CN113122221A - Acid liquor system for online acidification of water injection well for oil exploitation and preparation process thereof - Google Patents
Acid liquor system for online acidification of water injection well for oil exploitation and preparation process thereof Download PDFInfo
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Abstract
The invention discloses an acid liquor system for online acidification of a water injection well for oil exploitation and a preparation process thereof, wherein the acid liquor system comprises 30-40% of composite acid liquor by mass percent, 5-15% of retarder by mass percent, 5-10% of chelating agent by mass percent, 5-10% of composite additive by mass percent, and the balance of water; the method specifically comprises the following steps of S1, preparation of the composite acid liquid: s11, primary reaction, S12, secondary reaction; s2, preparing a retarding liquid; s3, preparing a chelating agent; s4, preparing a composite additive; and S5, mixing to obtain an acid liquor system. The acid liquor system for oil exploitation is a multi-component acid which is prepared by mixing hydrochloric acid as a main component and a plurality of organic acids, two different acids can have an acidification effect in different time ranges, the acidification range in oil exploitation can be effectively expanded, a preparation process is optimized to meet the requirement of online acidification of a water injection well, the operation is fine, the risk in the preparation process is reduced, and the acid liquor system is high in acid liquor performance and convenient to operate.
Description
Technical Field
The invention relates to the technical field of acidification of water injection wells for oil exploitation, in particular to an acid liquor system for online acidification of water injection wells for oil exploitation and a preparation process thereof.
Background
Water injection is one of effective yield increasing measures in the middle and later stages of oil field development in oil exploitation, most of crude oil yield in China comes from water injection development, but water injection effect is poor due to phenomena of high-pressure insufficient injection and the like of a water injection well along with the influence of factors such as water injection pressure rising year after year, bottom physical property deterioration and the like.
Acidification is a measure for improving the recovery ratio of an oil well, and is an effective technical measure for increasing the injection of an injection well. The principle is that the permeability of stratum pores and cracks is recovered or improved through the dissolving and corrosion effects of acid liquor on rock cement or stratum pores, plugs in cracks and the like. The acid washing is to inject a small amount of acid liquor into the shaft to remove acid-soluble particles, drill cuttings, scales and the like in the perforation of the shaft and dredge the perforation. Matrix acidizing is the injection of acid into the formation at a pressure below the fracture pressure of the rock, relying on the erosive effects of the acid to restore or increase the permeability of the formation in a larger area near the wellbore. Acid fracturing (acid fracturing) is to inject acid into a stratum under the pressure higher than the fracture pressure of rock to form cracks in the stratum, and the cracks with high conductivity are formed by uneven corrosion of acid liquor to the wall materials of the cracks. Acidizing construction an acidic aqueous solution (e.g., hydrochloric acid, hydrofluoric acid, organic acid) is injected into the formation using construction vehicles such as cement trucks, pump trucks, and the like. The injected acid liquor can dissolve stratum rock or cementing materials, so that the stratum permeability is increased, and the production of oil gas and the injection of displacement water are more convenient. In the acidification construction, in order to improve the acidification effect, a new process such as polymer thickening acid injection, organic retarding acid injection, variable viscosity acid acidification, viscoelastic surfactant acidification and the like can be adopted.
However, if the acid liquor injected into the water injection well is not drained back in time, corrosion to equipment such as oil pipes and casings can be caused, and therefore improvement on the existing acid liquor system and the processing technology is needed.
Disclosure of Invention
Aiming at the existing problems, the invention provides an acid liquor system for online acidification of a water injection well for oil exploitation and a preparation process thereof.
The technical scheme of the invention is as follows:
an acid liquor system for online acidification of a water injection well for oil exploitation comprises 30-40% of composite acid liquor by mass, 5-15% of retarder by mass, 5-10% of chelating agent by mass, 5-10% of composite additive by mass and the balance of water;
the composite acid solution is prepared from hydrochloric acid, naphthenic acid, oxalic acid and organic phosphonic acid according to a mass ratio of 26-32: 2.5: 7.5: 1 preparing an aqueous solution with the mass percentage concentration of 15-30%.
Further, hydrochloric acid in the composite acid solution can be replaced by composite fluoroboric acid, and the composite fluoroboric acid consists of hydrochloric acid with the mass concentration of 30-50% and fluoroboric acid with the mass concentration of 20-30% according to the mass ratio of 1: 2. Compared with the former acid liquid system, the permeability is stronger, the duration is longer, and different composite acid liquids can be selected according to different stratum conditions.
Further, the retarding liquid is prepared from benzaldehyde, a pyridinium corrosion inhibition synergist, hydrazine hydrate, absolute ethyl alcohol and bacterial cellulose according to a mass ratio of 3: 1: 2: 1:2 preparing into 50-70% water solution. The reaction speed of acid and stratum rock is delayed, the viscosity of the acid liquor is improved, the liquid convection is reduced, the retarder can be adsorbed on the surface of a rock crack to form an oily protective film, the reaction speed of the acid is delayed, and the acidification effect of a water injection well is improved
Further, the chelating agent is prepared from an aminophosphonic acid ion exchanger, a complex polyhydroxy chelating agent and a fluorine-containing complex according to a mass ratio of 3-5: 2-3: 1-2, preparing aqueous solution with mass percent concentration of 40-60%. The cementing agent has good acid solubility, thermal stability, tackifying capability, shearing resistance, salt resistance and the like, is less limited for the construction of an on-site water injection well, is suitable for not only a new well but also an old well, reduces the damage to a bottom layer, and has wider application range.
Further, the composite additive comprises 55-70% of foaming agent, 15-20% of surfactant and 20-30% of iron ion stabilizer by mass percentage. Insoluble residues are not easy to generate to cause secondary damage to the stratum.
Further, the surfactant is a 20-30% aqueous solution prepared from gemini fluorocarbon surfactant, hydrocarbon surfactant, ethanol and methanol according to a mass ratio of 1:4-5:2-3: 3-4. Is favorable for improving the stability of acid liquor flowback.
A preparation process of the acid liquor system comprises the following steps:
s1, preparation of the composite acid liquid:
s11, primary reaction: putting 40% of the total amount of the hydrochloric acid into a first reaction kettle, adjusting the temperature to 30-40 ℃, dropwise adding naphthenic acid into the first reaction kettle, continuously stirring at a stirring speed of 50-150r/min, and continuously stirring for reacting for 30min after dropwise adding is finished to obtain mixed acid liquid;
s12, secondary reaction: putting 60% of the total amount of the hydrochloric acid and oxalic acid into a second reaction kettle, pressing all the mixed solution in the first reaction kettle into the second reaction kettle by using compressed air, adjusting the temperature to 65-75 ℃, dropwise adding organic phosphonic acid into the second reaction kettle, continuously stirring at the stirring speed of 400-plus-one-agent 500r/min, and continuously stirring for reaction for 3 hours after the dropwise adding is finished to obtain composite acid solution;
s2, preparation of a retarder: heating deionized water to 50-60 ℃, adding benzaldehyde and hydrazine hydrate, stirring at the rotating speed of 600-1200r/min for 20-50min, and simultaneously sequentially adding absolute ethyl alcohol and a pyridinium corrosion inhibition synergist into the mixed solution; then adding bacterial cellulose at the temperature of 30-40 ℃, and stirring at the rotating speed of 1500-;
s3, preparation of a chelating agent: adding an aminophosphonic acid ion exchanger and a composite polyhydroxy chelating agent into a four-neck flask provided with a thermometer, a stirrer, a condenser and a dropping funnel, adjusting the pH value to 8.5-9.5, adjusting the temperature to 55 ℃, reacting for 2h, adding a fluorine-containing complex, heating to 85 ℃, stirring for 15min at the rotating speed of 200-300r/min, standing for 4h, condensing, and then drying in a vacuum drying box to obtain the chelating agent;
s4, preparation of the composite additive: sequentially adding a foaming agent, a surfactant and an iron ion stabilizer into a vacuum reaction kettle, and stirring for reaction;
s5, mixing: and (4) stirring and mixing the composite acid liquor prepared in the steps S1-S4, the retarder, the chelating agent and the composite additive at normal temperature to obtain an acid liquor system.
Further, in the step S12, oxalic acid is added after hydrochloric acid in the secondary reaction, and the addition mode of oxalic acid is titration, so that the secondary reaction is more uniform.
Further, the stirring speed in the step S4 is 20-30r/min, and the stirring speed is not too fast and the reaction is kept in a vacuum environment.
Further, carrying out an acidification effect test on the mixed acid solution obtained after the primary reaction in the step S11, the composite acid solution obtained after the secondary reaction in the step S12 and the acid solution system obtained after the mixing in the step S5, taking a core sample near a water injection well for oil washing and drying treatment, saturating simulated formation water into the core, carrying out displacement on the mixed acid solution obtained after the primary reaction in the step S11, controlling the displacement pressure difference to be 0.4MPa, and carrying out primary nuclear magnetic resonance T2 spectrum sampling after full displacement; displacing the obtained composite acid liquid after the secondary reaction in the step S12, controlling the displacement pressure difference to be 0.4MPa, and performing secondary nuclear magnetic resonance T2 spectrum sampling after full displacement; and (5) displacing by using the acid liquor system obtained after mixing in the step (S5), controlling the displacement pressure difference to be 0.4MPa, and carrying out third nuclear magnetic resonance T2 spectrum sampling after full displacement. And reflecting the corrosion degree of acid liquor at different stages to the rock core sample according to the measured result.
The invention has the beneficial effects that:
(1) the acid liquor system for the on-line acidification of the water injection well for oil exploitation is multi-component acid which is prepared by mixing hydrochloric acid as a main component and a plurality of organic acids, the hydrochloric acid has high reaction speed and strong corrosion capacity, the organic acid has low hydrolysis degree and low reaction speed, but the effective distance of the acidification effect is long, and the hydrochloric acid and the organic acid are mixed according to the same ion effect, so that the ionization degree of the organic acid can be greatly inhibited, and therefore, two different acids can play the acidification effect in different time ranges, and the acidification range can be effectively expanded.
(2) The acid liquor system for the on-line acidification of the water injection well for oil exploitation achieves the purpose of delaying the reaction speed of acid and formation rock by using the improved retarder, improves the viscosity of the acid liquor, reduces the liquid convection, and ensures that the retarder can be adsorbed on the surface of a rock crack to form an oily protective film, thereby delaying the reaction speed of the acid and improving the acidification effect of the water injection well.
(3) The acid liquor system for online acidification of the water injection well for oil exploitation, disclosed by the invention, uses the improved chelating agent, has better acid solubility, thermal stability, tackifying capability, shearing resistance, salt resistance and the like, is less limited for field water injection well construction, is suitable for not only a new well but also an old well, reduces the damage to a bottom layer, and has a wider application range.
(4) The acid liquor system for the online acidification of the water injection well for the oil exploitation and the preparation process thereof optimize the preparation of the acid liquor system to meet the requirement of the online acidification of the water injection well, have fine operation, reduce the risk in the preparation process, and have high acid liquor performance and convenient operation.
Drawings
FIG. 1 is a flow diagram of the acid system preparation process of the present invention;
FIG. 2 is a T2 relaxation time graph of the degree of influence of different acid solutions on the pore throat size of a core in example 1 of the present invention;
FIG. 3 is a T2 relaxation time graph of the degree of influence of different acid solutions on the pore throat size of a core in example 2 of the present invention;
FIG. 4 is a T2 relaxation time graph of the degree of influence of different acid solutions on the pore throat size of a core in example 5 of the present invention;
FIG. 5 is a T2 relaxation time graph of the degree of influence of different acid solutions on the pore throat size of a core in example 6 of the present invention;
Detailed Description
Example 1
An acid liquor system for online acidification of a water injection well for oil exploitation comprises 30% of composite acid liquor by mass, 10% of retarder by mass, 5% of chelating agent by mass, 10% of composite additive by mass and the balance of water;
the composite acid solution is prepared from hydrochloric acid, naphthenic acid, oxalic acid and organic phosphonic acid according to a mass ratio of 26: 2.5: 7.5: 1 preparing an aqueous solution with the mass percentage concentration of 30%.
The retarding solution is prepared from benzaldehyde, a pyridinium corrosion inhibition synergist, hydrazine hydrate, absolute ethyl alcohol and bacterial cellulose according to a mass ratio of 3: 1: 2: 1:2 preparing the aqueous solution with the mass percentage concentration of 50 percent.
The chelating agent is prepared from an aminophosphonic acid ion exchanger, a composite polyhydroxy chelating agent and a fluorine-containing complex in a mass ratio of 3: 2: 1 preparing an aqueous solution with the mass percentage concentration of 40 percent.
The composite additive comprises 55 mass percent of foaming agent, 20 mass percent of surfactant and 30 mass percent of iron ion stabilizer.
The surfactant is a 22.5 mass percent aqueous solution prepared from gemini fluorocarbon surfactant, hydrocarbon surfactant, ethanol and methanol according to the mass ratio of 1:4.5:2.5: 3.5.
As shown in fig. 1, the preparation process for preparing the acid system comprises the following steps:
s1, preparation of the composite acid liquid:
s11, primary reaction: putting 40% of the total amount of the hydrochloric acid into a first reaction kettle, adjusting the temperature to 30 ℃, dropwise adding naphthenic acid into the first reaction kettle, continuously stirring at a stirring speed of 50r/min, and continuously stirring for reacting for 30min after dropwise adding is finished to obtain a mixed acid solution;
s12, secondary reaction: putting 60% of the total amount of hydrochloric acid and oxalic acid into a second reaction kettle, adding the oxalic acid after the hydrochloric acid, wherein the adding mode of the oxalic acid is titration, pressing all mixed liquid in the first reaction kettle into the second reaction kettle by using compressed air, adjusting the temperature to 65 ℃, dropwise adding organic phosphonic acid into the second reaction kettle, continuously stirring at a stirring speed of 400r/min, and continuously stirring for reaction for 3 hours after the dropwise adding is finished to obtain a composite acid liquid;
s2, preparation of a retarder: heating deionized water to 50 ℃, adding benzaldehyde and hydrazine hydrate, stirring at the rotating speed of 600r/min for 20min, and simultaneously sequentially adding absolute ethyl alcohol and a pyridinium corrosion inhibition synergist into the mixed solution; then adding bacterial cellulose at the temperature of 30 ℃, and stirring at the rotating speed of 1500r/min for 30min to obtain a retarding solution;
s3, preparation of a chelating agent: adding an aminophosphonic acid ion exchanger and a composite polyhydroxy chelating agent into a four-neck flask provided with a thermometer, a stirrer, a condenser and a dropping funnel, adjusting the pH value to 8.5 and the temperature to 55 ℃, reacting for 2 hours, adding a fluorine-containing complex, heating to 85 ℃, stirring for 15 minutes at the rotating speed of 200r/min, standing for 4 hours, condensing, and then drying in a vacuum drying oven to obtain a chelating agent;
s4, preparation of the composite additive: sequentially adding a foaming agent, a surfactant and an iron ion stabilizer into a vacuum reaction kettle, and stirring for reaction at the stirring speed of 20 r/min;
s5, mixing: and (4) stirring and mixing the composite acid liquor prepared in the steps S1-S4, the retarder, the chelating agent and the composite additive at normal temperature to obtain an acid liquor system.
Carrying out an acidification effect test on the mixed acid solution obtained after the primary reaction in the step S11, the composite acid solution obtained after the secondary reaction in the step S12 and the acid solution system obtained after the mixing in the step S5, carrying out oil washing and drying treatment on a rock core sample near a water injection well, saturating simulated formation water into the rock core, carrying out displacement on the mixed acid solution obtained after the primary reaction in the step S11, controlling the displacement pressure difference to be 0.4MPa, and carrying out primary nuclear magnetic resonance T2 spectrum sampling after full displacement; displacing the obtained composite acid liquid after the secondary reaction in the step S12, controlling the displacement pressure difference to be 0.4MPa, and performing secondary nuclear magnetic resonance T2 spectrum sampling after full displacement; and (5) displacing by using the acid liquor system obtained after mixing in the step (S5), controlling the displacement pressure difference to be 0.4MPa, and carrying out third nuclear magnetic resonance T2 spectrum sampling after full displacement.
Example 2
This embodiment is substantially the same as embodiment 1, except that:
the composite acid solution is prepared from composite fluoboric acid, naphthenic acid, oxalic acid and organic phosphonic acid according to the mass ratio of 26: 2.5: 7.5: 1 preparing an aqueous solution with the mass percentage concentration of 20%, wherein the composite fluoboric acid consists of hydrochloric acid with the mass concentration of 30% and fluoboric acid with the mass concentration of 23% according to the mass ratio of 1: 2.
S1, preparation of the composite acid liquid:
s11, primary reaction: putting 40% of the total amount of the composite fluoboric acid into a first reaction kettle, adjusting the temperature to 40 ℃, dropwise adding naphthenic acid into the first reaction kettle, continuously stirring at a stirring speed of 150r/min, and continuously stirring for reacting for 30min after dropwise adding is finished to obtain mixed acid liquid;
s12, secondary reaction: putting 60% of the total amount of the composite fluoboric acid and oxalic acid into a second reaction kettle, adding the oxalic acid after the composite fluoboric acid, wherein the adding mode of the oxalic acid is titration, using compressed air to press all mixed liquid in the first reaction kettle into the second reaction kettle, adjusting the temperature to 75 ℃, dropwise adding organic phosphonic acid into the second reaction kettle, continuously stirring at a stirring speed of 500r/min, and continuously stirring for reacting for 3 hours after the dropwise adding is finished to obtain a composite acid liquid;
s2, preparation of a retarder: heating deionized water to 60 ℃, adding benzaldehyde and hydrazine hydrate, stirring at the rotating speed of 1200r/min for 50min, and simultaneously sequentially adding absolute ethyl alcohol and a pyridinium corrosion inhibition synergist into the mixed solution; then adding bacterial cellulose at the temperature of 40 ℃, and stirring for 40min at the rotating speed of 2000r/min to obtain a retarding solution;
s3, preparation of a chelating agent: adding an aminophosphonic acid ion exchanger and a composite polyhydroxy chelating agent into a four-neck flask provided with a thermometer, a stirrer, a condenser and a dropping funnel, adjusting the pH value to 9.5 and the temperature to 55 ℃, reacting for 2 hours, adding a fluorine-containing complex, heating to 85 ℃, stirring for 15 minutes at the rotating speed of 300r/min, standing for 4 hours, condensing, and then drying in a vacuum drying oven to obtain a chelating agent;
s4, preparation of the composite additive: sequentially adding a foaming agent, a surfactant and an iron ion stabilizer into a vacuum reaction kettle, and stirring for reaction at the stirring speed of 30 r/min;
s5, mixing: and (4) stirring and mixing the composite acid liquor prepared in the steps S1-S4, the retarder, the chelating agent and the composite additive at normal temperature to obtain an acid liquor system.
Example 3
This embodiment is substantially the same as embodiment 2, except that:
the composite acid solution is prepared from composite fluoboric acid, naphthenic acid, oxalic acid and organic phosphonic acid according to the mass ratio of 26: 2.5: 7.5: 1 preparing an aqueous solution with the mass percentage concentration of 20%, wherein the composite fluoboric acid consists of hydrochloric acid with the mass concentration of 40% and fluoboric acid with the mass concentration of 30% according to the mass ratio of 1: 2.
S1, preparation of the composite acid liquid:
s11, primary reaction: putting 40% of the total amount of the composite fluoboric acid into a first reaction kettle, adjusting the temperature to 32 ℃, dropwise adding naphthenic acid into the first reaction kettle, continuously stirring at a stirring speed of 67r/min, and continuously stirring for reacting for 30min after dropwise adding is finished to obtain mixed acid liquid;
s12, secondary reaction: putting 60% of the total amount of the composite fluoboric acid and oxalic acid into a second reaction kettle, adding the oxalic acid after the composite fluoboric acid, wherein the adding mode of the oxalic acid is titration, using compressed air to press all mixed liquid in the first reaction kettle into the second reaction kettle, adjusting the temperature to 69 ℃, dropwise adding organic phosphonic acid into the second reaction kettle, continuously stirring at a stirring speed of 430r/min, and continuously stirring for reacting for 3 hours after the dropwise adding is finished to obtain a composite acid liquid;
s2, preparation of a retarder: heating deionized water to 51 ℃, adding benzaldehyde and hydrazine hydrate, stirring at the rotating speed of 900r/min for 30min, and simultaneously sequentially adding absolute ethyl alcohol and a pyridinium corrosion inhibition synergist into the mixed solution; then adding bacterial cellulose at the temperature of 35 ℃, and stirring at the rotating speed of 1580r/min for 35min to obtain a retarder;
preparation of S3 chelating agent: adding an aminophosphonic acid ion exchanger and a composite polyhydroxy chelating agent into a four-neck flask provided with a thermometer, a stirrer, a condenser and a dropping funnel, adjusting the pH value to 9, adjusting the temperature to 55 ℃, reacting for 2 hours, adding a fluorine-containing complex, heating to 85 ℃, stirring for 15 minutes at the rotating speed of 225r/min, standing for 4 hours, condensing, and then drying in a vacuum drying oven to obtain a chelating agent;
s4, preparation of the composite additive: sequentially adding a foaming agent, a surfactant and an iron ion stabilizer into a vacuum reaction kettle, and stirring for reaction at the stirring speed of 20 r/min;
s5, mixing: and (4) stirring and mixing the composite acid liquor prepared in the steps S1-S4, the retarder, the chelating agent and the composite additive at normal temperature to obtain an acid liquor system.
Example 4
This embodiment is substantially the same as embodiment 2, except that:
the composite acid solution is prepared from composite fluoboric acid, naphthenic acid, oxalic acid and organic phosphonic acid according to the mass ratio of 26: 2.5: 7.5: 1 preparing an aqueous solution with the mass percentage concentration of 20%, wherein the composite fluoboric acid consists of hydrochloric acid with the mass concentration of 50% and fluoboric acid with the mass concentration of 20% according to the mass ratio of 1: 2.
S1, preparation of the composite acid liquid:
s11, primary reaction: putting 40% of the total amount of the composite fluoboric acid into a first reaction kettle, adjusting the temperature to 38 ℃, dropwise adding naphthenic acid into the first reaction kettle, continuously stirring at a stirring speed of 125r/min, and continuously stirring for reacting for 30min after dropwise adding is finished to obtain mixed acid liquid;
s12, secondary reaction: putting 60% of the total amount of the composite fluoboric acid and oxalic acid into a second reaction kettle, adding the oxalic acid after the composite fluoboric acid, wherein the adding mode of the oxalic acid is titration, using compressed air to press all mixed liquid in the first reaction kettle into the second reaction kettle, adjusting the temperature to 73 ℃, dropwise adding organic phosphonic acid into the second reaction kettle, continuously stirring at a stirring speed of 480r/min, and continuously stirring for reacting for 3 hours after the dropwise adding is finished to obtain a composite acid liquid;
s2, preparation of a retarder: heating deionized water to 59 ℃, adding benzaldehyde and hydrazine hydrate, stirring at the rotating speed of 1100r/min for 40min, and simultaneously sequentially adding absolute ethyl alcohol and a pyridinium corrosion inhibition synergist into the mixed solution; then adding bacterial cellulose at the temperature of 38 ℃, and stirring at the rotating speed of 1900r/min for 36min to obtain a retarder;
s3, preparation of a chelating agent: adding an aminophosphonic acid ion exchanger and a composite polyhydroxy chelating agent into a four-neck flask provided with a thermometer, a stirrer, a condenser and a dropping funnel, adjusting the pH value to 9, adjusting the temperature to 55 ℃, reacting for 2 hours, adding a fluorine-containing complex, heating to 85 ℃, stirring for 15 minutes at a rotating speed of 280r/min, standing for 4 hours, condensing, and then drying in a vacuum drying oven to obtain a chelating agent;
s4, preparation of the composite additive: sequentially adding a foaming agent, a surfactant and an iron ion stabilizer into a vacuum reaction kettle, and stirring for reaction at the stirring speed of 25 r/min;
s5, mixing: and (4) stirring and mixing the composite acid liquor prepared in the steps S1-S4, the retarder, the chelating agent and the composite additive at normal temperature to obtain an acid liquor system.
Example 5
The present embodiment is substantially the same as embodiment 1, and the difference is that the acid solution system ratio is different:
an acid liquor system for online acidification of a water injection well for oil exploitation comprises 33.5% of composite acid liquor by mass, 5% of retarder by mass, 10% of chelating agent by mass, 5% of composite additive by mass and the balance of water.
Example 6
The present embodiment is substantially the same as embodiment 1, and the difference is that the acid solution system ratio is different:
an acid liquor system for online acidification of a water injection well for oil exploitation comprises 40% of composite acid liquor by mass, 15% of retarder by mass, 7% of chelating agent by mass, 6.5% of composite additive by mass and the balance of water.
Example 7
The embodiment is basically the same as the embodiment 1, and the difference is that the compound acid solution has different proportions:
the composite acid solution is prepared from hydrochloric acid, naphthenic acid, oxalic acid and organic phosphonic acid according to a mass ratio of 30: 2.5: 7.5: 1 preparing an aqueous solution with the mass percentage concentration of 22%.
Example 8
The embodiment is basically the same as the embodiment 1, and the difference is that the compound acid solution has different proportions:
the composite acid solution is prepared from hydrochloric acid, naphthenic acid, oxalic acid and organic phosphonic acid according to a mass ratio of 32: 2.5: 7.5: 1 preparing an aqueous solution with the mass percentage concentration of 15%.
Example 9
The present embodiment is basically the same as embodiment 1, and the difference is that the retarder mixture ratio is different:
the retarding solution is prepared from benzaldehyde, a pyridinium corrosion inhibition synergist, hydrazine hydrate, absolute ethyl alcohol and bacterial cellulose according to a mass ratio of 3: 1: 2: 1:2 preparing the aqueous solution with the mass percentage concentration of 60 percent.
Example 10
The present embodiment is basically the same as embodiment 1, and the difference is that the retarder mixture ratio is different:
the retarding solution is prepared from benzaldehyde, a pyridinium corrosion inhibition synergist, hydrazine hydrate, absolute ethyl alcohol and bacterial cellulose according to a mass ratio of 3: 1: 2: 1:2 preparing the aqueous solution with the mass percentage concentration of 70%.
Example 11
This example is essentially the same as example 1, except that the chelating agent ratio is different:
the chelating agent is prepared from an aminophosphonic acid ion exchanger, a composite polyhydroxy chelating agent and a fluorine-containing complex in a mass ratio of 5: 3: 2 preparing the aqueous solution with the mass percentage concentration of 50 percent.
Example 12
This example is essentially the same as example 1, except that the chelating agent ratio is different:
the chelating agent is prepared from an aminophosphonic acid ion exchanger, a composite polyhydroxy chelating agent and a fluorine-containing complex in a mass ratio of 4: 2: 2 preparing the aqueous solution with the mass percentage concentration of 60 percent.
Example 13
This example is substantially the same as example 1, except that the compounding ratio of the complex additive is different:
the composite additive comprises 65 mass percent of foaming agent, 15 mass percent of surfactant and 20 mass percent of iron ion stabilizer.
Example 14
This example is essentially the same as example 1, except that the surfactant ratio is different:
the surfactant is a 29% aqueous solution prepared from gemini fluorocarbon surfactant, hydrocarbon surfactant, ethanol and methanol according to the mass ratio of 1:5:2: 4.
Examples of the experiments
The acid systems of examples 1, 2, 5 and 6 were extracted for comparison of acidification effects, and the results are shown in FIGS. 2 to 5.
As shown in fig. 2, the abscissa T2 represents the size of the pore throat in the core, and the ordinate pore signal represents the amount of acid liquor saturated at pore throats of different sizes in the core, and it can be seen that in example 1, the pore signal of the composite acid liquor in the smaller pore throat of 0-10ms is greater than the pore signal of the mixed acid liquor, which indicates that the composite acid liquor has a certain erosion effect on the pore throat of the core, and the pore signal of the composite acid liquor in the larger pore throat of 10-100ms is smaller than the pore signal of the mixed acid liquor, which indicates that the larger pore throat has a certain blockage, and the pore signal of the acid liquor system is the largest, which indicates that the acid liquor system has the best erosion effect on the pore throat of the core.
As shown in fig. 3, the trend of the three curves in example 2 is similar to that in example 1, and the same rule can also achieve the purpose of etching pore throats, but because different complex acid systems are used, the overall pore signal is lower than that in example 1, and the complex acid system in example 1 is more preferable.
As shown in fig. 4, the T2 curves of the composite acid liquid and the mixed acid liquid in example 5 coincide with each other, which indicates that the corrosion action of the mixed acid liquid and the composite acid liquid is similar, and the amplitude of the curved pore signal is increased after the acid liquid system is used, which indicates that the corrosion action of the acid liquid system is strongest;
as shown in fig. 5, the pore signal of the composite acid solution in the smaller pore throat of 0-10ms in example 6 is larger than that of the mixed acid solution, which indicates that the composite acid solution has a certain erosion effect on the pore throat of the core, and the pore signal of the composite acid solution in the larger pore throat of 10-100ms is smaller than that of the mixed acid solution, which indicates that the larger pore throat has a certain blockage, and the pore signal of the acid solution system is the largest, but the increase amplitude is slightly smaller than that in examples 1 and 5, so the acid solution system ratio in example 5 is selected as the optimum.
The acid liquid system performance tests in examples 1 to 14 show that the acid liquid system prepared by the complex acid liquid ratio in example 8 has the best performance, the acid liquid system prepared by the retarder liquid ratio in example 9 has the best performance, the acid liquid system prepared by the chelating agent ratio in example 12 has the best performance, and the acid liquid system prepared by the complex additive in example 14 has the best performance.
Claims (9)
1. An acid liquor system for online acidification of a water injection well for oil exploitation is characterized by comprising 30-40% of composite acid liquor by mass percent, 5-15% of retarder by mass percent, 5-10% of chelating agent by mass percent, 5-10% of composite additive by mass percent and the balance of water;
the composite acid solution is prepared from hydrochloric acid, naphthenic acid, oxalic acid and organic phosphonic acid according to a mass ratio of 26-32: 2.5: 7.5: 1 preparing an aqueous solution with the mass percentage concentration of 15-30%.
2. The acid liquor system for online acidification of a water injection well for oil exploitation as claimed in claim 1, wherein the hydrochloric acid in the composite acid liquor can be replaced by composite fluoroboric acid, and the composite fluoroboric acid is composed of hydrochloric acid with a mass concentration of 30-50% and fluoroboric acid with a mass concentration of 20-30% according to a mass ratio of 1: 2.
3. The acid liquor system for the on-line acidification of the water injection well for the oil exploitation as claimed in claim 1, wherein the retarder is prepared from benzaldehyde, pyridinium corrosion inhibition synergist, hydrazine hydrate, absolute ethyl alcohol, and bacterial cellulose in a mass ratio of 3: 1: 2: 1:2 preparing into 50-70% water solution.
4. The acid liquor system for online acidification of water injection wells for oil exploitation according to claim 1, wherein the chelating agent is selected from aminophosphonic acid ion exchangers, complex polyhydroxy chelating agents, fluorine-containing complexes according to a mass ratio of 3-5: 2-3: 1-2, preparing aqueous solution with mass percent concentration of 40-60%.
5. The acid liquor system for the online acidification of the water injection well for the oil exploitation as claimed in claim 1, wherein the complex additive comprises 55-70% of foaming agent, 15-20% of surfactant and 20-30% of iron ion stabilizer by mass percentage.
6. The acid liquor system for the online acidification of the water injection well for the oil exploitation as claimed in claim 1, wherein the surfactant is an aqueous solution prepared from a gemini fluorocarbon surfactant, a hydrocarbon surfactant, ethanol and methanol in a mass ratio of 1:4-5:2-3:3-4, and the mass percentage concentration of the aqueous solution is 20-30%.
7. Process for the preparation of acid systems according to any of claims 1 to 6, characterized in that it comprises the following steps:
s1, preparation of the composite acid liquid:
s11, primary reaction: putting 40% of the total amount of the hydrochloric acid into a first reaction kettle, adjusting the temperature to 30-40 ℃, dropwise adding naphthenic acid into the first reaction kettle, continuously stirring at a stirring speed of 50-150r/min, and continuously stirring for reacting for 30min after dropwise adding is finished to obtain mixed acid liquid;
s12, secondary reaction: putting 60% of the total amount of hydrochloric acid and oxalic acid into a second reaction kettle, pressing the mixed acid liquid in the first reaction kettle into the second reaction kettle by using compressed air, adjusting the temperature to 65-75 ℃, dropwise adding organic phosphonic acid into the second reaction kettle, continuously stirring at the stirring speed of 400-fold glass-cement r/min, and continuously stirring for reacting for 3 hours after the dropwise adding is finished to obtain the composite acid liquid;
s2, preparation of a retarder: heating deionized water to 50-60 ℃, adding benzaldehyde and hydrazine hydrate, stirring at the rotating speed of 600-1200r/min for 20-50min, and simultaneously sequentially adding absolute ethyl alcohol and a pyridinium corrosion inhibition synergist into the mixed solution; then adding bacterial cellulose at the temperature of 30-40 ℃, and stirring at the rotating speed of 1500-;
s3, preparation of a chelating agent: adding an aminophosphonic acid ion exchanger and a composite polyhydroxy chelating agent into a four-neck flask provided with a thermometer, a stirrer, a condenser and a dropping funnel, adjusting the pH value to 8.5-9.5, adjusting the temperature to 55 ℃, reacting for 2h, adding a fluorine-containing complex, heating to 85 ℃, stirring for 15min at the rotating speed of 200-300r/min, standing for 4h, condensing, and then drying in a vacuum drying box to obtain the chelating agent;
s4, preparation of the composite additive: sequentially adding a foaming agent, a surfactant and an iron ion stabilizer into a vacuum reaction kettle, and stirring for reaction to obtain a composite additive;
s5, mixing: and (4) stirring and mixing the composite acid liquor prepared in the steps S1-S4, the retarder, the chelating agent and the composite additive at normal temperature to obtain an acid liquor system.
8. The process for preparing an acid liquor system for online acidification of a water injection well for oil exploitation according to claim 7, wherein the oxalic acid is added after hydrochloric acid in the secondary reaction of step S12, and the addition manner of oxalic acid is titration.
9. The process for preparing the acid liquor system for the on-line acidification of the water injection well for the oil exploitation as claimed in claim 7, wherein the stirring speed in the step S4 is 20-30 r/min.
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