Method for comprehensively treating gas channeling through water-gas interactive injection and gel plugging

Abstract

The invention discloses a method for comprehensively treating gas channeling through water-gas interactive injection and gel plugging, and relates to the technical field of offshore oil reservoir gas injection development. The method comprises the steps that gas injection is conducted on a target offshore oil field reservoir, and gas driving is conducted till gas channeling starts; gas-water alternation is performed for two rounds to form a gas-water alternation slug; after the gas-water alternating section is plugged, emulsion gel mixed with nano micro-gel is injected for plugging; and carrying out gas driving until complete gas channeling. The technical problem that long-term effectiveness of channeling sealing is difficult to guarantee in a high-temperature and high-pressure environment in a conventional gas channeling treatment method is solved.

Description

Technical Field

[0001] The invention relates to the technical field of offshore oil reservoir gas injection development, in particular to a method for comprehensive treatment of gas channeling by water-gas alternating injection and gel plugging. Background Art

[0002] Due to the heterogeneity of offshore oilfield reservoirs and the strong breakthrough ability of gas, gas channeling in gas-injected oilfields has become an inevitable trend, among which Weizhou 12 Oilfield is a typical case of gas channeling. Usually, the use of gas injection development can effectively improve crude oil recovery, but after years of development, problems such as rapid increase in gas-oil ratio and serious gas channeling have obviously emerged. Commonly used gas channeling control methods include water-gas alternation, gel plugging, foam flooding, etc., most of which are single-agent use methods. The effect of single water-gas alternation in controlling gas channeling is not ideal. Conventional gel and foam flooding have high requirements on the injectability and temperature resistance of the agent, and it is difficult to ensure the long-term effectiveness of plugging under high temperature and high pressure environment. Summary of the invention

[0003] The purpose of the present invention is to provide a method for comprehensive treatment of gas channeling by alternate water-gas injection and gel plugging in order to solve at least one of the above technical problems.

[0004] In the first aspect, an embodiment of the present invention provides a method for comprehensive treatment of gas channeling by alternate water-gas injection and gel plugging, comprising: injecting gas into a target offshore oil field reservoir and driving the gas until gas channeling begins; alternating gas and water in two rounds to form a gas-water alternating segment plug; injecting a mixed nano-microgel emulsion gel behind the gas-water alternating segment plug for plugging; and driving the gas until the gas channeling is complete.

[0005] Furthermore, the concentration of the emulsion gel includes: 6500mg / L-9500mg / L.

[0006] Furthermore, the mass fraction of the nano-microgel added to the emulsion gel includes: 0.15%-0.35%.

[0007] Furthermore, the injection time of the mixed nano-microgel latex gel is when the gas-liquid ratio in the target offshore oil field reservoir is 500-1000.

[0008] Furthermore, the permeability range of the target offshore oil field reservoir includes 40mD-300mD.

[0009] The present invention provides a method for comprehensive treatment of gas channeling by water-gas alternating injection and gel plugging, which combines water-gas segment plug pressurization and drive regulation with emulsion gel cementation plugging, and enhances the gelling effect by adding nano-microgel, thereby enhancing the temperature and salt resistance and stability of the emulsion gel, and can significantly block strong gas channeling channels, improve the pressure distribution of post-drive gas drive and ultimately improve the gas drive effect, thereby alleviating the technical problem of conventional gas channeling treatment methods that it is difficult to ensure the long-term effectiveness of sealing under high temperature and high pressure environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0011] Figure 1 A flow chart of a method for comprehensive treatment of gas channeling by water-gas alternating injection and gel plugging provided in an embodiment of the present invention;

[0012] Figure 2 A dynamic characteristic curve diagram of the relationship between displacement pressure and injection volume provided by an embodiment of the present invention;

[0013] Figure 3 A dynamic characteristic curve diagram of the relationship between gas-liquid ratio and injection volume provided in an embodiment of the present invention;

[0014] Figure 4 A comparison of the microstructures before and after adding nano-microgel to the latex gel provided by the embodiment of the present invention;

[0015] Figure 5 A schematic diagram of the effect of a nano-microgel on gel strength provided by an embodiment of the present invention;

[0016] Figure 6 A dynamic characteristic curve diagram of displacement efficiency of an emulsion gel injected at a gas-liquid ratio of 500 provided in an embodiment of the present invention;

[0017] Figure 7 A dynamic characteristic curve diagram of displacement efficiency of an emulsion gel injected at a gas-liquid ratio of 1000 provided in an embodiment of the present invention;

[0018] Figure 8 A bar graph showing the effect of different injection times on the displacement efficiency of latex gel provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Figure 1 The flowchart of a method for comprehensive treatment of gas channeling by water-gas alternating injection and gel plugging provided in accordance with an embodiment of the present invention is shown in FIG. Figure 1 As shown, the method specifically comprises the following steps:

[0021] Step S102, injecting gas into the target offshore oil field reservoir until gas breakthrough begins.

[0022] Step S104: gas and water are alternately added for two rounds to form a gas-water alternating slug.

[0023] Specifically, the two rounds of gas-water alternation include: injecting a gas slug, a water slug, a gas slug, and a water slug in sequence into the target offshore oil field reservoir where gas drive begins to cause gas breakthrough, thereby forming a gas-water alternating slug.

[0024] Step S106, injecting mixed nano-microgel latex gel after the air-water alternating segment plug for plugging.

[0025] Optionally, the concentration of the emulsion gel used in the embodiments of the present invention includes: 6500 mg / L-9500 mg / L. Preferably, the concentration of the emulsion gel is 8000 mg / L.

[0026] Optionally, the mass fraction of the nano-microgel added to the latex gel in the embodiment of the present invention includes: 0.15%-0.35%. Preferably, the mass fraction of the nano-microgel is 0.3% of the latex gel.

[0027] Optionally, the injection time of the mixed nano-microgel emulsion gel is when the gas-liquid ratio in the target offshore oil field reservoir is 500-1000. Preferably, the injection time is when the gasoline ratio is 500.

[0028] Step S108, air driving until complete air breakthrough.

[0029] Preferably, the method for comprehensive treatment of gas channeling by water-gas alternating injection and gel plugging provided in the embodiment of the present invention is applied to a target offshore oil field reservoir having a permeability range of 40mD-300mD.

[0030] In order to illustrate the technical effect of the method provided by the embodiment of the present invention, it is verified by specific experimental data below.

[0031] (I) The influence of water-gas alternation on gas channeling inhibition and displacement efficiency:

[0032] Two artificial cores with the same permeability extreme difference (50 / 100 / 500) were selected, and continuous gas injection experiments (injection until complete gas channeling) and water-gas alternating sealing experiments (injection until gas channeling begins, two rounds of gas-water alternation, slug size 0.2PV, and finally injection until complete gas channeling) were carried out at an injection rate of 0.15ml / min. The gas channeling time and displacement efficiency of the two were compared. The displacement scheme and the increase in displacement efficiency at each stage are shown in Table 1.

[0033] Table 1 Water-gas alternation and continuous gas drive experimental results

[0034]

[0035] As can be seen from Table 1, the gas-water alternating method can significantly improve the displacement efficiency by inhibiting gas channeling. Compared with continuous gas drive, the gas-water alternating method can improve the displacement efficiency by more than 10.77. Figure 2 is a dynamic characteristic curve diagram of the relationship between displacement pressure and injection volume provided according to an embodiment of the present invention, Figure 3 1 is a dynamic characteristic curve diagram of the relationship between gas-liquid ratio and injection volume provided according to an embodiment of the present invention. Figure 2 and Figure 3 It can be seen that during the water slug injection stage, the injection pressure dropped significantly, and the pressure rose significantly during the subsequent gas drive, and the final pressure was higher than that during the initial gas injection stage, indicating that the gas-water slug has a certain pressure-boosting and drive-adjusting effect. In addition, the gas-water alternating method can significantly reduce the output gas-liquid ratio and significantly delay the time for complete gas channeling to occur.

[0036] (II) Evaluation of the compatibility between emulsion gel and target reservoir:

[0037] The effects of changing the injection concentration and the injection slug size on the injectability of the agent are shown in Table 2. After the injection concentration and the injection slug are fixed, the plugging rate of the emulsion gel to the target reservoir changes with the permeability as shown in Table 3.

[0038] Table 2 Effect of injection concentration and injection slug on injectivity

[0039]

[0040]

[0041] Table 3 Effect of reservoir permeability on plugging performance

[0042]

[0043]

[0044] It can be seen from Table 2 that when the permeability is constant, as the injection concentration increases, the resistance coefficient of the injected gel system gradually increases. When 8000 mg / L, the resistance coefficient is 29, and the subsequent injection of 6PV agent has a small increase in the resistance coefficient. After exceeding this concentration, the resistance coefficient surges and eventually causes blockage. It can be seen from Table 3 that when the initial gel concentration is selected as 8000 mg / L, each permeability segment (40-300 mD) of the target reservoir can be effectively injected and gelled inside the pores, and the plugging rate is above 90%. Therefore, the emulsion gel concentration used in the embodiment of the present invention is preferably 8000 mg / L.

[0045] (III) Effect of nano-microgel on the gel strength of latex gel:

[0046] Comparing the gel system with and without 0.3% mass fraction of nano-microgel, the internal structures of the two gel systems after gelation at 110℃ and 130℃ were observed. Figure 4 , gel strength comparison see Figure 5 .

[0047] Depend on Figure 4 and Figure 5 It can be seen that after adding nano-microgel to the emulsion gel, the larger gel cavities are filled, the gel strength is significantly improved, and the stability is significantly improved.

[0048] (IV) The influence of injecting plugging slugs at different times on gas channeling suppression and displacement efficiency:

[0049] A gas injection rate (0.15 mL / min) was selected to investigate the effect of injecting plugging slugs at different gas-oil ratios on inhibiting gas channeling and improving displacement efficiency. The displacement dynamic curves of injecting plugging slugs at gas-liquid ratios of 500 and 1000 are shown in Figure 2. Figure 6 and Figure 7 The recovery factor comparison under the two displacement timings is shown in Figure 8 .

[0050] from Figure 6-8 It can be seen that after injecting the emulsion gel, the gas-liquid ratio can be significantly reduced and gas channeling can be suppressed. It also has a significant effect of improving the displacement efficiency. The earlier the gel is injected, the greater the increase in displacement efficiency and the higher the final recovery rate (when the gel is injected at a gas-liquid ratio of 500, the displacement efficiency increases by 38.76%; when the gel is injected at a gas-liquid ratio of 1000, the displacement efficiency increases by 33.31%).

[0051] (V) Comprehensive treatment of gas channeling by alternating air and water and gel plugging:

[0052] The experimental comparison results of the displacement effect of the method provided in the embodiment of the present invention (i.e., gas-water alternating mode plus gel plugging) and four modes of continuous gas drive, gas-water alternating mode, and gel plugging (gas-liquid ratio 500) are shown in Table 4:

[0053] Table 4 Displacement efficiency experimental results

[0054]

[0055] As can be seen from Table 4, the gas-water alternating mode plus gel plugging method provided in the embodiment of the present invention has a stronger effect on improving the displacement efficiency than other methods when other conditions are fixed. The final displacement efficiency reaches 68.79%, an increase of 45.17% over the continuous gas drive stage, and has an excellent oil recovery effect under experimental conditions.

[0056] From the above description, it can be seen that the embodiment of the present invention provides a method for comprehensive treatment of gas channeling by water-gas alternating injection and gel plugging, which is highly targeted, achieves one solution for one reservoir, and completes a complete development system in a closed loop, providing technical support for effectively treating gas channeling problems in medium-low permeability, high-temperature, and high-pressure gas injection reservoirs. Compared with the prior art, the method provided by the embodiment of the present invention has the following technical effects:

[0057] (1) Injectability: Use an emulsion gel with a lower initial viscosity for gel sealing.

[0058] (2) Stability: The addition of nano-microgel fillers can enhance the temperature and salt resistance of the latex gel and enhance the gel strength to a certain extent.

[0059] (3) Effectiveness: The comprehensive sealing technology of gas-liquid alternation + gel plugging has been verified through experiments to significantly improve the displacement efficiency, reduce the gas-liquid ratio at the output end, and delay the occurrence of complete gas channeling.

[0060] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0061] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for comprehensive treatment of gas channeling by alternate water-gas injection and gel plugging, characterized in that: include: Inject gas into the target offshore oil field reservoir until gas breakthrough occurs; Two rounds of alternating gas and water form alternating gas and water slugs; Injecting mixed nano-microgel latex gel behind the gas-water alternating segment plug for plugging; The air is driven until it is completely exhausted.

2. The method according to claim 1, characterized in that: The concentration of the emulsion gel includes: 6500mg / L-9500mg / L.

3. The method according to claim 1, characterized in that: The mass fraction of the nano-microgel added to the emulsion gel includes: 0.15%-0.35%.

4. The method according to claim 1, characterized in that: The injection time of the mixed nano-microgel latex gel is when the gas-liquid ratio in the target offshore oil field reservoir is 500-1000.

5. The method according to claim 1, characterized in that: The permeability range of the target offshore oil field reservoir includes 40mD-300mD.

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