CN115873569A - Gel formation accelerant for profile control agent and application of gel formation accelerant in gel profile control agent - Google Patents
Gel formation accelerant for profile control agent and application of gel formation accelerant in gel profile control agent Download PDFInfo
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- CN115873569A CN115873569A CN202211153998.XA CN202211153998A CN115873569A CN 115873569 A CN115873569 A CN 115873569A CN 202211153998 A CN202211153998 A CN 202211153998A CN 115873569 A CN115873569 A CN 115873569A
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Abstract
The invention belongs to the technical field of profile control of oil fields, and particularly relates to a gel formation accelerant for a profile control agent and application of the gel formation accelerant in a gel profile control agent. The gel formation accelerant for the profile control agent comprises bicarbonate radical inorganic salt and thiourea according to the mass ratio (10-20): 1. In the case of oil field reinjection sewage, the viscosity of the polymer and cross-linking agent system is reduced along with the prolonging of time. The profile control agent system can enhance the degree of crosslinking reaction along with the addition of the promoter, finally form high-strength gel, meet the profile control requirement of an oil field, and enhance the adaptability of on-site profile control construction.
Description
Technical Field
The invention belongs to the technical field of profile control of oil fields, and particularly relates to a gel formation accelerant for a profile control agent and application of the gel formation accelerant in a gel profile control agent.
Background
The profile control technology ensures and improves the field application effect of chemical flooding, and becomes an important matching technology for improving the chemical flooding development effect. In chemical flooding applications, the use of a profile control agent to control the profile can serve the following functions: firstly, longitudinal and plane heterogeneity caused by long-term water injection scouring is relieved, and integral profile control needs to be carried out before chemical flooding. Secondly, the polymer channeling in the chemical flooding process seriously influences the oil displacement effect of the polymer and the profile control and channeling sealing must be carried out. Thirdly, the polymer slug is easy to be quickly broken through by the follow-up water drive, and the integral depth profile control should be carried out in time when the polymer injection is finished. At present, the research and application of deep profile control technology at home and abroad make great progress, and the adopted profile control agent is basically gel and mainly comprises three types: polyacrylamides, xanthan gums and pre-crosslinked bulk-expanded particles.
Among them, polyacrylamide profile control agents are the most widely used deep profile control system in oil fields at the earliest research. The main agent is polyacrylamide with the molecular weight of 500-2500 ten thousand and the concentration of 1500-5000 mg/L, the cross-linking agent is mainly a complex system of chromium salt or aluminum salt of polyvalent metal ions (trivalent chromium acetate, chromium lactate, aluminum citrate and the like), and the concentration of the cross-linking agent is 100-500 mg/L. Polyacrylamide and a chromium ion cross-linking agent form three-dimensional network structure body gel taking a polymer molecular chain as branches by intermolecular cross-linking reaction, and the three-dimensional network structure body gel blocks highly water-absorbing high-permeability intervals or large channels by physical blocking, adsorption and hydrodynamic trapping, so that the flow of subsequent fluid is forced to turn, and the sweep efficiency is improved. The gel forming process is influenced by the concentration and viscosity of the cross-linking agent and the polymer, and the higher the concentration of the cross-linking agent is, the higher the viscosity of the polymer concentration is, and the higher the gel forming strength is. Conversely, the lower the gel strength.
In the practice of profile control in oil fields, the profile control agent is generally prepared by using oil field reinjection sewage as a solvent in consideration of the water consumption and the influence on the environment. The oilfield reinjection wastewater is complex in composition, contains various ionic components, organic impurities, sulfur content, sulfate reducing bacteria, oil stains, iron rust and the like, and the components can influence the formation of gel and the strength of the gel. When the existing gel system is continuously used for profile control, no gel is formed or the viscosity of the system is reduced, and the expected changes of the casing pressure and the oil pressure do not occur during operation, so that the failure of the profile control operation is caused.
Disclosure of Invention
The invention aims to provide a gel formation accelerant for a profile control agent, which can solve the problems of no gelling or viscosity reduction of a gel system when the profile control agent is prepared by reinjection sewage of an oil field.
The second purpose of the invention is to provide the application of the gel formation accelerant in the gel profile control agent, so as to further improve the gel forming effect of the gel profile control agent when the oil field reinjection sewage is used.
In order to realize the technical scheme, the technical scheme adopted by the invention is as follows:
a gel formation accelerant for a profile control agent comprises bicarbonate radical inorganic salt and thiourea according to the mass ratio (10-20): 1.
Ionic components, organic impurities, sulfur content, sulfate reducing bacteria, oil stains, iron rust and other components in the field reinjection wastewater can have adverse effects on gelling of a gel system. Among them, elemental sulfur and its compounds can cause the molecular chain of the polymer to be broken, resulting in the viscosity of the polymer to be reduced and a stable three-dimensional network structure not to be formed. Ferric ions can be introduced into the rust, and according to the Stern double-layer model theory, the ferric ions can compress the double layers of the polymer, so that the molecular chains of the polymer are curled, and a stable three-dimensional network structure cannot be formed. Under the combined influence of the above substances, the polymer viscosity shows a tendency to decrease and the polymer ligands decrease, so that no gel is formed.
The present invention promotes the crosslinking reaction between the polymer and the crosslinking agent by using a gel formation promoter, based on the tendency of the viscosity of the polymer and crosslinking agent system to decrease over time. The profile control agent system can enhance the degree of crosslinking reaction along with the addition of the accelerator, finally form high-strength gel, meet the profile control requirements of oil fields, and enhance the adaptability of on-site profile control construction.
The mechanism of the gel formation promoter for profile control agent of the invention for enhancing gel strength comprises the following three aspects:
(1) The crosslinking process of polyacrylamide and chromium ion crosslinking agent is Cr 3+ The electron arrangement providing empty orbitals, COO in the polymer chain - Has conjugated electron pair to form stable Cr 3+ The polymer molecular chain is stable three-dimensional reticular macromolecular chelate of ligand as the core. After the bicarbonate radical inorganic salt is added, the Cr is 3+ More coordinated electron pairs are provided, and meanwhile, bicarbonate ions can combine with water molecules and hydrogen bonds in polymer molecular chains, so that a three-dimensional network structure becomes more compact, and the viscosity becomes larger after crosslinking.
(2) The pH of the solution was changed after addition of the bicarbonate inorganic salt. For chromium ion, cr is present at a lower pH (pH 4-6) 3+ The polynuclear hydroxyl bridged ions are disintegrated and easily form Cr 3+ Complexing ions; when the pH value is increased, chromium ions (pH: 6-8) dihydrate or chromium ions (pH: 8-10) trihydrate are easily formed. However, for polymers, the pH increase makes the solution more basic and can promote hydrolysis of amide groups in the polymer molecules to COO - Is Cr 3+ The empty orbitals provide more ligands and thus form a stronger three-dimensional network.
(3) Thiourea can consume oxidizing substances and has a certain protection effect on the viscosity of the polymer.
To further reduce reagent costs, preferably the inorganic bicarbonate salt is sodium bicarbonate.
The use of the above-mentioned gel formation accelerator for profile control agents in gel-type profile control agents.
The gel formation accelerant for the profile control agent can be used on the basis of not changing the original gel system formula, is simple in use process, obviously improves the gel forming strength of the profile control agent, and further improves the use effect and the applicability of the profile control agent.
Preferably, the gel profile control agent uses oil field reinjection sewage, and the application is to prevent the gel viscosity of the gel profile control agent from being reduced due to the oil field reinjection sewage. Because the condition that the oil field reinjection sewage is used in the current oil field exploitation is common, the gel system can be effectively prevented from gelling or gelling viscosity from being rapidly reduced due to the oil field reinjection sewage by using the accelerator.
Preferably, the gel profile control agent uses oil field reinjection sewage, and the application is to increase the gelling viscosity of the gel profile control agent. The accelerator can be added according to the requirement of gel forming viscosity.
Preferably, the gel profile control agent uses oil field reinjection sewage, and the application is to accelerate the gelling speed of the gel profile control agent. The accelerator can be added according to the requirement of gelling speed.
Preferably, the gel formation promoter is added to the gel profile control agent to a final concentration of 1000 to 3500mg/L. The gel forming accelerator is within the above range, and the requirements on the gelling viscosity and speed can be met.
Preferably, the gel profile control agent is a polyacrylamide profile control agent, the main agent of the polyacrylamide profile control agent is polyacrylamide, and the cross-linking agent is an organic chromium cross-linking agent. The gel profile control agent is a profile control agent variety with low cost and the most wide application range.
Further preferably, in the polyacrylamide profile control agent, the final concentration of the polyacrylamide is 1500-5000 mg/L, and the final concentration of the organic chromium crosslinking agent is 100-500 mg/L. More preferably, the molecular weight of the polyacrylamide is 500 to 2500 ten thousand. More preferably, the molecular weight of the polyacrylamide is 1600-2500 ten thousand, and the molecular weight is 25-30%. The polyacrylamide profile control agent within the parameter range can meet the use requirements of most oil fields, and the gel forming accelerant has very remarkable improvement effect on the polyacrylamide profile control agent.
Detailed Description
The following describes the practice of the present invention in detail with reference to specific examples.
1. Specific examples of the gel formation accelerator for profile control agents of the present invention are as follows:
example 1
The gel formation accelerator for the profile control agent comprises sodium bicarbonate and thiourea in a mass ratio of 10.
Example 2
The gel formation accelerator for the profile control agent comprises sodium bicarbonate and thiourea in a mass ratio of 15.
Example 3
The gel formation accelerator for the profile control agent comprises sodium bicarbonate and thiourea in a mass ratio of 20.
2. Comparative example
Comparative example 1
In the application of oil field gel profile control, well mouth sampling is carried out on a high-concentration crosslinking system formula and a low-concentration crosslinking system formula, and the change of the viscosity of the crosslinking systems with different concentrations along with time is detected.
The high-concentration crosslinking system comprises the following components: the concentration of the polymer is 1600mg/L, the concentration of the cross-linking agent is 150mg/L, and the solvent is oil field reinjection sewage. The formula of the low-concentration crosslinking system comprises: the polymer concentration is 1200mg/L, the cross-linking agent concentration is 100mg/L, and the solvent is oil field reinjection sewage. Wherein the polymer is polyacrylamide with molecular weight of 2500 ten thousand and hydrolysis degree of 30%, and the cross-linking agent is organic chromium cross-linking agent which is purchased from Shandongdeshi group. The sulfur content of the oil field reinjection sewage is 2mg/L, and the oxygen content is 1mg/L.
The viscosity changes of the cross-linked systems at different concentrations are shown in Table 1 below.
TABLE 1 viscosity of Polymer and crosslinker as a function of time
From the results in table 1, it is understood that the polymer and the crosslinking agent cannot effectively cause a crosslinking reaction and the wellhead sample does not gel due to the influence of ionic components in the oilfield reinjection wastewater, the influence of impurities, sulfur content, sulfate reducing bacteria, oil stain and rust.
Comparative example 2
In this comparative example, a reagent composed of NaCl and thiourea in a mass ratio of 10:1 was added as an additive to a profile control system (1200 mg/L P × 100g/L J, where P is a polymer and J is a crosslinking agent), and the profile control effect was examined, and the results are shown in table 2.
TABLE 2 Profile control Effect of control reagents
As can be seen from the results in table 2, the addition of NaCl + thiourea (ratio 10. The reasons for this are two: firstly, the chloride ions can not provide conjugated electron pairs, thereby promoting the three-dimensional network gel structure to become more compact. Secondly, the addition of sodium chloride can not change the pH value and thus can not provide more COO - A group.
3. Experimental example application of gel formation accelerator in gel profile control agent
Experimental example 1 application in high concentration crosslinking system formulation
On the premise that the polymer and the crosslinking agent are consistent with those of comparative example 1, the influence of the gel formation accelerator on the viscosity of the high-concentration crosslinking system formula is examined, wherein the high-concentration crosslinking system formula comprises the following components: the concentration of the polymer is 1600mg/L, the concentration of the cross-linking agent is 150mg/L, and the solvent is oil field reinjection sewage.
The viscosity of the gel formation accelerator of example 1 added to the high concentration crosslinking system at various concentrations (1000 to 3500 mg/L) as a function of time is shown in Table 3 below.
TABLE 3 Effect of the addition of different concentrations of gel formation Accelerator in high concentration crosslinking systems on viscosity
The concentration of the accelerator is 0, namely, the gel cannot be formed when no gel accelerator is added in the system. The gel strength is expressed in terms of viscosity, the greater the gel strength, the higher the viscosity, and vice versa. The results in Table 3 show that the gel formation accelerator of example 1 was added at a concentration of 1500mg/L, which results in a reduction in gel formation time (1-2 hours) and a high gel strength. The gel viscosity (gel strength) increases with further increase in the addition concentration.
Experimental example 2 application in formulation of crosslinking system at low concentration
The effect of the gel formation accelerator on the viscosity of the low-concentration crosslinking system formulation, consisting of: the concentration of the polymer is 1200mg/L, the concentration of the cross-linking agent is 100mg/L, and the solvent is oil field reinjection sewage.
The viscosity of the gel formation accelerator of example 1 was varied with time as shown in Table 4 below by adding the gel formation accelerator to a low concentration crosslinking system at various concentrations (1000 to 3500 mg/L).
TABLE 4 Effect of the addition of different concentrations of gel-forming accelerator on viscosity in Low concentration crosslinking systems
From the results shown in Table 4, it was found that the gel formation accelerator of example 1 rapidly gelled in 2 hours when the addition concentration was 1500mg/L or more, and the gelling viscosity increased with further increase in the addition concentration.
Experimental example 3
Polymer flooding well pattern control reserve of 155 multiplied by 10 for certain block of Henan oilfield 4 Ton, design the injection well 20. Designing a front edge profile control slug structure: front slug 0.06PV (polymer concentration 1200mg/L chromium crosslinker 100 mg/L). Early wellhead sampling detection shows that the viscosity is very low after the profile control slug is 24 hours, and the expected requirement is not met.
In the early injection process, under the influence of ionic components, impurities, sulfur content, sulfate reducing bacteria, oil stain and rust in oilfield reinjection sewage, the wellhead sampling time is 24 hours, the viscosity is very low, namely the polymer and the crosslinking agent do not form a stable three-dimensional network structure. None of the 20 well samples gelled (viscosity did not rise significantly). The water quality detection result shows that: sulfate Reducing Bacteria (SRB), S 2- The numerical values of several indexes of the content, the suspended solid content and the oil content are greatly changed, and most results exceed the standard for a long time, for example, the detection result of the sulfate reducing bacteria reaches 1400-2000/L. The presence of these substancesThe gelling effect of the polymer system is severely crosslinked.
After the gel formation accelerator (with the addition concentration of 1500 mg/L) in example 1 is added into a polymer cross-linking agent system in the later stage, the gelling viscosity is greatly increased, the overall viscosity is increased by about 10 times (gelling viscosity comparison is carried out for 24 h), and a stable three-dimensional network structure with high strength is formed.
The gel-forming viscosity change of each well before and after addition of the gel-forming accelerator of example 1 is shown in table 5, and the change in casing pressure and oil pressure is shown in table 6.
TABLE 5 Change in gel-forming viscosity before and after addition of the gel-forming accelerator of example 1
TABLE 6 Change in oil and casing pressure before and after addition of the gel formation Accelerator of example 1
From the results in tables 5 and 6, it is understood that 10 days after the gel-forming accelerator of example 1 was added during the application in the mine, the average increase in casing pressure of the profile control well was 0.6MPa and 2.1MPa at the maximum, the average increase in oil pressure was 0.8MPa and 3.3MPa at the maximum, and a good underground gel formation state was exhibited, and the production state continued to progress in a good direction.
Claims (10)
1. A gel formation accelerator for a profile control agent is characterized by comprising a bicarbonate radical inorganic salt and thiourea in a mass ratio of (10-20): 1.
2. The gel formation accelerator according to claim 1, wherein the bicarbonate inorganic salt is sodium bicarbonate.
3. Use of the gel formation accelerator for profile control agent according to claim 1 or 2 in a gel-type profile control agent.
4. The use of claim 3, wherein the gel-based profile control agent uses oilfield reinjection sewage, and the use is to prevent a gelling viscosity reduction of the gel-based profile control agent caused by oilfield reinjection sewage.
5. The use of claim 3, wherein the gel-based profile control agent uses oilfield reinjection wastewater, and wherein the use is to increase the gel-forming viscosity of the gel-based profile control agent.
6. The use of claim 3, wherein the gel-based profile control agent uses oilfield reinjection wastewater, and wherein the use is to accelerate the gelling rate of the gel-based profile control agent.
7. The use according to any one of claims 3 to 6, wherein the gel formation enhancer is added to the gel-based profile control agent to a final concentration of 1000 to 3500mg/L.
8. The use of claim 7, wherein the gel profile control agent is a polyacrylamide profile control agent, the main agent of the polyacrylamide profile control agent is polyacrylamide, and the cross-linking agent is an organic chromium cross-linking agent.
9. The use of claim 8, wherein the polyacrylamide profile control agent has a final polyacrylamide concentration of 1500 to 5000mg/L and the organic chromium crosslinking agent has a final concentration of 100 to 500mg/L.
10. The use according to claim 9, wherein the polyacrylamide has a molecular weight of 500 to 2500 ten thousand.
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| CN202211153998.XA CN115873569A (en) | 2022-09-21 | 2022-09-21 | Gel formation accelerant for profile control agent and application of gel formation accelerant in gel profile control agent |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1632042A (en) * | 2004-12-01 | 2005-06-29 | 大庆油田有限责任公司 | Phase permeability modifying agent and method for improving recovery efficiency of crude oil by using same |
| CN102174317A (en) * | 2011-03-09 | 2011-09-07 | 大庆润海科技发展有限公司 | Profile control agent suitable for ASP flooding |
| CN104371680A (en) * | 2014-10-13 | 2015-02-25 | 中国石油天然气股份有限公司 | Depth profile control agent applicable to low permeability oilfield wastewater reinjection |
| CN105733537A (en) * | 2016-03-22 | 2016-07-06 | 沈阳华盈环保材料有限公司 | Gel water shut-off and profile control agent and preparation method thereof |
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2022
- 2022-09-21 CN CN202211153998.XA patent/CN115873569A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1632042A (en) * | 2004-12-01 | 2005-06-29 | 大庆油田有限责任公司 | Phase permeability modifying agent and method for improving recovery efficiency of crude oil by using same |
| CN102174317A (en) * | 2011-03-09 | 2011-09-07 | 大庆润海科技发展有限公司 | Profile control agent suitable for ASP flooding |
| CN104371680A (en) * | 2014-10-13 | 2015-02-25 | 中国石油天然气股份有限公司 | Depth profile control agent applicable to low permeability oilfield wastewater reinjection |
| CN105733537A (en) * | 2016-03-22 | 2016-07-06 | 沈阳华盈环保材料有限公司 | Gel water shut-off and profile control agent and preparation method thereof |
Non-Patent Citations (1)
| Title |
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| 张振超; 刘立新; 章磊; 杨明全: "铬交联部分水解聚丙烯酰胺弱凝胶的剪切性能研究", 化工科技, vol. 24, no. 4, pages 53 - 56 * |
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