A hierarchical plugging method for assisting carbon dioxide huff and puff

Abstract

The present invention provides a graded plugging method for assisting carbon dioxide throughput, comprising the following steps: obtaining the permeability difference of different well sections in a single well; obtaining the oil saturation of different well sections in the single well; determining the type of plugging agent used in the well section and the plugging radius R according to the permeability difference and the oil saturation; being able to plug the dominant permeation channel by using the graded plugging methods of temporary plugging, weak plugging and strong plugging according to the actual conditions of different well sections, preventing carbon dioxide from flowing along the dominant seepage channel, effectively expanding the scope of carbon dioxide, and reducing the emission of carbon dioxide in the depressurization stage, thereby greatly improving the utilization efficiency and throughput effect of carbon dioxide.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field well development engineering, and in particular relates to a graded plugging method for assisting carbon dioxide throughput. Background Art

[0002] At present, domestic and foreign oil fields and research institutions have carried out many studies on the mechanism of CO2 single well huff and puff and field tests, but there are few studies on complex fault block heterogeneous reservoirs with small oil-bearing area, sufficient edge and bottom water energy, and severe reservoir heterogeneity. Especially in the later stage of multiple rounds of CO2 huff and puff, the dominant seepage channel is difficult to effectively control, and the CO2 impact range is significantly weakened.

[0003] Therefore, in view of the problems of sufficient edge and bottom water energy in complex fault blocks, serious reservoir heterogeneity, uneven advancement of edge and bottom water, and generally high water content in production wells, it is urgent to research and develop a carbon dioxide huff and puff oil production method suitable for this type of oil reservoir to prevent carbon dioxide from flowing along the dominant seepage channels, expand the scope of carbon dioxide, reduce the emission of carbon dioxide during the depressurization stage, and improve the utilization efficiency and huff and puff effect of carbon dioxide. Summary of the invention

[0004] The present invention provides a graded plugging method for assisting carbon dioxide throughput, which is used to solve the problems in the prior art of sufficient edge and bottom water energy in complex fault blocks, serious reservoir heterogeneity, uneven advancement of edge and bottom water, and generally high water content in production wells, resulting in poor carbon dioxide throughput oil production effect.

[0005] The present invention provides a hierarchical plugging method for assisting carbon dioxide throughput, comprising the following steps:

[0006] Obtain the permeability difference of different sections in a single well;

[0007] Obtain the oil saturation of different sections in a single well;

[0008] The type of plugging agent and the plugging radius R used in the well section are determined according to the permeability difference and the oil saturation.

[0009] Compared with the prior art, the present invention is advantageous in that the type of plugging agent and the plugging radius used in the well section are determined according to the permeability difference and the oil saturation, and the dominant permeation channel can be blocked by a graded plugging method of temporary plugging, weak plugging and strong plugging according to the actual conditions of different well sections, thereby preventing carbon dioxide from flowing along the dominant seepage channel, effectively expanding the scope of carbon dioxide, and reducing the emission of carbon dioxide in the depressurization stage, thereby greatly improving the utilization efficiency and throughput effect of carbon dioxide.

[0010] Furthermore, the determining the type of plugging agent used in the well section according to the permeability difference and the oil saturation includes:

[0011] The permeability difference of the well section is less than 3, and the oil saturation is less than 0.15, and the well section is not plugged.

[0012] Furthermore, the determining the type of plugging agent used in the well section according to the permeability difference and the oil saturation includes:

[0013] For a well section with a permeability difference of less than 3 and an oil saturation of 0.15≤less than or less than 0.25, and / or a well section with a permeability difference of 3≤less than or less than 5 and an oil saturation of less than 0.2, a temporary plugging agent is used to temporarily plug the well section; wherein the residual resistance coefficient RFF of the temporary plugging agent is not less than 2.5 and not more than 10.

[0014] Furthermore, the determining the type of plugging agent used in the well section according to the permeability difference and the oil saturation includes:

[0015] For a well section with a permeability difference of less than 3 and an oil saturation of ≥0.25, and / or a well section with a permeability difference of 3≤<5 and an oil saturation of ≥0.2, and / or a well section with a permeability difference of 5≤≤10 and an oil saturation of <0.25, a weak plugging agent is used to perform weak plugging treatment on the well section; wherein the residual resistance coefficient RFF of the weak plugging agent is higher than 10 and not higher than 15.

[0016] Furthermore, the determining the type of plugging agent used in the well section according to the permeability difference and the oil saturation includes:

[0017] For well sections with a permeability difference of 5≤≤10 and an oil saturation of ≥0.25, and / or for well sections with a permeability difference of >10, a strong plugging agent is used to perform strong plugging treatment on the well sections; wherein the residual resistance coefficient RFF of the strong plugging agent is higher than 15.

[0018] Further, the determining of the plugging radius R used in the well section according to the permeability difference and the oil saturation includes:

[0019] The well section is in a horizontal well, when the permeability difference is less than 3, 2m≤R<2.6m; when the permeability difference is 3≤R<5, R≥2.6m; and / or,

[0020] The well section is in a directional well. When the permeability difference of the well section is less than 3, 10m≤R<12m; when 3≤permeability difference is less than 5, R≥12m.

[0021] Further, the determining of the plugging radius R used in the well section according to the permeability difference and the oil saturation includes:

[0022] The well section is in a horizontal well, and when the permeability difference is less than 3, 2.1m≤R<2.9m; when 3≤permeability difference is less than 5, 2.9m≤R<4.5m; when 5≤permeability difference is less than 10, R≥4.5m; and / or,

[0023] In the directional well, when the permeability difference is less than 3, 12m≤R<14m; when 3≤permeability difference<5, 14m≤R<16m; ​​when 5≤permeability difference≤10, R≥16m.

[0024] Further, the determining of the plugging radius R used in the well section according to the permeability difference and the oil saturation includes:

[0025] The well section is in a horizontal well, when 5≤permeability difference≤10, 4.8m≤R<5.0m; when permeability difference>10, R≥5.0m; and / or,

[0026] In the directional well, when the permeability difference is 5≤≤10, 18m≤R<20m; when the permeability difference is>10, R≥20m.

[0027] Furthermore, the permeability recovery rate of the temporary plugging agent after plugging and setting for 24 hours is not less than 85%.

[0028] Further, the temporary plugging agent is a foam type temporary plugging agent; and / or,

[0029] The weak plugging agent is a gel-type plugging agent; and / or,

[0030] The strong plugging agent is a gel-type plugging agent and / or a jelly-type plugging agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The experimental results of oil production from a positive rhythm heavy oil reservoir using the method in Comparative Example 1 are as follows;

[0032] Figure 2 The experimental results of oil recovery from a positive rhythm heavy oil reservoir using the method in Example 1 are as follows;

[0033] Figure 3 The experimental results of oil recovery from an anti-rhythmic heavy oil reservoir using the method in Comparative Example 1 are as follows;

[0034] Figure 4 The experimental results of oil production from an anti-rhythm heavy oil reservoir using the method in Example 1 are shown. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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.

[0036] The present invention provides a hierarchical plugging method for assisting carbon dioxide throughput, comprising the following steps:

[0037] Obtain the permeability difference of different sections in a single well;

[0038] Obtain the oil saturation of different sections in a single well;

[0039] The type of plugging agent and the plugging radius R used in the well section are determined according to the permeability difference and the oil saturation.

[0040] The calculation formula of permeability difference is shown in formula (1):

[0041] J k =K max / k min Formula (1)

[0042] In the formula, J k is the permeability difference of different well sections; K max is the maximum permeability of different well sections; K min is the minimum permeability of different well sections.

[0043] The calculation formula of oil saturation is shown in formula (2):

[0044] S o =V o / V p Formula (2)

[0045] In the formula, S o is the oil saturation, V o is the oil-bearing volume in the effective pores of the oil layer rock, V p is the effective pore volume of the reservoir rock.

[0046] The present invention does not limit the testing instruments and methods for permeability difference and oil saturation, and the testing may be performed according to the commonly used methods in the art.

[0047] According to the permeability difference and the oil saturation, the plugging agent type and the plugging radius used in the well section are determined. According to the actual conditions of different well sections, the dominant permeation channel can be blocked by using a graded plugging method of temporary plugging, weak plugging and strong plugging to prevent carbon dioxide from flowing along the dominant seepage channel, effectively expand the scope of carbon dioxide, and at the same time reduce the emission of carbon dioxide in the pressure release stage, greatly improving the utilization efficiency and throughput effect of carbon dioxide.

[0048] Furthermore, the type of plugging agent used in the well section is determined according to the permeability difference and the oil saturation, as shown in Table 1.

[0049] Table 1 Types of plugging agents for graded plugging

[0050]

[0051] It can be seen from the table that the permeability difference of the well section is less than 3, and the oil saturation is less than 0.15, so the well section is not plugged.

[0052] For well sections with a permeability difference of less than 3 and an oil saturation of 0.15≤less than 0.25, and / or for well sections with a permeability difference of 3≤less than 5 and an oil saturation of less than 0.2, temporary plugging agents are used to temporarily plug the well sections. The residual resistance coefficient RFF of the temporary plugging agent is not less than 2.5 and not more than 10.

[0053] For well sections with permeability difference <3 and oil saturation ≥0.25, and / or, well sections with permeability difference 3≤<5 and oil saturation ≥0.2, and / or, well sections with permeability difference 5≤≤10 and oil saturation <0.25, weak plugging agent is used to perform weak plugging treatment on the well sections. The residual resistance coefficient RFF of the weak plugging agent is higher than 10 and not higher than 15.

[0054] For well sections with a permeability difference of 5≤≤10 and an oil saturation of ≥0.25, and / or for well sections with a permeability difference of >10, a strong plugging agent is used to perform strong plugging treatment on the well sections. The residual resistance coefficient RFF of the strong plugging agent is higher than 15.

[0055] The calculation formula of the residual resistance coefficient is shown in formula (3):

[0056] BFF=K b / K a Formula (3)

[0057] Where RFF is the residual resistance coefficient; K b is the permeability of the core before plugging; K a is the permeability of the core after plugging.

[0058] The present invention does not limit the specific type of the plugging agent used, as long as it can meet the required residual resistance coefficient.

[0059] Furthermore, the plugging radius R used in the well section is determined according to the permeability difference and the oil saturation, as shown in Table 2 and Table 3.

[0060] Table 2 Plugging radius in horizontal wells

[0061]

[0062] Table 3 Plugging radius in directional wells

[0063]

[0064] It can be seen from the table that when the temporary plugging agent is used to temporarily plug the horizontal well section, when the permeability difference is <3, 2m≤R<2.6m; when 3≤permeability difference is <5, R≥2.6m; when the temporary plugging agent is used to temporarily plug the directional well section, when the permeability difference of the well section is <3, 10m≤R<12m; when 3≤permeability difference is <5, R≥12m.

[0065] When using weak plugging agents to perform weak plugging treatment on horizontal well sections, when the permeability difference is <3, 2.1m≤R<2.9m; when 3≤permeability difference<5, 2.9m≤R<4.5m; when 5≤permeability difference≤10, R≥4.5m; when using weak plugging agents to perform weak plugging treatment on directional well sections, when the permeability difference is <3, 12m≤R<14m; when 3≤permeability difference<5, 14m≤R<16m; ​​when 5≤permeability difference≤10, R≥16m.

[0066] When strong plugging agents are used to carry out strong plugging treatment on horizontal well sections, when 5≤permeability difference≤10, 4.8m≤R<5.0m; when permeability difference>10, R≥5.0m; when strong plugging agents are used to carry out strong plugging treatment on directional well sections, when 5≤permeability difference≤10, 18m≤R<20m; when permeability difference>10, R≥20m.

[0067] In a specific embodiment, in the temporary plugging treatment, when 3≤permeability difference<5, the residual resistance coefficient RFF of the temporary plugging agent used is not less than 5 and not more than 10.

[0068] Specifically, the permeability recovery rate of the temporary plugging agent is not less than 85%. By further limiting the permeability recovery rate of the temporary plugging agent, the damage of the temporary plugging agent working fluid to the reservoir can be further reduced, its flowback capacity can be improved, and the throughput effect of carbon dioxide can be further improved.

[0069] The calculation formula of the permeability recovery rate is shown in formula (4):

[0070] Dk =K1 / K b Formula (4)

[0071] Where RFF is the residual resistance coefficient; K b is the permeability of the core before plugging; K1 is the permeability of the core after plugging and solidification for 24 hours.

[0072] In a specific embodiment, the temporary blocking agent is a foam-type temporary blocking agent; the weak blocking agent is a gel-type blocking agent; the strong blocking agent is a gel-type blocking agent and / or a jelly-type blocking agent.

[0073] Hereinafter, a graded plugging method for assisting carbon dioxide throughput provided by the present invention is described in detail through specific embodiments.

[0074] Example 1

[0075] The following steps are involved:

[0076] (1) Obtaining the permeability difference of different sections in a single well;

[0077] (2) Obtaining the oil saturation of different sections in a single well;

[0078] (3) According to the permeability difference and the oil saturation, the plugging agent type and the plugging radius R used in the well section are determined; different well sections are graded for plugging, and the execution parameters are shown in Table 4;

[0079] Table 4

[0080]

[0081] (4) Inject carbon dioxide at a pressure of 12-20 MPa, an injection rate of 3-5 t / h, and a soaking time of 20-30 days.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is that only step (4) is performed.

[0084] Test Example 1

[0085] Using the methods of the above embodiments and comparative examples, oil was produced from positive rhythm heavy oil reservoirs and reverse rhythm heavy oil reservoirs, and the oil production results are shown in Tables 5, 6 and Figure 1 to Figure 4 shown.

[0086] Table 5 Experimental results of positive rhythm heavy oil reservoir

[0087]

[0088] According to Table 5 and Figure 1 , Figure 2It can be seen that the recovery degree of the natural energy development stage model of the positive rhythm heavy oil reservoir is 26.89-27.77%.

[0089] In comparative example 1, CO2 huff and puff without plugging agent can improve the recovery of positive rhythm heavy oil reservoir by 8.40%. However, the water content increased rapidly in the later stage of CO2 huff and puff, and the water content increased to 98.57% at the end of the experiment. The injection volume of edge water in this stage was 220mL, and the average injection rate was 5mL / min.

[0090] In Example 1, the graded plugging assisted CO2 huff and puff provided by the present invention can increase the recovery of positive rhythm heavy oil reservoir by 18.20%. The water content in the initial stage of CO2 huff and puff can be reduced to 0, and the effective action period of huff and puff is relatively long. The injected plugging agent effectively blocks the high permeability layer in the reservoir. The graded plugging assisted CO2 huff and puff oil increase effect is significantly higher than the CO2 huff and puff experiment without plugging agent.

[0091] Table 6 Experimental results of anti-rhythmic heavy oil reservoir

[0092]

[0093] According to Table 6 and Figure 3 , Figure 4 It can be seen that the recovery degree of the model in the natural energy development stage of the anti-rhythmic heavy oil reservoir is 28.54-29.05%, the comprehensive water content of the model at the end of natural energy exploitation is 98.7-98.9%, the edge water injection volume is 1422mL-1440mL, 1.60-1.61PV, and the average injection rate is 3.52-3.6mL / min.

[0094] In comparative example 1, CO2 huff and puff without plugging agent can improve the recovery of anti-rhythmic heavy oil reservoir by 9.10%. The water content can be reduced to 41.15% in the early stage of CO2 huff and puff, but the water content increases rapidly in the later stage of CO2 huff and puff, and the water content rises to 98.82% at the end of the experiment. The injection amount of edge water in this stage is 221.5mL, and the average injection rate is 5.2mL / min.

[0095] In Example 1, the CO2 huff and puff assisted by the graded plugging method provided by the present invention can increase the recovery of the anti-rhythmic heavy oil reservoir by 19.11%. The water content in the initial stage of CO2 huff and puff can be reduced to 0, and the effective action period of the huff and puff is relatively long. The injected plugging agent effectively blocks the high permeability layer in the reservoir. The oil increase effect of the CO2 huff and puff assisted by the graded plugging method is significantly higher than that of the CO2 huff and puff experiment without the plugging agent.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents. If these modifications and variations fall within the scope of the claims of the present invention and their equivalent technologies, they should be considered to be within the protection scope of the present invention.

Claims

1. A hierarchical plugging method for assisting carbon dioxide throughput, characterized in that: The following steps are involved: Obtain the permeability difference of different sections in a single well; Obtain the oil saturation of different sections in a single well; The type of plugging agent and the plugging radius R used in the well section are determined according to the permeability difference and the oil saturation.

2. The hierarchical plugging method for assisting carbon dioxide throughput according to claim 1, characterized in that: Determining the type of plugging agent used in the well section according to the permeability difference and the oil saturation includes: The permeability difference of the well section is less than 3, and the oil saturation is less than 0.15, and the well section is not plugged.

3. The hierarchical plugging method for assisting carbon dioxide throughput according to claim 1, characterized in that: Determining the type of plugging agent used in the well section according to the permeability difference and the oil saturation includes: For a well section with a permeability difference of less than 3 and an oil saturation of 0.15≤less than or less than 0.25, and / or a well section with a permeability difference of 3≤less than or less than 5 and an oil saturation of less than 0.2, a temporary plugging agent is used to temporarily plug the well section; wherein the residual resistance coefficient RFF of the temporary plugging agent is not less than 2.5 and not more than 10.

4. The hierarchical plugging method for assisting carbon dioxide throughput according to claim 1, characterized in that: Determining the type of plugging agent used in the well section according to the permeability difference and the oil saturation includes: For a well section with a permeability difference of less than 3 and an oil saturation of ≥0.25, and / or a well section with a permeability difference of 3≤<5 and an oil saturation of ≥0.2, and / or a well section with a permeability difference of 5≤≤10 and an oil saturation of <0.25, a weak plugging agent is used to perform weak plugging treatment on the well section; wherein the residual resistance coefficient RFF of the weak plugging agent is higher than 10 and not higher than 15.

5. The hierarchical plugging method for assisting carbon dioxide throughput according to claim 1, characterized in that: Determining the type of plugging agent used in the well section according to the permeability difference and the oil saturation includes: For well sections with a permeability difference of 5≤≤10 and an oil saturation of ≥0.25, and / or for well sections with a permeability difference of >10, a strong plugging agent is used to perform strong plugging treatment on the well sections; wherein the residual resistance coefficient RFF of the strong plugging agent is higher than 15.

6. The hierarchical plugging method for assisting carbon dioxide throughput according to claim 3, characterized in that: Determining the plugging radius R used in the well section according to the permeability difference and the oil saturation includes: The well section is in a horizontal well, when the permeability difference is less than 3, 2m≤R<2.6m; when the permeability difference is 3≤R<5, R≥2.6m; and / or, The well section is in a directional well. When the permeability difference of the well section is less than 3, 10m≤R<12m; when 3≤permeability difference is less than 5, R≥12m.

7. The hierarchical plugging method for assisting carbon dioxide throughput according to claim 4, characterized in that: Determining the plugging radius R used in the well section according to the permeability difference and the oil saturation includes: The well section is in a horizontal well, and when the permeability difference is less than 3, 2.1m≤R<2.9m; when 3≤permeability difference is less than 5, 2.9m≤R<4.5m; when 5≤permeability difference is less than 10, R≥4.5m; and / or, In the directional well, when the permeability difference is less than 3, 12m≤R<14m; when 3≤permeability difference<5, 14m≤R<16m; ​​when 5≤permeability difference≤10, R≥16m.

8. The hierarchical plugging method for assisting carbon dioxide throughput according to claim 5, characterized in that: Determining the plugging radius R used in the well section according to the permeability difference and the oil saturation includes: The well section is in a horizontal well, when 5≤permeability difference≤10, 4.8m≤R<5.0m; when permeability difference>10, R≥5.0m; and / or, In the directional well, when the permeability difference is 5≤≤10, 18m≤R<20m; when the permeability difference is>10, R≥20m.

9. The hierarchical plugging method for assisting carbon dioxide throughput according to claim 3 or 6, characterized in that: The permeability recovery rate of the temporary plugging agent after plugging and setting for 24 hours is not less than 85%.

10. The hierarchical plugging method for assisting carbon dioxide throughput according to any one of claims 3 to 9, characterized in that: The temporary plugging agent is a foam type temporary plugging agent; and / or, The weak plugging agent is a gel-type plugging agent; and / or, The strong plugging agent is a gel-type plugging agent and / or a jelly-type plugging agent.

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