CN110792417A - Method for improving recovery ratio of high pour-point oil reservoir - Google Patents
Method for improving recovery ratio of high pour-point oil reservoir Download PDFInfo
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- CN110792417A CN110792417A CN201810870082.3A CN201810870082A CN110792417A CN 110792417 A CN110792417 A CN 110792417A CN 201810870082 A CN201810870082 A CN 201810870082A CN 110792417 A CN110792417 A CN 110792417A
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
- C09K8/582—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids characterised by the use of bacteria
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
- C09K8/584—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids characterised by the use of specific surfactants
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
- C09K8/588—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids characterised by the use of specific polymers
Abstract
The invention belongs to the technical field of oilfield development, and particularly relates to a method for improving the recovery efficiency of a high pour-point oil reservoir. The method specifically comprises the following steps: screening a test oil reservoir; screening a chemical pour point depressant; screening an activating agent; compounding a chemical pour point depressant and an activator to form a compound system; evaluating the compatibility of a compound system; optimizing the injection amount of a compound system; field test and evaluation of the effect. The invention effectively combines chemical pour point depression and microbial pour point depression, and has the advantages of low cost, quick response, long validity period, high input-output ratio and good pour point depression effect, wherein the input-output ratio is more than 1:10, and the field test improves the recovery ratio by more than 15%. Therefore, the method can be widely applied to the exploitation process of the high pour-point oil reservoir.
Description
Technical Field
The invention belongs to the technical field of oilfield development, and particularly relates to a method for improving the recovery ratio of a high pour-point oil reservoir.
Background
The high pour-point oil reservoir is widely distributed in the world, China is one of the most abundant countries of high pour-point oil resources, and the quantity of the high pour-point oil resources in China can reach 50 multiplied by 108More than one ton, which accounts for 30-40% of the world high-pour-point oil resources. The crude oil of the high pour point oil reservoir has the characteristics of three high, namely high wax content, high freezing point and high wax precipitation point. The wax content is 10-57%, generally 20-40%; the freezing point is generally 25-59 ℃, and the highest freezing point is 67 ℃; the wax precipitation point is generally 40-74 ℃.
At present, over 80 percent of high pour-point oil reservoirs are developed by conventional cold water injection, the injection water quantity is continuously increased along with the continuous development of oil fields, the formation temperature is gradually reduced, the phenomena of large wax precipitation of crude oil, cold damage and blockage of the reservoir are more and more serious, and the water absorption index of an oil reservoir injection well is rapidly reduced, so that the method has important significance for reducing the freezing point of the high pour-point oil and improving the fluidity of the high pour-point oil. At present, the exploitation of high pour-point oil reservoirs is mainly thermal exploitation or chemical pour point depressant addition, wherein the thermal exploitation cost is high, and part of oil reservoir layers are thin and are not suitable for exploitation in a thermal exploitation mode; the chemical pour point depressant has the advantages of quick response and good pour point depressing effect, but the chemical pour point depressant cannot inhibit the precipitation of wax crystals and only can change the form of the wax crystals to weaken the capability of the wax crystals for forming a three-dimensional space network structure, thereby enhancing the fluidity of crude oil and having the defects of higher price and shorter effective period.
The microbial pour point depression mainly utilizes microbes and metabolites thereof to change the form of wax crystals in the high pour point oil and reduce the aggregation and growth of the wax crystals, thereby inhibiting the wax crystals in the crude oil from separating out, aggregating and depositing on the solid surface. The microbial pour point depressant has the advantages of strong persistence and long validity period, but because the injection of an activator stratum needs a certain time to activate microbes in an oil layer, the microbial pour point depressant takes a relatively delayed effect.
CN1814987A discloses a metamorphic rock buried hill high pour point oil reservoir fire flooding oil extraction ignition method. The method mainly comprises the steps of performing artificial fracturing on a stratum, injecting high-temperature air into a vertical injection well, heating high-condensation oil in a rock fracturing fracture to a temperature higher than 400 ℃ to burn, enabling the crude oil to be in a high-temperature flowing state, extracting the crude oil from a horizontal production well to the ground, and discharging air in a combustion layer through a gas production well when an oil layer burns to enable the whole oil layer to be in a stable burning state, so that the recovery ratio is improved. The method has the disadvantages that as the vertical distance between the vertical gas injection well and the horizontal production well is only 5-10 meters, high-temperature air and a combustion front edge are easy to enter the horizontal production well at the bottom of the gas injection well in the field implementation process, so that the serious potential explosion hazard problem is generated, and the application does not mention what operation measures are adopted to avoid the potential safety hazard problem.
Disclosure of Invention
The invention provides a method for improving the recovery efficiency of a high pour-point oil reservoir aiming at the defects of the prior art, which effectively combines chemical pour point depression with microbial pour point depression and has the advantages of low cost, quick response, long validity period, high input-output ratio and good pour point depression effect, wherein the input-output ratio is more than 1:10, and the recovery efficiency is improved by more than 15% in a field test.
The invention discloses a method for improving the recovery ratio of a high pour-point oil reservoir, which is characterized by comprising the following steps:
1. screening of test reservoirs
The screening of the test oil reservoir needs to satisfy two conditions: (1) the oil deposit temperature is less than 90 ℃, and the mineralization degree of formation water is less than 100000 mg/L; (2) the viscosity of the crude oil is less than 10000mPa.s, the freezing point is less than 60 ℃, and the wax content is less than 40%.
2. Screening of chemical pour point depressant
The screening of the chemical pour point depressant comprises two aspects of chemical pour point depressant type and concentration screening, wherein the screening of the chemical pour point depressant type is firstly carried out, and the screening of the chemical pour point depressant concentration is secondly carried out.
3. Screening for activators
The activator is selected by static culture method.
4. Compounding chemical pour point depressant and activator to form a compound system
The compounding of the chemical pour point depressant and the activator comprises the following specific steps:
adding chemical pour point depressants and activators in different proportions into a container with stirring, uniformly mixing to form a compound system, wherein the total amount of the chemical pour point depressants and the activators is 5g, and then adding 100ml of formation water of a test oil reservoir and 100g of dehydrated and degassed crude oil of the test oil reservoir; placing the container in a constant-temperature incubator, and performing constant-temperature culture for 5-15 days, wherein the temperature of the constant-temperature incubator is the temperature of the tested oil reservoir; and testing the freezing point of the crude oil after the culture time is over, and screening out the optimal proportion of the chemical pour point depressant and the activator and the optimal compound system according to the amplitude of the freezing point depression.
5. Compatibility evaluation of compounded system
And (3) taking 100mL of stratum water of a tested oil reservoir, adding 5g of the compound system with the screened optimal proportion, uniformly mixing, standing for 20-30 min, observing whether the compound system has sedimentation, evaluating the compatibility of the compound system according to the sedimentation phenomenon, and screening the compound system with good compatibility.
6. Optimization of injection amount of compound system
The optimization of the injection amount of the compound system adopts a physical simulation experiment method.
7. On-site test and evaluation of Effect
And (3) performing a field test according to the injection quantity optimized in the steps, injecting the compound system from the injection well of the tested oil reservoir, evaluating the test effect after the field test, and inspecting the improved recovery rate value and the input-output ratio.
The specific method for screening the chemical pour point depressant comprises the following steps: adding 100g of dehydrated and degassed crude oil of a test oil reservoir and 5g of chemical pour point depressant into a triangular flask with the volume of 500ml while stirring; then placing the triangular flask in a constant-temperature water bath kettle, wherein the water bath kettle is heated at the temperature of the tested oil reservoir, and the triangular flask is heated for 0.5-1 h; and (5) testing the freezing point of the crude oil after the triangular flask is heated, and screening out the chemical pour point depressant with the largest freezing point depression amplitude.
The specific method for screening the concentration of the chemical pour point depressant is as follows: taking 100g of dehydrated and degassed crude oil of a tested oil reservoir and the screened chemical pour point depressant with different mass concentrations, and adding the mixture into a triangular flask with the volume of 500ml while stirring; then placing the triangular flask in a constant-temperature water bath, wherein the water bath is heated at the temperature of the oil reservoir to be tested, and the triangular flask is heated for 0.5-1 h; and (5) testing the freezing point of the crude oil after the triangular flask is heated, and screening out the optimal chemical pour point depressant concentration with the largest freezing point depression amplitude.
The chemical pour point depressant is one of a surfactant type and a polymer type pour point depressant.
The surfactant pour point depressant is petroleum sulfonate or polyoxyethylene alkylamine; the polymer pour point depressant is one of long-chain alkyl naphthalene, polyester and polyolefin.
The screening of the activating agent adopts a static culture method, and the specific method comprises the following steps: adding 100mL of stratum water of a test oil reservoir and 10-20g of dehydrated and degassed crude oil of the test oil reservoir into a container with a stirrer; then adding an activating agent and mixing uniformly; placing the container in a constant-temperature incubator, and carrying out constant-temperature culture for 5-15 days, wherein the temperature of the constant-temperature incubator is the temperature of the tested oil reservoir; and testing the freezing point of the crude oil after the culture time is over, and determining the formula of the activator according to the size of the reduction amplitude of the freezing point.
The activator consists of a carbon source, a nitrogen source and a phosphorus source, wherein the carbon source is starch or sucrose, the nitrogen source is potassium nitrate or peptone, and the phosphorus source is dipotassium hydrogen phosphate or disodium hydrogen phosphate.
The mass concentration of the carbon source is 1.0-3.0%, the mass concentration of the nitrogen source is 0.1-0.5%, and the mass concentration of the phosphorus source is 0.02-0.05%.
The optimization of the injection amount of the compound system adopts a physical simulation experiment method, and the specific method comprises the following steps: filling a sand-filled rock core with the same permeability as the tested oil reservoir; vacuumizing the core, saturating reservoir stratum water of the test, and calculating the pore volume of the core; the method comprises the following steps of (1) saturating dehydrated and degassed crude oil of an oil reservoir in a saturation test until the oil content in a produced liquid at a core outlet is 100%, and calculating the original oil saturation of a core; aging the core for 7d at the temperature of the test oil reservoir; performing primary water drive, and calculating the primary water drive recovery ratio until the outlet water content is consistent with the comprehensive water content of the test oil reservoir; respectively injecting different amounts of compound systems; and (4) performing secondary water flooding after culturing for 15-20 days until the water content of an outlet is 100%, calculating the value of the enhanced recovery ratio, and determining the optimal injection amount of the compound system according to the value of the enhanced recovery ratio.
According to the invention, a mode of combining chemical pour point depressing with microbial pour point depressing is adopted, and the characteristics of quick effect and good pour point depressing effect of the chemical pour point depressing agent are firstly utilized, so that the pour point depressing effect can be ensured to be quickly seen when a compound system is just injected into an oil reservoir, and the flowing property of high pour point oil is improved; then, by utilizing the characteristics of relative lag and long period of validity of the microbial pour point depressant, the microbial pour point depressant starts to take effect when the pour point depressing effect of the chemical pour point depressant is deteriorated, and the freezing point of the high pour point oil can be lowered for a long time. The invention fully utilizes the characteristics of quick effect and good pour point depressing effect of the chemical pour point depressing agent and relative lag and long validity period of the microbial pour point depressing effect, and the effective combination of the chemical pour point depressing agent and the microbial pour point depressing agent not only can effectively ensure the pour point depressing effect of the high pour point oil and greatly improve the validity period of the effect, but also greatly reduces the investment cost and effectively solves the problems of high cost of single chemical pour point depressing and slow effect of microbial pour point depressing. And simultaneously, the crude oil recovery rate of the high pour-point oil reservoir is greatly improved, the recovery rate is improved by more than 15% in a field test, and the input-output ratio is more than 1: 10.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) the invention has the characteristics of low cost, quick response and long validity period, and is beneficial to field popularization and application;
(2) the compound system adopted by the invention has the advantages of wide sources, low price, good compatibility, no damage to stratum and no influence on subsequent water treatment;
(3) the invention has wide application range of oil reservoirs, is suitable for both high pour-point oil reservoirs with medium and high permeability and high pour-point oil reservoirs with medium and low permeability;
(4) the invention has the characteristics of good field test effect and high input-output ratio, the field test improves the recovery ratio by more than 15 percent, and the input-output ratio is more than 1: 10.
Detailed Description
The invention will be further described in detail with reference to the following specific examples:
example 1:
experiment oil reservoir D of certain oil production plant of victory oil field12Overview: oil deposit temperature of 75 ℃, stratum water mineralization degree of 25682mg/L, crude oil viscosity of 160mPa.s, freezing point of 45 ℃, wax content of 35.2 percent and permeability of 1200 multiplied by 10-3μm2The comprehensive water content of oil reservoir is 95.2%, and the geological reserve is 3.5X 106t. The method for improving the recovery ratio of the block comprises the following specific steps:
(1) screening of test reservoirs
Test reservoir D12The temperature of the crude oil is 75 ℃, the mineralization degree of formation water is 25682mg/L, the viscosity of the crude oil is 160mPa.s, the freezing point is 45 ℃, and the wax content is 35.2%. Meets the screening criteria of the test reservoir of the present invention and thus can be practiced.
(2) Screening of chemical pour point depressant
The screening of the chemical pour point depressant comprises two aspects of chemical pour point depressant type and concentration screening, wherein the screening of the chemical pour point depressant type is firstly carried out, and the screening of the chemical pour point depressant concentration is secondly carried out.
The specific method for screening the chemical pour point depressant comprises the following steps: test reservoir D12100g of dehydrated and degassed crude oil and 5g of chemical pour point depressant are added while stirringA triangular flask with the volume of 500 ml; then placing the triangular bottle in a constant-temperature water bath kettle, wherein the heating temperature of the water bath kettle is 75 ℃, and the heating time of the triangular bottle is 0.5 h; and (3) testing the freezing point of the crude oil after the triangular flask is heated, wherein the test result is shown in table 1, and the chemical pour point depressant with the largest freezing point depression amplitude is screened out.
TABLE 1 freezing point depression results for different kinds of chemical pour point depressants
| Serial number | Chemical pour point depressant | Freezing point depression value, DEG C | Comprehensive ranking |
| 1 | Petroleum sulfonate type | 8 | 3 |
| 2 | Polyoxyethylene alkylamines | 6 | 5 |
| 3 | Long chain alkyl naphthalenes | 9 | 2 |
| 4 | Polyesters | 11 | 1 |
| 5 | Polyolefins | 7 | 4 |
As can be seen from Table 1, the polyester polymer type pour point depressant exhibits the best pour point depressing effect, and therefore the polyester chemical pour point depressant is selected.
The method for screening the concentration of the polyester chemical pour point depressant comprises the following steps: test reservoir D12Adding 100g of dehydrated and degassed crude oil and different amounts of polyester chemical pour point depressants into a 500ml triangular bottle while stirring; then placing the triangular flask in a constant-temperature water bath kettle, wherein the heating temperature of the water bath kettle is 75 ℃, and the heating time of the triangular flask is 0.5 h; and (3) testing the freezing point of the crude oil after the triangular flask is heated, wherein the testing result is shown in table 2, and the optimal chemical pour point depressant concentration with the largest freezing point depression amplitude is screened out.
TABLE 2 freezing point depression results for different mass concentrations of polyester chemical pour point depressants
| Serial number | Pour point depressant mass concentration% | Freezing point depression value, DEG C |
| 1 | 1 | 5 |
| 2 | 2 | 6 |
| 3 | 3 | 7 |
| 4 | 4 | 9 |
| 5 | 5 | 10 |
| 6 | 6 | 10.2 |
As can be seen from table 2: the higher the mass concentration of the pour point depressant is, the higher the freezing point depression value of the thick oil is, but when the mass concentration is more than 5 percent, the depression range of the freezing point is not obvious, so the optimal concentration of the polyester chemical pour point depressant is screened to be 5 percent.
(3) Screening for activators
The screening of the activating agent adopts a static culture method, and the specific method comprises the following steps: take 100mL test reservoir D12Formation water and 10g test reservoir D12The dehydrated and degassed crude oil is added into a container with stirring; then adding an activating agent and mixing uniformly; placing the container in a constant temperature incubator, and carrying out constant temperature culture for 5 days, wherein the temperature of the constant temperature incubator is 75 ℃; and (3) testing the freezing point of the crude oil after the culture time is over, wherein the test result is shown in table 3, and the formula of the activator is determined according to the reduction amplitude of the freezing point.
Table 3 freezing point depression results for different activators
As can be seen from table 3: the activator formulation 5 (2.0% sucrose, 0.3% peptone, 0.05% disodium hydrogen phosphate) gave the best pour point depressing effect, so the activator formulation was selected to be 2.0% sucrose, 0.3% peptone, 0.05% disodium hydrogen phosphate.
(4) Compounding chemical pour point depressant and activator to form a compound system
The compounding of the chemical pour point depressant and the activator comprises the following specific steps:
adding polyester chemical pour point depressant (with mass concentration of 5%) and activator (sucrose 2.0%, peptone 0.3%, disodium hydrogen phosphate 0.05%) in different proportions into a container with a stirrer, mixing uniformly to form a compound system, adding 5g of the total amount of the chemical pour point depressant and the activator, and adding 100ml of the test oil reservoir D12Formation water and 100g test reservoir D12The dehydrated and degassed crude oil of (2); placing the container in a constant temperature incubator, and performing constant temperature culture for 5 days, wherein the temperature of the incubator is 75 ℃; and (3) testing the freezing point of the crude oil after the culture time is over, wherein the test result is shown in table 4, and the optimal proportion of the chemical pour point depressant and the activator and the optimal compound system are screened out according to the amplitude of the freezing point depression.
TABLE 4 freezing point depression results for different formulation systems
As can be seen from table 4: the optimal ratio of the chemical pour point depressant to the activator is 3:2, so that the optimal selected complex ligand system is the chemical pour point depressant and the activator in the ratio of 3: 2.
(5) Compatibility evaluation of compounded system
Take 100mL test reservoir D12And 5g of the screened complex ligand system with the optimal ratio of 3:2 is added into the formation water, the mixture is uniformly mixed, and after standing for 20min, no settlement site appears in the complex system, which indicates that the screened complex system has good compatibility.
(6) Optimization of injection amount of compound system
The optimization of the injection amount of the compound system adopts a physical simulation experiment method, and the specific method comprises the following steps:filling permeability of 1200X 10-3μm2The sand-filled core; core vacuumizing and saturation test oil reservoir D12Calculating the pore volume PV of the rock core by using formation water; saturation test reservoir D12The dehydrated and degassed crude oil is saturated until the oil content in the output liquid of the core outlet is 100 percent, and the original oil saturation of the core is calculated; aging the core at 75 ℃ for 7 d; performing primary water drive until the water content at an outlet is 95.2%, and calculating the primary water drive recovery ratio; respectively injecting different amounts of compound systems; and (3) performing secondary water flooding after culturing for 15 days until the water content of an outlet is 100%, calculating the value of the enhanced recovery ratio, and determining the optimal injection amount of the compound system according to the value of the enhanced recovery ratio according to the test result shown in table 5.
Table 5 enhanced recovery values for different injection rate compounding systems
| Serial number | Amount of injection, PV | Increase the harvest rate% |
| 1 | 0.1 | 10.6 |
| 2 | 0.2 | 13.5 |
| 3 | 0.3 | 15.3 |
| 4 | 0.4 | 16.0 |
As can be seen from table 5: the higher the injection amount of the compound system, the higher the value of the recovery rate is, but the increase of the value of the recovery rate is not obvious when the injection amount is more than 0.3PV, so the optimal injection amount of the compound system is 0.3 PV.
(7) On-site test and evaluation of Effect
And (3) performing a field test according to the injection quantity optimized in the steps, injecting the compound system from the injection well of the tested oil reservoir, evaluating the test effect after the field test, and inspecting the improved recovery rate value and the input-output ratio.
Reservoir D after completion of the field test12The comprehensive water content is reduced from 95.2 percent to 78.0 percent, the water content is reduced by 17.2 percent, and the yield of crude oil is increased by 0.8225 multiplied by 106t, the recovery ratio is improved by 16 percent, the input-output ratio is 1:12.3, and the field test effect is good.
Example 2
Experiment oil reservoir E of certain oil production plant of victory oil field21Overview: oil deposit temperature is 70 ℃, stratum water mineralization degree is 18623mg/L, viscosity of crude oil is 220mPa.s, freezing point is 48 ℃, wax content is 38.5%, and permeability is 1500 multiplied by 10-3μm2The comprehensive water content of oil reservoir is 97.3%, and the geological reserve is 3.2X 106t. The method for improving the recovery ratio of the block comprises the following specific steps:
(1) screening of test reservoirs
Test reservoir E21The temperature of the crude oil is 70 ℃, the mineralization degree of formation water is 18623mg/L, the viscosity of the crude oil is 220mPa.s, the freezing point is 48 ℃, and the wax content is 38.5 percent. Meets the screening criteria of the test reservoir of the present invention and thus can be practiced.
(2) Screening of chemical pour point depressant
The screening of the chemical pour point depressant comprises two aspects of chemical pour point depressant type and concentration screening, wherein the screening of the chemical pour point depressant type is firstly carried out, and the screening of the chemical pour point depressant concentration is secondly carried out.
Chemical pour point depressantThe specific method for screening the types comprises the following steps: test reservoir E21Adding 100g of dehydrated and degassed crude oil and 5g of chemical pour point depressant into a triangular flask with the volume of 500ml while stirring; then placing the triangular flask in a constant-temperature water bath kettle, wherein the heating temperature of the water bath kettle is 70 ℃, and the heating time of the triangular flask is 0.6 h; and (5) testing the freezing point of the crude oil after the triangular flask is heated, wherein the test result is shown in table 6, and the chemical pour point depressant with the largest freezing point depression amplitude is screened out.
TABLE 6 freezing point depression results for different kinds of chemical pour point depressants
As can be seen from Table 6, the polyoxyethylene alkylamine surfactant-type pour point depressant has the best pour point depressing effect, and thus the polyoxyethylene alkylamine surfactant-type pour point depressant is selected.
The screening method of the concentration of the polyoxyethylene alkylamine surfactant pour point depressant comprises the following steps: sampling test oil reservoir E21Adding 100g of dehydrated and degassed crude oil and different amounts of polyoxyethylene alkylamine surfactant pour point depressant into a triangular flask with the volume of 500ml while stirring; then placing the triangular flask in a constant-temperature water bath kettle, wherein the heating temperature of the water bath kettle is 70 ℃, and the heating time of the triangular flask is 0.8 h; and (3) testing the freezing point of the crude oil after the triangular flask heating time is over, wherein the test result is shown in table 7, and the optimal pour point depressant concentration with the largest freezing point depression amplitude is screened out.
TABLE 7 freezing point depression results for varying mass concentrations of polyoxyethylenealkylamine surfactant-type pour point depressants
| Serial number | Pour point depressant mass concentration% | Freezing point depression value, DEG C |
| 1 | 1 | 6 |
| 2 | 2 | 8 |
| 3 | 3 | 9 |
| 4 | 4 | 11.5 |
| 5 | 5 | 12 |
As can be seen from table 7: the higher the mass concentration of the pour point depressant is, the higher the freezing point depression value of the thick oil is, but when the mass concentration is more than 4%, the freezing point depression range is not obvious, so the optimum concentration of the polyoxyethylene alkylamine surfactant type pour point depressant is 4% by screening.
(3) Screening for activators
The screening of the activating agent adopts a static culture method, and the specific method comprises the following steps: take 100mL test reservoir E21Formation water and 15g test reservoir E21The dehydrated and degassed crude oil is added into a container with stirring; then adding an activating agent and mixing uniformly; placing the container in a constant temperature incubator, and performing constant temperature culture for 10 days, wherein the temperature of the incubator is 70 ℃; coagulation of the test crude after the end of the incubation timeThe solidifying point, the test result is shown in Table 8, and the formula of the activator is determined according to the size of the reduction range of the solidifying point.
TABLE 8 freezing point depression results for different activators
As can be seen from table 8: the activator formulation 3 (2.0% starch, 0.5% potassium nitrate, 0.03% disodium hydrogen phosphate) had the best pour point depressing effect, so the activator formulation was selected to be 2.0% starch, 0.5% potassium nitrate, 0.03% disodium hydrogen phosphate.
(4) Compounding chemical pour point depressant and activator to form a compound system
The compounding of the chemical pour point depressant and the activator comprises the following specific steps:
adding polyoxyethylene alkylamine surfactant pour point depressant (mass concentration 4%) and activator (starch 2.0%, potassium nitrate 0.5% and disodium hydrogen phosphate 0.03%) in different proportions into a container with a stirrer, uniformly mixing to form a compound system, adding 5g of chemical pour point depressant and activator in total, and adding 100ml of test oil reservoir E21Formation water and 100g test reservoir E21The dehydrated and degassed crude oil of (2); placing the container in a constant-temperature culture box, and culturing at constant temperature for 10d, wherein the temperature of the constant-temperature box is 70 ℃; and (3) testing the solidification point of the crude oil after the culture time is over, wherein the test result is shown in table 9, and the optimal proportion of the chemical pour point depressant and the activator and the optimal compound system are screened out according to the amplitude of the freezing point depression.
TABLE 9 freezing point depression results for different formulation systems
As can be seen from table 9: the optimal ratio of the chemical pour point depressant to the activator is 1:1, so that the optimal selected complex ligand system is the chemical pour point depressant and the activator in the ratio of 1: 1.
(5) Compatibility evaluation of compounded system
Take 100mL test reservoir E21Formation water ofAnd then 5g of the screened compound system with the optimal ratio of 1:1 is added, the mixture is uniformly mixed, and after standing for 25min, no settlement site appears in the compound system, which indicates that the screened compound system has good compatibility.
(6) Optimization of injection amount of compound system
The optimization of the injection amount of the compound system adopts a physical simulation experiment method, and the specific method comprises the following steps: filling permeability of 1500X 10-3μm2The sand-filled core; core vacuumizing and saturation test oil reservoir E21Calculating the pore volume PV of the rock core by using formation water; saturation test reservoir E21The dehydrated and degassed crude oil is saturated until the oil content in the output liquid of the core outlet is 100 percent, and the original oil saturation of the core is calculated; aging the core at 70 ℃ for 7 d; performing primary water drive until the water content at an outlet is 97.3 percent, and calculating the primary water drive recovery ratio; respectively injecting different amounts of compound systems; and (3) performing secondary water flooding after 18d of culture until the water content of an outlet is 100%, calculating the value of the enhanced recovery ratio, and determining the optimal injection amount of the compound system according to the value of the enhanced recovery ratio according to the test result shown in the table 10.
TABLE 10 enhanced recovery values for different injection rate formulation systems
| Serial number | Amount of injection, PV | Increase the harvest rate% |
| 1 | 0.1 | 10.3 |
| 2 | 0.2 | 16.5 |
| 3 | 0.3 | 16.0 |
| 4 | 0.4 | 17.5 |
As can be seen from table 10: the higher the injection amount of the compound system, the higher the value of the recovery rate is, but the increase of the value of the recovery rate is not obvious when the injection amount is more than 0.2PV, so the optimal injection amount of the compound system is 0.2 PV.
(7) On-site test and evaluation of Effect
And (3) performing a field test according to the injection quantity optimized in the steps, injecting the compound system from the injection well of the tested oil reservoir, evaluating the test effect after the field test, and inspecting the improved recovery rate value and the input-output ratio.
Reservoir E after completion of the field test21The comprehensive water content is reduced from 97.3 percent to 78.9 percent, the water content is reduced by 18.4 percent, and the yield of crude oil is increased by 0.8064 multiplied by 106t, the recovery ratio is improved by 17.2 percent, the input-output ratio is 1:12.8, and the field test effect is good.
Example 3:
experiment oil reservoir D of certain oil production plant of victory oil field15Overview: oil deposit temperature 65 deg.c, stratum water mineralization 32567mg/L, crude oil viscosity 483mPa.s, solidifying point 48 deg.c, wax content 38.8%, and permeability 1100 x 10-3μm2The comprehensive water content of oil reservoir is 98.0%, and the geological reserve is 7.5X 106t. The method for improving the recovery ratio of the block comprises the following specific steps:
(1) screening of test reservoirs
Test reservoir D15The temperature of the crude oil is 65 ℃, the mineralization degree of formation water is 32567mg/L, the viscosity of the crude oil is 483mPa.s, the freezing point is 48 ℃, and the wax content is 38.8 percent. Satisfies the bookThe screening criteria of the inventive test reservoir, and thus the present invention can be practiced.
(2) Screening of chemical pour point depressant
The screening of the chemical pour point depressant comprises two aspects of chemical pour point depressant type and concentration screening, wherein the screening of the chemical pour point depressant type is firstly carried out, and the screening of the chemical pour point depressant concentration is secondly carried out.
The specific method for screening the chemical pour point depressant comprises the following steps: test reservoir D15Adding 100g of dehydrated and degassed crude oil and 5g of chemical pour point depressant into a triangular flask with the volume of 500ml while stirring; then placing the triangular bottle in a constant-temperature water bath kettle, wherein the heating temperature of the water bath kettle is 65 ℃, and the heating time of the triangular bottle is 1 h; and (5) testing the freezing point of the crude oil after the triangular flask is heated, wherein the test result is shown in table 11, and the chemical pour point depressant with the largest freezing point depression amplitude is screened out.
TABLE 11 freezing point depression results for different kinds of chemical pour point depressants
| Serial number | Chemical pour point depressant | Freezing point depression value, DEG C | Comprehensive ranking |
| 1 | Petroleum sulfonate type | 5 | 5 |
| 2 | Polyoxyethylene alkylamines | 10 | 3 |
| 3 | Long chain alkyl naphthalenes | 8 | 4 |
| 4 | Polyesters | 11 | 2 |
| 5 | Polyolefins | 13 | 1 |
As can be seen from Table 11, the polyolefin-based polymer pour point depressant exhibits the best pour point depressing effect, and therefore, polyolefin-based chemical pour point depressants have been selected.
The specific method for screening the concentration of the polyolefin chemical pour point depressant is as follows: test reservoir D15Adding 100g of dehydrated and degassed crude oil and different amounts of polyester chemical pour point depressant into a triangular flask with the volume of 500ml while stirring; then placing the triangular flask in a constant-temperature water bath kettle, wherein the heating temperature of the water bath kettle is 65 ℃, and the heating time of the triangular flask is 1 h; and (5) testing the freezing point of the crude oil after the triangular flask is heated, wherein the test result is shown in table 12, and the optimal chemical pour point depressant concentration with the largest freezing point depression amplitude is screened out.
TABLE 12 freezing point depression results for polyolefin-based chemical pour point depressants of varying mass concentrations
| Serial number | Pour point depressant mass concentration% | Freezing point depression value, DEG C |
| 1 | 1 | 3 |
| 2 | 2 | 6 |
| 3 | 3 | 8 |
| 4 | 4 | 10 |
| 5 | 5 | 13 |
| 6 | 6 | 13 |
As can be seen from table 12: the higher the mass concentration of the pour point depressant is, the higher the freezing point depression value of the thick oil is, but when the mass concentration is more than 5%, the depression range of the freezing point is not obvious, so that the optimal concentration of the polyolefin chemical pour point depressant is screened to be 5%.
(3) Screening for activators
The screening of the activating agent adopts a static culture method, and the specific method comprises the following steps: take 100mL test reservoir D15Formation water and 20g test reservoir D15Is added to the dehydrated and degassed crude oilA container with stirring; then adding an activating agent and mixing uniformly; placing the container in a constant temperature incubator, and carrying out constant temperature culture for 15d, wherein the temperature of the constant temperature incubator is 65 ℃; the freezing point of the crude oil was tested after the incubation time was over, the results are shown in Table 13, and the activator formulation was determined based on the magnitude of the freezing point depression.
TABLE 13 freezing point depression results for different activators
As can be seen from table 13: the activator formulation 5 (sucrose 1.0%, peptone 0.3%, disodium hydrogen phosphate 0.03%) had the best pour point depressing effect, so the activator formulation was selected to be sucrose 1.0%, peptone 0.3%, disodium hydrogen phosphate 0.03%.
(4) Compounding chemical pour point depressant and activator to form a compound system
The compounding of the chemical pour point depressant and the activator comprises the following specific steps:
adding polyolefin chemical pour point depressant (mass concentration 5%) and activator (sucrose 1.0%, peptone 0.3%, disodium hydrogen phosphate 0.03%) in different proportions into a container with stirring, mixing uniformly to form a compound system, adding 5g of the total amount of the chemical pour point depressant and the activator, and adding 100ml of test oil reservoir D15Formation water and 100g test reservoir D15The dehydrated and degassed crude oil of (2); placing the container in a constant temperature incubator, and performing constant temperature culture for 15 days, wherein the temperature of the incubator is 65 ℃; and (3) testing the freezing point of the crude oil after the culture time is over, wherein the test result is shown in Table 14, and the optimal proportion of the chemical pour point depressant and the activator and the optimal compound system are screened out according to the amplitude of the freezing point depression.
TABLE 14 freezing point depression results for different formulation systems
As can be seen from table 14: the optimal ratio of the chemical pour point depressant to the activator is 4:1, so that the optimal selected complex ligand system is the chemical pour point depressant and the activator in the ratio of 4: 1.
(5) Compatibility evaluation of compounded system
Take 100mL test reservoir D15And adding 5g of the screened compound system with the optimal ratio of 4:1, uniformly mixing, standing for 30min, and finding that no settlement site appears in the compound system, which indicates that the screened compound system has good compatibility.
(6) Optimization of injection amount of compound system
The optimization of the injection amount of the compound system adopts a physical simulation experiment method, and the specific method comprises the following steps: filling permeability of 1100X 10-3μm2The sand-filled core; core vacuumizing and saturation test oil reservoir D15Calculating the pore volume PV of the rock core by using formation water; saturation test reservoir D15The dehydrated and degassed crude oil is saturated until the oil content in the output liquid of the core outlet is 100 percent, and the original oil saturation of the core is calculated; aging the core at 65 ℃ for 7 d; performing primary water drive until the water content at an outlet is 98.0 percent, and calculating the primary water drive recovery ratio; respectively injecting different amounts of compound systems; and (3) performing secondary water flooding after culturing for 20 days until the water content of an outlet is 100%, calculating the value of the enhanced recovery ratio, and determining the optimal injection amount of the compound system according to the value of the enhanced recovery ratio, wherein the test result is shown in table 15.
Table 15 enhanced recovery values for different injection rate formulation systems
| Serial number | Amount of injection, PV | Increase the harvest rate% |
| 1 | 0.1 | 10.2 |
| 2 | 0.2 | 16.6 |
| 3 | 0.3 | 18.2 |
| 4 | 0.4 | 18.5 |
As can be seen from table 15: the higher the injection amount of the compound system, the higher the value of the recovery rate is, but the increase of the value of the recovery rate is not obvious when the injection amount is more than 0.3PV, so the optimal injection amount of the compound system is 0.3 PV.
(7) On-site test and evaluation of Effect
And (3) performing a field test according to the injection quantity optimized in the steps, injecting the compound system from the injection well of the tested oil reservoir, evaluating the test effect after the field test, and inspecting the improved recovery rate value and the input-output ratio.
Reservoir D after completion of the field test15The comprehensive water content is reduced from 98.0% to 76.2%, the water content is reduced by 21.8%, and the crude oil yield is increased by 1.6725X 106t, the recovery ratio is improved by 17.3 percent, the input-output ratio is 1:13.2, and the field test effect is good.
Claims (9)
1. The method for improving the recovery ratio of the high pour-point oil reservoir is characterized by comprising the following steps:
(1) screening of test reservoirs
The screening of the test oil reservoir needs to meet two conditions that the temperature of the ① oil reservoir is less than 90 ℃, the formation water mineralization degree is less than 100000mg/L, the viscosity of ② crude oil is less than 10000mPa.s, the freezing point is less than 60 ℃, and the wax content is less than 40 percent;
(2) screening of chemical pour point depressant
The screening of the chemical pour point depressant comprises the two aspects of screening the type and the concentration of the chemical pour point depressant, wherein the screening of the type of the chemical pour point depressant is firstly carried out, and the screening of the concentration of the chemical pour point depressant is secondly carried out;
(3) screening for activators
The screening of the activating agent adopts a static culture method;
(4) compounding chemical pour point depressant and activator to form a compound system
The compounding of the chemical pour point depressant and the activator comprises the following specific steps:
adding chemical pour point depressants and activators in different proportions into a container with stirring, uniformly mixing to form a compound system, wherein the total amount of the chemical pour point depressants and the activators is 5g, and then adding 100ml of formation water of a test oil reservoir and 100g of dehydrated and degassed crude oil of the test oil reservoir; placing the container in a constant-temperature incubator, and performing constant-temperature culture for 5-15 days, wherein the temperature of the constant-temperature incubator is the temperature of the tested oil reservoir; testing the freezing point of the crude oil after the culture time is over, and screening out the optimal proportion of the chemical pour point depressant and the activator and the optimal compound system according to the amplitude of the freezing point depression;
(5) compatibility evaluation of compounded system
Taking 100mL of stratum water of a tested oil reservoir, adding 5g of the compound system with the screened optimal proportion, uniformly mixing, standing for 20-30 min, observing whether the compound system has sedimentation, evaluating the compatibility of the compound system according to the sedimentation phenomenon, and screening the compound system with good compatibility;
(6) optimization of injection amount of compound system
The optimization of the injection amount of the compound system adopts a physical simulation experiment method;
(7) on-site test and evaluation of Effect
And (3) performing a field test according to the injection quantity optimized in the steps, injecting the compound system from a water injection well of the tested oil reservoir, evaluating the test effect after the field test, and inspecting and improving the recovery rate value and the input-output ratio.
2. The method for enhanced oil recovery of a high pour point oil reservoir according to claim 1, wherein the screening of the chemical pour point depressant type is carried out by the following steps: adding 100g of dehydrated and degassed crude oil of a test oil reservoir and 5g of chemical pour point depressant into a triangular flask with the volume of 500ml while stirring; then placing the triangular flask in a constant-temperature water bath, wherein the water bath is heated at the temperature of the oil reservoir to be tested, and the triangular flask is heated for 0.5-1 h; and (5) testing the freezing point of the crude oil after the triangular flask is heated, and screening out the chemical pour point depressant with the largest freezing point depression amplitude.
3. The method for enhanced oil recovery of a high pour point oil reservoir according to claim 1 or 2, wherein the concentration of the chemical pour point depressant is selected by the following specific method: taking 100g of dehydrated and degassed crude oil of a tested oil reservoir and the screened chemical pour point depressant with different mass concentrations, and adding the mixture into a triangular flask with the volume of 500ml while stirring; then placing the triangular flask in a constant-temperature water bath, wherein the water bath is heated at the temperature of the oil reservoir to be tested, and the triangular flask is heated for 0.5-1 h; and (5) testing the freezing point of the crude oil after the triangular flask is heated, and screening out the optimal chemical pour point depressant concentration with the largest freezing point depression amplitude.
4. The method for enhanced oil recovery of a high pour point oil reservoir according to claim 1 or 2, wherein the chemical pour point depressant is one of a surfactant type and a polymer type pour point depressant.
5. The enhanced oil recovery method for high pour point oil reservoir according to claim 4, wherein the surfactant-type pour point depressant is petroleum sulfonate type or polyoxyethylene alkylamine; the polymer pour point depressant is one of long-chain alkyl naphthalene, polyester and polyolefin.
6. The enhanced oil recovery method for high pour-point oil reservoir according to claim 1, characterized in that the activator is screened by a static culture method, which comprises the following steps: adding 100mL of formation water of a test oil reservoir and 10-20g of dehydrated and degassed crude oil of the test oil reservoir into a container with a stirrer; then adding an activating agent and mixing uniformly; placing the container in a constant-temperature incubator, and performing constant-temperature culture for 5-15 days, wherein the temperature of the constant-temperature incubator is the temperature of the tested oil reservoir; and testing the freezing point of the crude oil after the culture time is over, and determining the formula of the activator according to the size of the freezing point depression amplitude.
7. The method for enhanced oil recovery of a high pour point oil reservoir according to claim 6, wherein the activator comprises a carbon source, a nitrogen source and a phosphorus source, wherein the carbon source is starch or sucrose, the nitrogen source is potassium nitrate or peptone, and the phosphorus source is dipotassium hydrogen phosphate or disodium hydrogen phosphate.
8. The method for enhanced oil recovery of a high pour-point oil reservoir according to claim 7, wherein the mass concentration of the carbon source is 1.0-3.0%, the mass concentration of the nitrogen source is 0.1-0.5%, and the mass concentration of the phosphorus source is 0.02-0.05%.
9. The enhanced oil recovery method for the high pour-point oil reservoir according to claim 1, characterized in that the optimization of the injection amount of the compound system adopts a physical simulation experiment method, and the specific method is as follows: filling a sand-filled rock core with the same permeability as the tested oil reservoir; vacuumizing the core, saturating formation water of the reservoir in the test, and calculating the pore volume of the core; the method comprises the following steps of (1) saturating dehydrated and degassed crude oil of an oil reservoir in a saturation test until the oil content in a produced liquid at a core outlet is 100%, and calculating the original oil saturation of a core; aging the core for 7d at the temperature of the test oil reservoir; performing primary water drive, and calculating the primary water drive recovery ratio until the outlet water content is consistent with the comprehensive water content of the test oil reservoir; respectively injecting different amounts of compound systems; and (4) performing secondary water drive after culturing for 15-20 days until the water content of an outlet is 100%, calculating the value of the enhanced recovery ratio, and determining the optimal injection amount of the compound system according to the value of the enhanced recovery ratio.
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