An inorganic gel blocking agent with delayed crosslinking, its preparation method and application

Abstract

This invention provides an inorganic gel plugging agent with delayed crosslinking, its preparation method, and its application. The inorganic gel plugging agent comprises 0.2–0.4 parts by weight of a salt-resistant polymer, 0.5–2 parts by weight of a silicate, and 0.1–0.4 parts by weight of a complex. By selecting the above three materials in combination, and utilizing the electrostatic repulsion of the cations in the salt-resistant polymer and the complexation effect of the complex, the gelation time of the inorganic gel plugging agent is prolonged. Therefore, when applied to plugging deep, high-permeability channel oilfields, it can expand the injected water wave and volume, effectively improving the oil recovery rate in waterflooding, which has significant research value.

Description

Technical Field

[0001] This invention belongs to the field of oilfield development technology, specifically relating to an inorganic gel plugging agent with delayed crosslinking, its preparation method, and its application. Background Technology

[0002] During deep well drilling, the temperature increases with the depth of the formation. As drilling progresses towards deeper wells, the drilling fluid remains in the formation for a longer period of time, which places more stringent requirements on the temperature resistance of drilling fluid treatment agents.

[0003] Currently, waterflooding is the main development method for oilfields. Long-term waterflooding and other factors have led to the formation of medium-to-high permeability large pores in underground reservoirs, resulting in inefficient and ineffective circulation of injected water. It is difficult to effectively displace a large amount of crude oil underground, resulting in high oilfield development and production costs and low efficiency. Deep fluid flow diversion and regulation technology is an important means to solve the problem of inefficient and ineffective circulation of water injection in waterflooded oilfields and improve the recovery rate of waterflooded development. CN109735314A discloses an organic-inorganic composite silicate high-temperature film-forming drilling fluid system. The drilling fluid system is composed of the following raw materials: bentonite-based slurry, viscosifier, filtration reducer, plugging agent, weighting agent, inorganic silicate, and organic silicate. The amount of each raw material is based on the weight of the bentonite-based slurry, with a mass fraction of 1-4% for the bentonite-based slurry, a concentration of 0.05-0.5 mol / L for the organic silicate, and a mass fraction of 0.1-5% for the inorganic silicate. This invention provides a silicate high-temperature film-forming drilling fluid system that improves the drilling fluid's ability to inhibit collapse, better meeting the needs of wellbore stability and safe drilling, and achieving the purposes of inhibition, plugging, and chemical wall solidification.

[0004] However, in high-salinity reservoirs, especially those with high calcium and magnesium ion content, the inorganic silicate gel plugging system provided in the prior art, including the invention mentioned above, will rapidly precipitate after silicates meet divalent metal ions. The gelation rate is difficult to control, and deep fluid flow diversion cannot be achieved, resulting in poor waterflooding development.

[0005] Therefore, in order to solve the above-mentioned technical problems, it is urgent to develop an inorganic gel blocking agent that can effectively delay gelation time. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an inorganic gel plugging agent with delayed crosslinking, its preparation method, and its application. This inorganic gel plugging agent, by selecting a combination of salt-resistant polymers, silicates, and complexes, utilizes the electrorepulsion of the salt-resistant polymers and the complexing effect of the complexes to effectively delay the gelation time of the inorganic gel plugging agent, thereby expanding the injected water sweep volume and effectively improving oil recovery. This has significant research value.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an inorganic gel blocking agent that delays crosslinking, wherein the inorganic gel blocking agent comprises the following components in parts by weight:

[0009] Salt-resistant polymer, 0.2–0.4 parts by weight;

[0010] Silicate 0.5 to 2 parts by weight;

[0011] The complex is 0.1 to 0.4 parts by weight.

[0012] The salt-resistant polymer can be 0.22 parts by weight, 0.24 parts by weight, 0.26 parts by weight, 0.28 parts by weight, 0.3 parts by weight, 0.32 parts by weight, 0.34 parts by weight, 0.36 parts by weight, or 0.38 parts by weight, etc.

[0013] The silicate can be 0.7 parts by weight, 0.9 parts by weight, 1.1 parts by weight, 1.3 parts by weight, 1.5 parts by weight, 1.7 parts by weight, or 1.9 parts by weight, etc.

[0014] The complex can be 0.15 parts by weight, 0.2 parts by weight, 0.25 parts by weight, 0.3 parts by weight, 0.35 parts by weight, or 0.4 parts by weight, etc.

[0015] The inorganic gel plugging agent provided by this invention comprises a specific proportion of salt-resistant polymer, silicate, and complex. By selecting and combining the above three materials, and utilizing the electrostatic repulsion between the cations and metal ions in the salt-resistant polymer and the complexing effect of the complex, the resulting inorganic gel plugging agent has a longer gelation time. Therefore, when applied to plugging deep high-permeability channels, it can expand the injected water wave and volume, thereby improving the oil recovery rate in waterflooding, which has significant research value.

[0016] Preferably, the raw materials for preparing the salt-resistant polymer include monomers, initiators, and deionized water.

[0017] Preferably, the monomer comprises any one or a combination of at least two of the following: acrylamide, acrylic acid, sodium 3-acrylamido-3-methylbutyrate (NaNMB), sodium 2-acrylamido-2-methylpropanesulfonate (AMPS), sodium p-styrenesulfonate (NaVBS), sodium vinylsulfonate, methacryloyloxyethyltrimethylammonium chloride (DMC), N,N-dimethyldiallylammonium chloride, acryloyloxyethyltrimethylammonium chloride (DAC), dodecyl dimethylallylammonium chloride, or octadecyl dimethylallylammonium bromide.

[0018] Preferably, the monomer comprises any one or a combination of at least two of acrylamide, sodium 3-acrylamido-3-methylbutyrate, sodium p-styrenesulfonate, or octadecyldimethylallylammonium bromide.

[0019] Preferably, the initiator comprises any one or a combination of at least two of ammonium persulfate, potassium persulfate, sodium metabisulfite, sodium sulfite, ethylenediamine, or triethylamine.

[0020] Preferably, the initiator includes triethylamine, potassium persulfate, and sodium metabisulfite.

[0021] Preferably, the silicate includes any one or a combination of at least two of sodium silicate, lithium silicate, potassium silicate, or magnesium aluminum silicate.

[0022] Preferably, the silicate comprises sodium silicate.

[0023] Preferably, the complex comprises any one or a combination of at least two of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium citrate, or sodium tartrate.

[0024] Preferably, the complex comprises sodium citrate and / or tetrasodium ethylenediaminetetraacetate.

[0025] Preferably, the inorganic gel sealing agent also includes water.

[0026] Preferably, the water content in the inorganic gel sealing agent is 97.2 to 99.2 parts by weight, such as 97.2 parts by weight, 97.4 parts by weight, 97.6 parts by weight, 97.8 parts by weight, 98 parts by weight, 98.2 parts by weight, 98.4 parts by weight, 98.6 parts by weight, 98.8 parts by weight, or 99 parts by weight.

[0027] In a second aspect, the present invention provides a method for preparing an inorganic gel blocker as described in the first aspect, the method comprising: mixing an anti-salt polymer, a silicate and a complex in water to obtain the inorganic gel blocker.

[0028] Thirdly, the present invention provides an application of the inorganic gel plugging agent as described in the first aspect in oilfield development.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The inorganic gel blocking agent provided by the present invention comprises 0.2-0.4 parts by weight of salt-resistant polymer, 0.5-2 parts by weight of silicate, and 0.1-0.4 parts by weight of complex. By selecting the above three materials for combination, it has a longer gelation time. Specifically, based on a concentration of 10×10 4 mg / L of simulated saline (Ca 2+=4000mg / L), at 80℃, compared with conventional HPAM polymer plugging agent, it can delay the gelation time of inorganic gel by up to 7 hours;

[0031] (2) The inorganic gel plugging agent provided by this invention also has high deep migration and plugging performance. Specifically, based on 10×10 4 mg / L of simulated saline (Ca 2+ =4000mg / L), using a sand-filled tube 100cm long and 2.5cm in diameter (divided into three sections: the first end L1, the middle section L2, and the last end L3). Because the inorganic gel sealing agent provided by this invention has shielding and complexing effects, it reduces the reaction between silicates and Ca. 2+ The opportunity for contact gelation occurs, and as the inorganic gel plugging agent migrates within the core, the cationic groups in the salt-resistant polymer of the inorganic gel plugging agent adsorb and retain the negatively charged quartz sand, weakening the shielding effect of the salt-resistant polymer and allowing silicates to react with Ca. 2+ Rapid gel formation; compared with simulated brine, it can achieve deep migration and sealing, and expand the volume of injected water. The sealing system prepared by simulated brine + silicate is mainly used for sealing in the L1 section of the sand-filled pipe, and only a small part of it is used for sealing in the L3 section, with poor deep migration effect. Detailed Implementation

[0032] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0033] Preparation Example 1

[0034] A salt-resistant polymer is prepared by means of: sequentially adding 72.7 parts by weight of deionized water, 20 parts by weight of acrylamide, 3 parts by weight of sodium 3-acrylamido-3-methylbutyrate (NaNMB), 2 parts by weight of sodium p-styrenesulfonate, and 2 parts by weight of octadecyldimethylallylammonium bromide to a stoppered wide-mouth bottle; purging with nitrogen gas for 20 min; controlling the polymerization temperature at 15°C; adding 0.3 parts by weight of triethylamine, 0.2 parts by weight of potassium persulfate, and 0.1 parts by weight of sodium metabisulfite; continuing to purge with nitrogen gas for 10 min; and performing the polymerization reaction for 4 h; granulating the polymer colloid; drying at 70°C for 4 h; and passing through a 50-mesh standard sieve to obtain the salt-resistant polymer.

[0035] Preparation Example 2

[0036] A salt-resistant polymer is prepared by means of: sequentially adding 71.6 parts by weight of deionized water, 20 parts by weight of acrylamide, 3 parts by weight of sodium 3-acrylamido-3-methylbutyrate (NaNMB), 3 parts by weight of sodium p-styrenesulfonate, and 2 parts by weight of octadecyldimethylallylammonium bromide to a stoppered wide-mouth bottle; purging with nitrogen gas for 20 min; controlling the polymerization temperature at 15°C; adding 0.4 parts by weight of triethylamine, 0.26 parts by weight of potassium persulfate, and 0.13 parts by weight of sodium metabisulfite; continuing to purge with nitrogen gas for 10 min; performing the polymerization reaction for 4 h; granulating the polymer colloid; drying at 70°C for 4 h; and passing through a 50-mesh standard sieve to obtain the salt-resistant polymer.

[0037] Preparation Example 3

[0038] A salt-resistant polymer is prepared by means of: sequentially adding 89.6 parts by weight of deionized water, 20 parts by weight of acrylamide, 4 parts by weight of sodium 3-acrylamido-3-methylbutyrate (NaNMB), 3 parts by weight of sodium p-styrenesulfonate, and 3 parts by weight of octadecyldimethylallylammonium bromide to a stoppered wide-mouth bottle; purging with nitrogen for 20 min; controlling the polymerization temperature at 15°C; adding 0.4 parts by weight of triethylamine, 0.26 parts by weight of potassium persulfate, and 0.13 parts by weight of sodium metabisulfite; continuing to purge with nitrogen for 10 min; performing the polymerization reaction for 4 h; granulating the polymer colloid; drying at 70°C for 4 h; and passing through a 60-mesh standard sieve to obtain the salt-resistant polymer.

[0039] Preparation Example 4

[0040] A salt-resistant polymer is prepared by means of: sequentially adding 89.6 parts by weight of deionized water, 20 parts by weight of acrylamide, 4 parts by weight of sodium 3-acrylamido-3-methylbutyrate (NaNMB), 3 parts by weight of sodium p-styrenesulfonate, and 2 parts by weight of octadecyldimethylallylammonium bromide to a stoppered wide-mouth bottle; purging with nitrogen for 20 min; controlling the polymerization temperature at 15°C; adding 0.5 parts by weight of triethylamine, 0.32 parts by weight of potassium persulfate, and 0.16 parts by weight of sodium metabisulfite; continuing to purge with nitrogen for 10 min; performing the polymerization reaction for 4 h; granulating the polymer colloid; drying at 70°C for 4 h; and passing through a 40-mesh standard sieve to obtain the salt-resistant polymer.

[0041] Example 1

[0042] An inorganic gel blocking agent with delayed cross-linking is prepared by means of: adding 99.2 parts by weight of a 10×10⁻⁶ solution to a 250 mL beaker. 4 mg / L of simulated saline (Ca 2+=4000mg / L), turn on the electric stirrer, add 0.1 parts by weight of tetrasodium ethylenediaminetetraacetate, 0.2 parts by weight of salt-resistant polymer (Preparation Example 1) and 0.5 parts by weight of sodium silicate in sequence, stir continuously for 60 min until completely dissolved, pour into a 100mL blue cap reagent bottle and place in an 80℃ water bath to obtain the delayed crosslinking inorganic gel blocking agent.

[0043] Example 2

[0044] An inorganic gel blocking agent with delayed cross-linking is prepared by means of: adding 98.5 parts by weight of a 10×10⁻⁶ concentration to a 250 mL beaker. 4 mg / L of simulated saline (Ca 2+ =4000mg / L), turn on the electric stirrer, add 0.2 parts by weight of sodium citrate, 0.3 parts by weight of salt-resistant polymer (Preparation Example 2) and 1 part by weight of sodium silicate in sequence, stir continuously for 60 min until completely dissolved, pour into a 100mL blue cap reagent bottle and place in an 80°C water bath to obtain the delayed crosslinking inorganic gel blocking agent.

[0045] Example 3

[0046] An inorganic gel blocking agent with delayed cross-linking is prepared by means of: adding 98.3 parts by weight of a 10×10⁻⁶ solution to a 250 mL beaker. 4 mg / L of simulated saline (Ca 2+ =4000mg / L), turn on the electric stirrer, add 0.3 parts by weight of sodium citrate, 0.4 parts by weight of salt-resistant polymer (Preparation Example 3) and 1 part by weight of sodium silicate in sequence, stir continuously for 60 min until completely dissolved, pour into a 100mL blue cap reagent bottle and place in an 80°C water bath to obtain the delayed crosslinking inorganic gel blocking agent.

[0047] Example 4

[0048] An inorganic gel blocking agent with delayed cross-linking is prepared by means of: adding 97.2 parts by weight of a 10×10⁻⁶ solution to a 250 mL beaker. 4 mg / L of simulated saline (Ca 2+ =4000mg / L), turn on the electric stirrer, add 0.4 parts by weight of sodium citrate, 0.4 parts by weight of salt-resistant polymer (Preparation Example 4) and 2 parts by weight of sodium silicate in sequence, stir continuously for 60 min until completely dissolved, pour into a 100mL blue cap reagent bottle and place in an 80°C water bath to obtain the delayed crosslinking inorganic gel blocking agent.

[0049] Comparative Example 1

[0050] An inorganic gel blocking agent differs from Example 1 only in that the amount of salt-resistant polymer added is 0.5 parts by weight and the amount of sodium silicate added is 0.2 parts by weight. The other components, amounts and preparation methods are the same as in Example 1.

[0051] Comparative Example 2

[0052] An inorganic gel blocking agent differs from Example 1 only in that the amount of salt-resistant polymer added is 0.1 parts by weight and the amount of sodium silicate added is 0.6 parts by weight. The other components, amounts and preparation methods are the same as in Example 1.

[0053] Comparative Example 3

[0054] An inorganic gel blocking agent, which differs from Example 1 only in that the salt-resistant polymer provided in Preparation Example 1 is replaced with HPAM polymer, while the other components, amounts and preparation methods are the same as in Example 1.

[0055] Performance testing:

[0056] (1) Delayed gelation properties:

[0057] The gelation time of the inorganic gel blocking agents provided in Examples 1-4 and Comparative Examples 1-3 was tested at 80°C, and the test results are shown in Table 1.

[0058] Table 1

[0059] Delay gelation time / h Example 1 4 Example 2 6 Example 3 7 Example 4 6 Comparative Example 1 3 Comparative Example 2 5 Comparative Example 3 3.2

[0060] (2) Deep migration and sealing performance:

[0061] Quartz sand of 60-100 mesh was used to fill a sand-filled tube 100 cm long and 2.5 cm in diameter. The sand-filled tube had four pressure measurement points (the two middle pressure measurement points were located at the inlet and 30 cm from the end of the sand-filled tube, respectively). Simulated brine was injected into the sand-filled tube at a rate of 0.5 mL / min to measure its permeability before plugging. Then, 1 / 3 PV polymer solution, 1 / 3 PV delayed crosslinking inorganic gel plugging agent, and 1 / 3 PV 1% sodium silicate solution were injected into the sand-filled tube respectively. The two ends of the core tube were sealed and placed in an 80℃ drying oven for 24 h. Then, 1 / 3 PV simulated brine was injected at a rate of 0.5 mL / min to displace the core tube and to investigate the deep migration and plugging performance of the system.

[0062] The inorganic gel blocking agents provided in Examples 1-4 and Comparative Examples 1-2 were tested according to the above test methods. The test results are shown in Table 2.

[0063] Table 2

[0064]

[0065]

[0066] Note: The permeability of segment L1 is calculated by the pressure difference between P1 and P2 and the length of L1; the permeability of segment L2 is calculated by the pressure difference between P3 and P2 and the length of L2; and the permeability of segment L3 is calculated by the pressure difference between P3 and P4 and the length of L3.

[0067] Based on the data in Tables 1 and 2, it can be seen that:

[0068] First, the inorganic gel blocking agent provided by this invention exhibits excellent delayed gelation properties. This is because the salt-resistant polymer used has a chain hydrophobic group association effect, resulting in higher apparent viscosity and greater molecular motion resistance compared to conventional HPAM. Furthermore, the shielding effect of the cationic groups on the polymer chain reduces the adhesion between silicates and calcium to a certain extent. 2+ The increased contact opportunities delayed the gelation time of the inorganic silicate system, while the complexing agent it contained affected Ca. 2+ The complexation effect further slowed down the gelation rate of the inorganic gel blocker;

[0069] Secondly, the inorganic gel plugging agent provided by this invention exhibits excellent deep migration and plugging performance. After the inorganic gel plugging agent and silicate are injected into the sand-filled pipe, the shielding effect of the cationic groups in the salt-resistant polymer of the inorganic gel plugging agent provided by this invention, as well as the complexing effect of the complex, reduces the reaction between silicate and Ca. 2+ Opportunity for contact gelation; as the salt-resistant polymer migrates within the core, the polymer's cationic groups adsorb and retain the negatively charged quartz sand, weakening the shielding effect of the salt-resistant polymer, and allowing silicates and Ca... 2+ The gel forms rapidly, and the inorganic gel plugging agent provided by this invention has high plugging performance in both L2 and L3 segments, while the comparative ratio is relatively weak, exhibiting poor deep migration plugging performance.

[0070] Finally, comparing the data from Example 1 and Comparative Examples 1-3, it can be seen that the inorganic gel plugging agent with a higher amount of salt-resistant polymer added (Comparative Example 1) has better gelation delay performance, but the plugging performance is worse due to the lower amount of silicate added; the inorganic gel plugging agent with a lower amount of salt-resistant polymer added (Comparative Example 2) will result in poorer gelation delay performance; and the plugging agent prepared from the HPAM polymer provided in Comparative Example 3 has poor gelation delay performance and poor plugging performance.

[0071] The applicant declares that this invention illustrates an inorganic gel blocking agent that can effectively delay gelation time, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials in the product of this invention, the addition of auxiliary components, and the selection of specific methods, all fall within the protection and disclosure scope of this invention.

Claims

1. An inorganic gel blocking agent that delays cross-linking, characterized in that, The inorganic gel sealing agent comprises the following components in parts by weight: Salt-resistant polymer, 0.2~0.4 parts by weight; Silicate 0.5~2 parts by weight; 0.1 to 0.4 parts by weight of the complex; The raw materials for preparing the salt-resistant polymer include monomers, initiators, and deionized water; The monomers are acrylamide, sodium 3-acrylamido-3-methylbutyrate, sodium p-styrenesulfonate, and octadecyl dimethylallyl ammonium bromide; The silicate includes any one or a combination of at least two of sodium silicate, lithium silicate, and potassium silicate.

2. The inorganic gel blocking agent according to claim 1, characterized in that, The initiator comprises a combination of triethylamine, potassium persulfate, and sodium metabisulfite.

3. The inorganic gel blocking agent according to claim 1, characterized in that, The silicate includes sodium silicate.

4. The inorganic gel sealing agent according to claim 1, characterized in that, The complex comprises any one or a combination of at least two of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium citrate, or sodium tartrate.

5. The inorganic gel sealing agent according to claim 4, characterized in that, The complex comprises sodium citrate and / or tetrasodium ethylenediaminetetraacetate.

6. The inorganic gel blocking agent according to claim 1, characterized in that, The inorganic gel sealing agent also includes water.

7. The inorganic gel blocking agent according to claim 6, characterized in that, The inorganic gel sealing agent contains 97.2 to 99.2 parts by weight of water.

8. A method for preparing an inorganic gel blocking agent as described in any one of claims 1 to 7, characterized in that, The preparation method includes: mixing the salt-resistant polymer, silicate and complex in water to obtain the inorganic gel blocker.

9. The application of an inorganic gel plugging agent as described in any one of claims 1 to 7 in oilfield development.

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