| 摘要 |
Oil recovery by low tension waterflooding in which the common-ion effect is employed to suppress divalent metal ions in the low tension slug. A low tension slug comprising an aqueous medium containing an agent effective to reduce the oil-water interfacial tension is injected into a subterranean oil reservoir in order to displace oil therein to a production system. The low tension slug contains a salt having an anion in common with an alkaline earth metal salt which forms part of the reservoir rock material and which acts as a potential contributor of divalent ions to the slug. Thus where the reservoir rock contains calcium sulfate, sodium sulfate may be used in the low tension slug to suppress solubilization of the calcium sulfate into the low tension slug by the common-ion effect. The low tension slug may be preceded by a pretreatment slug also containing a salt having a common anion with an alkaline earth metal salt in the reservoir rock material.
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