US4624314A — Modified waterflood technique for enhanced hydroc…

Claim 1

Independent Claim 203 words

A method of recovering hydrocarbons from an argillaceous subterranean rock formation by a modified waterflood technique involving injecting an aqueous solution into an input well drilled into the formation and recovering oil displaced by said solution from at least one production well drilled into said formation, wherein the method comprises: increasing the permeability of the formation adjacent to the input well by injecting a strongly acidic aqueous solution into the formation; displacing said strongly acidic solution into the formation by injecting an aqueous acidic surfactant treatment solution containing a clay stabilizing agent into the formation through said input well, said treatment solution initially injected having a total ionic concentration approaching that of said acidic aqueous solution but the concentration of said treatment solution being gradually reduced as more of said treatment solution is injected until a threshold concentration is reached, said threshold concentration being substantially the lowest concentration of the acid, surfactant and clay stabilizing agent capable of maintaining acceptable permeability of the formation and a mobility ratio between the treatment solution and hydrocarbons displaced from the formation of about 1.0 or less; and continuing the injection of said treatment solution having said threshold concentration in order to displace hydrocarbons from the formation.

Claim 2

Independent Claim 203 words

A method of recovering hydrocarbons from an argillaceous subterranean rock formation by a modified waterflood technique involving injecting an aqueous solution into an input well drilled into the formation and recovering oil displaced by said solution from at least one production well drilled into said formation, wherein the method comprises: increasing the permeability of the formation adjacent to the input well by injecting a strongly acidic aqueous solution into the formation; displacing said strongly acidic solution into the formation by injecting an aqueous acidic surfactant treatment solution containing a clay stabilizing agent into the formation through said input well, said treatment solution initially injected having a total ionic concentration approaching that of said acidic aqueous solution but the concentration of said treatment solution being gradually reduced as more of said treatment solution is injected until a threshold concentration is reached, said threshold concentration being substantially the lowest concentration of the acid, surfactant and clay stabilizing agent capable of maintaining acceptable permeability of the formation and a mobility ratio between the treatment solution and hydrocarbons displaced from the formation of about 1.0 or less; and continuing the injection of said treatment solution having said threshold concentration in order to displace hydrocarbons from the formation.

Claim 3

Dependent Claim 41 words

A method according to claim 1 wherein the treatment solution initially injected into said formation has a total ionic concentration at least 20% as high as that of the strongly acidic aqueous solution used for increasing the permeability of the formation.

Claim 4

Dependent Claim 48 words

A method according to claim 2 wherein the concentration of the treatment solution is gradually reduced in a stepwise manner and wherein the concentration of the treatment used in each step is about one fifth to one half that of the solution used in the immediately preceding step.

Claim 5

Dependent Claim 35 words

A method according to claim 1 wherein the reduction of concentration of the treatment solution is sufficiently gradual that the increased permeability achieved by the injection of the strongly acidic solution is not substantially reduced.

Claim 6

Dependent Claim 26 words

A method according to claim 1 wherein the treatment solution contains one or more acids capable of reacting with carbonate or bicarbonate to generate carbon dioxide.

Claim 7

Dependent Claim 29 words

A method according to claim 1 wherein the treatment solution contains one or more acids selected from the group consisting of hydrochloric, phosphoric, nitric, sulfuric, formic, acetic and citric.

Claim 8

Dependent Claim 42 words

A method according to claim 1 wherein the treatment solution contains one or more surfactants selected from the group consisting of petroleum sulfonates, alkyl polyethoxylated sulfonates, alpha olefinic sulfonates, alkylphenoxypolyethanols, C 10 to C 18 amine oxides and polyethoxylated quaternary ammonium salts.

Claim 9

Dependent Claim 24 words

A method according to claim 7 wherein the treatment solution also contains a co-surfactant selected from the group consisting of methanol and butyl cellusolve.

Claim 10

Dependent Claim 17 words

A method according to claim 1 wherein the clay stabilizing agent is a highly ionizable inorganic salt.

Claim 11

Dependent Claim 17 words

A method according to claim 9 wherein the salt is selected from KCl and NH 4 Cl.

Claim 12

Dependent Claim 15 words

A method according to claim 1 wherein the clay stabilizing agent is an organic material.

Claim 13

Dependent Claim 36 words

A method according to claim 11 wherein the organic material is selected from the group consisting of low molecular weight cyclic imides, poly quaternary ammonium polymers of about 500,000 molecular weight and organic poly cationic polymers.

Claim 14

Dependent Claim 22 words

A method according to claim 1 wherein the strongly acidic aqueous solution has a pH in the range of 1 to 3.

Claim 15

Dependent Claim 22 words

A method according to claim 1 wherein the strongly acidic aqueous solution has a pH in the range of 1 to 2.

Claim 16

Dependent Claim 28 words

A method according to claim 1 wherein the strongly acidic aqueous solution contains one or more acids selected from the group consisting of phosphoric, hydrochloric, formic and acetic.

Claim 17

Dependent Claim 16 words

A method according to claim 1 wherein said treatment solution contains at least one corrosion inhibitor.

Claim 18

Dependent Claim 15 words

A method according to claim 1 wherein said treatment solution contains at least one sequesterant.

Claim 19

Dependent Claim 59 words

A method according to claim 1 wherein the treatment solution is prepared for use prior to its injection into the formation by adding a concentrated formulation to water from a source readily available at the input well, and wherein the concentration of the treatment solution is gradually reduced by reducing the amount of said formulation added to said water.

Claim 20

Independent Claim 167 words

A method of recovering hydrocarbons from an argillaceous subterranean rock formation of suitably high permeability by a waterflood technique involving injecting an aqueous solution into an input well drilled into the formation and recovering oil displaced by said solution from at least one production well drilled into said formation, wherein the method comprises: injecting an aqueous acidic surfactant treatment solution containing a clay stabilizing agent into said formation through said input well, the treatment solution initially injected being strongly acidic but the concentration of said acidic treatment solution being gradually reduced as more of said acidic treatment solution is injected until a threshold concentration is reached, said threshold concentration being substantially the lowest concentration of acid, surfactant and clay stabilizing agent capable of maintaining acceptable permeability and a mobility ratio between the acidic surfactant solution and hydrocarbons displaced from the formation of about 1.0 or less; and then continuing the injection of said treatment solution having said threshold concentration in order to displace hydrocarbons from the formations.

Claim 21

Independent Claim 167 words

A method of recovering hydrocarbons from an argillaceous subterranean rock formation of suitably high permeability by a waterflood technique involving injecting an aqueous solution into an input well drilled into the formation and recovering oil displaced by said solution from at least one production well drilled into said formation, wherein the method comprises: injecting an aqueous acidic surfactant treatment solution containing a clay stabilizing agent into said formation through said input well, the treatment solution initially injected being strongly acidic but the concentration of said acidic treatment solution being gradually reduced as more of said acidic treatment solution is injected until a threshold concentration is reached, said threshold concentration being substantially the lowest concentration of acid, surfactant and clay stabilizing agent capable of maintaining acceptable permeability and a mobility ratio between the acidic surfactant solution and hydrocarbons displaced from the formation of about 1.0 or less; and then continuing the injection of said treatment solution having said threshold concentration in order to displace hydrocarbons from the formations.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1989-11-24	1990-05-26	1990-11-25	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1993-11-24	1994-05-26	1994-11-25	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1997-11-24	1998-05-26	1998-11-25	$7700.00	Window Closed / Lapsed

Modified waterflood technique for enhanced hydrocarbon recovery from argillaceous subterranean reservoirs

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