Gas channeling prevention system and nitrogen flooding gas channeling prevention method

Abstract

The invention provides a gas channeling prevention system and a nitrogen flooding gas channeling prevention method. The anti-gas-channeling system comprises a temperature-resistant and salt-resistant gel system, a nitrogen gel foam system and a nitrogen thickened foam system. According to the nitrogen flooding gas channeling prevention method, the gas channeling prevention system is adopted, and gas channeling prevention is carried out in a slug combination mode, specifically, the temperature-resistant and salt-resistant gel system serves as a front slug, and a nitrogen gas channeling channel with the width of 100-500 m is plugged; the nitrogen gel foam system is used as a first main body slug, and a nitrogen gas channeling channel with the width of 10-100 m is plugged; taking the nitrogen thickened foam system as a second main body slug, and blocking a nitrogen gas channeling channel with the width of 0.1-10m; and finally, preferably injecting water as a displacement slug, and extruding the slug into the stratum, so that the anti-gas channeling effect is enhanced, and meanwhile, the slug is prevented from being blocked in a shaft.

Description

Technical Field

[0001] The invention belongs to the technical field of nitrogen drive development of fracture-cavity oil reservoirs, and in particular relates to a gas channeling prevention system and a nitrogen drive gas channeling prevention method. Background Art

[0002] The fracture-cavity reservoir has strong heterogeneity, diverse spatial relationships between fractures and caves, diverse distribution of inter-well reservoirs, and is characterized by high temperature and high salt. As the unit water injection development of the oil field enters the middle and late stages, the unit nitrogen drive was promoted and applied on site after a breakthrough was made in 2015. However, with the expansion of the scale of nitrogen drive, gas channeling occurred in some well groups, resulting in a significant reduction in nitrogen utilization. The nitrogen anti-gas channeling method developed in the early stage mainly used a composite of multi-segment thickening foam segment and nitrogen segment, which had the disadvantages of poor temperature and salt resistance, short plugging effective period, and unobvious oil increase. At present, the research and development of gas injection anti-gas channeling mainly focuses on sandstone CO 2 In terms of anti-channeling plugging agents, they are not suitable for preventing nitrogen gas channeling in fracture-cavity reservoirs with strong heterogeneity, and there is also a lack of a complete nitrogen anti-gas channeling plug design method. In summary, it is urgent to develop a fracture-cavity reservoir nitrogen drive anti-gas channeling plug design method that can improve the gas channeling status of nitrogen drive well groups and provide support for the efficient operation of nitrogen drive in fracture-cavity reservoir units. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide a method for preventing gas channeling in nitrogen drive of fracture-cavity oil reservoir units, so as to improve the gas channeling status of nitrogen drive well groups and provide support for the efficient operation of nitrogen drive of fracture-cavity oil reservoir units.

[0004] One of the present inventions provides an anti-gas channeling system, which includes a temperature-resistant and salt-resistant gel system, a nitrogen gel foam system and a nitrogen thickened foam system.

[0005] According to a specific embodiment of the present invention, the temperature-resistant and salt-resistant jelly system comprises a first anionic polyacrylamide, carboxymethyl cellulose, a first phenolic crosslinking agent and a first aldehyde crosslinking agent; and / or

[0006] The nitrogen jelly foam system comprises nitrogen and jelly foam; and / or

[0007] The nitrogen-densified foam system comprises nitrogen and densified foam;

[0008] Preferably, the jelly foam comprises a second anionic polyacrylamide, a polyurethane, a second phenolic crosslinking agent, a second aldehyde crosslinking agent and a surfactant; and / or

[0009] The thickened foam includes a foaming agent and a foam stabilizer.

[0010] According to a specific embodiment of the present invention, the mass of the heat-resistant and salt-resistant jelly system is calculated as 100%, and the heat-resistant and salt-resistant jelly system includes 0.6 to 1 wt% of the first anionic polyacrylamide, 0.4 to 1 wt% of the carboxymethyl cellulose, 0.2 to 0.6 wt% of the first phenolic cross-linking agent, 0.2 to 0.6 wt% of the first aldehyde cross-linking agent and the balance water.

[0011] According to a specific embodiment of the present invention, taking the mass of the jelly foam as 100%, the jelly foam includes 0.8 to 1 wt% of the second anionic polyacrylamide, 1 to 1.2 wt% of the polyurethane, 0.4 to 0.6 wt% of the second phenolic crosslinker, 0.4 to 0.6 wt% of the second aldehyde crosslinker, 0.6 to 1 wt% of the surfactant and the balance water.

[0012] According to a specific embodiment of the present invention, taking the mass of the thickened foam as 100%, the thickened foam comprises 1 to 1.5 wt % of the foaming agent, 1 to 1.5 wt % of the foam stabilizer and the balance of water.

[0013] According to a specific embodiment of the present invention, the weight average molecular weight of the first anionic polyacrylamide is 10×10 4 ; and / or

[0014] The weight average molecular weight of the second anionic polyacrylamide is 14×10 4 ; and / or

[0015] The weight average molecular weight of the polyurethane is 322; and / or

[0016] The first phenolic cross-linking agent and the second phenolic cross-linking agent are hydroquinone; and / or

[0017] The first aldehyde cross-linking agent and the second aldehyde cross-linking agent are urotropine; and / or

[0018] The surfactant is sodium dodecylbenzene sulfonate; and / or

[0019] The foaming agent is dodecyldimethylamine betaine; and / or the foam stabilizing agent is polyacrylamide.

[0020] The second invention provides a nitrogen flooding gas channeling prevention method, which adopts the gas channeling prevention system described in the first invention to carry out nitrogen flooding gas channeling prevention in a slug combination manner;

[0021] 1) injecting the temperature-resistant and salt-resistant gel system as a front segment plug to block the nitrogen gas channel with a width of 100 to 500 m;

[0022] 2) injecting the nitrogen gel foam system as the first main segment plug to block the nitrogen gas channel with a width of 10 to 100 m;

[0023] 3) Injecting the nitrogen thickened foam system as the second main segment plug to block the nitrogen gas channel with a width of 0.1 to 10 m.

[0024] According to a specific embodiment of the present invention, the method further comprises step 4), injecting water as a displacement plug.

[0025] According to a specific embodiment of the present invention, the total injection volume of the leading slug, the jelly foam in the first main body slug, the thickened foam in the second main body slug and the replacement slug is calculated as 100%, the injection volume of the leading slug accounts for 10 to 15%, the injection volume of the jelly foam in the first main body slug accounts for 20 to 25%, the injection volume of the thickened foam in the second main body slug accounts for 30 to 35% and the injection volume of the replacement slug accounts for 25 to 40%.

[0026] In the present invention, the injection rates and total injection volumes of the pre-slug, the gel foam in the first main body slug, the thickened foam in the second main body slug and the displacement slug can be determined according to the actual on-site construction conditions of the target oil reservoir.

[0027] The gas channeling prevention system according to one embodiment of the present invention or the nitrogen flooding gas channeling prevention method according to another embodiment of the present invention is used in nitrogen flooding gas channeling prevention in fracture-cavity reservoir units.

[0028] Beneficial effects of the present invention:

[0029] In view of the problems of poor temperature and salt resistance, short plugging validity period, and unobvious oil increase in existing nitrogen anti-gas channeling methods, the present invention provides an anti-gas channeling system and a nitrogen drive anti-gas channeling method. The anti-gas channeling system includes a temperature-resistant and salt-resistant gel system, a nitrogen gel foam system, and a nitrogen thickening foam system. The nitrogen drive anti-gas channeling method adopts the anti-gas channeling system to prevent gas channeling in the form of segment plug combination. Specifically, the temperature-resistant and salt-resistant gel system is used as a pre-segment plug to plug a nitrogen gas channeling channel with a width of 100 to 500m; the nitrogen gel foam system is used as the first main segment plug to plug a nitrogen gas channeling channel with a width of 10 to 100m; the nitrogen thickening foam system is used as the second main segment plug to plug a nitrogen gas channeling channel with a width of 0.1 to 10m; finally, water is preferably injected as a displacement segment plug to squeeze the aforementioned segment plug into the formation, thereby increasing the anti-gas channeling effect while avoiding the aforementioned segment plug from being blocked in the wellbore. The gas channeling prevention system and nitrogen drive gas channeling prevention method provided by the present invention have been actually applied to gas channeling wells in fracture-cavity oil reservoirs. After treatment, the production conditions of THX1 well, THX2 well and THX3 well are as follows: the daily oil production increases from 9.9t, 9.1t and 11.3t before treatment to 16.9t, 15.8t and 21.1t after treatment, respectively; the production continues for 170 days, 160 days and 70 days; the cumulative oil production increases are 643.4t, 697.2t and 612.7t, respectively, and the oil production is still increasing, and the treatment effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The results show that the gas channeling prevention system and nitrogen flooding gas channeling prevention method provided by the present invention were used to treat the THX1 well in Example 1;

[0031] Figure 2 The results show that the gas channeling prevention system and nitrogen flooding gas channeling prevention method provided by the present invention were used to treat the THX2 well in Example 2;

[0032] Figure 3 The results show that in Example 3, the gas channeling prevention system and the nitrogen drive gas channeling prevention method provided by the present invention were used to treat the THX3 well. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with examples, but the examples of the present invention are only exemplary descriptions, and the implementation methods do not constitute limitations of the present invention under any circumstances.

[0034] One of the present inventions provides an anti-gas channeling system, which includes a temperature-resistant and salt-resistant gel system, a nitrogen gel foam system and a nitrogen thickened foam system.

[0035] According to a specific embodiment of the present invention, the temperature-resistant and salt-resistant jelly system comprises a first anionic polyacrylamide, carboxymethyl cellulose, a first phenolic crosslinking agent and a first aldehyde crosslinking agent; and / or

[0036] The nitrogen jelly foam system comprises nitrogen and jelly foam; and / or

[0037] The nitrogen-densified foam system comprises nitrogen and densified foam;

[0038] Preferably, the jelly foam comprises a second anionic polyacrylamide, a polyurethane, a second phenolic crosslinking agent, a second aldehyde crosslinking agent and a surfactant; and / or

[0039] The thickened foam includes a foaming agent and a foam stabilizer.

[0040] According to a specific embodiment of the present invention, the mass of the temperature-resistant and salt-resistant jelly system is calculated as 100%, and the temperature-resistant and salt-resistant jelly system includes 0.6 to 1 wt% of the first anionic polyacrylamide, 0.4 to 1 wt% of the carboxymethyl cellulose, 0.2 to 0.6 wt% of the first phenolic crosslinking agent, 0.2 to 0.6 wt% of the first aldehyde crosslinking agent and the balance of water; and / or

[0041] Taking the mass of the jelly foam as 100%, the jelly foam comprises 0.8 to 1 wt % of the second anionic polyacrylamide, 1 to 1.2 wt % of the polyurethane, 0.4 to 0.6 wt % of the second phenolic crosslinking agent, 0.4 to 0.6 wt % of the second aldehyde crosslinking agent, 0.6 to 1 wt % of the surfactant and the balance of water; and / or

[0042] The mass of the thickened foam is calculated as 100%, and the thickened foam includes 1 to 1.5 wt % of the foaming agent, 1 to 1.5 wt % of the foam stabilizer, and the balance of water.

[0043] According to a specific embodiment of the present invention, the mass of the temperature-resistant and salt-resistant jelly system is calculated as 100%, and the temperature-resistant and salt-resistant jelly system includes 0.6wt% of the first anionic polyacrylamide, 0.4wt% of the carboxymethyl cellulose, 0.2wt% of the first phenolic crosslinking agent, 0.2wt% of the first aldehyde crosslinking agent and the balance water; and / or

[0044] The mass of the jelly foam is taken as 100%, and the jelly foam comprises 0.8wt% of the second anionic polyacrylamide, 1wt% of the polyurethane, 0.4wt% of the second phenolic crosslinking agent, 0.4wt% of the second aldehyde crosslinking agent, 0.6wt% of the surfactant and the balance of water; and / or

[0045] The mass of the thickened foam is calculated as 100%, and the thickened foam includes 1 wt % of the foaming agent, 1 wt % of the foam stabilizer, and the balance of water.

[0046] According to a specific embodiment of the present invention, the mass of the temperature-resistant and salt-resistant jelly system is calculated as 100%, and the temperature-resistant and salt-resistant jelly system includes 0.8wt% of the first anionic polyacrylamide, 0.6wt% of the carboxymethyl cellulose, 0.4wt% of the first phenolic crosslinking agent, 0.4wt% of the first aldehyde crosslinking agent and the balance water; and / or

[0047] The mass of the jelly foam is taken as 100%, and the jelly foam comprises 0.9wt% of the second anionic polyacrylamide, 1.1wt% of the polyurethane, 0.5wt% of the second phenolic crosslinking agent, 0.5wt% of the second aldehyde crosslinking agent, 0.8wt% of the surfactant and the balance of water; and / or

[0048] The mass of the thickened foam is calculated as 100%, and the thickened foam includes 1.2 wt % of the foaming agent, 1.2 wt % of the foam stabilizer, and the balance of water.

[0049] According to a specific embodiment of the present invention, the mass of the temperature-resistant and salt-resistant jelly system is calculated as 100%, and the temperature-resistant and salt-resistant jelly system includes 1wt% of the first anionic polyacrylamide, 1wt% of the carboxymethyl cellulose, 0.6wt% of the first phenolic crosslinking agent, 0.6wt% of the first aldehyde crosslinking agent and the balance water; and / or

[0050] The mass of the jelly foam is taken as 100%, and the jelly foam comprises 1wt% of the second anionic polyacrylamide, 1.2wt% of the polyurethane, 0.6wt% of the second phenolic crosslinking agent, 0.6wt% of the second aldehyde crosslinking agent, 1wt% of the surfactant and the balance of water; and / or

[0051] The mass of the thickened foam is calculated as 100%, and the thickened foam includes 1.5 wt % of the foaming agent, 1.5 wt % of the foam stabilizer, and the balance of water.

[0052] According to a specific embodiment of the present invention, the temperature-resistant and salt-resistant gel system has a temperature resistance of not less than 130°C; and / or a salt resistance of not less than 20×10 4 mg / L; and / or the gelling time at 130℃ is 1 to 4h; and / or the gelling strength is not less than Grade H;

[0053] and / or the foaming multiple of the gel foam under the conditions of 130° C. and 3 MPa is not less than 3 times; and / or the foam half-life is not less than 250 min; and / or

[0054] The thickened foam has a foaming multiple of not less than 6 times under the conditions of 130° C. and 3 MPa; and / or a foam half-life of not less than 210 min.

[0055] In the present invention, the gel strength grade H is the gel strength grade measured by the Sydansk visual code method. The gel strength grade H refers to a slightly deformable non-flowing gel, and only the gel surface deforms when flipped.

[0056] In the present invention, the waring-blender method is used to determine the foaming volume, foam half-life and liquid separation half-life of the jelly foam and thickened foam.

[0057] According to a specific embodiment of the present invention, the weight average molecular weight of the first anionic polyacrylamide is 10×10 4 ; and / or

[0058] The weight average molecular weight of the second anionic polyacrylamide is 14×10 4 ; and / or

[0059] The weight average molecular weight of the polyurethane is 322; and / or

[0060] The first phenolic cross-linking agent and the second phenolic cross-linking agent are hydroquinone; and / or

[0061] The first aldehyde cross-linking agent and the second aldehyde cross-linking agent are urotropine; and / or

[0062] The surfactant is sodium dodecylbenzene sulfonate; and / or

[0063] The foaming agent is dodecyldimethylamine betaine; and / or the foam stabilizing agent is polyacrylamide;

[0064] Preferably, the CAS number of the carboxymethyl cellulose is 9000-11-7; and / or

[0065] The molecular weight of the polyacrylamide is 14×10 4 .

[0066] The second invention provides a nitrogen flooding gas channeling prevention method, which adopts the gas channeling prevention system described in the first invention to carry out nitrogen flooding gas channeling prevention in a slug combination manner;

[0067] 1) injecting the temperature-resistant and salt-resistant gel system as a front segment plug to block the nitrogen gas channel with a width of 100 to 500 m;

[0068] 2) injecting the nitrogen gel foam system as the first main segment plug to block the nitrogen gas channel with a width of 10 to 100 m;

[0069] 3) Injecting the nitrogen thickened foam system as the second main segment plug to block the nitrogen gas channel with a width of 0.1 to 10 m.

[0070] According to a specific embodiment of the present invention, the method further comprises step 4), injecting water as a displacement plug.

[0071] According to a specific embodiment of the present invention, the total injection volume of the leading slug, the jelly foam in the first main body slug, the thickened foam in the second main body slug and the replacement slug is calculated as 100%, the injection volume of the leading slug accounts for 10 to 15%, the injection volume of the jelly foam in the first main body slug accounts for 20 to 25%, the injection volume of the thickened foam in the second main body slug accounts for 30 to 35% and the injection volume of the replacement slug accounts for 25 to 40%.

[0072] According to a specific embodiment of the present invention, the injection speeds of the pre-slug, the gel foam in the first main body slug, the thickened foam in the second main body slug and the displacement slug are independently 18 to 30 m / s. 3 / h;

[0073] Preferably, the injection speed of the pre-slug, the gel foam in the first main body slug, the thickened foam in the second main body slug and the displacement slug is 24 m / s. 3 / h.

[0074] According to a specific embodiment of the present invention, in order to ensure the anti-gas channeling effect, the total injection volume of the pre-slug, the gel foam in the first main body slug, the thickened foam in the second main body slug and the displacement slug is not more than 3000m 3 .

[0075] The gas channeling prevention system according to one embodiment of the present invention or the nitrogen flooding gas channeling prevention method according to another embodiment of the present invention is used in nitrogen flooding gas channeling prevention in fracture-cavity reservoir units.

[0076] The nitrogen flooding and gas channeling prevention method provided by the present invention is first based on the characteristics of large scale, strong heterogeneity and unit nitrogen gas channeling of fracture-cavity oil reservoirs, and injects a temperature-resistant and salt-resistant gel system as a pre-segment plug into the well. After the temperature-resistant and salt-resistant gel is injected into the well, it slowly condenses under the action of formation pressure and temperature to block the large-scale nitrogen gas channeling channel of 100 to 500 m; then, the nitrogen gel foam system is injected into the well as the first main segment plug. Specifically, while nitrogen is injected into the well, the gel foam is injected into the well using a foam generator at the wellhead, and the gel foam itself is relied on to block the larger-scale nitrogen gas channeling channel of 10 to 100 m, and the nitrogen introduced together with the gel foam is based on the continuous disturbance of the gel foam, so that the gel foam is regenerated, and can enter the high position between the well groups. The affected area is used to activate the remaining oil; then the nitrogen thickening foam system is injected into the wellbore through the foam generator at the wellhead as the second main segment plug. Specifically, while injecting nitrogen into the well, the thickening foam is injected into the wellbore by using the foam generator at the wellhead. On the basis of the aforementioned segment plug blocking the large-sized and relatively large-sized nitrogen gas channeling channels, the thickening foam uniformly blocks the small-sized nitrogen gas channeling channels of 0.1 to 10m, and the nitrogen injected together with the thickening foam gives the thickening foam continuous disturbance to regenerate the thickening foam, and continues to enter the unaffected area of ​​the well formation elevation to further activate the remaining oil; finally, oilfield water is preferably injected into the wellbore as a displacement segment plug to squeeze the aforementioned segment plug into the formation, further enhancing the gas channeling prevention effect of the aforementioned segment plug, and at the same time, blockage in the wellbore can be avoided.

[0077] Anti-gas channeling system

[0078] The raw material information used in Examples 1 to 3 is as follows:

[0079] The first anionic polyacrylamide: purchased from Hebei Wanrui Chemical Co., Ltd., with a molecular weight of 10×10 4 ;

[0080] Second anionic polyacrylamide: purchased from Henan Duohui Chemical Products Co., Ltd., with a molecular weight of 14×10 4 ;

[0081] Carboxymethyl cellulose: purchased from Jinan Xinguan Chemical Products Co., Ltd., CAS No. 9000-11-7;

[0082] Polyurethane: purchased from Guangzhou Haoyi New Materials Technology Co., Ltd., Guangdong Province, with a molecular weight of 322.36;

[0083] The first phenolic cross-linking agent and the second phenolic cross-linking agent: hydroquinone;

[0084] The first aldehyde cross-linking agent, the second aldehyde cross-linking agent: hexamethylenetetramine;

[0085] Surfactant: sodium dodecylbenzene sulfonate, purchased from Shandong Xingang Chemical Co., Ltd.;

[0086] Foaming agent: dodecyl dimethylaminoethyl lactone, purchased from Sichuan Guanghan Rongxin Fine Chemical Co., Ltd., liquid precipitation half-life ≥ 250min;

[0087] Foam stabilizer: (for oil displacement in type II zone) polyacrylamide, molecular weight 14×10 4 , purchased from Shandong Juxing Petroleum Technology Co., Ltd.

[0088] Example 1

[0089] The anti-gas channeling system provided in this embodiment is as follows:

[0090] (1) Heat-resistant and salt-resistant gel system: The total mass of the heat-resistant and salt-resistant gel system is 100%, and the heat-resistant and salt-resistant gel system includes 0.6 wt% of a first anionic polyacrylamide, 0.4 wt% of carboxymethyl cellulose, 0.2 wt% of a first phenolic crosslinking agent hydroquinone, 0.2 wt% of a first aldehyde crosslinking agent urotropine, and the balance of water;

[0091] (2) Nitrogen gel foam system: comprising nitrogen and gel foam; the total mass of the gel foam is taken as 100%, and the gel foam comprises 0.8 wt% of a second anionic polyacrylamide, 1.0 wt% of polyurethane, 0.4 wt% of a second phenolic crosslinking agent hydroquinone, 0.4 wt% of a second aldehyde crosslinking agent urotropine, 0.6 wt% of a surfactant and the remainder of water;

[0092] (3) Nitrogen-thickened foam system: comprising nitrogen and thickened foam; the total mass of the thickened foam is taken as 100%, and the thickened foam comprises 1 wt % of a foaming agent, 1 wt % of a foam stabilizer and the balance of water.

[0093] Example 2

[0094] The anti-gas channeling system provided in this embodiment is as follows:

[0095] (1) Heat-resistant and salt-resistant gel system: The total mass of the heat-resistant and salt-resistant gel system is 100%, and the heat-resistant and salt-resistant gel system includes 0.8 wt% of a first anionic polyacrylamide, 0.6 wt% of carboxymethyl cellulose, 0.4% of a first phenolic crosslinking agent hydroquinone, 0.4 wt% of a first aldehyde crosslinking agent urotropine, and the balance of water;

[0096] (2) Nitrogen gel foam system: comprising nitrogen and gel foam; the total mass of the gel foam is taken as 100%, and the gel foam comprises 0.9 wt% of a second anionic polyacrylamide, 1.1 wt% of polyurethane, 0.5 wt% of a second phenolic crosslinking agent hydroquinone, 0.5 wt% of a second aldehyde crosslinking agent urotropine, 0.8 wt% of a surfactant and the remainder of water;

[0097] (3) Nitrogen-thickened foam system: comprising nitrogen and thickened foam; the total mass of the thickened foam is taken as 100%, and the thickened foam comprises 1.2 wt % of a foaming agent, 1.2 wt % of a foam stabilizer and the balance of water.

[0098] Example 3

[0099] The anti-gas channeling system provided in this embodiment is as follows:

[0100] (1) Heat-resistant and salt-resistant gel system: The total mass of the heat-resistant and salt-resistant gel system is 100%, and the heat-resistant and salt-resistant gel system includes 1.0 wt% of a first anionic polyacrylamide, 1.0 wt% of carboxymethyl cellulose, 0.6 wt% of a first phenolic crosslinking agent hydroquinone, 0.6 wt% of a first aldehyde crosslinking agent urotropine, and the balance of water;

[0101] (2) Nitrogen gel foam system: comprising nitrogen and gel foam; the total mass of the gel foam is calculated as 100%, and the gel foam comprises 1.0 wt% of a second anionic polyacrylamide, 1.2 wt% of polyurethane, 0.6 wt% of a second phenolic crosslinking agent hydroquinone, 0.6 wt% of hexamethylenetetramine, 1.0 wt% of a surfactant and the balance of water;

[0102] (3) Nitrogen-thickened foam system: comprising nitrogen and thickened foam; the total mass of the thickened foam is taken as 100%, and the thickened foam comprises 1.5 wt % of a foaming agent, 1.5 wt % of a foam stabilizer and the balance of water.

[0103] Test Example 1- Performance Evaluation of Anti-gas Channeling System

[0104] ⅰ Determination of heat and salt resistance of gelling agent

[0105] At room temperature, the mineralization degree was 20×10 4 The raw materials were weighed according to the dosage ratio of each component recorded in Examples 1 to 3, and each raw material was completely dissolved in the simulated formation water to obtain the temperature-resistant and salt-resistant gel-1, the temperature-resistant and salt-resistant gel-2, and the temperature-resistant and salt-resistant gel-3 to be tested in turn;

[0106] Determination of gelling time and gelling strength: 10 g of each of the heat-resistant and salt-resistant gelling gel-1 to the heat-resistant and salt-resistant gelling gel-3 prepared in this test example were weighed and placed in a thermostat set at 130° C. for aging. During the aging process, the gelling state of each gelling gel was observed, and the gelling time and gelling strength of each gelling gel were measured according to the Sydansk visual code method. The results are shown in Table 1.

[0107] High temperature stability determination: Weigh 30 g of each of the heat-resistant and salt-resistant gel-1 to the heat-resistant and salt-resistant gel-3 prepared in this test example, place them in containers, seal them, and then start aging in a constant temperature box set at 130°C; after gelling, continue aging at 130°C and observe the dehydration of the heat-resistant and salt-resistant gel after gelling, observe the dehydration amount of the heat-resistant and salt-resistant gel after gelling by visual observation, and divide the dehydration amount by the volume of the heat-resistant and salt-resistant gel after gelling to obtain the dehydration rate; the aging days when the dehydration rate reaches 10% are taken as the duration of high temperature stability, and the results are shown in Table 1.

[0108] Table 1. Performance determination of temperature-resistant and salt-resistant gel in anti-gas channeling system

[0109] Gel No. Gelation time Gel strength High temperature stability Heat and salt resistant gel-1 3 to 4 hours H-Class 90 days Heat and salt resistant gel-2 2 to 3 hours Level I 100 days Heat and salt resistant gel-3 1 to 2 hours Level I 120 days

[0110] ⅱ Determination of properties of gel foam and thickened foam

[0111] The waring-blender method was used to determine the foaming multiple, liquid separation half-life and foam half-life of the foam system, and to evaluate the performance of the gel foam and thickened foam.

[0112] The specific steps are as follows:

[0113] Step 1: The gel foam in the anti-gas channeling composition provided in Examples 1 to 3 is weighed in proportion and then prepared to obtain test solutions 1 to 3 in sequence, and the thickened foam is weighed in proportion and then prepared to obtain test solutions 4 to 6 in sequence;

[0114] Step 2: Under the test conditions of (25±1)°C and normal pressure, use a measuring cylinder to measure 10 mL of any one of the test liquids 1 to 6, record the initial height of the liquid, start the stirrer, stir at a speed of 4000 to 13000 r / min for 30 seconds, stop stirring, record the initial height of the foam, and continuously observe the height of the foam and the height of the precipitated liquid;

[0115] When the height of the precipitated liquid is half of the initial height of the liquid, the recorded time is the precipitated liquid half-life;

[0116] The foaming multiple is the initial height of the foam divided by the initial height of the liquid;

[0117] When the foam height decreases to half of the initial foam height, the recorded time is the foam half-life;

[0118] According to step 2, the foaming multiples, liquid separation half-life and foam half-life of the test solutions 1 to 6 prepared in step 1 were measured. The specific results are shown in Table 2;

[0119] The test conditions in step 2 were adjusted to 130° C. and 3 MPa, and the foaming multiples and foam half-lives of the test solutions 1 to 6 prepared in step 1 were measured. The specific results are shown in Table 3.

[0120] Table 2. Foaming multiple, liquid separation half-life and foam half-life at (25±1)℃ and normal pressure

[0121]

[0122] Table 3. Foaming multiple and foam half-life at 130℃ and 3MPa

[0123]

[0124] It can be seen from the measurement results in Tables 1 to 3 that the anti-gas channeling system provided by the present invention has suitable gelling time, sufficient gelling strength, good high-temperature stability and excellent foaming performance, and is suitable for preventing gas channeling during nitrogen flooding in fracture-cavity oil reservoir well groups.

[0125] Implementing nitrogen flooding to prevent gas channeling

[0126] During the nitrogen flooding development of fracture-cavity reservoir well groups, gas channeling occurred in 20 well groups out of 93 well groups, accounting for 21.5%. The gas channeling prevention system and nitrogen flooding gas channeling prevention method provided by the present invention were used to treat the gas channeling well groups. The following is a detailed description taking THX1 well, THX2 well, and THX3 well as examples.

[0127] Example 4

[0128] Using the gas channeling prevention system provided in Example 1, the nitrogen flooding gas channeling prevention method provided by the present invention was implemented in the THX1 well, and the construction was carried out by the fixed pipe string back injection method:

[0129] 1) injecting the temperature-resistant and salt-resistant gel system provided in Example 1 as a front segment plug to block the nitrogen gas channel with a width of 100 to 500 m;

[0130] 2) Inject the nitrogen gel foam system provided in Example 1 as the first main body plug: 1000m 3 Inject nitrogen into the well at a rate of / h, and use the foam generator at the wellhead to inject gel foam into the well to block the nitrogen gas channel 10 to 100m wide;

[0131] 3) Injecting the nitrogen-thickened foam system provided in Example 1 as the second main body plug: 1000m 3 Nitrogen is injected into the well at an injection rate of / h, and thickened foam is injected into the well using a foam generator at the wellhead to block nitrogen gas channel with a width of 0.1 to 10m;

[0132] 4) Inject oilfield water as a displacement plug to squeeze the front plug, the first main plug and the second main plug into the formation to help plug the nitrogen gas channel. After the well is soaked, it will be sprayed for production;

[0133] During the construction process, the injection speed of the front plug, the gel foam in the first main plug, the thickened foam in the second main plug and the displacement plug was 18m / s. 3 / h, cumulative injection 1000m 3 , of which the injection volume of the front slug accounts for 10%, and the cumulative injection volume is 100m 3 The injection volume of the first main body plug is 20%, and the cumulative injection volume is 200m 3 The injection volume of thickened foam in the second main segment accounts for 30%, and the cumulative injection volume is 300m 3 ; The injection volume of the displacement plug accounts for 40%, and the cumulative injection volume is 400m 3 .

[0134] Figure 1 The treatment of the THX1 well in this embodiment is shown. It can be seen that after treatment, the THX1 well produces 23.3 tons of liquid per day, and the daily oil production increases from 9.9 tons before treatment to 16.9 tons after treatment, with a water content of 27.6%. At present, the well has been in continuous production for 170 days, with a cumulative increase of 643.4 tons of oil, and is still increasing oil.

[0135] Example 5

[0136] Using the gas channeling prevention system provided in Example 2, the nitrogen flooding gas channeling prevention method provided by the present invention was implemented in the THX2 well, and the construction was carried out by the fixed pipe string reverse injection method. Specifically:

[0137] 1) injecting the temperature-resistant and salt-resistant gel system provided in Example 2 as a front segment plug to block the nitrogen gas channel with a width of 100 to 500 m;

[0138] 2) Inject the nitrogen gel foam system provided in Example 2 as the first main body plug: 1000m 3 Inject nitrogen into the well at a rate of / h, and use the foam generator at the wellhead to inject gel foam into the well to block the nitrogen gas channel 10 to 100m wide;

[0139] 3) Injecting the nitrogen-thickened foam system provided in Example 2 as the second main body plug: 1000m 3 Nitrogen is injected into the well at an injection rate of / h, and thickened foam is injected into the well using a foam generator at the wellhead to block nitrogen gas channel with a width of 0.1 to 10m;

[0140] 4) Inject oilfield water as a displacement plug to squeeze the front plug, the first main plug and the second main plug into the formation to help plug the nitrogen gas channel. After the well is soaked, it will be sprayed for production;

[0141] During the construction process, the injection speed of the front plug, the gel foam in the first main plug, the thickened foam in the second main plug and the displacement plug was 24m / s. 3 / h, cumulative injection 1500m 3 The injection volume of the front slug accounts for 12%, and the cumulative injection volume is 180m 3 The injection volume of the first main body plug is 22%, and the cumulative injection volume is 330m 3 The injection volume of thickened foam in the second main segment accounted for 32%, and the cumulative injection volume was 480m 3 The displacement plug injection volume accounts for 34%, and the cumulative oilfield water injection is 510m 3 .

[0142] Figure 2 The treatment of the THX2 well in this embodiment is shown. It can be seen that after treatment, the THX2 well produces 29.5 tons of liquid per day, and the daily oil production increases from 9.1 tons before treatment to 15.8 tons after treatment, with a water content of 46.5%. At present, the well has been in continuous production for 160 days, with a cumulative increase of 697.2 tons of oil, and is still increasing oil.

[0143] Example 6

[0144] Using the gas channeling prevention system provided in Example 3, the nitrogen flooding gas channeling prevention method provided by the present invention was implemented in the THX3 well, and the construction was carried out by the fixed pipe string reverse injection method. Specifically:

[0145] 1) injecting the temperature-resistant and salt-resistant gel system provided in Example 3 as a front segment plug to block the nitrogen gas channel with a width of 100 to 500 m;

[0146] 2) Inject the nitrogen gel foam system provided in Example 3 as the first main body plug: 1000m 3 Inject nitrogen into the well at a rate of / h, and use the foam generator at the wellhead to inject gel foam into the well to block the nitrogen gas channel 10 to 100m wide;

[0147] 3) Injecting the nitrogen-thickened foam system provided in Example 3 as the second main body plug: 1000m 3 Nitrogen is injected into the well at an injection rate of / h, and thickened foam is injected into the well using a foam generator at the wellhead to block nitrogen gas channel with a width of 0.1 to 10m;

[0148] 4) Inject oilfield water as a displacement plug to squeeze the front plug, the first main plug and the second main plug into the formation to help plug the nitrogen gas channel. After the well is soaked, it will be sprayed for production;

[0149] During the construction process, the injection speed of the front plug, the gel foam in the first main plug, the thickened foam in the second main plug and the displacement plug was 30m / s. 3 / h, cumulative injection 2000m 3 , of which the injection volume of the front slug accounts for 15%, and the cumulative injection volume is 300m 3 ; The injection volume of the gel foam in the first main segment plug accounts for 25%, and the cumulative injection volume is 500m 3 The injection volume of thickened foam in the second main segment accounts for 35%, and the cumulative injection volume is 700m 3 ; The displacement plug injection volume accounts for 25%, and the cumulative injection volume is 500m 3 .

[0150] Figure 3 The treatment of the THX3 well in this embodiment is shown. It can be seen that after treatment, the THX3 well produces 29.3 tons of liquid per day, and the daily oil production increases from 11.3 tons before treatment to 21.1 tons after treatment, with a water content of 27.9%. At present, the well has been in continuous production for 70 days, with a cumulative increase of 612.7 tons of oil, and is still increasing oil.

[0151] Although the present invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that various changes may be made without departing from the true spirit and scope of the present invention. In addition, the subject matter, spirit and scope of the present invention may be varied to accommodate specific situations, materials, material combinations and methods. All of these changes are included within the scope of the claims of the present invention.

Claims

1. A gas channeling prevention system, comprising a temperature-resistant and salt-resistant gel system, a nitrogen gel foam system and a nitrogen thickened foam system.

2. The anti-gas channeling system according to claim 1, It is characterized in that The temperature-resistant and salt-resistant jelly system comprises a first anionic polyacrylamide, carboxymethyl cellulose, a first phenolic crosslinking agent and a first aldehyde crosslinking agent; and / or The nitrogen jelly foam system comprises nitrogen and jelly foam; and / or The nitrogen-densified foam system comprises nitrogen and densified foam; Preferably, the jelly foam comprises a second anionic polyacrylamide, a polyurethane, a second phenolic crosslinking agent, a second aldehyde crosslinking agent and a surfactant; and / or The thickened foam includes a foaming agent and a foam stabilizer.

3. The anti-gas channeling system according to claim 2, It is characterized in that The mass of the heat-resistant and salt-resistant jelly system is calculated as 100%, and the heat-resistant and salt-resistant jelly comprises 0.6 to 1 wt % of the first anionic polyacrylamide, 0.4 to 1 wt % of the carboxymethyl cellulose, 0.2 to 0.6 wt % of the first phenolic crosslinking agent, 0.2 to 0.6 wt % of the first aldehyde crosslinking agent and the balance water.

4. The anti-gas channeling system according to claim 2, It is characterized in that Taking the mass of the jelly foam as 100%, the jelly foam includes 0.8 to 1 wt % of the second anionic polyacrylamide, 1 to 1.2 wt % of the polyurethane, 0.4 to 0.6 wt % of the second phenolic crosslinking agent, 0.4 to 0.6 wt % of the second aldehyde crosslinking agent, 0.6 to 1 wt % of the surfactant and the balance water.

5. The anti-gas channeling system according to claim 2, It is characterized in that The mass of the thickened foam is calculated as 100%, and the thickened foam includes 1 to 1.5 wt % of the foaming agent, 1 to 1.5 wt % of the foam stabilizer, and the balance of water.

6. The anti-gas channeling system according to any one of claims 2 to 5, It is characterized in that The weight average molecular weight of the first anionic polyacrylamide is 10×10 4 ; and / or The weight average molecular weight of the second anionic polyacrylamide is 14×10 4 ; and / or The weight average molecular weight of the polyurethane is 322; and / or The first phenolic cross-linking agent and the second phenolic cross-linking agent are hydroquinone; and / or The first aldehyde cross-linking agent and the second aldehyde cross-linking agent are urotropine; and / or The surfactant is sodium dodecylbenzene sulfonate; and / or The foaming agent is dodecyldimethylamine betaine; and / or the foam stabilizing agent is polyacrylamide.

7. A nitrogen flooding gas channeling prevention method, It is characterized in that Using the anti-gas channeling system according to any one of claims 1 to 6, nitrogen flooding is carried out to prevent gas channeling in a slug combination manner; 1) injecting the temperature-resistant and salt-resistant gel system as a front segment plug to block the nitrogen gas channel with a width of 100 to 500 m; 2) injecting the nitrogen gel foam system as the first main segment plug to block the nitrogen gas channel with a width of 10 to 100 m; 3) Injecting the nitrogen thickened foam system as the second main segment plug to block the nitrogen gas channel with a width of 0.1 to 10 m.

8. The method according to claim 7, It is characterized in that The method further comprises step 4) of injecting water as a displacement plug.

9. The method according to claim 8, It is characterized in that The total injection volume of the leading slug, the jelly foam in the first main body slug, the thickened foam in the second main body slug and the replacement slug is calculated as 100%, the injection volume of the leading slug accounts for 10 to 15%, the injection volume of the jelly foam in the first main body slug accounts for 20 to 25%, the injection volume of the thickened foam in the second main body slug accounts for 30 to 35% and the injection volume of the replacement slug accounts for 25 to 40%.

10. Use of the gas channeling prevention system according to any one of claims 1 to 6 or the nitrogen flooding gas channeling prevention method according to any one of claims 7 to 9 in nitrogen flooding gas channeling prevention in fracture-cavity reservoir units.

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