Preparation method of water control material for natural gas well

Abstract

The invention relates to a preparation method of a natural gas well water control material, and belongs to the technical field of oilfield chemistry. An organic solution of a hydrophobic polymer is prepared through copolymerization of a hydrophobic monomer, a silicon-containing monomer and a cross-linking agent in an organic solvent. The solution is stable in property after being mixed with natural gas, and after the solution is mixed with formation water, a dense hydrophobic polymer porous resin structure is formed due to the change of the polarity of the solvent and condensation reaction after silicate ester is hydrolyzed, and conversion from large-scale pores to micro-scale pores is realized, so that the trafficability of water is reduced, and the permeability of the natural gas is improved. And the gas passing capacity is slightly influenced. In addition, a hydrophobic skeleton based on porous resin is relatively good in long-term stability. The material can overcome the defect that a traditional water plugging material is difficult to match with gas reservoir conditions, and has application potential under harsh conditions.

Description

Technical Field

[0001] The invention relates to a method for preparing a natural gas well water control material, belonging to the technical field of oilfield chemistry. Background Art

[0002] In the process of gas reservoir development, water production is inevitable. Water and gas flow in the seepage channel and the pipe column, which increases the energy loss of the gas reservoir, reduces the gas permeability, forms a dead gas zone in the gas reservoir, and greatly reduces the gas production rate. Compared with oil production technology, gas production technology is more risky and difficult. Chemical water control technology for natural gas wells mainly injects chemical agents to plug water-producing layers and water-producing fractures, or injects plugging agents to significantly reduce the water permeability while reducing the gas permeability less, so as to give full play to the potential of low-permeability reservoirs and solve the problem of water production in gas wells.

[0003] Selective water control agents are mainly used for situations where there is no obvious boundary between the gas layer and the water layer. The selective water control agents currently used on site mainly include polymer gels, nano-active oils and microemulsions, among which polymer gels are usually composed of acrylamide polymers and cross-linking agents, and have high plugging strength and good temperature and salt resistance. Nano-active oil is a condensate oil solution containing W / O emulsifiers and nanoparticles. Under the action of nanoparticles, the droplets of the emulsion adhere after high-temperature aging, and the high viscosity and Jamin effect are used to control the formation water flow and reduce the water production rate; in addition, nanoparticles are adsorbed on the surface of the formation, changing the wettability to oil-philic, which can also prevent the entry of water. In this process, due to the low viscosity of the active oil, it has little effect on the gas production channel. Microemulsion is a mixture of water phase, oil phase, surfactant and additives. The most representative microemulsion water control material is siloxane microemulsion, and its water control mechanism is mainly reflected in two aspects: first, siloxane can change the wettability of the reservoir into oil-wetting; second, after the microemulsion is diluted and demulsified in the pores, siloxane precipitates and aggregates to form larger emulsion droplets, blocking the pore throats. However, with the development of exploration, especially the discovery of some special gas reservoirs with extremely deep burial depths and complex reservoir characteristics, the existing water plugging agents have shown many shortcomings in the application process. First, the material is not selective enough for water / gas, and it is difficult to unblock after blocking in the gas reservoir; second, the material's plugging strength is not enough, and it is difficult to achieve the plugging of fractures and high permeability strips; third, the material's temperature and salt resistance is not enough, and the long-term stability under harsh conditions is poor. Therefore, it is of great significance to develop water-gas selectivity water control materials for gas reservoirs with complex working conditions and harsh conditions. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing a natural gas well water control material. SUMMARY OF THE INVENTION

[0006] The present invention obtains an organic solution of a hydrophobic polymer by copolymerizing a hydrophobic monomer, a silicon-containing monomer and a cross-linking agent in an organic solvent. The solution is stable when mixed with natural gas. When mixed with formation water, due to the change in solvent polarity and the condensation reaction after hydrolysis of silicate, a dense hydrophobic polymer porous resin structure is formed, realizing the transformation of pores from "large scale" to "micro scale", thereby reducing the water passing capacity and having little effect on the gas passing capacity. In addition, the hydrophobic skeleton based on the porous resin has excellent temperature resistance, salt resistance and long-term stability. DETAILED DESCRIPTION OF THE INVENTION

[0008] The technical solution of the present invention is as follows.

[0009] A method for preparing a natural gas well water control material is as follows:

[0010] Add hydrophobic monomer, silicon-containing monomer, crosslinking agent, initiator and organic solvent into a flask equipped with a stirrer, a nitrogen tube and a thermometer, stir until all the raw materials are evenly mixed, then introduce nitrogen for 30 minutes, control the polymerization temperature at 55-90°C, and carry out the polymerization reaction for 4-18 hours to obtain; the mass ratio of hydrophobic monomer, silicon-containing monomer, crosslinking agent and organic solvent is 1:(0.001-0.1):(0.001-0.1):(1-10), and the mass ratio of organic solvent to initiator is 1:(0.0005-0.02).

[0011] According to the present invention, preferably, the hydrophobic monomer is one of 1-octene, 1-dodecene, 1-hexadecene, styrene, methyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, dodecyl acrylate, and octadecyl acrylate;

[0012] Preferably, the silicon-containing monomer is one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-tert-butoxysilane, allyltrimethoxysilane, allyltriethoxysilane, dimethylvinylmethoxysilane, dimethylvinylethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane and 3-(methacryloyloxy)propyltriethoxysilane;

[0013] Preferably, the crosslinking agent is one of divinylbenzene, 1,3,5-trivinylbenzene, ethylene glycol dimethacrylate, triallyl cyanurate, triallyl isocyanurate, and trimethylolpropane trimethacrylate;

[0014] Preferably, the initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisobutylimidazoline hydrochloride, azoisobutylcyanamide, and benzoyl peroxide;

[0015] Preferably, the organic solvent is one or a mixture of two or more of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, polyethylene glycol 200, polyethylene glycol 300, formamide, acetamide, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylpropionamide;

[0016] Preferably, the mass ratio of the hydrophobic monomer, the silicon-containing monomer, the crosslinking agent, and the organic solvent is 1:(0.005-0.05):(0.005-0.05):(1-6);

[0017] Preferably, the mass ratio of organic solvent to initiator is 1:(0.001-0.015);

[0018] Preferably, the polymerization temperature is 65-85° C., and the polymerization time is 6-12 h.

[0019] The excellent effects of the present invention are as follows:

[0020] 1. The raw materials of the present invention are easily available, the reaction conditions are mild, the process is simple and safe, and large-scale industrial production can be realized.

[0021] 2. The present invention achieves the purpose of gradually precipitating the polymer to form a material with a porous structure by utilizing the change of solvent components after the hydrophobic polymer solution meets the aqueous solution. In addition, the hydrolysis and condensation properties of silicate after meeting water are utilized to further improve the mechanical strength of the material, thereby achieving good pressure-bearing and plugging capabilities of the material in the gas reservoir.

[0022] 3. The water control material prepared by the present invention has a hydrophobic porous structure, which significantly reduces the water phase permeability through capillary action, Jamin effect, etc., while having little effect on the gas phase permeability, showing good selective water control ability of gas reservoirs.

[0023] 4. The water control material prepared by the present invention is injected into the formation in the form of a solution, and has better adaptability to pore size, and can still show a good plugging effect on large-sized pores.

[0024] 5. The water control material prepared by the present invention is a hydrophobic resin material. Compared with conventional hydrophilic polymer water control materials, it has more superior chemical stability, high temperature stability, salt stability and long-term aging stability under formation conditions.

[0025] 6. The product prepared by the present invention is convenient to store, transport and use, and is conducive to on-site promotion and application in oil fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of a porous resin structure formed when the polymer organic solution of the present invention meets water;

[0027] Figure 2 The pore size distribution diagram of the porous resin. DETAILED DESCRIPTION

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0029] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0030] Embodiment 1:

[0031] 8.1 g of tert-butyl acrylate, 0.13 g of vinyltriethoxysilane, 0.2 g of divinylbenzene, 0.05 g of benzoyl peroxide and 21 g of polyvinyl alcohol 200 were added into a flask equipped with a stirrer, a nitrogen tube and a thermometer. After stirring until all the raw materials were evenly mixed, nitrogen was introduced for 30 minutes. The polymerization temperature was controlled at 70°C and the polymerization reaction was carried out for 10 hours to obtain an organic solution of a hydrophobic polymer.

[0032] Embodiment 2:

[0033] As described in Example 1, except that the hydrophobic monomer was 10.5 g of dodecyl acrylate.

[0034] Embodiment 3:

[0035] As described in Example 1, except that the hydrophobic monomer was 4.2 g styrene.

[0036] Embodiment 4:

[0037] As described in Example 1, except that the silicon-containing monomer is 0.05 g of vinyltrimethoxysilane.

[0038] Embodiment 5:

[0039] As described in Example 1, except that the silicon-containing monomer is 0.4 g of dimethylvinylmethoxysilane.

[0040] Embodiment 6:

[0041] As described in Example 1, except that the crosslinking agent was 0.05 g of 1,3,5-trivinylbenzene.

[0042] Embodiment 7:

[0043] As described in Example 1, except that the crosslinking agent was 0.4 g of ethylene glycol dimethacrylate.

[0044] Embodiment 8:

[0045] As described in Example 1, except that the initiator was 0.25 g of azobisisobutyronitrile.

[0046] Embodiment 9:

[0047] As described in Example 1, except that the amount of organic solvent added was 15 g.

[0048] Embodiment 10:

[0049] As described in Example 1, except that the amount of organic solvent added was 45 g.

[0050] Embodiment 11:

[0051] As described in Example 1, except that the organic solvent was 14 g ethylene glycol and 7 g propylene glycol.

[0052] Embodiment 12:

[0053] As described in Example 1, except that the organic solvent is N,N-dimethylformamide.

[0054] Embodiment 13:

[0055] As described in Example 1, except that the polymerization temperature was 80°C and the polymerization time was 8 hours.

[0056] Performance Evaluation

[0057] ① Dry the core (Φ2.5cm×10cm) at 105℃ for 4h, record the dry weight, put it in the core holder, evacuate for 20min, saturate it with deionized water at a rate of 1mL / min, record the stable water drive pressure difference at the core inlet, take out the core and weigh its wet weight to obtain the pore volume, then use a nitrogen bottle to ventilate the core at a rate of 1mL / min, and record the stable gas drive pressure difference at the core inlet. Calculate the water phase permeability k of the core w and gas phase effective permeability k g ;

[0058] ②Take out the core and put it into a 105℃ oven to dry until constant weight, then put the core into the core holder and measure the water permeability k of the core again under the same conditions as in step ①. wd and gas phase effective permeability k gd ;

[0059] ③ Compare the water and gas permeability values ​​before and after the core is dried (see Table 1) to confirm that there is no significant change in the water and gas permeability before and after the core is dried;

[0060] ④ Take out the core, dry it again, put it into the core holder, inject 0.5PV polymer solution at a rate of 1mL / min, then take out the core, put it into the aging tank, immerse the core with deionized water, seal the aging tank, and place it in an environment of 150℃ for aging for 7 days;

[0061] ⑤ Take out the core, put it into the core holder, replace it with deionized water at a rate of 1 mL / min, and record the stable water drive pressure difference at the core inlet; use a nitrogen bottle to ventilate the core at a rate of 1 mL / min at a pressure of 0.1 MPa, record the stable gas drive pressure difference at the core inlet, and calculate the water phase permeability k after plugging. w ′ and gas phase effective permeability k g ′;

[0062] ⑥ Calculate the water phase plugging rate E w and gas phase plugging rate E g .

[0063] Single-phase blocking rate calculation formula:

[0064]

[0065] Where E is the plugging rate, %;

[0066] k is the permeability before plugging, μm 2 ;

[0067] k′ is the permeability after plugging, μm 2 .

[0068] Table 1 Selective water control performance of different samples

[0069]

[0070] It can be seen from Table 1 that the water phase blocking rate of the product of the present invention reaches more than 85%, while the gas phase blocking rate is less than 25%, which shows that the product has a good selective water control effect.

Claims

1. A method for preparing a natural gas well water control material, comprising the following steps: Add the hydrophobic monomer, silicon-containing monomer, crosslinking agent, initiator and organic solvent into a flask equipped with a stirrer, a nitrogen tube and a thermometer, stir until all the raw materials are evenly mixed, then introduce nitrogen for 30 minutes, control the polymerization temperature at 55-90°C, and carry out the polymerization reaction for 4-18 hours to obtain the product; the mass ratio of the hydrophobic monomer, silicon-containing monomer, crosslinking agent and organic solvent is 1:(0.001-0.1):(0.001-0.1):(1-10), and the mass ratio of the organic solvent to the initiator is 1:(0.0005-0.02); The hydrophobic monomer is one of 1-octene, 1-dodecene, 1-hexadecene, styrene, methyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, dodecyl acrylate, and octadecyl acrylate; The silicon-containing monomer is one of vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tri-tert-butoxysilane, allyl trimethoxysilane, allyl triethoxysilane, dimethyl vinyl methoxysilane, dimethyl vinyl ethoxysilane, 3-(methacryloyloxy)propyl trimethoxysilane and 3-(methacryloyloxy)propyl triethoxysilane; The crosslinking agent is one of 1,2-divinylbenzene, 1,3-divinylbenzene, 1,4-divinylbenzene, 1,3,5-trivinylbenzene, ethylene glycol dimethacrylate, triallyl cyanurate, triallyl isocyanurate, and trimethylolpropane trimethacrylate; The initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisobutylimidazoline hydrochloride, azoisobutylcyanoformamide, and benzoyl peroxide; The organic solvent is one of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, polyethylene glycol-200, polyethylene glycol-300, formamide, acetamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, or a mixture of two or more thereof.

2. The method for preparing the natural gas well water control material according to claim 1, characterized in that: The mass ratio of the hydrophobic monomer, the silicon-containing monomer, the crosslinking agent and the organic solvent is 1:(0.005-0.05):(0.005-0.05):(1-6).

3. The method for preparing the natural gas well water control material according to claim 1, characterized in that: The mass ratio of the organic solvent to the initiator is 1:(0.001-0.015).

4. The method for preparing the natural gas well water control material according to claim 1, characterized in that: The polymerization temperature is 65-85°C, and the polymerization time is 6-12h.

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