CA1278747C - Method of controlling permeability damage of hydrocarbon formations during steam injection using ammonium ions, bicarbonate ions, and potassium ions - Google Patents
Method of controlling permeability damage of hydrocarbon formations during steam injection using ammonium ions, bicarbonate ions, and potassium ionsInfo
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- CA1278747C CA1278747C CA000547278A CA547278A CA1278747C CA 1278747 C CA1278747 C CA 1278747C CA 000547278 A CA000547278 A CA 000547278A CA 547278 A CA547278 A CA 547278A CA 1278747 C CA1278747 C CA 1278747C
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Abstract
ABSTRACT OF THE DISCLOSURE
A method is disclosed for inhibiting permeability damage of clay minerals-containing hydro-carbon formations in the vicinity of a well during steam injection and for improving the injectivity of steam into that formation. That method comprises injecting a wet steam that comprises a sufficient amount of a source of ammonium ions to form an ammonium ion concentration of at least 0.01 N in the vapor phase condensate of the wet steam, a sufficient amount of either sodium bicarbonate, potassium bicarbonate, or mixtures thereof to raise the pH
of the liquid phase of the wet steam to within the range of from 7.5 to 10.5; and a sufficient amount of a source of potassium ions to form a potassium ion concentration of at least 0.01 N in the liquid phase of the wet steam. The ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of the injected wet steam and to improve the injectivity of the wet steam into the formation in the vicinity of the vapor phase of the injected wet steam. The potassium ions serve, in the vicinity of the liquid phase to inhibit permeability damage of hydrocarbon formations containing clay minerals and to improve the injectivity of the wet steam into the formation.
A method is disclosed for inhibiting permeability damage of clay minerals-containing hydro-carbon formations in the vicinity of a well during steam injection and for improving the injectivity of steam into that formation. That method comprises injecting a wet steam that comprises a sufficient amount of a source of ammonium ions to form an ammonium ion concentration of at least 0.01 N in the vapor phase condensate of the wet steam, a sufficient amount of either sodium bicarbonate, potassium bicarbonate, or mixtures thereof to raise the pH
of the liquid phase of the wet steam to within the range of from 7.5 to 10.5; and a sufficient amount of a source of potassium ions to form a potassium ion concentration of at least 0.01 N in the liquid phase of the wet steam. The ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of the injected wet steam and to improve the injectivity of the wet steam into the formation in the vicinity of the vapor phase of the injected wet steam. The potassium ions serve, in the vicinity of the liquid phase to inhibit permeability damage of hydrocarbon formations containing clay minerals and to improve the injectivity of the wet steam into the formation.
Description
1~787i~7 :
METHOD OF CONTROLLING PERMEABILITY DAMAGE OF
HYDROCARBON FORMATIONS D~RING STEAM INJECTION USING
AMMONI~M IONS, BICARBONATE IONS,_AND POTASSIUM IONS
The present invention relates to a method for inhibiting permeability damage of a hydrocarbon formation containing clay minerals. Furthermore, the present inven-tion relates to a method for improving the injectivity ofsteam into that formation.
BACKGROUND OF THE INVENTION
Steam injection techniques, such as steam stimulation and steam flooding, have been used to recover immobile heavy oils and to enhance the oil recovery from older wells where the natural field pressures are too low for unassisted production. They are designed to reduce the reservoir flow resistance by reducing the viscosity of the crude.
These techniques involve injection into the well of a high temperature wet st0am in cycles of thousands of cubic meters at a time. W0t steam is a mixture of steam and varying amount of hot liquid water, the quality of wet steam generally ranging from 35~ to 80~. Because of the density difference between the two phases of the wet steam, the vapor phase preferentially enters the upper part of the injection interval and the liquid phase preferentially enters the lower part.
When groundwater, river water, or lake water is used as feedwater to generate wet steam, the liquid ; water phase is generally basic (having a pH in excess of ll) and the vapor phase of the wet steam, when condensed, is acidic (having a pH of about 4.0 to 4.5). This partitioning is due to the bicarbonate contained in the source water decomposing to CO2 and OH-, as shown in Equation l below:
Feed Water Vapor Phase Liquid Phase HCO3 - > C2 + OH- (l) ~0 :
. -~
~, . . . . . . . .. . . ~ .. .,. ., , ..... - . .. . . . .
~'~'787~7 The C02 is volatile and enters the vapor phase, which produces a low pH in the liquids condensed from the vapor phase. The OH- ion enters the liquid phase and causes a high pH in the liquid phase.
Associated with using these wet steams in steam injection is the problem of silica dissolution. Coupled with high fluid temperatures, both the liquid phase and the liquids from the condensed vapor phase are capable of rapidly dissolving reservoir rocks, such as sandstone, carbonate, diatomite, porcellanite and the like. For pH values above 11.0 and temperatures above 177C, the silica and silicate dissolution rates are orders of magnitude higher than at neutral/ambient conditions. Also, because the reactions for dissolving siliceous reservoir rocks are base consumers, the liquid pH decreases rapidly as the fluid moves away from the wellbore, causing the dissolution reactions and solubility to diminish rapidly and causing the reaction products downstream (such as alumino-silicates and other metal silicates) to precipitate in the pores. This precipitation decrQases the formation permeability and decreases well injectivity.
This problem of silica di~solution was addressed in U.S. Patent 4,475,595; U.S. Patent 4,572,296; and U.S.
Patent 4,580,633. U.S. Patent 4,475,595 discloses adding an ammonium inhibitor to the feedwater or to the wet steam. U.S. Patent ~,572,296 discloses adding an ammonium inhibitor and a compound which hydrolyzes in steam, providing a buffering effect in the liquid phase to prevent excessive pH reduction. U.S. Patent 4,5~0,633 discloses adding an ammonium inhibitor and an organosilicon compound. In each case, the amount of added ammonium inhibitor is determined by the bicarbonate concentration of the steam.
Also associated with using these wet steams is the problem of permeability damage of hydrocarbon formations containing clay. Formations that contain clay minerals are susceptible to water-rock interactions that cause ~."
3 1,'~87~
the clay to disperse and migrate. When they move downstream, they tend to bridge in pore constrictions to form miniature filter-cakes throughout the pore network.
This can decrease steam injectivity in the lower interval where liquid water is injected and also in the upper interval where vapor phase condensation takes place. In some cases, clay structural expansion may contribute to this decrease in permeability.
U.S. Patent 4,549,609 discloses an attempt to solve the problem of permeability ~amage by injecting an ammoniacal nitrogen-containing compound. Since the ammoniacal nitrogen-containing compound stays in the vapor phase of the wet steam, the method disclosed in U.S. Patent 4,549,609 fails to prevent permeability damage in those areas exposed to the liquid phase.
Also, the amount of ammoniacal nitrogen-containing compound that can be added without acidic corrosion of the well pipe is limited by the bicarbonate concentration found in the feedwater.
SUMH~RY OF THB INV~NTION
The present invention solves the problem of permeability damage by in~ecting a wet steam that has:
(a) at least a 0.01 N concentration of ammonium ions in the vapor phase condensate of the wet steam, (b) enough bicarbonate ions to raise the pH of the liquid phase of the wet steam to the range of from 7.5 to 10.5, and (c) at least a 0.01 N concentration of potassium ions in the liquid phase of the wet steam.
The ammonium ions serve, in the vicinity of the vapor phase of the injected wet steam, to inhibit permeability damage and to improve steam injectivity.
Preferably, the concentration of ammonium ion in the vapor phase condensate of the wet steam is from 0.01 N
to 2 N, more preferably from 0.01 N to 0.5 N.
Preferably, the source of ammonium ions is either ammonium sulfate, ammonium chloride, ammonium hydroxide, ammonium acetate, . ~
~7~747 Ol _4_ ammonium nitrate, or a mixture thereof. More preferably, that source is either ammonium sulfate or ammonium 05 chloride.
The bicarbonate ions serve to neutralize the pH
of the liquid phase and the vapor phase condensate of the - wet steam, thereby preventing acidic corrosion of the well pipe and adverse dissolution reactions in the reservoir rocks. The source of bicarbonate ions is selected from the group consisting of sodium bicarbonate, potassium bicarbonate, and mixtures thereof. Preferably, there is a sufficient amount of bicarbonate ions to raise the pH of the liquid phase of the wet steam to within the range of from 8.5 to 9.5.
The potassium ions serve, in the vicinity of the liquid phase of the injected wet steam, to inhibit permeability damage and to improve the steam injectivity.
Preferably, the concentration of potassium ions in the liquid phase of the wet steam is from 0.01 N to 2 N, more preferably from 0.01 N to 1 N. Preferably, the source of potassium ions is either potassium sulfate, potassium chloride, potassium acetate, potassium nitrate, potassium bicarbonate, potassium carbonate, or a mixture thereof.
More preferably, that source is potassium chloride or potassium bicarbonate.
DETAILED DESC~IPTION OF THE INVENTION
In its broadest aspects, the present invention involves a method for inhibiting permeability damage of hydrocarbon formations containing clay minerals and for improving the injectivity of steam into those formations.
That method comprises injecting a wet steam that comprises:
` a sufficient amount of a source of ammonium ions to form an ammonium ion concentration of at least 0.01 N in the vapor phase condensate of the wet steam, wherein the ` ammonium ions serve to inhibit permeability damage of the formation in the vicinity of the vapor phase of the injected wet steam and to improve the injectivity of the .. .
5 1~787~7 wet steam into the formation in the vicinity of the vapor phase of the injected wet steam;
a sufficient amount of a source of bicarbonate ions selected from the group consisting of sodium bicarbonate, potassium bicarbonate, and mixtures thereof to raise the pH of the liquid phase of the wet steam to within the range of from 7.5 to 10.5; and a sufficient amount of a source of potassium ions to form a potassium ion concentration of at least 0.01 N
in the liquid phase of the wet steam, wherein the - potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid phase of the injected wet steam and to improve the injectivity of the wet steam into the formation in the vicinity of the liquid phase of the injected wet steam.
Other aspects of this invention are as follows:
A method for inhibiting permeability damage of hydrocarbon formations containing clay minerals in the vicinity of a well during steam injection into said formation and for improving the injectivity of steam into said formation comprising adding into the boiler feed water used to generate said wet steam:
a sufficient amount of ammonium chloride to form an ammonium ions concentration in the vapor phase condensate of said wet steam of from 0.01 N to 0.5 N, wherein said ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of said in;ected wet steam and to improve the in;ectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam;
a sufficient amount of potassium chloride to form a potassium ions concentration in the liquid phase of said wet steam of from 0.01 N to l N, wherein said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid vapor phase of the injected wet steam and to ~' .
1~78747 improve the injectivity of said wet steam into said formation in the vicinity of the liquid phase of the injected wet steam; and a sufficient amount of sodium bicarbonate to S maintain the pH of the liquid phase of said wet steam to within the range of from 8.5 to 9.5.
A method for inhibiting permeability damage of hydrocarbon formations containing clay minerals in the vicinity of a well during steam injection into said formation and for improving the injectivity of steam into said formation comprising adding into the boiler feed water used to generate said wet steam:
a sufficient amount of ammonium chloride to form an ammonium ions concentration in the vapor phase condensate of said wet steam of from 0.01 N to 0.5 N, wherein said ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of said injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam; and a sufficient amount of potassium bicarbonate to form a potassium ions concentration in the liquid phase of said wet steam of Prom 0.01 N to 1 N, wherein said bicarbonate ions serve to maintain the pH of the liquid phase of ~aid wet steam to within the range of from 8.5 to 9.5 and said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid phase of the injected wet steam and to improve the injectivity of said wet steam into said formation in the viçinity of the liquid phase of the injected wet steam.
One of the considered causes of poor injectivity and productivity is the dissolution of gravel packs and formation sands. Products of this dissolution precipitate downstream of the dissolution zone and cause permeability damage which results in loss of injectivity. Another mechanism causing the decline is ~. -1~78747 permeability damage resulting from interactions between formation clay minerals and condensed steam or injected liquid phase water. The present invention solves both the problem of silica dissolution and the problem of permeability damage by clay minerals.
CLAY STABILIZA~ION IN VAPOR
PHASE CONDENSATION R~GION
Ammonium salts are highly effective for clay stabilization in the vapor phase condensation region.
When the ammonium passes through the generator, it decomposes to ammonia and acid. The ammonia is an alkaline gas that partitions to the gas phase, the acid partitions to the liquid phase. This is opposite to the way bicarbonate decomposes, where the acid component partitions to the gas phase and the base component partitions to the liquid phase. When one adds an amount of ammonium salt chemically equivalent to the I
concentratlon ~78747 '~'' of bicarbonate, both the liquid phase and the vapor phase ~ condensate of the generator effluent are neutralized by - 05 the decomposition reactions, as shown by Equation 2 below.
., Vapor Phase Liquid Phase : Additive NH4+ _ > NH3 + H+ (2) .: + +
Feedwater HCO3- - > CO2 + OH
,, ~ l, neutral neutral The ammonium ions at the point of vapor phase condensation help prevent permeability damage and maintain near neutral pH's on both the vapor phase condensation region and the liquid phase injection region.
; ~ In the present invention, a sufficient amount of a source of ammonium ions are added to form an ammonium ion concentration of at least 0.0l N in the vapor phase condensate of the wet steam. The ammonium ions serve to inhibit permeability damage of clay mineral-containing hydrocarbon formations in the vicinity of the vapor phase of the injected wet steam and to improve the injectivity of the wet steam into the formation at the same location.
Preferably, the ammonium ion concentration in the vapor phase condensate of the wet steam is from 0.0l N to 2 N, more preferably, from 0.0l N to 0.5 N. Preferably, the `` source of ammonium ions is ammonium sulfate, ammonium chloride, ammonium hydroxide, ammonium acetate, ammonium nitrate, or mixtures thereof, more preferably either ammonium sulfate or ammonium chloride.
To determine the desired amount of ammonium ~ ions, the preferred method is to take core samples in the ; region in question and determine the permeability of the core to solutions containing different ammonium ion concentrations, starting at the highest concentration.
Permeability is plotted as a function of ammonium ion concentration. The results will be a curve of diminishing : .
'':
;, 12~7~7~7 effect. Each added increment of ammonium ion concentra-tion will give improved permeability, but the improvement 05 will be smaller for each added increment. In other words, doubling the ammonium ion concentration will always improve permeability, but not by double. The decision of a particular desired amount of ammonium ions is a trade-off between the cost of the added ammonium ions and the value of the increased permeability.
Normally, the amount of ammonium salts which can be added to feedwater is limited by the chemistry of feed-water. If the bicarbonate concentration is lower than the total ammonium concentration, decomposition of the excessive ammonium can lower the pH sufficiently to cause severe corrosion of steel tubular goods in the steam injection lines. When one wishes to add more ammonium to the feedwater than can be neutralized by the bicarbonate in the feedwater, one adds source of bicarbonate ions to feedwater to balance the over-corrected feedwater. The source of bicarbonate ions is added to raise the pH of the liquid phase of the wet steam to within the range of from 7.5 to 10.5, preferably from 8.5 to 9.5. The source of bicarbonate ions can be sodium bicarbonate, potassium bicarbonate, and mixtures thereof. The preferred method of determining the amount of bicarbonate ions added is to determine the desired amount of ammonium ions, determine the amount of bicarbonate ions already in the feedwater, then calculate the equivalent amount of bicarbonate ions needed to neutralize the ammonium ions.
Clay Stabilization in the Liquid Phase Many clay stabilizers, such as zirconyl salts, hydroxyaluminum, cationic polymers, quaternary ammonium salts and fluoboric acid, are available from commercial 3S oil field service companies for use in the liquid phase.
Because of the high cost of these chemicals, they are generally used to control clay problems within a very few feet of the wellbore.
The portion of the well receiving liquid phase water can be protected by maintaining a high total metal '~
1;~'787~
salt concentration in the injected liquid phase. Only alkali metals are practical because of precipitation and S scaling problems associated with salts of polyvalent cations. Some of the alkali metal salts are especially effective because of their special reactions with some clay minerals. This special group includes potassium, rubidium, and cesium salts, but of these only potassium is practical because of cost and availability. Thus, chemical additions to feedwater for protecting the forma-tion receiving the liquid phase is practically limited to potassium salts. It is important to note that these metal salts do not enter the vapor phase and therefore they do not protect the formation rock in the vapor phase condensation zone.
~ sufficient amount of a source of potassium ions is added to form a potassium ion concentration of at least 0.0l N in the liquid phase of the wet steam. The potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid vapor phase of the injected wet steam and to improve the injectivity of the wet steam into the formation in the vicinity of the liquid phase of the injected wet steam. Preferably, the potassium ion concentration in the liquid phase of the wet steam should be from 0.0l N to 2 N, more preferably from 0.0l N to l N. The source of potassium ions can be potassium sulfate, potassium chloride, potassium acetate, potassium nitrate, potassium carbonate, or mixtures thereof.
To determine the desired amount of potassium ions, the preferred method is to take core samples in the region in question and determine the permeability of the core to different solutions containing potassium concen-trations, starting at its highest concentration.Permeability is plotted a function of potassium ion concentration. The results will be a curve of diminishing effect. The decision of a particular desired amount of - potassium ions is a trade-off between the cost of the ~0 ., ~ '~787~
:
01 _9_ added potassium ions and the value of the increased ' permeability.
05 In one embodiment of the present invention, there are three sources of ions: ammonium chloride to supply ammonium ions, potassium chloride to supply potas-sium ions, and sodium bicarbonate to supply bicarbonate ions. In that embodiment, the three sources are added into the boiler feed water used to generate the wet steam Sufficient ammonium chloride is added to form an ammonium ions concentration in the vapor phase condensate of the wet steam of from 0.0l N to 0.5 N. Sufficient potassium chloride is added to form a potassium ions concentration in the liquid phase of the wet steam of from 0.0l N to l N. Sufficient sodium bicarbonate is added to maintain the pH of the liquid phase of the wet steam to within the range of from 8.5 to 9.5.
In another embodiment, there are only two sources of ions: ammonium chloride to supply ammonium ions, and potassium bicarbonat~ to supply both potassium ions and bicarbonate ions. In that embodiment, the two sources are added into the boiler feed water used to generate the wet steam. Sufficient ammonium chloride is added to form an ammonium ions concentration in the vapor phase condensate of the wet steam of from 0.0l N to 0.5 N
Sufficient potassium bicarbonate is added to form a potassium ions concentration in the liquid phase of the wet steam of from 0.0l N to l N and to maintain the pH of the liquid phase of the wet steam to within the range of from 8.5 to 9.5. While this embodiment has the advantage of eliminating the need for a third source of ions, it is limited to those cases where the amount of potassium ions can equal the amount of added bicarbonate ions.
Oxygen in the feedwater to the steam generator cannot be tolerated since severe corrosion will occur. A
chemical oxygen scavenger, such as sodium sulfite, should be used in the feedwater to keep the oxygen concentration in the feedwater below 30 ppb.
~0 .
~787~7 Additives which are liquid at ambient temperatures can be added directly either to the boiler 05 feedwater or to the steam itself. If added to the steam, the addition can be made either at the surface as the steam is being injected into the formation or down a well penetrating the formation to be treated, or the additive can be injected downhole via a separate conduit and mixed with the steam downhole prior to its entering the forma-tion. Additives which are solids at ambient temperaturecan be added directly to the feedwater or a concentrated solution thereof can be prepared and then employed as described above for a liquid additive.
If one of the chief objectives in the application of this treatment to an enhanced oil recovery method is to use steam to mobilize oil which otherwise would be difficult to recover, the amount of steam to be used is well known in the art and is the same as for steam treatments in general. If mobilization of oil is of secondary importance, as in treating a surface formation or a water injection well completed in a fines-containing formation to stabilize tha fines, it is recommended that there be used the steam generated from about 250 to 3,000 barrels of feedwater to be treated. Preferably the steam should be injected at a rate of about 200 to 1500 barrels of feedwater per day per well.
While the applicants do not wish to be bound by any particular theory as to how his invention works, it is thought that the following theory may account for the observed beneficial results of the present invention.
Clay minerals are made up of layers. Between those layers are ions (such as potassium and sodium) that are neutralized and are not very exchangeable. During steam injection, those ions are slowly removed and are replaced - by sodium ions. Those sodium ions have a relatively high hydration energy, so water molecules also go in between the layers with the sodium ions. The hydrated sodium ions - are much larger than the potassium ions they replace, and, being larger, they force the layers apart. This leads to .
1'~78"~47 particles breaking off and plugging up the flow channels downstream. The hydrated ammonium ions and hydrated 05 potassium ions are much smaller than the hydrated sodium ions, so they do not cause as much damage.
EXAMPLES
- The invention will be further illustrated by the following examples which set forth particularly advanta~
geous methods and composition embodiments. While the examples illustrate the present invention, they are not intended to limit it.
Steam was injected into a formation at the rate of approximately 800 Bbl/d (cold water equivalent) of feedwater. The average steam quality was about 50%. Two solutions were injected with the feedwater. The first solution, which had 80.0 lb/bbl of potassium chloride ; (2.86 M) and 15/bbl sodium bicarbonate (0.56 M), was injected at a rate of 500 gal/d. The second solution, 20 which had 50.0 lb/bbl o ammonium chloride (2.42 M) was injected at a rate of 125 gal/d.
The injection pressures were in the range of 650 to 800 psi. This is over 20% lower than that observed for other wells in the same area without the salt addition.
While the present invention has been described with reference to specific embodiments, this application is intended to cover those various changes and substitu-tions which may be made by those skilled in the art without departing from the spirit and scope of the appended claims.
' '
METHOD OF CONTROLLING PERMEABILITY DAMAGE OF
HYDROCARBON FORMATIONS D~RING STEAM INJECTION USING
AMMONI~M IONS, BICARBONATE IONS,_AND POTASSIUM IONS
The present invention relates to a method for inhibiting permeability damage of a hydrocarbon formation containing clay minerals. Furthermore, the present inven-tion relates to a method for improving the injectivity ofsteam into that formation.
BACKGROUND OF THE INVENTION
Steam injection techniques, such as steam stimulation and steam flooding, have been used to recover immobile heavy oils and to enhance the oil recovery from older wells where the natural field pressures are too low for unassisted production. They are designed to reduce the reservoir flow resistance by reducing the viscosity of the crude.
These techniques involve injection into the well of a high temperature wet st0am in cycles of thousands of cubic meters at a time. W0t steam is a mixture of steam and varying amount of hot liquid water, the quality of wet steam generally ranging from 35~ to 80~. Because of the density difference between the two phases of the wet steam, the vapor phase preferentially enters the upper part of the injection interval and the liquid phase preferentially enters the lower part.
When groundwater, river water, or lake water is used as feedwater to generate wet steam, the liquid ; water phase is generally basic (having a pH in excess of ll) and the vapor phase of the wet steam, when condensed, is acidic (having a pH of about 4.0 to 4.5). This partitioning is due to the bicarbonate contained in the source water decomposing to CO2 and OH-, as shown in Equation l below:
Feed Water Vapor Phase Liquid Phase HCO3 - > C2 + OH- (l) ~0 :
. -~
~, . . . . . . . .. . . ~ .. .,. ., , ..... - . .. . . . .
~'~'787~7 The C02 is volatile and enters the vapor phase, which produces a low pH in the liquids condensed from the vapor phase. The OH- ion enters the liquid phase and causes a high pH in the liquid phase.
Associated with using these wet steams in steam injection is the problem of silica dissolution. Coupled with high fluid temperatures, both the liquid phase and the liquids from the condensed vapor phase are capable of rapidly dissolving reservoir rocks, such as sandstone, carbonate, diatomite, porcellanite and the like. For pH values above 11.0 and temperatures above 177C, the silica and silicate dissolution rates are orders of magnitude higher than at neutral/ambient conditions. Also, because the reactions for dissolving siliceous reservoir rocks are base consumers, the liquid pH decreases rapidly as the fluid moves away from the wellbore, causing the dissolution reactions and solubility to diminish rapidly and causing the reaction products downstream (such as alumino-silicates and other metal silicates) to precipitate in the pores. This precipitation decrQases the formation permeability and decreases well injectivity.
This problem of silica di~solution was addressed in U.S. Patent 4,475,595; U.S. Patent 4,572,296; and U.S.
Patent 4,580,633. U.S. Patent 4,475,595 discloses adding an ammonium inhibitor to the feedwater or to the wet steam. U.S. Patent ~,572,296 discloses adding an ammonium inhibitor and a compound which hydrolyzes in steam, providing a buffering effect in the liquid phase to prevent excessive pH reduction. U.S. Patent 4,5~0,633 discloses adding an ammonium inhibitor and an organosilicon compound. In each case, the amount of added ammonium inhibitor is determined by the bicarbonate concentration of the steam.
Also associated with using these wet steams is the problem of permeability damage of hydrocarbon formations containing clay. Formations that contain clay minerals are susceptible to water-rock interactions that cause ~."
3 1,'~87~
the clay to disperse and migrate. When they move downstream, they tend to bridge in pore constrictions to form miniature filter-cakes throughout the pore network.
This can decrease steam injectivity in the lower interval where liquid water is injected and also in the upper interval where vapor phase condensation takes place. In some cases, clay structural expansion may contribute to this decrease in permeability.
U.S. Patent 4,549,609 discloses an attempt to solve the problem of permeability ~amage by injecting an ammoniacal nitrogen-containing compound. Since the ammoniacal nitrogen-containing compound stays in the vapor phase of the wet steam, the method disclosed in U.S. Patent 4,549,609 fails to prevent permeability damage in those areas exposed to the liquid phase.
Also, the amount of ammoniacal nitrogen-containing compound that can be added without acidic corrosion of the well pipe is limited by the bicarbonate concentration found in the feedwater.
SUMH~RY OF THB INV~NTION
The present invention solves the problem of permeability damage by in~ecting a wet steam that has:
(a) at least a 0.01 N concentration of ammonium ions in the vapor phase condensate of the wet steam, (b) enough bicarbonate ions to raise the pH of the liquid phase of the wet steam to the range of from 7.5 to 10.5, and (c) at least a 0.01 N concentration of potassium ions in the liquid phase of the wet steam.
The ammonium ions serve, in the vicinity of the vapor phase of the injected wet steam, to inhibit permeability damage and to improve steam injectivity.
Preferably, the concentration of ammonium ion in the vapor phase condensate of the wet steam is from 0.01 N
to 2 N, more preferably from 0.01 N to 0.5 N.
Preferably, the source of ammonium ions is either ammonium sulfate, ammonium chloride, ammonium hydroxide, ammonium acetate, . ~
~7~747 Ol _4_ ammonium nitrate, or a mixture thereof. More preferably, that source is either ammonium sulfate or ammonium 05 chloride.
The bicarbonate ions serve to neutralize the pH
of the liquid phase and the vapor phase condensate of the - wet steam, thereby preventing acidic corrosion of the well pipe and adverse dissolution reactions in the reservoir rocks. The source of bicarbonate ions is selected from the group consisting of sodium bicarbonate, potassium bicarbonate, and mixtures thereof. Preferably, there is a sufficient amount of bicarbonate ions to raise the pH of the liquid phase of the wet steam to within the range of from 8.5 to 9.5.
The potassium ions serve, in the vicinity of the liquid phase of the injected wet steam, to inhibit permeability damage and to improve the steam injectivity.
Preferably, the concentration of potassium ions in the liquid phase of the wet steam is from 0.01 N to 2 N, more preferably from 0.01 N to 1 N. Preferably, the source of potassium ions is either potassium sulfate, potassium chloride, potassium acetate, potassium nitrate, potassium bicarbonate, potassium carbonate, or a mixture thereof.
More preferably, that source is potassium chloride or potassium bicarbonate.
DETAILED DESC~IPTION OF THE INVENTION
In its broadest aspects, the present invention involves a method for inhibiting permeability damage of hydrocarbon formations containing clay minerals and for improving the injectivity of steam into those formations.
That method comprises injecting a wet steam that comprises:
` a sufficient amount of a source of ammonium ions to form an ammonium ion concentration of at least 0.01 N in the vapor phase condensate of the wet steam, wherein the ` ammonium ions serve to inhibit permeability damage of the formation in the vicinity of the vapor phase of the injected wet steam and to improve the injectivity of the .. .
5 1~787~7 wet steam into the formation in the vicinity of the vapor phase of the injected wet steam;
a sufficient amount of a source of bicarbonate ions selected from the group consisting of sodium bicarbonate, potassium bicarbonate, and mixtures thereof to raise the pH of the liquid phase of the wet steam to within the range of from 7.5 to 10.5; and a sufficient amount of a source of potassium ions to form a potassium ion concentration of at least 0.01 N
in the liquid phase of the wet steam, wherein the - potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid phase of the injected wet steam and to improve the injectivity of the wet steam into the formation in the vicinity of the liquid phase of the injected wet steam.
Other aspects of this invention are as follows:
A method for inhibiting permeability damage of hydrocarbon formations containing clay minerals in the vicinity of a well during steam injection into said formation and for improving the injectivity of steam into said formation comprising adding into the boiler feed water used to generate said wet steam:
a sufficient amount of ammonium chloride to form an ammonium ions concentration in the vapor phase condensate of said wet steam of from 0.01 N to 0.5 N, wherein said ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of said in;ected wet steam and to improve the in;ectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam;
a sufficient amount of potassium chloride to form a potassium ions concentration in the liquid phase of said wet steam of from 0.01 N to l N, wherein said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid vapor phase of the injected wet steam and to ~' .
1~78747 improve the injectivity of said wet steam into said formation in the vicinity of the liquid phase of the injected wet steam; and a sufficient amount of sodium bicarbonate to S maintain the pH of the liquid phase of said wet steam to within the range of from 8.5 to 9.5.
A method for inhibiting permeability damage of hydrocarbon formations containing clay minerals in the vicinity of a well during steam injection into said formation and for improving the injectivity of steam into said formation comprising adding into the boiler feed water used to generate said wet steam:
a sufficient amount of ammonium chloride to form an ammonium ions concentration in the vapor phase condensate of said wet steam of from 0.01 N to 0.5 N, wherein said ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of said injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam; and a sufficient amount of potassium bicarbonate to form a potassium ions concentration in the liquid phase of said wet steam of Prom 0.01 N to 1 N, wherein said bicarbonate ions serve to maintain the pH of the liquid phase of ~aid wet steam to within the range of from 8.5 to 9.5 and said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid phase of the injected wet steam and to improve the injectivity of said wet steam into said formation in the viçinity of the liquid phase of the injected wet steam.
One of the considered causes of poor injectivity and productivity is the dissolution of gravel packs and formation sands. Products of this dissolution precipitate downstream of the dissolution zone and cause permeability damage which results in loss of injectivity. Another mechanism causing the decline is ~. -1~78747 permeability damage resulting from interactions between formation clay minerals and condensed steam or injected liquid phase water. The present invention solves both the problem of silica dissolution and the problem of permeability damage by clay minerals.
CLAY STABILIZA~ION IN VAPOR
PHASE CONDENSATION R~GION
Ammonium salts are highly effective for clay stabilization in the vapor phase condensation region.
When the ammonium passes through the generator, it decomposes to ammonia and acid. The ammonia is an alkaline gas that partitions to the gas phase, the acid partitions to the liquid phase. This is opposite to the way bicarbonate decomposes, where the acid component partitions to the gas phase and the base component partitions to the liquid phase. When one adds an amount of ammonium salt chemically equivalent to the I
concentratlon ~78747 '~'' of bicarbonate, both the liquid phase and the vapor phase ~ condensate of the generator effluent are neutralized by - 05 the decomposition reactions, as shown by Equation 2 below.
., Vapor Phase Liquid Phase : Additive NH4+ _ > NH3 + H+ (2) .: + +
Feedwater HCO3- - > CO2 + OH
,, ~ l, neutral neutral The ammonium ions at the point of vapor phase condensation help prevent permeability damage and maintain near neutral pH's on both the vapor phase condensation region and the liquid phase injection region.
; ~ In the present invention, a sufficient amount of a source of ammonium ions are added to form an ammonium ion concentration of at least 0.0l N in the vapor phase condensate of the wet steam. The ammonium ions serve to inhibit permeability damage of clay mineral-containing hydrocarbon formations in the vicinity of the vapor phase of the injected wet steam and to improve the injectivity of the wet steam into the formation at the same location.
Preferably, the ammonium ion concentration in the vapor phase condensate of the wet steam is from 0.0l N to 2 N, more preferably, from 0.0l N to 0.5 N. Preferably, the `` source of ammonium ions is ammonium sulfate, ammonium chloride, ammonium hydroxide, ammonium acetate, ammonium nitrate, or mixtures thereof, more preferably either ammonium sulfate or ammonium chloride.
To determine the desired amount of ammonium ~ ions, the preferred method is to take core samples in the ; region in question and determine the permeability of the core to solutions containing different ammonium ion concentrations, starting at the highest concentration.
Permeability is plotted as a function of ammonium ion concentration. The results will be a curve of diminishing : .
'':
;, 12~7~7~7 effect. Each added increment of ammonium ion concentra-tion will give improved permeability, but the improvement 05 will be smaller for each added increment. In other words, doubling the ammonium ion concentration will always improve permeability, but not by double. The decision of a particular desired amount of ammonium ions is a trade-off between the cost of the added ammonium ions and the value of the increased permeability.
Normally, the amount of ammonium salts which can be added to feedwater is limited by the chemistry of feed-water. If the bicarbonate concentration is lower than the total ammonium concentration, decomposition of the excessive ammonium can lower the pH sufficiently to cause severe corrosion of steel tubular goods in the steam injection lines. When one wishes to add more ammonium to the feedwater than can be neutralized by the bicarbonate in the feedwater, one adds source of bicarbonate ions to feedwater to balance the over-corrected feedwater. The source of bicarbonate ions is added to raise the pH of the liquid phase of the wet steam to within the range of from 7.5 to 10.5, preferably from 8.5 to 9.5. The source of bicarbonate ions can be sodium bicarbonate, potassium bicarbonate, and mixtures thereof. The preferred method of determining the amount of bicarbonate ions added is to determine the desired amount of ammonium ions, determine the amount of bicarbonate ions already in the feedwater, then calculate the equivalent amount of bicarbonate ions needed to neutralize the ammonium ions.
Clay Stabilization in the Liquid Phase Many clay stabilizers, such as zirconyl salts, hydroxyaluminum, cationic polymers, quaternary ammonium salts and fluoboric acid, are available from commercial 3S oil field service companies for use in the liquid phase.
Because of the high cost of these chemicals, they are generally used to control clay problems within a very few feet of the wellbore.
The portion of the well receiving liquid phase water can be protected by maintaining a high total metal '~
1;~'787~
salt concentration in the injected liquid phase. Only alkali metals are practical because of precipitation and S scaling problems associated with salts of polyvalent cations. Some of the alkali metal salts are especially effective because of their special reactions with some clay minerals. This special group includes potassium, rubidium, and cesium salts, but of these only potassium is practical because of cost and availability. Thus, chemical additions to feedwater for protecting the forma-tion receiving the liquid phase is practically limited to potassium salts. It is important to note that these metal salts do not enter the vapor phase and therefore they do not protect the formation rock in the vapor phase condensation zone.
~ sufficient amount of a source of potassium ions is added to form a potassium ion concentration of at least 0.0l N in the liquid phase of the wet steam. The potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid vapor phase of the injected wet steam and to improve the injectivity of the wet steam into the formation in the vicinity of the liquid phase of the injected wet steam. Preferably, the potassium ion concentration in the liquid phase of the wet steam should be from 0.0l N to 2 N, more preferably from 0.0l N to l N. The source of potassium ions can be potassium sulfate, potassium chloride, potassium acetate, potassium nitrate, potassium carbonate, or mixtures thereof.
To determine the desired amount of potassium ions, the preferred method is to take core samples in the region in question and determine the permeability of the core to different solutions containing potassium concen-trations, starting at its highest concentration.Permeability is plotted a function of potassium ion concentration. The results will be a curve of diminishing effect. The decision of a particular desired amount of - potassium ions is a trade-off between the cost of the ~0 ., ~ '~787~
:
01 _9_ added potassium ions and the value of the increased ' permeability.
05 In one embodiment of the present invention, there are three sources of ions: ammonium chloride to supply ammonium ions, potassium chloride to supply potas-sium ions, and sodium bicarbonate to supply bicarbonate ions. In that embodiment, the three sources are added into the boiler feed water used to generate the wet steam Sufficient ammonium chloride is added to form an ammonium ions concentration in the vapor phase condensate of the wet steam of from 0.0l N to 0.5 N. Sufficient potassium chloride is added to form a potassium ions concentration in the liquid phase of the wet steam of from 0.0l N to l N. Sufficient sodium bicarbonate is added to maintain the pH of the liquid phase of the wet steam to within the range of from 8.5 to 9.5.
In another embodiment, there are only two sources of ions: ammonium chloride to supply ammonium ions, and potassium bicarbonat~ to supply both potassium ions and bicarbonate ions. In that embodiment, the two sources are added into the boiler feed water used to generate the wet steam. Sufficient ammonium chloride is added to form an ammonium ions concentration in the vapor phase condensate of the wet steam of from 0.0l N to 0.5 N
Sufficient potassium bicarbonate is added to form a potassium ions concentration in the liquid phase of the wet steam of from 0.0l N to l N and to maintain the pH of the liquid phase of the wet steam to within the range of from 8.5 to 9.5. While this embodiment has the advantage of eliminating the need for a third source of ions, it is limited to those cases where the amount of potassium ions can equal the amount of added bicarbonate ions.
Oxygen in the feedwater to the steam generator cannot be tolerated since severe corrosion will occur. A
chemical oxygen scavenger, such as sodium sulfite, should be used in the feedwater to keep the oxygen concentration in the feedwater below 30 ppb.
~0 .
~787~7 Additives which are liquid at ambient temperatures can be added directly either to the boiler 05 feedwater or to the steam itself. If added to the steam, the addition can be made either at the surface as the steam is being injected into the formation or down a well penetrating the formation to be treated, or the additive can be injected downhole via a separate conduit and mixed with the steam downhole prior to its entering the forma-tion. Additives which are solids at ambient temperaturecan be added directly to the feedwater or a concentrated solution thereof can be prepared and then employed as described above for a liquid additive.
If one of the chief objectives in the application of this treatment to an enhanced oil recovery method is to use steam to mobilize oil which otherwise would be difficult to recover, the amount of steam to be used is well known in the art and is the same as for steam treatments in general. If mobilization of oil is of secondary importance, as in treating a surface formation or a water injection well completed in a fines-containing formation to stabilize tha fines, it is recommended that there be used the steam generated from about 250 to 3,000 barrels of feedwater to be treated. Preferably the steam should be injected at a rate of about 200 to 1500 barrels of feedwater per day per well.
While the applicants do not wish to be bound by any particular theory as to how his invention works, it is thought that the following theory may account for the observed beneficial results of the present invention.
Clay minerals are made up of layers. Between those layers are ions (such as potassium and sodium) that are neutralized and are not very exchangeable. During steam injection, those ions are slowly removed and are replaced - by sodium ions. Those sodium ions have a relatively high hydration energy, so water molecules also go in between the layers with the sodium ions. The hydrated sodium ions - are much larger than the potassium ions they replace, and, being larger, they force the layers apart. This leads to .
1'~78"~47 particles breaking off and plugging up the flow channels downstream. The hydrated ammonium ions and hydrated 05 potassium ions are much smaller than the hydrated sodium ions, so they do not cause as much damage.
EXAMPLES
- The invention will be further illustrated by the following examples which set forth particularly advanta~
geous methods and composition embodiments. While the examples illustrate the present invention, they are not intended to limit it.
Steam was injected into a formation at the rate of approximately 800 Bbl/d (cold water equivalent) of feedwater. The average steam quality was about 50%. Two solutions were injected with the feedwater. The first solution, which had 80.0 lb/bbl of potassium chloride ; (2.86 M) and 15/bbl sodium bicarbonate (0.56 M), was injected at a rate of 500 gal/d. The second solution, 20 which had 50.0 lb/bbl o ammonium chloride (2.42 M) was injected at a rate of 125 gal/d.
The injection pressures were in the range of 650 to 800 psi. This is over 20% lower than that observed for other wells in the same area without the salt addition.
While the present invention has been described with reference to specific embodiments, this application is intended to cover those various changes and substitu-tions which may be made by those skilled in the art without departing from the spirit and scope of the appended claims.
' '
Claims (15)
1. A method for inhibiting permeability damage of a hydrocarbon formation containing clay minerals in the vicinity of a well during steam injection into said formation and for improving the injectivity of steam into said formation comprising injecting a wet steam that comprises:
a sufficient amount of a source of ammonium ions to form an ammonium ion concentration of at least 0.01 N in the vapor phase condensate of said wet steam, wherein said ammonium ions serve to inhibit the permeability damage of said formation in the vicinity of the vapor phase of said injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam;
a sufficient amount of a source of bicarbonate ions selected from the group consisting of sodium bicarbonate, potassium bicarbonate, and mixtures thereof to raise the pH of the liquid phase of said wet steam to within the range of from 7.5 to 10.5; and a sufficient amount of a source of potassium ions to form a potassium ion concentration of at least 0.01 N in the liquid phase of said wet steam, wherein said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid vapor phase of the injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the liquid phase of the injected wet steam.
a sufficient amount of a source of ammonium ions to form an ammonium ion concentration of at least 0.01 N in the vapor phase condensate of said wet steam, wherein said ammonium ions serve to inhibit the permeability damage of said formation in the vicinity of the vapor phase of said injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam;
a sufficient amount of a source of bicarbonate ions selected from the group consisting of sodium bicarbonate, potassium bicarbonate, and mixtures thereof to raise the pH of the liquid phase of said wet steam to within the range of from 7.5 to 10.5; and a sufficient amount of a source of potassium ions to form a potassium ion concentration of at least 0.01 N in the liquid phase of said wet steam, wherein said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid vapor phase of the injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the liquid phase of the injected wet steam.
2. The method according to Claim 1 wherein the ammonium ion concentration in the vapor phase condensate of said wet steam is from 0.01 N to 2 N.
3. The method according to Claim 2 wherein the ammonium ion concentration in the vapor phase condensate of said wet steam is of from 0.01 N to 0.5 N.
4. The method according to Claim 1 wherein said source of ammonium ions is selected from the group consisting of ammonium sulfate, ammonium chloride, ammonium hydroxide, ammonium acetate, ammonium nitrate, and mixtures thereof.
5. The method according to Claim 4 wherein said source of ammonium ions is ammonium sulfate.
6. The method according to Claim 4 wherein said source of ammonium ions is ammonium chloride.
7. The method according to Claim 1 wherein said potassium ion concentration in the liquid phase of said wet steam is from 0.01 N to 2 N.
8. The method according to Claim 7 wherein said potassium ion concentration in the liquid phase of said wet steam is from 0.01 N to 1 N.
9. The method according to Claim 1 wherein said source of potassium ions is selected from the group consisting of potassium sulfate, potassium chloride, potassium acetate, potassium nitrate, potassium carbonate, and mixtures thereof.
10. The method according to Claim 1 wherein said source of ammonium ions is added into the boiler feed water used to generate said wet steam or into the wet steam itself.
11. The method according to Claim 1 wherein said source of bicarbonate ions is added into the boiler feed water used to generate said wet steam or into the wet steam itself.
12. The method according to Claim 1 wherein said source of potassium ions is added into the boiler feed water used to generate said wet steam or into the wet steam itself.
13. The method according to Claim 1 wherein the pH
of the liquid phase of said wet steam is maintained within the range of from 8.5 to 9.5.
of the liquid phase of said wet steam is maintained within the range of from 8.5 to 9.5.
14. A method for inhibiting permeability damage of hydrocarbon formations containing clay minerals in the vicinity of a well during steam injection into said formation and for improving the injectivity of steam into said formation comprising adding into the boiler feed water used to generate said wet steam:
a sufficient amount of ammonium chloride to form an ammonium ions concentration in the vapor phase condensate of said wet steam of from 0.01 N to 0.5 N, wherein said ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of said injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam;
a sufficient amount of potassium chloride to form a potassium ions concentration in the liquid phase of said wet steam of from 0.01 N to 1 N, wherein said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid vapor phase of the injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the liquid phase of the injected wet steam; and a sufficient amount of sodium bicarbonate to maintain the pH of the liquid phase of said wet steam to within the range of from 8.5 to 9.5.
a sufficient amount of ammonium chloride to form an ammonium ions concentration in the vapor phase condensate of said wet steam of from 0.01 N to 0.5 N, wherein said ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of said injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam;
a sufficient amount of potassium chloride to form a potassium ions concentration in the liquid phase of said wet steam of from 0.01 N to 1 N, wherein said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid vapor phase of the injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the liquid phase of the injected wet steam; and a sufficient amount of sodium bicarbonate to maintain the pH of the liquid phase of said wet steam to within the range of from 8.5 to 9.5.
15. A method for inhibiting permeability damage of hydrocarbon formations containing clay minerals in the vicinity of a well during steam injection into said formation and for improving the injectivity of steam into said formation comprising adding into the boiler feed water used to generate said wet steam:
a sufficient amount of ammonium chloride to form an ammonium ions concentration in the vapor phase condensate of said wet steam of from 0.01 N to 0.5 N, wherein said ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of said injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam; and a sufficient amount of potassium bicarbonate to form a potassium ions concentration in the liquid phase of said wet steam of from 0.01 N to 1 N, wherein said bicarbonate ions serve to maintain the pH of the liquid phase of said wet steam to within the range of from 8.5 to 9.5 and and said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid phase of the injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the liquid phase of the injected wet steam.
a sufficient amount of ammonium chloride to form an ammonium ions concentration in the vapor phase condensate of said wet steam of from 0.01 N to 0.5 N, wherein said ammonium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the vapor phase of said injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the vapor phase of the injected wet steam; and a sufficient amount of potassium bicarbonate to form a potassium ions concentration in the liquid phase of said wet steam of from 0.01 N to 1 N, wherein said bicarbonate ions serve to maintain the pH of the liquid phase of said wet steam to within the range of from 8.5 to 9.5 and and said potassium ions serve to inhibit permeability damage of hydrocarbon formations containing clay minerals in the vicinity of the liquid phase of the injected wet steam and to improve the injectivity of said wet steam into said formation in the vicinity of the liquid phase of the injected wet steam.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US90997186A | 1986-09-22 | 1986-09-22 | |
| US909,971 | 1986-09-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1278747C true CA1278747C (en) | 1991-01-08 |
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ID=25428126
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000547278A Expired - Fee Related CA1278747C (en) | 1986-09-22 | 1987-09-18 | Method of controlling permeability damage of hydrocarbon formations during steam injection using ammonium ions, bicarbonate ions, and potassium ions |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1278747C (en) |
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1987
- 1987-09-18 CA CA000547278A patent/CA1278747C/en not_active Expired - Fee Related
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