Block bottom water reservoir gas injection gravity drive gas channeling prevention regulation and parameter design method

Abstract

The invention discloses a blocky bottom water reservoir gas injection gravity drive gas channeling prevention regulation and parameter design method, which comprises the following steps of: after a secondary gas top and an enriched oil zone are formed by gas injection, continuously maintaining the underground injection-production ratio to be more than 1.0; determining a daily oil production curve and possible gas channeling time of a target well in the target oil reservoir under the current production allocation condition based on a numerical simulation method; in a preset time period before gas channeling occurs, the perforation well section is lowered in a staged mode, and production is conducted according to the perforation well section after the perforation well section is lowered; and / or, within a preset time period before gas channeling occurs, the injection-production ratio is lowered in stages, and production is conducted according to the lowered injection-production ratio. According to the method, the gas channeling phenomenon can be effectively slowed down, the beneficial effects that the initial yield is high, the middle and later periods are stable, the oil extraction speed is increased, and the gas injection development effect is improved are achieved, efficient exploitation of the enriched oil zone is facilitated, and the gas injection gravity flooding wave, the volume and the technical and economic benefits are increased.

Description

Technical Field

[0001] The invention relates to the technical field of oil reservoir development, and in particular to a method for controlling and designing parameters of gas injection gravity drive to prevent gas channeling in a blocky bottom water oil reservoir. Background Art

[0002] Reference Figure 1 As shown in Figure 2, a layered reservoir is one in which the oil column height is greater than the reservoir thickness, also called a layered edge-water reservoir. Figure 2 As shown in the figure, a massive reservoir is one in which the oil column height is less than the reservoir thickness, also called a massive bottom water reservoir, such as anticline structure, fault nose structure, and buried hill structure reservoir. Massive bottom water reservoirs benefit from their massive storage space and large oil column closure height, which is conducive to the formation of secondary gas caps and is very suitable for gas injection gravity drive.

[0003] Reference Figure 3 As shown in the figure, in the process of water flooding development of massive bottom water reservoirs, the top retained attic oil, inter-well residual oil, weak water flooding residual oil, etc. are difficult to produce. Figure 4 As shown in the figure, during the gas injection gravity drive development process, due to the buoyancy formed by the density difference between oil, gas and water, the injected gas continuously drives the remaining oil and formation water in the high position to migrate downward. The larger the secondary gas cap formed by the gas injection, the more enriched oil is formed, and the greater the extent of the possible gas injection enhanced recovery factor.

[0004] Since gas, oil and water coexist vertically, and the viscosity of the gas phase is much lower than that of the oil phase, oil wells are faced with the threat of gas breakthrough to the production wells when exploiting the oil-rich zone. Figure 5 As shown in the figure, the specific manifestation is that after the gas breakthrough, the gas-liquid ratio of the production well increases rapidly, and the oil pump gas locks the oil well, resulting in a decrease in liquid volume or even shutting down without liquid. The conventional solution is to slow down the gas channeling phenomenon by limiting the production allocation, which will cause the gas drive oil production rate to decrease, the development period to increase, and the economic benefits of the project to be difficult to guarantee. Therefore, effective anti-gas channeling control measures can increase the oil production rate, shorten the development period, and effectively improve the gas injection gravity drive production effect. After searching, there is no report on the anti-gas channeling control method of gas injection gravity drive. Summary of the invention

[0005] The inventors found that during the gas production process after the formation of an enriched oil zone by gas injection gravity drive, the gas-oil interface gradually moves downward while the oil-water interface remains basically stable, and the enriched oil zone becomes thinner and thinner. As gas injection and oil production proceed, the oil-gas interface gets closer and closer to the perforation position of the oil well, and the risk of gas channeling increases rapidly. In order to ensure that the oil well has a good anti-gas channeling production effect throughout its life cycle, its perforation position should be at the bottom of the enriched oil zone. In order to enrich the process route and increase the selection space, the embodiment of the present invention provides a method for controlling and designing gas channeling prevention and parameters of gas injection gravity drive in a massive bottom water reservoir that overcomes the above problems or at least partially solves the above problems.

[0006] In a first aspect, an embodiment of the present invention provides a method for controlling gas injection gravity flooding to prevent gas channeling in a massive bottom water reservoir, which may include:

[0007] After the secondary gas cap and the enriched oil zone are formed by gas injection, the daily oil production curve of the target well in the target reservoir under the current production allocation conditions and the time when gas channeling may occur are determined based on the numerical simulation method under the condition of maintaining the underground injection-production ratio above 1.0;

[0008] Within a predetermined period of time before gas breakthrough occurs, the perforation interval is downgraded in stages to produce in accordance with the downgraded perforation interval; and / or,

[0009] Within a preset time period before gas channeling occurs, the injection-production ratio is lowered in stages so that production can be carried out according to the lowered injection-production ratio.

[0010] Optionally, lowering the perforation well section may include: lowering the perforation well section to within a range of 50% to 90% of the longitudinal thickness of the oil-rich zone.

[0011] Optionally, the perforation well section is adjusted downward to within a range of 60% to 80% of the longitudinal thickness of the oil-rich zone.

[0012] Optionally, the perforation interval is lowered to 70% of the longitudinal thickness of the oil-rich zone.

[0013] Optionally, lowering the perforation section may include: lowering the perforation section to 70% of the longitudinal thickness of the oil-rich zone in the early stage of production, lowering the perforation section to 80% of the longitudinal thickness of the oil-rich zone in the middle stage of production, and lowering the perforation section to 90% of the longitudinal thickness of the oil-rich zone in the late stage of production.

[0014] Optionally, lowering the injection-production ratio may include: lowering the injection-production ratio in stages based on the production cycle.

[0015] Optionally, before lowering the perforation section and lowering the injection-production ratio, the following steps may also be included:

[0016] After injecting gas into the massive bottom water target reservoir to form a secondary gas cap and an enriched oil zone, gas injection is continued to supplement the deficit formed by liquid production.

[0017] Optionally, the gas injected during gas injection is oxygen-reduced air, natural gas or flue gas.

[0018] Optionally, before lowering the perforation section and the injection-production ratio, the method may further include: judging whether the original oil column height of the target reservoir is greater than a preset first height threshold, and whether the thickness of the formed enriched oil zone is greater than a preset first thickness threshold; if it is greater than the preset first height threshold and the first thickness threshold, executing the step of lowering the perforation section and / or lowering the injection-production ratio.

[0019] In a second aspect, an embodiment of the present invention provides a parameter design method for a massive bottom water reservoir, which may include: designing target well parameters of the massive bottom water reservoir based on the gas injection gravity drive and gas channeling prevention control method for the massive bottom water reservoir as described in the first aspect.

[0020] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

[0021] The embodiment of the present invention provides a method for gas injection gravity drive anti-gas channeling control and parameter design in a massive bottom water oil reservoir. The method can effectively slow down the gas channeling phenomenon, achieve high initial production, stable production in the middle and late stages, increase oil production speed, shorten the development period, and improve the beneficial effects of gas injection development effect. The above method provided by the embodiment of the present invention is conducive to the efficient exploitation of enriched oil belts, and increases the swept volume and technical and economic benefits of gas injection gravity drive.

[0022] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 This is a schematic diagram of anticline structural layered edge water reservoir;

[0026] Figure 2 This is a schematic diagram of anticline structural massive bottom water reservoir;

[0027] Figure 3 This is a schematic diagram of the remaining oil in the bottom water drive of a massive buried hill reservoir;

[0028] Figure 4 This is a schematic diagram of the gas injection gravity drive development mode;

[0029] Figure 5 This is a schematic diagram of the gas channeling phenomenon when an oil well exploits an oil-rich zone;

[0030] Figure 6 It is a flow chart of a method for controlling gas injection gravity flooding and preventing gas channeling in a massive bottom water reservoir provided in an embodiment of the present invention;

[0031] Figure 7 A schematic diagram of implementing downward perforation section control in three stages provided in an embodiment of the present invention;

[0032] Figure 8 The three-stage implementation of adjusting the perforation well section to control the daily oil production curve is provided in the embodiment of the present invention;

[0033] Fig. 9 A schematic diagram of fluid interface distribution for variable speed gas injection in four stages provided in an embodiment of the present invention;

[0034] Fig.10 The daily oil production curve for implementing variable speed gas injection control in four stages provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0035] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0036] In the embodiment of the present invention, a method for preventing gas channeling in a massive bottom water reservoir gas injection gravity drive is provided. In the gas supplementation production process after the formation of the enriched oil zone, the method realizes gas channeling prevention and control by down-regulating the perforation section and / or variable speed gas injection. In the specific implementation, the down-regulation of the perforation section or the variable speed gas injection can be used, or both can be performed. Figure 6 As shown, the method may include the following steps:

[0037] Step S61: After the secondary gas cap and the enriched oil zone are formed by gas injection, the daily oil production curve of the target well in the target reservoir under the current production allocation conditions and the time when gas breakthrough may occur are determined based on the numerical simulation method while continuing to maintain the underground injection-production ratio above 1.0.

[0038] This step predicts the daily oil production curve of the target well under a certain production allocation condition and the time when gas channeling may occur based on the numerical simulation method. The daily oil production curve can be used to compare the daily oil production after subsequent regulation with the daily oil production before adjustment to analyze the degree of oil recovery in different stages and screen out a better adjustment interval. The gas channeling time predicted in this step refers to the time when the gas channeling risk occurs. Human intervention is performed before the gas channeling time to regulate the target well by lowering the perforation section and / or lowering the injection-production ratio.

[0039] In the specific implementation of this step, it is assumed that the thickness of the enriched oil zone formed after gas injection in a certain massive bottom water reservoir is H (meters), and the target production period is T (years). Due to continuous gas injection production, the oil-gas interface gradually moves downward, the secondary gas cap continues to expand and has a good inhibitory effect on the bottom water coning.

[0040] Step S62: within a preset time period before gas channeling occurs, the perforation section is lowered in stages to produce according to the lowered perforation section; and / or, within a preset time period before gas channeling occurs, the injection-production ratio is lowered in stages to produce according to the lowered injection-production ratio.

[0041] In this step, the perforation section is adjusted down in stages or the injection-production ratio is adjusted down in stages, and the gas supplement production period can be divided into 3 to 10 oil production stages according to actual needs. In the specific division, in view of the technical difficulty, complicated operation and increased cost of multiple supplementary perforations and plugging of the original well section, the number of oil production stages should not be too many, and the specific division stages should be determined in combination with the need for gas channeling prevention and control and the current perforation process level. In this step, when the anti-gas channeling control is carried out by adjusting the perforation section down, the injection-production ratio is kept above 1.0, which has a good inhibitory effect on the bottom water coning. As the gas-oil interface decreases and the oil-water interface is basically stable, the enriched oil zone becomes thinner and thinner. In this step, "the preset time period before gas channeling occurs" means that the time when gas channeling may occur is predicted by step S61, and the perforation section is adjusted down at a certain time before this time. If gas channeling still occurs when the perforation section after the adjustment is continued to be produced, the perforation section is further adjusted down at a certain time before gas channeling, and so on.

[0042] In the specific implementation of this step, lowering the perforation section may include: lowering the perforation section to within 50% to 90% of the longitudinal thickness of the rich oil zone. Preferably, lowering the perforation section to within 60% to 80% of the longitudinal thickness of the rich oil zone. More preferably, lowering the perforation section to 70% of the longitudinal thickness of the rich oil zone.

[0043] In this step, the injection-production ratio can be specifically lowered in stages based on the production cycle, that is, the injection-production ratio is kept at 1.0 in the initial stage. As the gas cap expands, the gas-oil interface is closer and closer to the perforation position, so as to achieve gas channeling prevention control by gradually reducing the injection-production ratio. The injection-production ratio can be gradually reduced as follows: it is recommended that the reservoir volume injection-production ratio is greater than or equal to 1.0 in this stage to make up for the deficit formed by oil production, which can effectively inhibit the bottom water cone advance, reduce the water content, and obtain the effect of high production in the early stage. In the middle and late stages (T / 3~T), as the enriched oil zone is produced thinner and thinner, the risk of gas channeling in the oil well becomes the main contradiction, and the bottom water cone advance becomes a secondary contradiction. The main task of regulation is to slow down gas channeling and control the gas-liquid ratio production. It is recommended that the injection-production ratio in the middle stage (T / 3~2T / 3) is gradually reduced from 1.0 to 0.6, and the injection-production ratio in the late stage (2T / 3~T) is gradually reduced from 0.6 to 0.4. In this way, the advancement speed of the gas-oil interface slows down, slowing down or even avoiding gas breakthrough. The method of lowering the injection-production ratio is different from the method of lowering the perforation section. After the injection-production ratio is lowered, the inhibitory effect on the bottom water will be weakened, the gas-oil interface will drop, the oil-water interface will rise, and the enriched oil zone will become thinner and thinner. In the specific regulation, the injection-production ratio is lowered by 0.1-0.3 at a certain time before the gas channeling time. If gas channeling still occurs when production continues according to the lowered injection-production ratio, the injection-production ratio is further lowered by 0.1-0.3 at a certain time before the gas channeling, and so on.

[0044] The above-mentioned gas injection gravity drive anti-gas channeling control method for massive bottom water oil reservoirs provided in the embodiment of the present invention can effectively slow down the gas channeling phenomenon, achieve high initial production, stable production in the middle and late stages, increase oil production speed, shorten the development period, and improve the beneficial effects of gas injection development effect. The above-mentioned method provided in the embodiment of the present invention is conducive to the efficient exploitation of enriched oil belts, and increases the swept volume and technical and economic benefits of gas injection gravity drive.

[0045] In an optional embodiment, the above-mentioned lowering of the perforation section may also include: lowering the perforation section to 70% of the longitudinal thickness of the rich oil zone in the early stage of production, lowering the perforation section to 80% of the longitudinal thickness of the rich oil zone in the middle stage of production, and lowering the perforation section to 90% of the longitudinal thickness of the rich oil zone in the late stage of production.

[0046] In another alternative embodiment, referring to Figure 6 As shown, before lowering the perforation well section and lowering the injection-production ratio, the gas injection gravity drive gas channeling prevention control method for the massive bottom water reservoir may further include the following steps:

[0047] Step S60, inject gas into the massive bottom water target reservoir to form a secondary gas cap and an enriched oil zone, and then continue to inject gas to make up for the deficit formed by the produced liquid. In this step, when the oil well exploits the enriched oil zone during the gas supplement production process, it faces the dual threats of bottom water cone advancement and gas breakthrough. By implementing staged perforation control, or variable speed gas injection control, or a combination of the two controls, the beneficial effects of high initial production, stable production in the middle and late stages, and shortened development period are achieved.

[0048] It should be noted that the gas injected during the gas injection in this step is oxygen-reduced air, natural gas or flue gas.

[0049] In another optional embodiment, before lowering the perforation section and lowering the injection-production ratio, the method may further include: judging whether the original oil column height of the target reservoir is greater than a preset first height threshold, and whether the thickness of the formed enriched oil zone is greater than a preset first thickness threshold; if it is greater than the preset first height threshold and the first thickness threshold, executing the step of lowering the perforation section and / or lowering the injection-production ratio.

[0050] This step is limited to gas injection gravity drive. For example, the original oil column height of a massive bottom water reservoir should be greater than 50 meters, and the thickness of the formed enriched oil zone should be greater than 20 meters before gas injection gravity drive development can be carried out.

[0051] The following are three specific examples to verify and illustrate the above method:

[0052] Example 1

[0053] The gas drive of a certain block bottom water reservoir can be used for oil-bearing height of 140 meters and geological reserves of 6.76 million tons. It is planned to realize a substantial increase in the recovery rate of the "double high" buried hill oil reservoir by carrying out top gas injection gravity drive. After rapid injection of 54 million cubic meters of nitrogen, a secondary gas cap of 80 meters was formed, the thickness of the enriched oil zone was 60 meters, the oil-gas interface was -3000 meters, and the oil-water interface was -3060 meters. Deploy a 3-injection 18-production gas injection gravity drive well network, and select the oil well perforation positions at 50%, 60%, 70%, 80%, and 90% of the enriched oil zone, respectively. Refer to Figure 8 As shown, when the oil well is perforated for 3 meters, that is, the perforation positions are respectively -3029 to -3031 meters, -3035 to -3037 meters, -3041 to -3043 meters, -3047 to -3049 meters, and -3053 to -3055 meters, the production indicators of 20 years of gas supplement production are respectively predicted by the reservoir numerical simulation method. When the injection-production ratio is 1.0, the cumulative oil production of the oil well perforated at 60% to 80% of the enriched oil zone is larger, and 70% of the enriched oil zone is the optimal perforation position. The production indicators of gas supplement production after gas injection are shown in Table 1 below:

[0054] Table 1 Production indicators of rapid gas injection and gas supplement production

[0055]

[0056] Example 2

[0057] The basic situation of the reservoir is the same as that in Example 1. The underground volume injection-production ratio is maintained at 1.0 for gas supplementation production. Combined with the current perforation technology level, it is planned to gradually reduce the perforation in three stages, keeping the perforation section at 70% of the oil-rich zone at the beginning of each stage.

[0058] According to numerical simulation prediction, the reservoir showed obvious gas channeling in the 7th year and 10th month, and the perforation section was lowered to -3048 to -3050 meters in the 6th year. When the well section was kept in production, the reservoir showed obvious gas channeling again in the 12th year, and the perforation section was lowered to -3052 to -3054 meters in the 10th year. By lowering the perforation twice, the time of obvious gas channeling was postponed from January 2029 to August 2035, and the anti-gas channeling effect was significant, as shown in Table 2. Figure 7 and Figure 8 It is predicted that the cumulative oil production in 20 years will be 1.017 million tons, and the stage recovery rate will be 15.04%, which is 6.12 percentage points higher than that in Example 1.

[0059] Table 2 Implementation parameters for adjusting the perforation position in stages

[0060] stage Time (nth year) Oil-rich zone location (m) Perforation location (m) Phase 1 1-5 -3000～3060 -3041～-3043 Phase II 6-9 -3025～3059 -3048～-3050 Phase 3 10-20 -3040～3057 -3052～-3054

[0061] Example 3

[0062] The basic situation of the reservoir is the same as that of Example 1 and Example 2. The initial injection-production ratio is maintained at 1.0 for gas supplementation production. After numerical simulation prediction, the reservoir has obvious gas channeling at 7 years and 10 months, and the injection-production ratio is adjusted to 0.7 in the 6th year. When the injection-production ratio is maintained at 0.7, the reservoir has obvious gas channeling again at 9 years and 8 months, and the injection-production ratio is adjusted to 0.4 in the 9th year. When the injection-production ratio is maintained at 0.4, the reservoir has obvious gas channeling again at 13 years and 10 months, and the injection-production ratio is adjusted to 0.2 in the 13th year. Fig. 9 and Fig.10 It is predicted that the cumulative oil production in 20 years will be 1.026 million tons, and the stage recovery rate will be 15.18%, which is 6.26 percentage points higher than that in Example 1.

[0063] Based on the same inventive concept, an embodiment of the present invention also provides a parameter design method for a massive bottom water reservoir, which may include: designing the target well parameters of the massive bottom water reservoir based on the aforementioned gas injection gravity drive and gas channeling prevention control method for the massive bottom water reservoir. The principle of the problem solved by the parameter design method is similar to the aforementioned gas injection gravity drive and gas channeling prevention control method for the massive bottom water reservoir, and the parameters in the method include but are not limited to injection and production parameters, and may also include other parameters, so its implementation can refer to the implementation of the aforementioned method, and the repeated parts will not be repeated.

[0064] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for controlling gas injection gravity flooding to prevent gas channeling in a massive bottom water reservoir, characterized in that: include: After the secondary gas cap and the enriched oil zone are formed by gas injection, the daily oil production curve of the target well in the target reservoir under the current production allocation conditions and the time when gas channeling may occur are determined based on the numerical simulation method under the condition of maintaining the underground injection-production ratio above 1.0; Within a predetermined period of time before gas breakthrough occurs, the perforation interval is downgraded in stages to produce in accordance with the downgraded perforation interval; and / or, Within a preset time period before gas channeling occurs, the injection-production ratio is lowered in stages so that production can be carried out according to the lowered injection-production ratio.

2. The method according to claim 1, characterized in that Lowering the perforation well section includes: lowering the perforation well section to within a range of 50% to 90% of the longitudinal thickness of the oil-rich zone.

3. The method according to claim 2, characterized in that Lower the perforation section to within 60% to 80% of the longitudinal thickness of the oil-rich zone.

4. The method according to claim 3, characterized in that Lower the perforation section to 70% of the longitudinal thickness of the oil-rich zone.

5. The method according to claim 2, characterized in that: Lowering the perforation section includes: lowering the perforation section to 70% of the longitudinal thickness of the rich oil zone in the early stage of production, lowering the perforation section to 80% of the longitudinal thickness of the rich oil zone in the middle stage of production, and lowering the perforation section to 90% of the longitudinal thickness of the rich oil zone in the late stage of production.

6. The method according to claim 1, characterized in that Lowering the injection-production ratio includes: lowering the injection-production ratio in stages based on the production cycle.

7. The method according to any one of claims 1 to 6, characterized in that: Before lowering the perforation section and the injection-production ratio, it also includes: After injecting gas into the massive bottom water target reservoir to form a secondary gas cap and an enriched oil zone, gas injection is continued to supplement the deficit formed by liquid production.

8. The method according to claim 7, characterized in that The gas injected during gas injection is oxygen-reduced air, natural gas or flue gas.

9. The method according to any one of claims 1 to 6, characterized in that: Before lowering the perforation well section and lowering the injection-production ratio, the method further includes: judging whether the original oil column height of the target reservoir is greater than a preset first height threshold, and whether the thickness of the formed enriched oil zone is greater than a preset first thickness threshold; If it is greater than the preset first height threshold and first thickness threshold, the step of down-adjusting the perforation section and / or down-adjusting the injection-production ratio is performed.

10. A parameter design method for a massive bottom water reservoir, characterized in that: include: Based on the gas injection gravity drive and gas channeling prevention control method for a massive bottom water reservoir as claimed in any one of claims 1 to 9, target well parameters of the massive bottom water reservoir are designed.

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