Gel plugging agent, heavy oil reservoir steam flooding method and heavy oil reservoir

Abstract

The invention relates to the technical field of oilfield development, and discloses a gel plugging agent, a heavy oil reservoir steam flooding method and a heavy oil reservoir, the gel plugging agent comprises an acrylamide copolymer and a cross-linking agent, the cross-linking agent can enable the acrylamide copolymer to be cross-linked at the temperature of 50 DEG C or above, and the viscosity of a cross-linked product is reduced by 90% or above 120 days at the temperature of 100 DEG C or above. The gel plugging agent is added in the steam injection process, so that the effects of expanding steam sweep and dynamically adjusting the steam profile can be achieved, the steam flooding effect is improved, the oil-steam ratio is increased, and the recovery efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, specifically to a gel plugging agent and a steam drive method for heavy oil reservoirs and heavy oil reservoirs. Background Technology

[0002] For the development of heavy oil reservoirs, modern petroleum industry systems mostly adopt thermal oil recovery systems represented by steam drive. However, under normal circumstances, steam drive suffers from crossflow and over-coverage problems in the later stages of development. In the former case, the formation of dominant channels causes steam to escape rapidly from the formation, resulting in the steam not being able to widely reach other pores in the reservoir, and the sweep efficiency cannot be further improved. In the latter case, the upward flow of steam leads to uneven distribution of the injection profile, with large differences in the distribution of steam heat at different locations, resulting in unsatisfactory crude oil heating and viscosity reduction effects and poor fluid heat utilization efficiency.

[0003] Therefore, in steam drive, the main direction for improving steam utilization is to expand the steam displacement range, primarily through the injection of plugging agents to adjust the steam profile. Early methods mainly utilized inorganic materials such as cement and fly ash, which, while having good temperature resistance, could cause permanent blockages, hindering subsequent production adjustments. Currently, the development of high-temperature resistant organic profile control agents for steam drive has matured, with gels, particles, and foams already being used as media in the steam drive extraction of heavy oil reservoirs. Guo Daji, Wang Long, and others conducted in-depth analysis of steam overlap and steam channeling phenomena that easily occur during steam injection in horizontal wells of the Shengli Oilfield. They used the high-temperature resistant foaming agent HTF-BZ to adjust and plug steam profiles, effectively improving steam utilization efficiency, suppressing steam channeling, and improving the fluidity of heavy oil through steam heat energy. Zhang Enchen developed a high-temperature resistant profile control agent using polyacrylamide aqueous solution with hydroquinone and formaldehyde. By combining profile control agents with heat stabilizers, the temperature resistance of profile control agents was effectively improved. This technology was applied to heavy oil steam extraction in the Liaohe Oilfield, with a success rate exceeding 95% in 98 wells. It effectively improved problems such as gravity over-coverage and steam channeling during steam extraction, thereby increasing heavy oil recovery. Han Shubo, Wang Xiaoping, and others studied a self-generating, high-temperature resistant gel foam system. This system exhibits good stability at 150℃ and can effectively increase oil recovery by 4.68%-47.73% in parallel core-driven oil recovery tests. RLEson and RW Cooke developed a novel high-temperature gel system, which has been successfully tested in a California heavy oil field and applied in several other oilfields.

[0004] Existing technologies for steam flooding in heavy oil reservoirs have poor effects, with limited steam sweep and low oil-to-steam ratio and enhanced oil recovery. Therefore, there is an urgent need for a new gel plugging agent and a steam flooding method for heavy oil reservoirs. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of poor steam drive effect in heavy oil reservoirs in the prior art, and to provide a gel plugging agent, a steam drive method for heavy oil reservoirs, and a heavy oil reservoir.

[0006] To achieve the above objectives, the first aspect of the present invention provides a gel plugging agent, wherein the gel plugging agent comprises an acrylamide copolymer and a crosslinking agent, wherein the crosslinking agent enables the acrylamide copolymer to crosslink at a temperature above 50°C and the viscosity of the crosslinked product decreases by more than 90% after 120 days at a temperature above 100°C.

[0007] A second aspect of the present invention provides a method for preparing the gel plugging agent, wherein the acrylamide polymer is mixed with a crosslinking agent.

[0008] A third aspect of the present invention provides a steam drive method for heavy oil reservoirs, wherein the method includes:

[0009] (1) Inject steam from the injection well to break through the production well, stop the steam injection, inject the gel plugging agent according to any one of claims 1-6 to form a blockage, continue to inject steam to drive crude oil;

[0010] (2) After the gel plugging agent degrades with the steam until the steam breaks through the production well again, stop the steam injection, inject the gel plugging agent again, and continue to inject steam to drive the crude oil;

[0011] (3) Optionally, repeat step (2) at least once.

[0012] The fourth aspect of the present invention provides a heavy oil reservoir obtained by the steam drive method for heavy oil reservoirs.

[0013] Through the above technical solution, the present invention provides a gel plugging agent and a steam drive method for heavy oil reservoirs, and a heavy oil reservoir. By adding a gel plugging agent during the steam injection process, the viscosity of the gel plugging agent decreases by more than 90% after 120 days at temperatures above 100°C. The gel plugging agent can be injected multiple times to expand the steam sweep and dynamically adjust the steam profile, thereby improving the steam drive effect, increasing the oil-steam ratio, and improving the recovery rate. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of steam leakage;

[0015] Figure 2 This is a schematic diagram showing the placement of the gel plugging agent after vapor leakage;

[0016] Figure 3 This is a schematic diagram of vapor flow around the gelling agent after it gels. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of this invention provides a gel plugging agent, comprising an acrylamide copolymer and a crosslinking agent. The crosslinking agent enables the acrylamide copolymer to crosslink at temperatures above 50°C, and the crosslinked product exhibits a viscosity reduction of over 90% after 120 days at temperatures above 100°C. In this invention, "viscosity" refers to the apparent viscosity of the polymer aqueous solution, 7.34 s. -1 Viscosity under certain conditions is measured using a viscometer or rheometer.

[0019] In this invention, the gel plugging agent formed by the acrylamide polymer and crosslinking agent has a good plugging effect, and the gel plugging agent can degrade with steam without causing well blockage. Through multiple plugging, the steam sweep can be expanded, and the steam profile can be dynamically adjusted, thereby improving the steam drive effect, increasing the oil-steam ratio, and improving the recovery rate.

[0020] In some specific embodiments of the present invention, the weight ratio of the acrylamide copolymer to the crosslinking agent is 0.5-1.5:1.

[0021] In some specific embodiments of the present invention, the crosslinking agent is selected from one or more of polyethyleneimine, hexamethylenetetramine, resorcinol, aluminum citrate, chromium oxalate, phenol, and formaldehyde.

[0022] In some specific embodiments of the present invention, the gel plugging agent further includes a crosslinking time control agent and water, wherein the crosslinking time control agent is selected from acidic and / or alkaline substances, preferably selected from one or more of sodium carbonate, sodium hydroxide, sodium bicarbonate, ammonia, acetic acid, and hydrochloric acid (HCl).

[0023] In this invention, the acrylamide copolymer refers to the product of polymerizing acrylamide with another monomer (non-acrylamide), that is, the acrylamide copolymer includes structural unit A provided by acrylamide and structural unit B provided by another monomer (non-acrylamide). In some specific embodiments of this invention, in the acrylamide copolymer, structural unit A is derived from acrylamide, and structural unit B is derived from one or more of acrylic acid, sodium acrylate, 2-acrylamidododecylsulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid.

[0024] In some specific embodiments of the present invention, in the acrylamide polymer, based on the total amount of structural units, the content of structural unit A is 50-95 wt%, preferably 70-85 wt%, and the content of structural unit B is 5-50 wt%, preferably 10-30 wt%.

[0025] In some specific embodiments of the present invention, the weight-average molecular weight of the acrylamide polymer is 15 million to 25 million g / mol.

[0026] In some specific embodiments of the present invention, the crosslinking agent is selected from a mixture of polyethyleneimine, hexamethylenetetramine, and resorcinol.

[0027] In some specific embodiments of the present invention, the weight-average molecular weight of the polyethyleneimine is 600-100000 g / mol, preferably 2000-50000 g / mol.

[0028] In some specific embodiments of the present invention, the crosslinking agent is a mixture (M) of polyethyleneimine, hexamethylenetetramine, and resorcinol, wherein the mass ratio of polyethyleneimine, hexamethylenetetramine, and resorcinol is 1-3:0.5-2:1. When the crosslinking agent is a mixture of polyethyleneimine, hexamethylenetetramine, and resorcinol, the gel plugging agent has a better crosslinking effect, thereby having a better sealing effect.

[0029] In some specific embodiments of the present invention, the content of the acrylamide polymer is 0.05-1 wt%, the content of the crosslinking agent is 0.05-1 wt%, the content of the crosslinking time control agent is 0-0.5 wt%, and the remainder is water, relative to the total amount of the gel plugging agent.

[0030] In some specific embodiments of the present invention, preferably, relative to the total amount of the gel plugging agent, the content of the acrylamide polymer is 0.15-0.5 wt%, the content of the crosslinking agent is 0.1-0.4 wt%, and the content of the crosslinking time control agent is 0-0.2 wt%, that is, the crosslinking time control agent may be absent, and the remainder is water.

[0031] In some preferred embodiments of the present invention, in the gel plugging agent, the crosslinking agent is selected from a mixture M of polyethyleneimine, hexamethylenetetramine, and resorcinol, wherein the mass ratio of polyethyleneimine, hexamethylenetetramine, and resorcinol is 1-3:0.5-2:1; in the acrylamide copolymer, structural unit A is derived from acrylamide, and structural unit B is derived from 2-acrylamido-2-methyl-propanesulfonic acid; in the acrylamide polymer, based on the total amount of structural units, the content of structural unit A is 70-85 wt%, and the content of structural unit B is 10-30 wt%. Relative to the total amount of the gel plugging agent, the content of the acrylamide polymer is 0.15-0.5 wt%, the content of the crosslinking agent is 0.1-0.4 wt%, the content of the crosslinking time control agent is 0.001-0.2 wt%, and the remainder is water.

[0032] In some specific embodiments of the present invention, the acrylamide copolymer and the crosslinking agent are stored separately and mixed only when used.

[0033] A second aspect of the present invention provides a method for preparing the gel plugging agent, wherein the acrylamide polymer is mixed with a crosslinking agent.

[0034] In some specific embodiments of the present invention, the method further includes adding a crosslinking time control agent and water to a mixture of acrylamide polymer and crosslinking agent.

[0035] A third aspect of the present invention provides a steam drive method for heavy oil reservoirs, wherein the method includes:

[0036] (1) Inject steam from the injection well to break through the production well, stop the steam injection, inject the gel plugging agent to form a blockage, continue to inject steam to drive the crude oil;

[0037] (2) After the gel plugging agent degrades with the steam until the steam breaks through the production well again, stop the steam injection, inject the gel plugging agent again, and continue to inject steam to drive the crude oil;

[0038] (3) Optionally, repeat step (2) at least once.

[0039] In some specific embodiments of the present invention, in order to further improve the effect of steam drive, the method includes:

[0040] (1) Inject steam from the injection well to break through the production well, stop the steam injection, inject the gel plugging agent, inject displacement fluid to push the gel plugging agent to 1 / 4-1 / 3 of the injection well on the injection-production flow line, wait for it to solidify, and inject steam to drive the crude oil.

[0041] (2) After the gel plugging agent degrades with steam until the steam breaks through the production well again, stop the steam injection, inject the gel plugging agent again, inject the displacement fluid to push the gel plugging agent to the injection-production flow line near the injection well at 1 / 3-1 / 2, wait for solidification, and inject steam to drive the crude oil.

[0042] (3) After the gel plugging agent degrades with the steam until the steam breaks through the production well again, stop the steam injection and inject the gel plugging agent again. The injected displacement fluid will break through and push to the injection-production flow line near the injection well at 1 / 2-3 / 5. Wait for it to solidify and then inject steam to drive the crude oil.

[0043] In this invention, there are no particular restrictions on the type of displacement liquid, and any displacement liquid type known to those skilled in the art can be used. The displacement liquid is selected from water, polyacrylamide aqueous solution or xanthan gum aqueous solution.

[0044] In some specific embodiments of the present invention, the amount of injected steam is determined based on conditions such as reservoir thickness, porosity, and heterogeneity, and the volume of the injected gel plugging agent is determined based on reservoir parameters. The wells described in this application are selected from the heavy oil reservoirs of Shengli Oilfield, and the volume of the gel plugging agent injected each time is 300-700 m³. 3 Within the range.

[0045] In some specific embodiments of the present invention, the condensation time is 1-5 days.

[0046] In some specific embodiments of the present invention, such as Figure 1-3 As shown, before injecting the gel plugging agent, the steam injection time is determined according to the required displacement agent placement location to reduce the formation temperature and control the gelation time of the plugging agent. The initial placement position of the plugging agent is determined according to the degree of steam channeling. If the steam channeling is very slow and the near-wellbore area of ​​the injection well has been well displaced, the plugging agent is placed further away.

[0047] In some specific embodiments of the present invention, the method further includes: in step (1), before injecting the gel plugging agent, the reservoir temperature is reduced to 100-120°C;

[0048] And / or, in step (2), the reservoir temperature is lowered to 90-100°C before the gel plugging agent is injected;

[0049] And / or, in step (3), the reservoir temperature is lowered to below 90°C before the gel plugging agent is injected.

[0050] High temperatures promote the coagulation of gel plugging agents, so the reservoir temperature needs to be lowered to prevent the gel plugging agents from solidifying prematurely. If the reservoir temperature is lowered too slowly, water needs to be injected to accelerate the cooling process. The farther the plugging agent is placed, the longer the time required for the plugging agent to solidify, and the lower the reservoir temperature needs to be.

[0051] The present invention will be described in detail below through embodiments.

[0052] The oil-to-steam ratio is measured by dividing the mass of crude oil produced by steam by the amount of water-equivalent steam injected. The oil-to-steam ratio is dimensionless or measured in t / t.

[0053] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0054] Preparation Example

[0055] Preparation of the gel plugging agent: The acrylamide polymer, crosslinking agent, and crosslinking time control agent were mixed. The components and contents of each preparation example and comparative example are shown in Table 1. The ammonia content in the ammonia water was 35%.

[0056] Table 1

[0057]

[0058]

[0059] The gel stability of the preparation examples and the preparation comparison examples was determined at different temperatures over time, and the results are shown in Table 2-6.

[0060] Table 2. Gel stability in Preparation Example 1

[0061]

[0062]

[0063] Table 3. Gel stability in Preparation Example 2

[0064]

[0065] Table 4. Gel stability in Preparation Example 3

[0066]

[0067] Table 5. Gel stability in Preparation Example 4

[0068]

[0069] Table 6. Gel stability in Preparation Example 5

[0070]

[0071]

[0072] Table 7. Stability of gels prepared in Comparative Example 1

[0073]

[0074] As can be seen from Table 2-6, the viscosity of the gel plugging agent decreases continuously over time, indicating that the gel plugging agent can degrade with steam and will not cause well blockage. Through repeated plugging, it can expand the steam sweep and dynamically adjust the steam profile, thereby improving the steam drive effect, increasing the oil-steam ratio, and improving the recovery rate.

[0075] Example 1

[0076] The well described in this embodiment of the invention is selected from a heavy oil reservoir in the Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and injection-production well spacing of 150m. The gel plugging agent formulation of Preparation Example 1 is used.

[0077] (1) Inject steam from the injection well to break through and enter the production well, stop steam injection, and inject 300m. 3 After cooling the bottom of the well with clean water until the reservoir temperature drops to 120°C, inject 300m³ of the gel plugging agent. 3 Water is pushed to about 1 / 4 of the injection well along the injection-production flow line, and after 4 days of condensation, steam is injected to drive the crude oil.

[0078] (2) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop injecting steam and inject 500m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 100°C, inject another 500m³ of the gel plugging agent. 3 Water is injected to push the gel plugging agent onto the injection-production flow line near the injection well at 1 / 3 of its length. After 3 days of solidification, steam is injected to drive the crude oil.

[0079] (3) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop steam injection and inject 800m... 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 90°C, inject another 800m³ of the gel plugging agent. 3 Water was injected to push the gel plugging agent onto the injection-production flow line near the injection well's midpoint. After two days of settling, steam was injected to drive the crude oil. The procedure ended once the steam reached the production well. The oil-to-steam ratio was measured to be 0.18 after the procedure.

[0080] Example 2

[0081] The well described in this embodiment of the invention is selected from the heavy oil reservoir of Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and injection-production well spacing of 150m. The gel plugging agent formulation of Preparation Example 2 is used.

[0082] (1) Inject steam from the injection well to break through and enter the production well, stop steam injection, and inject 500m. 3Use clean water to cool the bottom of the well. After the reservoir temperature drops to 100°C, inject 500m of the gel plugging agent. 3 Water is pushed to about 1 / 3 of the injection well along the injection-production flow line, and after condensation for 3 days, steam is injected to drive the crude oil.

[0083] (2) After the gel plugging agent degrades with the steam and causes the steam to leak into the production well, stop the steam injection, cool down to below 90°C, and inject the gel plugging agent again. Place the gel plugging agent on the injection-production flow line near the injection well 1 / 2 to drive the crude oil.

[0084] (3) After the gel plugging agent degrades with the steam, causing steam to leak into the production well, the steam injection is stopped, and the measure ends. The oil-steam ratio was measured to be 0.20 after the measure.

[0085] Example 3

[0086] The well described in this embodiment of the invention is selected from the heavy oil reservoir of Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and injection-production well spacing of 150m. The gel plugging agent formulation of Preparation Example 3 is used.

[0087] (1) Inject steam from the injection well to break through and enter the production well, stop steam injection, and inject 300m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops to 100°C, inject 300m of the gel plugging agent. 3 Water is pushed to about 1 / 4 of the injection well along the injection-production flow line, and after condensation for 3 days, steam is injected to drive the crude oil.

[0088] (2) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop injecting steam and inject 500m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 100°C, inject another 500m³ of the gel plugging agent. 3 Water injection pushes the gel plugging agent to the injection-production flow line near the injection well at 1 / 3 of its length. After 3 days of solidification, steam is injected to drive the crude oil.

[0089] (3) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop steam injection and inject 800m... 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 90°C, inject another 800m³ of the gel plugging agent. 3 Water was injected to push the gel plugging agent onto the injection-production flow line near the injection well's midpoint. After two days of settling, steam was injected to drive the crude oil. The procedure ended once the steam reached the production well. The oil-to-steam ratio was measured to be 0.24 after the procedure.

[0090] Example 4

[0091] The procedure was carried out according to Example 3, except that the composition of the gel plugging agent used was the same as in Preparation Example 4. The oil-to-gas ratio was measured to be 0.15 after the procedure.

[0092] Example 5

[0093] The well described in this embodiment of the invention is selected from a heavy oil reservoir in the Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and injection-production well spacing of 150m. The gel plugging agent formulation of Preparation Example 5 is used.

[0094] (1) Inject steam from the injection well to break through and enter the production well, stop steam injection, and inject 300m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops to 100°C, inject 300m of the gel plugging agent. 3 Water is pushed to about 1 / 4 of the injection well along the injection-production flow line, and after condensation for 3 days, steam is injected to drive the crude oil.

[0095] (2) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop injecting steam and inject 500m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 100°C, inject another 500m³ of the gel plugging agent. 3 Water injection pushes the gel plugging agent to the injection-production flow line near the injection well at 1 / 3 of its length. After 3 days of solidification, steam is injected to drive the crude oil.

[0096] (3) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop steam injection and inject 800m... 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 90°C, inject another 800m³ of the gel plugging agent. 3 Water was injected to push the gel plugging agent onto the injection-production flow line near the injection well's midpoint. After two days of settling, steam was injected to drive the crude oil. The procedure ended once the steam reached the production well. The oil-to-steam ratio was measured to be 0.28 after the procedure.

[0097] Example 6

[0098] The well described in this embodiment of the invention is selected from a heavy oil reservoir in the Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and injection-production well spacing of 150m. The gel plugging agent formulation of Preparation Example 5 is used.

[0099] (1) Inject steam from the injection well to break through and enter the production well, stop steam injection, and inject 300m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops to 100°C, inject 300m of the gel plugging agent. 3 Water is pushed to about 1 / 8 of the injection well along the injection-production flow line, and after condensation for 3 days, steam is injected to drive the crude oil.

[0100] (2) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop injecting steam and inject 500m. 3Use clean water to cool the bottom of the well. After the reservoir temperature drops below 100°C, inject another 500m³ of the gel plugging agent. 3 Water injection pushes the gel plugging agent to the injection-production flow line near the injection well at 1 / 4 of its length. After 3 days of solidification, steam is injected to drive the crude oil.

[0101] (3) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop steam injection and inject 800m... 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 90°C, inject another 800m³ of the gel plugging agent. 3 Water was injected to push the gel plugging agent onto the injection-production flow line at approximately 3 / 8 of the injection well's length. After two days of solidification, steam was injected to drive the crude oil. The procedure ended once the steam reached the production well. The oil-to-steam ratio was measured to be 0.18 after the procedure.

[0102] Example 7

[0103] The well described in this embodiment of the invention is selected from a heavy oil reservoir in the Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and injection-production well spacing of 150m. The gel plugging agent formulation of Preparation Example 5 is used.

[0104] (1) Inject steam from the injection well to break through and enter the production well, stop steam injection, and inject 300m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops to 100°C, inject 250m of the gel plugging agent. 3 Water is pushed to about 1 / 2 of the injection well on the injection-production flow line, and after condensation for 3 days, steam is injected to drive the crude oil.

[0105] (2) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop injecting steam and inject 500m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 100°C, inject another 500m³ of the gel plugging agent. 3 Water injection pushes the gel plugging agent onto the injection-production flow line near the injection well at 5 / 8, waits for it to solidify for 3 days, and then injects steam to drive the crude oil.

[0106] (3) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop steam injection and inject 800m... 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops below 90°C, inject another 800m³ of the gel plugging agent. 3 Water was injected to push the gel plugging agent onto the injection-production flow line at approximately 3 / 4 of the injection well length. After two days of settling, steam was injected to drive the crude oil. The procedure ended once the steam reached the production well. The oil-to-steam ratio was measured to be 0.15 after the procedure.

[0107] Example 8

[0108] The well was selected from a heavy oil reservoir in the Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and injection-production well spacing of 150m. The gel plugging agent formulation of Preparation Example 3 was used.

[0109] (1) Inject steam from the injection well to break through the production well, stop steam injection, and inject 300m of the gel plugging agent. 3 Water is pushed to about 1 / 4 of the injection well along the injection-production flow line, and after condensation for 3 days, steam is injected to drive the crude oil.

[0110] (2) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop injecting steam and then inject the gel plugging agent again for 500m. 3 Water injection pushes the gel plugging agent to the injection-production flow line near the injection well at 1 / 3 of its length. After 3 days of solidification, steam is injected to drive the crude oil.

[0111] (3) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop injecting steam and then inject the gel plugging agent again for 800m. 3 Water injection was used to push the gel plugging agent onto the injection-production flow line near the injection well's midpoint. After two days of settling, steam was injected to drive the crude oil production. The procedure ended once the steam reached the production well. The result was premature degradation and failure of the plugging agent, premature steam leakage, a short effective period, and poor economic efficiency. The oil-to-steam ratio was measured to be 0.12 after the procedure.

[0112] Example 9

[0113] The well was selected from a heavy oil reservoir in the Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and injection-production well spacing of 150m. The gel plugging agent formulation of Preparation Example 3 was used.

[0114] (1) Inject steam from the injection well to break through and enter the production well, stop steam injection, and inject 300m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops to 130°C, inject 300 ml of the gel plugging agent. 3 Water is pushed to about 1 / 4 of the injection well along the injection-production flow line, and after condensation for 3 days, steam is injected to drive the crude oil.

[0115] (2) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop injecting steam and inject 500m. 3 Use clean water to cool the bottom of the well. After the reservoir temperature drops to 110°C, inject another 500m³ of the gel plugging agent. 3 Water injection pushes the gel plugging agent to the injection-production flow line near the injection well at 1 / 3 of its length. After 3 days of solidification, steam is injected to drive the crude oil.

[0116] (3) After the gel plugging agent degrades with steam, causing steam to leak into the production well, stop steam injection and inject 800m... 3Use clean water to cool the bottom of the well. After the reservoir temperature drops to 90°C, inject another 800m³ of the gel plugging agent. 3 Water injection was used to push the gel plugging agent onto the injection-production flow line near the injection well's midpoint. After two days of settling, steam was injected to drive the crude oil production. The procedure ended once the steam reached the production well. The result was premature degradation and failure of the plugging agent, premature steam leakage, a short effective period, and poor economic efficiency. The oil-to-steam ratio was measured to be 0.14 after the procedure.

[0117] Comparative Example 1

[0118] The well described in this comparative example was selected from a heavy oil reservoir in the Shengli Oilfield, with a reservoir thickness of 10m, porosity of 30%, formation temperature of 65℃, and a well-to-production distance of 150m. The gel plugging agent formulation used in Comparative Example 1 was selected.

[0119] The method of Example 3 was followed, except that the composition of the gel plugging agent used was the same as that in Comparative Example 1. The result was that the plugging agent strength was too low, it degraded and failed prematurely, steam leaked out too early, its effective period was too short, and its economic benefits were poor. After the measures were taken, the oil-to-steam ratio was measured to be 0.11.

[0120] As can be seen from the embodiments and comparative examples of this invention, the gel plugging agent prepared by the preferred formulation of this invention has better gel stability, thereby having a higher oil-to-gas ratio. Examples 5 and 6 show that the injection location described in this application has a significantly better steam drive effect. Examples 5 and 7 show that the volume of the gel plugging agent injected each time is 300-700 m³. 3 Within the specified range, the steam drive effect is significantly better. As can be seen from Examples 3, 8, and 9, cooling the reservoir temperature to the temperature range described in this invention before injecting the gel plugging agent results in a significantly better steam drive effect.

[0121] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A gel plugging agent, characterized in that, The gel plugging agent comprises an acrylamide copolymer and a crosslinking agent, wherein the crosslinking agent enables the acrylamide copolymer to crosslink at temperatures above 50°C and the viscosity of the crosslinked product decreases by more than 90% after 120 days at temperatures above 100°C.

2. The gel plugging agent according to claim 1, wherein, The weight ratio of the acrylamide copolymer to the crosslinking agent is 0.5-1.5:1; The crosslinking agent is selected from one or more of polyethyleneimine, hexamethylenetetramine, resorcinol, aluminum citrate, chromium oxalate, phenol, and formaldehyde; And / or, the gel blocker further includes a crosslinking time control agent and water, wherein the crosslinking time control agent is selected from acidic and / or alkaline substances, preferably selected from one or more of sodium carbonate, sodium hydroxide, sodium bicarbonate, ammonia, acetic acid, and hydrochloric acid.

3. The gel plugging agent according to claim 1 or 2, wherein, In the acrylamide copolymer, structural unit A is derived from acrylamide, and structural unit B is derived from one or more of acrylic acid, sodium acrylate, 2-acrylamidododecyl sulfonic acid, and 2-acrylamido-2-methyl-propanesulfonic acid; Preferably, in the acrylamide polymer, based on the total amount of structural units, the content of structural unit A is 50-95 wt%, preferably 70-85 wt%, and the content of structural unit B is 5-50 wt%, preferably 10-30 wt%. Preferably, the weight-average molecular weight of the acrylamide polymer is 15 million to 25 million g / mol.

4. The gel plugging agent according to any one of claims 1-3, characterized in that, The crosslinking agent is selected from a mixture M of polyethyleneimine, hexamethylenetetramine, and resorcinol; Preferably, when the crosslinking agent is a mixture M of polyethyleneimine, hexamethylenetetramine, and resorcinol, the mass ratio of polyethyleneimine, hexamethylenetetramine, and resorcinol is 1-3:0.5-2:1; Preferably, the weight-average molecular weight of the polyethyleneimine is 600-100000 g / mol, and more preferably 2000-50000 g / mol.

5. The gel plugging agent according to any one of claims 2-4, wherein, Relative to the total amount of the gel plugging agent, the content of the acrylamide polymer is 0.05-1 wt%, the content of the crosslinking agent is 0.05-1 wt%, the content of the crosslinking time control agent is 0-0.5 wt%, and the remainder is water; Preferably, relative to the total amount of the gel plugging agent, the content of the acrylamide polymer is 0.15-0.5 wt%, the content of the crosslinking agent is 0.1-0.4 wt%, the content of the crosslinking time control agent is 0.001-0.2 wt%, and the remainder is water.

6. A method for preparing the gel plugging agent according to any one of claims 1-5, characterized in that, The acrylamide copolymer is mixed with a crosslinking agent.

7. The preparation method according to claim 6, wherein, The method further includes adding a crosslinking time control agent and water to a mixture of acrylamide copolymer and crosslinking agent.

8. A steam drive method for heavy oil reservoirs, characterized in that, The method includes: (1) Inject steam from the injection well to break through the production well, stop the steam injection, inject the gel plugging agent according to any one of claims 1-5 to form a blockage, continue to inject steam to drive crude oil; (2) After the gel plugging agent degrades with the steam until the steam breaks through the production well again, stop the steam injection, inject the gel plugging agent again, and continue to inject steam to drive the crude oil; (3) Optionally, repeat step (2) at least once.

9. The method according to claim 8, wherein, The method includes: (1) Inject steam from the injection well to break through the production well, stop the steam injection, inject the gel plugging agent, inject displacement fluid to push the gel plugging agent to 1 / 4-1 / 3 of the injection well on the injection-production flow line, wait for it to solidify, and inject steam to drive the crude oil. (2) After the gel plugging agent degrades with steam until the steam breaks through the production well again, stop the steam injection, inject the gel plugging agent again, inject the displacement fluid to push the gel plugging agent to the injection-production flow line near the injection well at 1 / 3-1 / 2, wait for solidification, and inject steam to drive the crude oil. (3) After the gel plugging agent degrades with the steam until the steam breaks through the production well again, stop the steam injection and inject the gel plugging agent again. The injected displacement fluid will break through and push to the injection-production flow line near the injection well at 1 / 2-3 / 5. Wait for it to solidify and then inject steam to drive the crude oil.

10. The method according to claim 9, wherein, The volume of the gel plugging agent injected each time is 300-700 m³. 3 Within the range; Preferably, the condensation time is 1-5 days.

11. The method according to any one of claims 8-10, wherein, The method further includes: In step (1), the reservoir temperature is lowered to 100-120℃ before injecting the gel plugging agent; And / or, in step (2), the reservoir temperature is lowered to 90-100°C before the gel plugging agent is injected; And / or, in step (3), the reservoir temperature is lowered to below 90°C before the gel plugging agent is injected.

12. A heavy oil reservoir obtained by the steam drive method for heavy oil reservoirs according to any one of claims 7-11.

Images