Recovering oil by injecting ammoniated and nitrited seawater

• US 4,620,595 A
• Filed: 08/22/1985
• Issued: 11/04/1986
• Est. Priority Date: 08/22/1985
• Status: Expired due to Term

• Current Assignee: Shell Offshore, Inc. (Shell Plc)
• Original Assignee: Shell Offshore, Inc. (Shell Plc)
• Inventors: Schutt, Hans U.
• Primary Examiner(s): Novosad, Stephen J.
• Assistant Examiner(s): Odar, Thomas J.
• Application Number:
  US06/768,263
• Time in Patent Office: 439 Days
• Field of Search: 166/273, 166/271, 166/274, 166/275, 166/300, 252/8.55 D, 252/8.5 A
• US Class Current: 166/275
• CPC Class Codes: C09K 8/58 Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
• CPC Class Codes: E21B 43/20 Displacing by water

Abstract

An improved floodwater for oil recovery comprises seawater which is free of undesirable proportions of bacteria, solids and oxygen, has a pH at least near, but not more than, about 9.5, and contains a minor amount of ammonium and nitrite ions and, optionally, surfactant, effective for increasing its capability of displacing oil.

Claims

1. A waterflood process for recovering oil from a subterranean reservoir in a location in which seawater is economically available, comprising:

incorporating within the seawater, at least prior to its injection into the reservoir, about 10 to 100 ppm ammonia or ammonia-yielding material to raise the pH to near, but less than, about 9.5, plus enough nitrite ion-containing or ion-yielding material to increase the oil displacing capability of the ammoniated seawater without causing an undesirable increase of the rate of growth of sessile bacteria; and

injecting the ammoniated and nitrited seawater into the reservoir to displace the reservoir fluid at substantially the natural reservoir temperature toward a production location from which oil is recovered.

2. The process of claim 1 in which the seawater is treated to the extent required for removing bacteria, solids and oxygen prior to its injection into the reservoir.

3. The process of claim 2 in which chlorine or chlorine-releasing material is added to the seawater being treated and a bisulfite ion-containing or ion-releasing material is added to that seawater.

4. The process of claim 1 in which a portion of seawater substantially free of bacteria, solids and oxygen, is injected prior to the injection of the ammoniated and nitrited seawater.

5. The process of claim 4 in which a surfactant effective for increasing oil displacing capability is incorporated within the ammoniated and nitrited seawater.

6. The process of claim 1 in which a surfactant capable of increasing oil displacing capability is incorporated within the ammoniated and nitrited seawater.