Abstract Improved flooding of an oil-bearing subterranean reservoir with an aqueous slug containing a salt-sensitive polymer (example of such a polymer is a partially hydrolyzed, high molecular weight polyacrylamide) and a subsequent drive water which, due to the salt content, tends to degrade the back portion of the aqueous polymer slug, is realized by following the aqueous, saltsensitive polymer slug with a sufficient volume of an aqueous biopolymer slug to ''''insulate'''' the salt-sensitive polymer from the drive water. Drive water having salt concentrations above 1,000 ppm (parts per million) of TDS (total dissolved solids) and especially those waters containing above 50 ppm of polyvalent cations, tends to adversely affect the mobility reducing capabilities of a salt-sensitive polymer. More efficient mobility control is obtained by interjecting the biopolymer slug between the salt-sensitive polymer slug and the drive water. Optionally, a miscible or miscible-like slug can precede the salt-sensitive polymer slug.
The process of claim 1 wherein the salt-sensitive polymer is a partially hydrolyzed, high molecular weight polyacrylamide.
Claim 2
Dependent Claim
28 words
The process of claim 1 wherein about 1 to about 50 per cent formation pore volume of the aqueous slug containing the biopolymer is injected into the formation.
Claim 3
Dependent Claim
28 words
The process of claim 1 wherein about 2 to about 30 per cent formation pore volume of the aqueous slug containing the biopolymer is injected into the formation.
Claim 4
Dependent Claim
20 words
The process of claim 1 wherein the biopolymer concentration in the aqueous slug is about 25 to about 1,000 ppm.
Claim 5
Dependent Claim
26 words
The process of claim 1 wherein a micellar dispersion is injected into the formation previous to the injection of the aqueous slug containing the salt-sensitive polymer.
Claim 6
Dependent Claim
107 words
An improved process for recovering crude oil from an oil-bearing subterranean formation wherein an aqueous slug containing a partially hydrolyzed, high molecular weight polyacrylamide is injected into the formation to impart desired mobility control to the process, and wherein the aqueous slug is displaced by a drive water toward a production means to recover crude oil therethrough and wherein the water drive contains a salt concentration above about 500- 1,000 ppm which adversely influences the mobility characteristics imparted by the polyacrylamide, the improvement comprising injecting after the aqueous polyacrylamide slug about 1 to about 50 per cent formation pore volume of an aqueous slug containing a biopolymer.
Claim 7
Dependent Claim
23 words
The process of claim 7 wherein the biopolymer concentration is about 25 to about 1,000 ppm within the aqueous slug containing the biopolymer.
Claim 8
Dependent Claim
22 words
The process of claim 7 wherein a micellar dispersion is injected previous to the injection of the aqueous slug containing the polyacrylamide.
Claim 9
Dependent Claim
25 words
The process of claim 7 wherein about 2 to about 30 per cent formation pore volume of the aqueous slug containing the biopolymer is injected.