Treatment of steam feedwater with CO2 to reduce oil well reservoir gravel and sand dissolution during steam injection

Claim 2

A process of inhibiting the dissolution of the gravel pack and/or silicate containing hydrocarbon-bearing formation subjected to steam enhanced oil recovery stimulation comprising: creating steam, said steam comprises a vapor phase and a residual liquid phase; monitoring the pH of said residual liquid phase; injecting a sufficient amount of CO 2 gas into the residual liquid phase of the steam to reduce the pH of the residual liquid phase to from about pH 5 to about pH 9, and injecting said steam into said formation, wherein the reduced pH of the steam inhibits the dissolution of the gravel pack and/or silicate containing hydrocarbon-bearing formation.

Claim 3

The process according to claim 1 wherein the flow of CO 2 is from about 10 to about 1000 standard cubic feet of CO 2 per barrel of cold water equivalent of injected steam.

Claim 4

The process according to claim 2 wherein the flow rate is from about 400 to about 600 standard cubic feet of CO 2 per barrel of cold water equivalent of injected steam.

Claim 5

The process according to claim 2 which further comprises adding a surfactant selected from the group consisting of anionic surfactant, cationic surfactant, nonionic surfactant, and mixtures thereof, to the injected steam.

Claim 6

The process according to claim 4 wherein the steam injection is selected from the group consisting of cyclic steam injection, patterned steam flood, and mixtures thereof.

Claim 7

In a process for the recovery of hydrocarbons from a silicate containing hydrocarbon formation penetrated by at least one steam injection well and at least one production well spaced therefrom, the process which comprises: creating steam, said steam comprises a vapor phase and a residual liquid phase; monitoring the pH of the residual liquid phase of the steam; injecting CO 2 gas into said residual liquid phase at a rate of from about 10 to about 1000 standard cubic feet of CO 2 per barrel of cold water equivalent of steam so as to reduce the pH of the residual liquid phase to from about pH 7 to about pH 8; driving said steam from said injection well into said formation and away from said injection well to assist the movement of hydrocarbons toward said production well; and recovering the hydrocarbons at said production well.

Claim 8

In a process for the recovery of hydrocarbons from a silicate containing hydrocarbon formation penetrated by at least one steam injection well and at least one production well spaced therefrom, the process which comprises: creating steam, said steam comprises a vapor phase and a residual liquid phase; monitoring the pH of the residual liquid phase of the steam; injecting CO 2 gas into said residual liquid phase at a rate of from about 10 to about 1000 standard cubic feet of CO 2 per barrel of cold water equivalent of steam so as to reduce the pH of the residual liquid phase to from about pH 7 to about pH 8; driving said steam from said injection well into said formation and away from said injection well to assist the movement of hydrocarbons toward said production well; and recovering the hydrocarbons at said production well.

Claim 9

The process according to claim 6, which further comprises adding a surfactant selected from the group consisting of anionic, cationic and nonionic surfactants to the injected steam.