CA1205007A - Solvent stimulation in heavy oil wells producing a large fraction of water - Google Patents
Solvent stimulation in heavy oil wells producing a large fraction of waterInfo
- Publication number
- CA1205007A CA1205007A CA000434415A CA434415A CA1205007A CA 1205007 A CA1205007 A CA 1205007A CA 000434415 A CA000434415 A CA 000434415A CA 434415 A CA434415 A CA 434415A CA 1205007 A CA1205007 A CA 1205007A
- Authority
- CA
- Canada
- Prior art keywords
- solvent
- water
- oil
- formation
- well
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
SOLVENT STIMULATION IN HEAVY OIL WELLS PRODUCING
A LARGE FRACTION OF WATER
ABSTRACT
A method for the solvent stimulation of a well producing heavy oil containing large fractions of free water comprises injecting into the producing well a solvent having a density and viscosity substantially less than the viscous formation oil and a viscosity equal to or slightly greater than water at formation conditions, shutting-in the producing well to allow a soak period, and returning the well to production with substantially less water production than prior to stimulation.
A LARGE FRACTION OF WATER
ABSTRACT
A method for the solvent stimulation of a well producing heavy oil containing large fractions of free water comprises injecting into the producing well a solvent having a density and viscosity substantially less than the viscous formation oil and a viscosity equal to or slightly greater than water at formation conditions, shutting-in the producing well to allow a soak period, and returning the well to production with substantially less water production than prior to stimulation.
Description
SOLVENT STIMULATION IN HEAVY OIL WELLS PRODUCING
A LARGE FRACTION OF WATER
This invention relates to a method for stimulating a production well producing oil having a large ~raction of free water.
Repetitive stimulation of oil-producing wells is a production practice of long standing. The phrase l'cyclic stimulation" is o~ten used to reflect anticipated production rate increases~ the duration o~ which is relatively short as conpared to the total life of the well. The cause o~ the production increase arises ~rom either (1) an increase in pressure driving reservoir fluids toward the producing well, or (2) a decrease in resistance to ~low of the ~luids such as reduction in viscosity or removal of impediments to flow in the reservoir rock surrounding the well. The viscosity reduction may be achieved through use of a low viscosity fluid solvent and/or by increasing the temperature o~ the reservoir fluids and rock in the proximity of the reservoir.
This invention provides a method for the solvent stimulation of a production well producing oil containing large fractions o~ free water wherein production is enhanced and the oil recovered with substantially less water production than prior to stimulation.
The present invention provides a method ~or stimulating the recovery of oil having a lar~e ~raction of free water flowing from a production well penetrating a subterranean, viscous oil-containing formation comprising injecting a predetermined amount o~ a solvent into the production well to displace water away from the production well, which solvent has a density and viscosity substantially less than the viscous ~ormation oil and a viscosity equal to or sligh-tly greater than water at formation conditions, shutting-in the production well to allow the formation around the production well to ~1"~
undergo a soak period whereby the solvent ~hich has a density less than the viscous oil fingers upwardly under the influence o~ gravity dissolving in the oil and reducing its viscosity, and opening the production well and recovering oil from the well with substantially less water production than prior to solvent injection. The amount of solvent injected is suitably 2 to 30 ana preferably 20 barrels per foot of productive formation thickness.
The method of the invention involves solvent stimulatian o~
a producing well penetrating a subterranean, viscous oil-containing formation that is producing oil containing a large fraction of free water, up to 9~0 by volume.
In carrying out the invention, a predetermined amount, suitably 2 to 30 and preferably 20 barrels per foot o~ productive formation thickness, of a solven-t having a density and viscosity substantially less than the viscous formation oil and a viscosity equal to or slightly more than water, is injected into a producing well which was previously producing oil containing a large fraction of free water, for example water that separates from the produced oil easily on standing. Free water~ in the absence of obvious water ~ones on a log of the ~ormation, is interpreted as coming from thin stringers of water-bearing sandD The injected solvent ra~ially invades the formation displacing this water away from the production well.
Following the injection period, the production well is shut in ~or a predetermined soak time and then returned to production.
The soak period will vary depending upon the characteristics of the formation and will vary from about 1 to about 10 days.
The steps of lnjecting a predetermined amount of solvent followed by a soak period and subsequent production may be repeated for a plurality of cycles until the fluids produced contain an unfavorable amount of water. In the case of repeated stimulations, the initial soak period is suitably for 1 to 5 days and thereafter from about 5 to 10 days.
F~1872-L -3-During the soak period, the lnjected solvent fingers upwardly by gravity dissolving in the viscous oil and reducing its viscosity thereby enhancing its recovery. The produced oil after injection of the solvent followed by a soak period contains only a small amount of water.
The injected solvent can be any gas or liquid that is miscible with the reservoir oil at the pressure and temperature at which it contacts the formation oil, while at the same time being less dense and less viscous than the reservoir oil but equal or slightly more viscous than the format.ion water at ~ormation pressure and temperature. Suitanle solvents for injection include mixtures of hydrocarbons, such as petroleum fractions, exemplified by gasoline, naphtha, kerosene, gas oils, diesel oils, light crude oil7 light refinery cuts,"cutter stock" (a refinery product use~ for thinning ~uel oil for ships~, aromatic-containing condensates, mixed aromatic-paraffinic hydrocarbon materials as are sometimes available as waste streams of refinery operations, and the like. In addition, such solvents may include saturated liquid hydrocarbons having from two to ten carbon atoms in the molecules such as ethane, propane, or LPGt butane, pentane, hexane, cyclohexane; octane, nonane, decane~
and/or their mixtures with each other. Also aromatic hydrocarbons such as henzene, toluene, xylene and aromatic fractions o~ petroleum distillates may be used or mixtures thereoft Suita~ly such solvents may also contain significant quantities of gas dissolved therein, such as carbon dioxide7 which promote di~fusion in the reservoir.
Gaseous hydrocarbons, for example methane7 ethane7 propane and butane, may be used. Carbon dioxide may also be used and is an extremely desirable gas because o~ its high solubility in hydrocarbons.
A LARGE FRACTION OF WATER
This invention relates to a method for stimulating a production well producing oil having a large ~raction of free water.
Repetitive stimulation of oil-producing wells is a production practice of long standing. The phrase l'cyclic stimulation" is o~ten used to reflect anticipated production rate increases~ the duration o~ which is relatively short as conpared to the total life of the well. The cause o~ the production increase arises ~rom either (1) an increase in pressure driving reservoir fluids toward the producing well, or (2) a decrease in resistance to ~low of the ~luids such as reduction in viscosity or removal of impediments to flow in the reservoir rock surrounding the well. The viscosity reduction may be achieved through use of a low viscosity fluid solvent and/or by increasing the temperature o~ the reservoir fluids and rock in the proximity of the reservoir.
This invention provides a method for the solvent stimulation of a production well producing oil containing large fractions o~ free water wherein production is enhanced and the oil recovered with substantially less water production than prior to stimulation.
The present invention provides a method ~or stimulating the recovery of oil having a lar~e ~raction of free water flowing from a production well penetrating a subterranean, viscous oil-containing formation comprising injecting a predetermined amount o~ a solvent into the production well to displace water away from the production well, which solvent has a density and viscosity substantially less than the viscous ~ormation oil and a viscosity equal to or sligh-tly greater than water at formation conditions, shutting-in the production well to allow the formation around the production well to ~1"~
undergo a soak period whereby the solvent ~hich has a density less than the viscous oil fingers upwardly under the influence o~ gravity dissolving in the oil and reducing its viscosity, and opening the production well and recovering oil from the well with substantially less water production than prior to solvent injection. The amount of solvent injected is suitably 2 to 30 ana preferably 20 barrels per foot of productive formation thickness.
The method of the invention involves solvent stimulatian o~
a producing well penetrating a subterranean, viscous oil-containing formation that is producing oil containing a large fraction of free water, up to 9~0 by volume.
In carrying out the invention, a predetermined amount, suitably 2 to 30 and preferably 20 barrels per foot o~ productive formation thickness, of a solven-t having a density and viscosity substantially less than the viscous formation oil and a viscosity equal to or slightly more than water, is injected into a producing well which was previously producing oil containing a large fraction of free water, for example water that separates from the produced oil easily on standing. Free water~ in the absence of obvious water ~ones on a log of the ~ormation, is interpreted as coming from thin stringers of water-bearing sandD The injected solvent ra~ially invades the formation displacing this water away from the production well.
Following the injection period, the production well is shut in ~or a predetermined soak time and then returned to production.
The soak period will vary depending upon the characteristics of the formation and will vary from about 1 to about 10 days.
The steps of lnjecting a predetermined amount of solvent followed by a soak period and subsequent production may be repeated for a plurality of cycles until the fluids produced contain an unfavorable amount of water. In the case of repeated stimulations, the initial soak period is suitably for 1 to 5 days and thereafter from about 5 to 10 days.
F~1872-L -3-During the soak period, the lnjected solvent fingers upwardly by gravity dissolving in the viscous oil and reducing its viscosity thereby enhancing its recovery. The produced oil after injection of the solvent followed by a soak period contains only a small amount of water.
The injected solvent can be any gas or liquid that is miscible with the reservoir oil at the pressure and temperature at which it contacts the formation oil, while at the same time being less dense and less viscous than the reservoir oil but equal or slightly more viscous than the format.ion water at ~ormation pressure and temperature. Suitanle solvents for injection include mixtures of hydrocarbons, such as petroleum fractions, exemplified by gasoline, naphtha, kerosene, gas oils, diesel oils, light crude oil7 light refinery cuts,"cutter stock" (a refinery product use~ for thinning ~uel oil for ships~, aromatic-containing condensates, mixed aromatic-paraffinic hydrocarbon materials as are sometimes available as waste streams of refinery operations, and the like. In addition, such solvents may include saturated liquid hydrocarbons having from two to ten carbon atoms in the molecules such as ethane, propane, or LPGt butane, pentane, hexane, cyclohexane; octane, nonane, decane~
and/or their mixtures with each other. Also aromatic hydrocarbons such as henzene, toluene, xylene and aromatic fractions o~ petroleum distillates may be used or mixtures thereoft Suita~ly such solvents may also contain significant quantities of gas dissolved therein, such as carbon dioxide7 which promote di~fusion in the reservoir.
Gaseous hydrocarbons, for example methane7 ethane7 propane and butane, may be used. Carbon dioxide may also be used and is an extremely desirable gas because o~ its high solubility in hydrocarbons.
Claims (8)
1. A method for stimulating the recovery of oil having a large fraction of free water flowing from a production well penetrating a subterranean, viscous oil-containing formation comprising:
(a) injecting a predetermined amount of a solvent into the production well to displace water away from the production well, the solvent having a density and viscosity substantially less than the viscous formation oil and a viscosity equal to or slightly greater than water at formation conditions;
(b) shutting-in the production well for a predetermined period of time to allow the formation around the production well to undergo a soak period whereby the injected solvent fingers upwardly under the influence of gravity dissolving in the oil and reducing its viscosity; and (c) opening the production well and recovering fluids including oil from the well containing substantially less water than from the unstimulated well.
(a) injecting a predetermined amount of a solvent into the production well to displace water away from the production well, the solvent having a density and viscosity substantially less than the viscous formation oil and a viscosity equal to or slightly greater than water at formation conditions;
(b) shutting-in the production well for a predetermined period of time to allow the formation around the production well to undergo a soak period whereby the injected solvent fingers upwardly under the influence of gravity dissolving in the oil and reducing its viscosity; and (c) opening the production well and recovering fluids including oil from the well containing substantially less water than from the unstimulated well.
2. The method of claim 1 wherein steps (a), (b) and (c) are repeated for a plurality of cycles.
3. The method of claim 2 wherein production according to step (c) is continued until the fluid being recovered contains an unfavorable amount of water.
4. The method of claim 1 wherein the solvent is selected from light crudes, light refinery cuts, mixed aromatic-paraffinic condensates and mixtures thereof.
5. The method of claim 1 wherein the amount of solvent injected is from 2 to 30 barrels per foot of productive formation.
6. The method of claim 1 wherein the amount of solvent injected is 20 barrels per foot of production formation.
7. The method of claim 1 wherein the soak period is from 1 day to 10 days.
8. The method of claim 2 wherein the initial soak period is from 1 to 5 days and subsequent soak periods are from 5 to 10 days.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US42041882A | 1982-09-20 | 1982-09-20 | |
| US420,418 | 1982-09-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1205007A true CA1205007A (en) | 1986-05-27 |
Family
ID=23666390
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000434415A Expired CA1205007A (en) | 1982-09-20 | 1983-08-11 | Solvent stimulation in heavy oil wells producing a large fraction of water |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1205007A (en) |
-
1983
- 1983-08-11 CA CA000434415A patent/CA1205007A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |