Preparation method of phase permeability improver for gas well water control, improver and application thereof

Abstract

The present invention belongs to the technical field of gas well water control agents and preparation methods thereof, and specifically relates to a preparation method and improver of a phase permeability improver for gas well water control, and its application, aiming to solve the problems of salt resistance and poor selectivity of phase permeability change in existing phase permeability improvers. The preparation method of the improver comprises the following steps: step one: adding itaconic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hexadecyldimethylallyl ammonium chloride, and diallyldimethylammonium chloride to a reaction vessel, dissolving the above five monomers in water, drying and grinding to obtain a phase permeability improver main agent; step two: dissolving the phase permeability improver main agent in water to prepare a main agent solution with a concentration of 0.2-0.5%; step three: adding a metal cross-linking agent to the main agent solution, and obtaining a phase permeability improver gel after the reaction. The improver has strong salt resistance, expands in contact with water, reduces permeability, and has little change in contact with gas permeability, meeting the needs of water-containing gas stratum water control fracturing construction.

Description

Technical Field

[0001] The invention belongs to the technical field of gas well water control agents and preparation methods thereof, and particularly relates to a preparation method of a phase permeability improver for gas well water control, the improver and application thereof. Background Art

[0002] As exploration and development of large gas fields deepen, the proportion of water-bearing reservoirs is increasing. High water saturation within these reservoirs leads to significant water production during gas testing, resulting in poor fracturing effectiveness. For reservoirs with a water layer at the bottom vertically, existing technologies such as fracture height control and pulverized clay sedimentation are unable to effectively control formation water production, resulting in formation water production and impacting gas production. Water control agents are generally added during fracturing to control post-fracturing water production.

[0003] Chinese patent CN102120929A provides a method for preparing a gas well water control agent, which reduces water permeability by over 80% and limits the reduction in gas permeability to under 20%. Chinese patent CN102093880A provides an oil well water control agent and its preparation method, which reduces water permeability by over 70% and limits the impact on oil permeability to under 20%. Currently commonly used permeability improvers have shortcomings such as salt tolerance and poor selectivity in permeability modification, and their performance needs to be further improved. Summary of the Invention

[0004] The invention provides a preparation method of a phase permeability improver for gas well water control, so as to alleviate the problems of salt resistance and poor phase permeability change selectivity of existing phase permeability improvers.

[0005] In order to alleviate the above technical problems, the technical solution provided by the present invention is:

[0006] A method for preparing a phase permeability improver for gas well water control comprises the following steps:

[0007] Step 1: Add itaconic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hexadecyldimethylallyl ammonium chloride, and diallyldimethylammonium chloride into a reaction vessel, dissolve the five monomers in water, and dry and grind them after the reaction to obtain a phase permeability improver main agent;

[0008] Step 2: dissolving the phase permeability improver main agent in water to prepare a main agent solution with a concentration of 0.2-0.5%;

[0009] Step 3: Add the metal cross-linking agent to the main agent solution to obtain the phase permeability improver gel after reaction.

[0010] With N +The cationic groups are adsorbed on the negatively charged rock surface through electrostatic interaction. The introduced itaconic acid monomer has two carboxyl groups, which react with metal crosslinkers to crosslink the polymer molecular chains, making the crosslinking more efficient. The hydrophobic groups and rigid rings can play a viscosity-increasing role; when there is Ca in the local environment, 2+ Mg 2+ When metal cations are present, the sulfonate anion group can be neutralized with it, and the polymer still shows a stretched state in a saline environment, and the solution maintains a certain viscosity; the non-ionic chain stretches in water, the molecular chain is fully stretched, and the amide group on the molecular chain forms hydrogen bonds with water, which produces a large drag force on the water flowing through the pores, thereby greatly reducing the permeability of the formation water phase and achieving the purpose of water control.

[0011] The phase permeability improver for gas well water control swells when in contact with water, reducing the permeability, and has little change in permeability when in contact with gas. It has a strong adsorption capacity on the rock surface and meets the needs of water control fracturing construction in water-bearing gas formations.

[0012] Furthermore, in step 1, itaconic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hexadecyldimethylallylammonium chloride and diallyldimethylammonium chloride are prepared into a 25-35% aqueous solution in a mass ratio of (10-15):(40-50):(5-10):(5-10):(8-12).

[0013] Furthermore, in step 1, after the monomer is dissolved in water, the pH value of the reaction system is adjusted to 4-6 using a 20% sodium hydroxide aqueous solution.

[0014] Furthermore, after adjusting the pH value in step 1, nitrogen gas was introduced into the reaction system for 30 minutes to remove oxygen.

[0015] Furthermore, step 1 further includes the following steps between the introduction of nitrogen and the drying and grinding: heating the reaction system to 45-60° C., adding an initiator, reacting for 3-5 hours, and then cooling to room temperature.

[0016] Furthermore, the initiator is a 20% aqueous solution of azobisisobutylimidazoline hydrochloride, and the amount of the initiator added is 0.02%-0.05% of the total weight of the monomers.

[0017] Furthermore, step three further includes the following step before adding the metal cross-linking agent: adding a pH regulator to the main agent solution to adjust the pH value to 9-11.

[0018] Furthermore, the metal cross-linking agent is aluminum citrate, and the amount of the metal cross-linking agent added is 0.2%-0.4% of the mass of the main agent solution.

[0019] A phase permeability improver for gas well water control is prepared by adopting the preparation method of the phase permeability improver for gas well water control.

[0020] An application of the above-mentioned phase permeability improver for gas well water control is that the improver is applied to water-control fracturing construction of water-bearing gas layers to control water production from the formation after fracturing.

[0021] The preparation method of the phase permeability improver for gas well water control in the present invention and the beneficial effects of the improver are analyzed as follows:

[0022] 1. It swells when it encounters water, reduces permeability, and has little change in permeability when it encounters gas. It has strong adsorption capacity on the rock surface and meets the needs of water-controlled fracturing construction in water-gas strata.

[0023] 2. Good salt tolerance and good selectivity of phase permeability change;

[0024] 3. The preparation method has simple steps and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in related technologies, the following briefly introduces the drawings required for use in the specific embodiments or related technical descriptions. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a diagram showing changes in reservoir rock permeability before and after injection of the phase permeability improver for water control in gas wells in Examples 1 to 5 provided in accordance with the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, rather than all embodiments.

[0028] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0029] Example 1: A phase permeability improver for gas well water control

[0030] 10 g of itaconic acid, 40 g of acrylamide, 5 g of 2-acrylamido-2-methylpropanesulfonic acid, 5 g of hexadecyldimethylallyl ammonium chloride, 8 g of diallyldimethylammonium chloride and water were added to the reaction container respectively, and stirred to dissolve. The reaction monomer accounted for 25% of the solution mass ratio. Nitrogen was passed through for 30 minutes to deoxygenate. The reaction system was raised to 45° C. and an initiator was slowly added dropwise in an amount of 0.02% of the monomer mass. The reaction was continued for 3 hours, cooled to room temperature, dried and ground to obtain the main agent of the phase permeability improver.

[0031] The main agent of the prepared phase permeability improver was dissolved in water with a salinity of 50,000 to prepare a 0.2% aqueous solution. A pH regulator was added to adjust the pH value of the system to 9. 0.2% aluminum citrate was added to cross-link the phase permeability improver gel, which was marked as C1.

[0032] Example 2: A phase permeability improver for gas well water control

[0033] 15 g of itaconic acid, 50 g of acrylamide, 8 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of hexadecyldimethylallyl ammonium chloride, 12 g of diallyldimethylammonium chloride and water were added to the reaction container respectively, and the mixture was stirred to dissolve. The mass ratio of the reaction monomer to the solution was 35%. Nitrogen was passed through to deoxygenate for 30 minutes. The reaction system was raised to 60° C. and an initiator was slowly added dropwise in an amount of 0.05% of the monomer mass. The reaction was continued for 5 hours, cooled to room temperature, dried and ground to obtain the main agent of the phase permeability improver.

[0034] The main agent of the prepared phase permeability improver was dissolved in water with a salinity of 50,000 to prepare a 0.5% aqueous solution. A pH regulator was added to adjust the pH value of the system to 11. 0.4% aluminum citrate was added to cross-link the phase permeability improver gel, which was marked as C2.

[0035] Example 3: A phase permeability improver for gas well water control

[0036] 12 g of itaconic acid, 45 g of acrylamide, 10 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of hexadecyldimethylallyl ammonium chloride, 10 g of diallyldimethylammonium chloride and water were added to the reaction container respectively, and stirred to dissolve. The reaction monomer accounted for 30% of the solution mass ratio. Nitrogen was passed through for deoxygenation for 30 minutes. The reaction system was raised to 55° C. and an initiator was slowly added dropwise in an amount of 0.04% of the monomer mass. The reaction was continued for 4 hours, cooled to room temperature, dried and ground to obtain the main agent of the phase permeability improver.

[0037] The main agent of the prepared phase permeability improver was dissolved in water with a salinity of 50,000 to prepare a 0.4% aqueous solution. A pH regulator was added to adjust the pH value of the system to 11. 0.3% aluminum citrate was added to cross-link the phase permeability improver gel, which was marked as C3.

[0038] Example 4: A phase permeability improver for gas well water control

[0039] 10 g of itaconic acid, 48 g of acrylamide, 6 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of hexadecyldimethylallyl ammonium chloride, 10 g of diallyldimethylammonium chloride and water were added to the reaction container respectively, and stirred to dissolve. The mass ratio of the reaction monomer to the solution was 35%. Nitrogen was passed through to deoxygenate for 30 minutes. The reaction system was raised to 50° C. and an initiator was slowly added dropwise in an amount of 0.03% of the monomer mass. The reaction was continued for 4 hours, cooled to room temperature, dried and ground to obtain the main agent of the phase permeability improver.

[0040] The main agent of the prepared phase permeability improver was dissolved in water with a salinity of 50,000 to prepare a 0.3% aqueous solution. A pH regulator was added to adjust the pH value of the system to 10. 0.4% aluminum citrate was added to cross-link the phase permeability improver gel, which was marked as C4.

[0041] Example 5: A phase permeability improver for gas well water control

[0042] 15 g of itaconic acid, 40 g of acrylamide, 5 g of 2-acrylamido-2-methylpropanesulfonic acid, 10 g of hexadecyldimethylallyl ammonium chloride, 8 g of diallyldimethylammonium chloride and water were added to the reaction container respectively, and stirred to dissolve. The mass ratio of the reaction monomer to the solution was 25%. Nitrogen was passed through for deoxygenation for 30 minutes. The reaction system was raised to 45° C. and an initiator was slowly added dropwise in an amount of 0.05% of the monomer mass. The reaction was continued for 4 hours, cooled to room temperature, dried and ground to obtain the main agent of the phase permeability improver.

[0043] The main agent of the prepared phase permeability improver was dissolved in water with a salinity of 50,000 to prepare a 0.5% aqueous solution. A pH regulator was added to adjust the pH value of the system to 11. 0.2% aluminum citrate was added to cross-link the phase permeability improver gel, which was marked as C5.

[0044] Performance testing:

[0045] 1. Penetration test

[0046] The original permeability of the core before the injection of the water control agent was tested according to the industry standard SY / T 5358-2010 reservoir sensitivity flow test evaluation method. After the test, the phase permeability improver prepared in the embodiment was squeezed into the core from the reverse phase until 1.5PV of liquid flowed out of the outlet. The core was removed, placed in standard brine, heated to 90°C and solidified for 60 minutes. The change in the permeability of the reservoir core after the injection of the water control agent was tested according to the industry standard SY / T 5358-2010 reservoir sensitivity flow test evaluation method. The test results are as follows:

[0047] Table 1 Water control performance

[0048]

[0049] From the test results in Table 1, it can be seen that the permeability improver for gas well water control in the present invention can significantly reduce the water phase permeability to more than 95%, and has little effect on the gas phase permeability, with the decline controlled within 13%, showing a good water control effect.

[0050] 2. Application effect of phase permeability improver for gas well water control in water control fracturing construction

[0051] The phase permeability improvers for gas well water control in Examples 1 to 5 were field tested in Well X of Changqing Gas Field. For the logging results, please refer to Figure 1 , the details are as follows:

[0052] The first black box in the figure shows that the 44# and 46# wells are to be transformed into the target reservoir. The perforation section is 3290.6-3292.6m, and the sand body thickness is 7.0m. The second black box is the water-bearing coal seam. The X well adopts the bridge-shooting joint technology with a displacement of 8m 3 / min. The full fracturing process may lead to the communication of coal seams and water production in the reservoir. Phase permeability improver was added to the fracturing fluid. The flowback rate after fracturing was 58.7%, and the test open flow rate was 35×10 4 m 3 / d, after testing, no water was produced in the formation and the effect after pressure was good.

[0053] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing a phase permeability improver for gas well water control, characterized in that: The steps include: Step 1: Add itaconic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hexadecyldimethylallyl ammonium chloride, and diallyldimethylammonium chloride into a reaction vessel, dissolve the five monomers in water, and dry and grind them after the reaction to obtain a phase permeability improver main agent; Step 2: dissolving the phase permeability improver main agent in water to prepare a main agent solution with a concentration of 0.2-0.5%; Step 3: adding a metal cross-linking agent to the main agent solution to obtain a phase permeability improver gel after reaction; The itaconic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, hexadecyldimethylallyl ammonium chloride and diallyldimethylammonium chloride described in step 1 are prepared into a 25-35% aqueous solution in a mass ratio of (10-15):(40-50):(5-10):(5-10):(8-12).

2. The method for preparing the phase permeability improver for gas well water control according to claim 1, characterized in that: After the monomers in step 1 are dissolved in water, the pH value of the reaction system is adjusted to 4-6 with 20% sodium hydroxide aqueous solution.

3. The method for preparing the phase permeability improver for gas well water control according to claim 2, characterized in that: After adjusting the pH in step 1, nitrogen was introduced into the reaction system for 30 minutes to remove oxygen.

4. The method for preparing the phase permeability improver for gas well water control according to claim 3, characterized in that: In step 1, the following steps are further included between the introduction of nitrogen and the drying and grinding: After heating the reaction system to 45-60°C, add the initiator and react for 3-5 hours, then cool to room temperature.

5. The method for preparing the phase permeability improver for gas well water control according to claim 4, characterized in that: The initiator is a 20% aqueous solution of azobisisobutylimidazoline hydrochloride, and the amount of the initiator added is 0.02%-0.05% of the total weight of the monomer.

6. The method for preparing the phase permeability improver for gas well water control according to claim 1, characterized in that: In step 3, the following steps are further included before adding the metal cross-linking agent: A pH regulator is added to the main agent solution to adjust the pH value to 9-11.

7. The method for preparing the phase permeability improver for gas well water control according to claim 6, characterized in that: The metal cross-linking agent is aluminum citrate, and the amount of the metal cross-linking agent added is 0.2%-0.4% of the mass of the main agent solution.

8. A phase permeability improver for gas well water control, characterized in that: The phase permeability improver for gas well water control is prepared by the preparation method of any one of claims 1 to 7.

9. A use of the phase permeability improver for gas well water control according to claim 8, characterized in that: The improver is applied to water-controlled fracturing construction of water-bearing gas layers to control water production from the formation after fracturing.

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