisted of a 5% salt solution.
- Assignee:
- Cities Service Oil Co.
- Patent Number(s):
- US 3369602
- OSTI ID:
- 7093133
- Country of Publication:
- United States
- Language:
- English
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