Method and system for selectively plugging high-gas-yield section of horizontal well and application

Abstract

The invention discloses a method and a system for selectively blocking a high-gas-yield section of a horizontal well and application. The method comprises the steps that at a determined plugging position, a selected slug system is adopted to plug a high gas production section of the horizontal well; the slug system comprises a slug 1, a slug 2 and a slug 3, the slug 1 is a foaming system, the foaming system comprises a foaming agent, or the foaming system comprises the foaming agent and a foam stabilizer; the slug 2 is medium-low-concentration gel mother liquor with the acrylamide monomer concentration lower than 6%; and the slug 3 is water. The gas channeling problem of a part of production layer sections of the horizontal well can be effectively solved, meanwhile, the low gas yield is reduced on the premise that the oil yield is not affected, oil stabilization and even oil increasing and gas blocking are achieved, and the oilfield development effect is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field development, and particularly relates to a method and system for selectively plugging a high-yield gas section of a horizontal well and application thereof. BACKGROUND

[0002] In the process of gas injection development, due to the heterogeneity of the oil reservoir and the high mobility of the gas, the injected gas will preferentially enter the high-porosity and high-permeability channels of the oil reservoir, and then rapidly flow out from the production well to cause gas channeling, resulting in the increase of the gas-oil ratio of the production well, which seriously affects the oil production of the single well. Compared with the vertical well, the influence of gas channeling on the horizontal well production is particularly obvious, because local gas channeling will seriously reduce the swept volume of the horizontal well section in the process of gas injection development, and as the production proceeds, the gas-oil ratio will continue to rise, eventually leading to the shut-in of the well. At the same time, due to the uneven sweep, the remaining oil saturation around the wellbore is still high, and it is difficult to achieve efficient development of the oil reservoir. Therefore, it is necessary to apply the gas plugging technology to plug the gas channeling section, increase the swept volume of the gas injection development, and realize the efficient tapping of the remaining oil.

[0003] The current conventional solutions include mechanical plugging and chemical plugging. The existing conventional chemical plugging is to inject a chemical plugging agent into the wellbore. The mechanical plugging is to use a drilling rig to lower a pipe string, and at the same time, to lower a packer and other tools to achieve the plugging of the gas channeling section. SUMMARY

[0004] The present application inventors find that the conventional chemical plugging method can plug the high-yield gas section to a certain extent, but it also has certain damage to the oil production section, especially for the horizontal well, it cannot achieve the selective plugging of only plugging the high-yield gas section without affecting the oil production section, that is, it cannot achieve selective plugging. Although the conventional mechanical plugging can achieve selective plugging for the horizontal well, the process flow of this method is relatively complex, and it requires more manpower and material resources, and it needs to lower a packer and other tools, which has a higher cost compared with the chemical plugging method.

[0005] In view of the above problems, the present application is proposed to provide a method, system and application for selectively plugging a high-yield gas section of a horizontal well to overcome the above problems or at least partially solve the above problems.

[0006] The present application embodiment provides a method for selectively plugging a high-yield gas section of a horizontal well, comprising:

[0007] At the determined plugging position, a selected plug system is used to plug the high-yield gas section of the horizontal well;

[0008] The plug system comprises: plug 1, plug 2, and plug 3:

[0009] The plug 1 is a foaming system, and the foaming system comprises a foaming agent, or the foaming system comprises a foaming agent and a foam stabilizer;

[0010] The slug 2 is a medium-low concentration gel mother liquor with an acrylamide monomer concentration less than 6%;

[0011] The slug 3 is water.

[0012] In some optional embodiments, the foaming system includes a foaming agent with a mass concentration of 0.1%-0.3%, or the foaming system includes a foaming agent with a mass concentration of 0.1%-0.3% and a foam stabilizer with a mass concentration of 0.1-0.2%.

[0013] In some optional embodiments, the foaming agent includes one or any combination of sodium a-alkenyl sulfonate, sodium lauryl sulfate, cocamidopropyl betaine, and lauramidopropyl betaine.

[0014] The foam stabilizer includes one or any combination of carboxymethyl cellulose, magnesium lithium silicate, and xanthan gum.

[0015] In some optional embodiments, the slug system further includes a slug 4 between the slug 2 and the slug 3, and the slug 4 is a high-concentration gel mother liquor with an acrylamide monomer concentration higher than 6%.

[0016] In some optional embodiments, the medium-low concentration gel mother liquor includes an acrylamide monomer with a mass concentration of 3%-6% and a crosslinking agent with a mass concentration of 0.5%-1% and an initiator with a mass concentration of 0.01%.

[0017] The high-concentration gel mother liquor includes an acrylamide monomer with a mass concentration of 6%-8% and a crosslinking agent with a mass concentration of 0.5%-1% and an initiator with a mass concentration of 0.01%.

[0018] In some optional embodiments, the crosslinking agent includes one or any combination of phenol formaldehyde, PEI, and urotropine.

[0019] The initiator includes one or any combination of azo and ammonium persulfate.

[0020] In some optional embodiments, the plugging of the high-yield gas section of the horizontal well using the selected slug system at the determined plugging position includes:

[0021] Based on the dynamic monitoring data of the horizontal well with a high gas-oil ratio, the position, length, physical property, and gas production intensity of the high-yield gas section with a gas production greater than a first threshold value in the horizontal well are determined.

[0022] Based on the position, length, physical property, and gas production intensity of the high-yield gas section, the injection position and injection amount of the selected slug system are determined.

[0023] At the injection position of the determined slug system, the chemical agents of each slug section in the slug system are sequentially injected in accordance with the determined injection amount, and the well is shut in after the injection is completed to wait for the completion of plugging.

[0024] In some alternative embodiments, the injection position and injection volume of the slug system are determined based on the location, length, physical property and gas production intensity of the high-yield gas section, comprising:

[0025] The injection position of each slug section included in the slug system is determined based on the location of the high-yield gas section.

[0026] The injection volume of each slug section in the slug system is determined according to the location, length, physical property and gas production intensity of the high-yield gas section; the physical property includes the porosity, temperature, pressure and flow rate of the high-yield gas section.

[0027] In some alternative embodiments, the injection volume of the slug system is determined according to the length, physical property and gas production intensity of the high-yield gas section, comprising:

[0028] The treatment depth of the high-yield gas section is determined according to the location and gas production intensity of the high-yield gas section.

[0029] The injection volume of the slug system is determined based on the length, porosity and treatment depth of the high-yield gas section using the following formula:

[0030]

[0031] wherein V is the total injection volume of the slug system.

[0032] α is the dosage coefficient, the value of which ranges from 0.3 to 1.0.

[0033] r i is the treatment depth of the i-th treatment layer section.

[0034] h i is the length of the i-th treatment layer section.

[0035] is the porosity of the i-th treatment layer section.

[0036] The injection volume of each slug in the slug system should be determined according to the location and gas production intensity of the high-yield gas section.

[0037] In some alternative embodiments, the chemical reagents of each slug section in the slug system are sequentially injected at the determined injection position of the slug system according to the determined injection volume, and the well is shut in after the injection is completed to wait for the completion of plugging, comprising:

[0038] The first injection stage: the foaming system is injected at the injection position of the determined slug 1 in the horizontal well to reach the designed injection volume, and the time length is 7-10 days.

[0039] The second injection stage: the medium-low concentration gel mother liquor is injected at the injection position of the determined slug 2 in the horizontal well to reach the designed injection volume.

[0040] The third injection stage: injecting formation water into the determined injection position of the slug 3 in the horizontal well to reach the designed injection amount;

[0041] After the injection is completed, the well is closed and the slug system is gelled, and the waiting time is 3-5 days.

[0042] In some optional embodiments, the method further comprises:

[0043] After the second injection stage is completed, high-concentration gel mother liquor is injected into the determined injection position of the slug 4 in the horizontal well to reach the designed injection amount, and then the third injection stage is performed, and the total injection time is 3-5 days.

[0044] In some optional embodiments, the method as claimed in any one of the above further comprises:

[0045] Obtaining the gas production evaluation index of the horizontal well after plugging and the retention time thereof; the gas production evaluation index comprises at least one of the average single-well gas production reduction and the gas-oil ratio of the production well;

[0046] According to the gas production evaluation index and the retention time thereof, and the corresponding relationship between the gas production evaluation index and the plugging effect, the plugging effect of the high-gas-production section of the horizontal well is determined.

[0047] If the gas production evaluation index is the average single-well gas production reduction, the determination of the plugging effect of the high-gas-production section of the horizontal well according to the gas production evaluation index and the retention time thereof, and the corresponding relationship between the gas production evaluation index and the plugging effect comprises:

[0048] If the average single-well gas production reduction of the horizontal well is greater than or equal to 20% and the retention time is 3 months or more, the plugging effect is determined to be excellent;

[0049] If the average single-well gas production reduction of the horizontal well is greater than or equal to 10% and less than 20% and the retention time is 2 months or more, the plugging effect is determined to be good;

[0050] If the average single-well gas production reduction of the horizontal well is greater than 3% and less than 10% and the retention time is 1 month or more, the plugging effect is determined to be medium;

[0051] If the average single-well gas production reduction of the horizontal well is less than or equal to 3%, the plugging effect is determined to be poor.

[0052] The embodiments of the present application also provide an application of the method for selectively plugging the high-gas-production section of the horizontal well in a high-temperature and high-salinity reservoir.

[0053] In some optional embodiments, the formation temperature of the reservoir is not less than 120℃, and the salinity is not less than 200000 mg / L.

[0054] The embodiment of the present application also provides a system for selectively plugging a high-yield gas section of a horizontal well, comprising:

[0055] A determination unit is configured to determine a plugging position of the high-yield gas section of the horizontal well.

[0056] A plugging device is configured to plug the high-yield gas section of the horizontal well by using a selected plug system at the determined plugging position.

[0057] The plug system comprises a plug 1, a plug 2, and a plug 3.

[0058] The plug 1 is a foaming system, wherein the foaming system comprises a foaming agent, or the foaming system comprises a foaming agent and a foam stabilizer.

[0059] The plug 2 is a medium-low concentration gel mother liquor with an acrylamide monomer concentration less than 6%.

[0060] The plug 3 is water.

[0061] The beneficial effects of the above technical solution provided by the embodiment of the present application at least include:

[0062] The method for selectively plugging a high-yield gas section of a horizontal well provided by the embodiment of the present application determines a plugging position of the high-yield gas section of the horizontal well, and then plugs the high-yield gas section of the horizontal well by using a selected plug system, wherein the plugging is performed by sequentially injecting a foaming system of the plug 1 to foam, injecting a medium-low concentration gel mother liquor of the plug 2 with an acrylamide monomer concentration less than 6%, and injecting water of the plug 3. By using the chemical plugging method, compared with mechanical plugging, the construction can be performed without moving the pipe column, and the cost is reduced. Compared with the conventional chemical plugging method, in the selected plug system, the plug 1 is a foaming system, the generated foam is “foamed when encountering gas, and unchanged when encountering oil”, and the selective plugging of “plugging gas but not oil” can be achieved in the case of general injection. The gel mother liquor used by the plug 2 has low viscosity and has the characteristics of “gelation and viscosity increase when encountering gas, and unchanged viscosity when encountering oil”, which also greatly reduces the damage to the oil production layer section caused by the current general injection. By injecting the plug system, the gas phase existing in the gas channeling layer section is used to generate foam in situ in the porous medium, the plugging capacity of the gas channeling channel is strengthened, and the treatment depth is improved, thereby solving the problem of small swept volume in the gas injection development process caused by gas channeling. At the same time, the gas production can be reduced without affecting the oil production, the oil can be stabilized or even increased, the gas can be plugged, and the oilfield development effect can be effectively improved.

[0063] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and achieved by the structure particularly pointed out in the written description, claims, and drawings.

[0064] The technical solutions of the present application will be further described in detail below with the aid of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0065] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application and explain the technical solutions of the present application, and do not constitute a limitation on the present application. In the drawings:

[0066] Figure 1 The flow chart of the method for selectively plugging the high-yield gas section of the horizontal well in the embodiment of the present application;

[0067] Figure 2 The flow chart of the method for selectively plugging the high-yield gas section of the horizontal well in the first embodiment of the present application;

[0068] Figure 3 The flow chart of the field application of the method for selectively plugging the high-yield gas section of the horizontal well in the second embodiment of the present application;

[0069] Figure 4 The change of the foaming volume and the liquid separation half-life period of the foaming system in the fourth embodiment of the present application after aging for 90 days under the conditions of the formation temperature and the salinity;

[0070] Figure 5 The strength and stability of the gel mother liquor in the fifth embodiment of the present application after aging for 120 days under the conditions of the formation temperature and the salinity;

[0071] Figure 6 The structural schematic diagram of the system for selectively plugging the high-yield gas section of the horizontal well in the embodiment of the present application. DETAILED DESCRIPTION

[0072] The exemplary embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described 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.

[0073] In order to solve the problems in the prior art that the conventional chemical plugging cannot achieve selective plugging of only plugging the high-yield gas section without affecting the oil production section of the horizontal well, and the process flow of the mechanical plugging method for achieving selective plugging of the horizontal well is complex and the input cost is high, the embodiment of the present application provides a method for selectively plugging the high-yield gas section of the horizontal well, and the flow thereof is as shown in the figure Figure 1 The method comprises the following steps:

[0074] S1: determining the plugging position of the high-yield gas section of the horizontal well.

[0075] S2: At the determined plugging position, a selected plug system is used to plug the high-yield gas section of the horizontal well.

[0076] In order to achieve effective chemical plugging, only the high-yield gas section of the horizontal well is plugged without affecting the oil production section during plugging, and it is necessary to select a suitable plugging position and a suitable plug system. One optional plug system can include: plug 1, plug 2, and plug 3:

[0077] Plug 1 is a foaming system, which includes a foaming agent, or the foaming system includes a foaming agent and a foam stabilizer;

[0078] Plug 2 is a medium-low concentration gel mother liquor with an acrylamide monomer concentration less than 6%;

[0079] Plug 3 is water.

[0080] The plug system further includes plug 4 between plug 2 and plug 3,

[0081] The plug system can include: plug 1, plug 2, plug 4, and plug 3:

[0082] Plug 1 is a foaming system, which includes a foaming agent, or the foaming system includes a foaming agent and a foam stabilizer;

[0083] Plug 2 is a medium-low concentration gel mother liquor with an acrylamide monomer concentration less than 6%;

[0084] Plug 4 is a high-concentration gel mother liquor with an acrylamide monomer concentration higher than 6%;

[0085] Plug 3 is water. In the above plug system, plug 1 is a foaming system, which generates foam through a foaming agent, and the generated foam "foams when encountering gas and does not change when encountering oil", which can achieve selective plugging of "plugging gas but not plugging oil" in the case of general injection; the addition of a foam stabilizer can further improve the foaming effect and generate more stable foam. The gel mother liquor used in plug 2 and plug 4 has low viscosity and has the characteristics of "gelation and viscosity increase when encountering gas, and viscosity does not change when encountering oil", which can greatly reduce the damage to the oil production section. Different plug sections are injected in sequence, and the chemical reagents injected in each plug section are reasonably selected, which can obtain better injection effect compared with the general injection without segmentation.

[0086] The above method plugs the high-yield gas section of the horizontal well at the determined plugging position based on the selected plug system, and the injection of the plug system can effectively solve the gas channeling problem of the horizontal well, thereby inhibiting the continuous rise of the gas-oil ratio of the horizontal well, reducing the gas production under the premise of not affecting the oil production, achieving stable oil or even increased oil plugging gas, and effectively improving the oilfield development effect.

[0087] In some optional embodiments, the foaming system comprises 0.1-0.3% mass concentration of the foaming agent, or the foaming system comprises 0.1-0.3% mass concentration of the foaming agent and 0.1-0.2% mass concentration of the foam stabilizer.

[0088] The foaming agent comprises one or any combination of sodium a-olefin sulfonate, sodium lauryl sulfate, cocamidopropyl betaine, lauramidopropyl betaine; and the foam stabilizer comprises one or any combination of carboxymethyl cellulose, magnesium lithium silicate, xanthan gum.

[0089] In some optional embodiments, the low-concentration gel mother liquor comprises 3-6% mass concentration of the acrylamide monomer, 0.5-1% mass concentration of the crosslinking agent, and 0.01% mass concentration of the initiator.

[0090] The high-concentration gel mother liquor comprises 6-8% mass concentration of the acrylamide monomer, 0.5-1% mass concentration of the crosslinking agent, and 0.01% mass concentration of the initiator.

[0091] The crosslinking agent comprises one or any combination of phenol formaldehyde, PEI, and urotropine; and the initiator comprises one or any combination of azo and ammonium persulfate.

[0092] In some optional embodiments, the water selected for the segment 4 is formation water.

[0093] Embodiment one

[0094] The embodiment one of the present application provides a specific implementation process of the method for selectively plugging the high-yield gas segment of the horizontal well, and the implementation process of the method is as shown in the figure Figure 2 and comprises the following steps.

[0095] S101: Based on the dynamic monitoring data of the horizontal well with high gas-oil ratio, the position, length, physical property, and gas production intensity of the high-yield gas segment with a gas production greater than a first threshold value in the horizontal well are determined.

[0096] In combination with the geological data of the oilfield, it is generally believed that the production well with a gas-oil ratio greater than a certain threshold value in the reservoir is a production well with high gas-oil ratio.

[0097] In this embodiment, the PLT test is performed on the horizontal well with a gas-oil ratio greater than a certain threshold value in the target reservoir, and the position, length, and gas production intensity of the high-yield gas segment are determined based on the test data obtained by the PLT test, wherein the high-yield gas segment refers to a well segment with a gas production greater than a first threshold value in the horizontal well.

[0098] S102: Based on the position, length, physical property, and gas production intensity of the high-yield gas segment, the injection position and injection amount of the selected segment system are determined.

[0099] The main operations in this step include: 1) determining the injection position of each slug segment included in the slug system based on the position of the high-yield gas section, the injection position being the arrival position of each slug segment included in the slug system when injection is performed;

[0100] When each slug segment included in the slug system is injected into the high-yield gas section, it can be selected to be injected from the wellhead position or to be directly injected at the fixed position of the high-yield gas section, as long as each slug segment can reach the injection position.

[0101] 2) determining the injection amount of each slug segment in the slug system according to the position, length, physical property and gas production intensity of the high-yield gas section; wherein the physical property includes one of porosity, temperature, pressure and flow rate of the high-yield gas section.

[0102] The treatment depth of the high-yield gas section can be determined according to the position and gas production intensity of the high-yield gas section;

[0103] Based on the length, porosity and treatment depth of the high-yield gas section, the injection amount of the slug system is determined by using the following formula:

[0104]

[0105] Wherein, V is the total injection amount of the slug system;

[0106] α is the dosage coefficient, the value range of which is 0.3-1.0;

[0107] r i is the treatment depth of the i th treatment layer section;

[0108] h i is the length of the i th treatment layer section;

[0109] is the porosity of the i th treatment layer section;

[0110] The injection amount of each slug in the slug system is determined according to the position and gas production intensity of the high-yield gas section, and is distributed based on the total injection amount of the slug system. The injection amount of the foaming system in the slug system should achieve the effect of preliminary plugging of gas channeling, and the injection amount of the gel mother liquor should achieve the effect of strengthening the plugging of gas channeling.

[0111] S103: At the injection position of the determined slug system, the chemical reagents of each slug segment in the slug system are sequentially injected according to the determined injection amount, and after the injection is completed, the well is closed and waiting for plugging to be completed.

[0112] In this step, each plug section in the plug system is injected into the corresponding injection position in turn according to the order, and the injection order is determined based on the selected plug system; the injection position of each plug section can be determined respectively, and can be the same or different, which is adjusted according to the injection effect of the previous plug section; the injection amount of each plug section can be determined according to the algorithm in the above step. For example, one optional injection process of each plug section in the plug system is as follows:

[0113] The first injection stage: injecting the foaming system into the injection position of the determined plug 1 in the horizontal well to reach the designed injection amount, and the time length is 7-10 days;

[0114] The second injection stage: injecting the medium-low concentration gel mother liquor into the injection position of the determined plug 2 in the horizontal well to reach the designed injection amount;

[0115] The third injection stage: injecting the formation water into the injection position of the determined plug 3 in the horizontal well to reach the designed injection amount;

[0116] After the injection is completed, the well is closed and waiting for the plug system to gel, and the waiting time length is 3-5 days.

[0117] According to the gas production intensity of the high-yield gas section, after the second injection stage is completed, the high-concentration gel mother liquor is injected into the injection position of the determined plug 4 in the horizontal well to reach the designed injection amount, and after the injection is completed, the third injection stage is executed again, and the total injection time length is 3-5 days.

[0118] The injection time of each plug section can be determined according to the empirical data, or can be determined based on the simulation algorithm, or can be adjusted in time according to the real-time plugging effect.

[0119] Embodiment two

[0120] Embodiment two of the present application provides a field application method for selectively plugging a high-yield gas section of a horizontal well, and the flowchart is as shown in Figure 3 The method comprises the following steps:

[0121] Step S201: based on the dynamic monitoring data of the horizontal well with high gas-oil ratio, the position, length, physical property and gas production intensity of the high-yield gas section with a gas production greater than a first threshold value in the horizontal well are determined.

[0122] In combination with the oilfield geological data, the PLT test is carried out on the horizontal well with a gas-oil ratio of 5000 cubic feet / bbl in the target reservoir, and the position, length and gas production intensity of the high-yield gas section are determined based on the test result data, and the high-yield gas section refers to the position with a gas production greater than the first threshold value in the horizontal well.

[0123] Step S202: based on the position, length, physical property and gas production intensity of the high-yield gas section, the injection position and injection amount of the selected plug system are determined.

[0124] determining the injection position of each plug section included in the plug system based on the position of the high-yield gas section;

[0125] determining the injection amount of each plug section in the plug system according to the position, length, physical property and gas production intensity of the high-yield gas section; the physical property includes one of porosity, temperature, pressure and flow rate of the high-yield gas section.

[0126] The calculation formula of the injection amount has been introduced in the above method, and alternatively, the injection amount can be calculated according to other physical property factors.

[0127] Step S203: Based on the determined injection position and injection amount of the plug system, the oilfield site preparation is started.

[0128] This step mainly includes the arrival of chemical reagents, site equipment preparation and inspection, and the duration is 3-5 days; the inspection mainly includes the injection capacity test of the equipment and the ground joint leakage test of the equipment.

[0129] Step S204: At the determined injection position of the plug system, the chemical reagents of each plug section in the plug system are sequentially injected according to the determined injection amount, and after the injection is completed, the well is closed for waiting for the plugging to be completed.

[0130] Based on the selected plug system, the injection process of this step includes:

[0131] The foaming system is configured, and the first injection stage is implemented based on the configured foaming system; the first injection stage is to inject the foaming system to the injection position of the determined plug 1 in the horizontal well to reach the designed injection amount, and the duration is 3-5 days;

[0132] The medium-low concentration gel mother liquor is configured, and the second injection stage is implemented based on the configured medium-low concentration gel mother liquor; the second injection stage is to inject the medium-low concentration gel mother liquor to the injection position of the determined plug 2 in the horizontal well to reach the designed injection amount;

[0133] The third injection stage is implemented based on the prepared formation water; the third injection stage is to inject the formation water to the injection position of the determined plug 3 in the horizontal well to reach the designed injection amount;

[0134] After the injection is completed, the well is closed for waiting for the plug system to gel, and the waiting duration is 3-5 days.

[0135] According to the gas production intensity of the high-yield gas section, after the completion of the second injection stage, the high-concentration gel mother liquor is configured, the high-concentration gel mother liquor is injected to the injection position of the determined plug 4 in the horizontal well to reach the designed injection amount, after the injection is completed, the third injection stage is executed again, and the total injection duration is 3-5 days.

[0136] Step S205: carry out production test and effect evaluation.

[0137] The gas production evaluation index of the plugged horizontal well and its retention time are obtained; according to the gas production evaluation index and its retention time, and the corresponding relationship between the gas production evaluation index and the plugging effect, the plugging effect of the high gas production section of the horizontal well is determined. The gas production evaluation index includes at least one of the average single-well gas production reduction and the gas-oil ratio of the production well.

[0138] If the gas production evaluation index is the average single-well gas production reduction, the corresponding relationship table between the gas production evaluation index and the plugging effect is shown in Table 1 below.

[0139] Table 1

[0140] Serial number Evaluation grade Quantitative evaluation index after technical implementation 1 Excellent Gas production reduction >= 20%, valid period 3 months and above 2 Good Gas production reduction >= 10% and < 20%, valid period 2 months and more 3 Medium Gas production reduction > 3% and < 10%, effective period 1 month and above 4 Poor Gas production reduction amount <= 3%

[0141] In the above table, the evaluation index is that the average gas production reduction is greater than or equal to 20%, the retention time is 3 months or more, and the corresponding evaluation level is excellent;

[0142] The evaluation index is that the average gas production reduction is greater than or equal to 10% and less than 20%, the retention time is 2 months or more, and the corresponding evaluation level is good;

[0143] The evaluation index is that the average gas production reduction is greater than 3% and less than 10%, the retention time is 1 month or more, and the corresponding evaluation level is medium;

[0144] The evaluation index is that the average gas production reduction is less than or equal to 3%, and the corresponding evaluation level is poor.

[0145] Correspondingly, if the gas production evaluation index is the average single-well gas production reduction, according to the gas production evaluation index and its retention time, and the corresponding relationship between the gas production evaluation index and the plugging effect, the plugging effect of the high gas production section of the horizontal well is determined, which includes:

[0146] The average single-well gas production reduction of the horizontal well is obtained, and the corresponding relationship table in Table 1 is searched. If the average single-well gas production reduction of the horizontal well is greater than or equal to 20%, the retention time is 3 months or more, then it can be determined that the plugging effect is excellent; if the average single-well gas production reduction of the horizontal well is greater than or equal to 10% and less than 20%, the retention time is 2 months or more, then it can be determined that the plugging effect is good; if the average single-well gas production reduction of the horizontal well is greater than 3% and less than 10%, the retention time is 1 month or more, then it can be determined that the plugging effect is medium; if the average single-well gas production reduction of the horizontal well is less than or equal to 3%, then it can be determined that the plugging effect is poor. For example, the reduction is 21%, and it has been maintained for 5 months, then it is considered that the plugging effect is excellent; the reduction is 2%, then it is considered that the plugging effect is poor.

[0147] The above method of the embodiment can be theoretically applied to selective plugging of the high-yield gas section of low, medium and high permeability reservoirs, and includes an integrated process from design, implementation to evaluation.

[0148] Embodiment three

[0149] The embodiment three provides application of the method for selectively plugging the high-yield gas section of the horizontal well in the high-temperature and high-salt reservoir.

[0150] Based on the above method for selectively plugging the high-yield gas section of the horizontal well, single well test is carried out in the fracture-cave carbonate reservoir, and effect evaluation is carried out. The method of the embodiment is successfully applied in the medium-high permeability fracture-cave carbonate reservoir. The typical well of the reservoir can still realize 90% reduction of gas-oil ratio and 4400t increase of oil within 8 months after the implementation of the method. It is planned to carry out test in the low-permeability pore-type carbonate reservoir in the Middle East. It is expected that the first batch of 5 wells can increase the annual income of 1000 million US dollars.

[0151] Embodiment four

[0152] The embodiment four provides experimental data of the foaming system in the above-mentioned embodiment one. The foams generated by different foaming systems have different bubble volumes and liquid separation half-lives, and the bubble volumes and liquid separation half-lives will affect the plugging effect. Therefore, the foaming volume and liquid separation half-life of the foaming system are mainly evaluated in this embodiment, so as to provide a more suitable foaming system and better plugging effect. Table 2 below is the foaming volume and liquid separation half-life of the foaming liquid of different components. Table 2 exemplifies the related indexes of different foaming systems. The component part gives the proportion of the material components of the foaming agent and the foam stabilizer, and the remaining part is water.

[0153] The definition of the liquid separation half-life is the time for the liquid in the foam to separate to half of the initial liquid. For example: 100ml of liquid forms a foam after high-speed stirring. The time is counted from the time when the stirring is stopped until 50ml of liquid is separated. The longer the liquid separation half-life, the more stable the foam generated by the foaming system.

[0154] Table 2

[0155]

[0156]

[0157] The foaming system in Table 2 above can include a foaming agent, or a foaming agent and a foam stabilizer. In this embodiment, the foaming agent is selected to be cocamide propyl betaine, and the foam stabilizer is selected to be carboxymethyl cellulose. In the foaming system, the mass concentration of the foaming agent is 0.1%-0.3%, and the mass concentration of the foam stabilizer is 0.1-0.2%. The bubble volume and the liquid separation half-life period that satisfy the plugging effect can be obtained.

[0158] In addition, the inventors of the present application have conducted experiments in which the foaming agent is cocamide propyl betaine and no foam stabilizer is used. The inventors have also conducted experiments in which the foaming agent is selected to be sodium α-olefin sulfonate, sodium lauryl sulfate or lauryl amide propyl betaine, or any combination of sodium α-olefin sulfonate, sodium lauryl sulfate, cocamide propyl betaine and lauryl amide propyl betaine. No foam stabilizer is used, or the foam stabilizer is selected to be magnesium lithium silicate or xanthan gum, or any combination of carboxymethyl cellulose, magnesium lithium silicate and xanthan gum. The experiments prove that, when the foaming agent and the foam stabilizer are used in these combinations, the mass concentration of the foaming agent is 0.1%-0.3%, and the mass concentration of the foam stabilizer is 0.1-0.2%, the foaming effect is not much different from that in Table 2, and the bubble volume and the liquid separation half-life period that satisfy the plugging effect can be obtained.

[0159] The foaming system is suitable for a wide range of reservoir conditions. It can still produce foam under the conditions of a high-temperature and high-salinity reservoir (temperature 120°C, salinity 200,000 mg / L) and is used for preliminary plugging of gas channeling. Its initial viscosity is similar to that of water, and it is easy to pump and beneficial to selective entry into a high-permeability gas channeling zone. Figure 4 As shown in FIG. 5, the foam produced by a foaming system has a liquid separation half-life period of about 200 seconds after aging for 90 days under high temperature and high salinity, and it can be seen that it has good stability.

[0160] Embodiment Five

[0161] This embodiment five provides experimental data related to the plugging agents 2 and 3 (gel mother liquor systems) in the above embodiment one. Different gel mother liquor systems have different plugging effects. In this embodiment, the gelation time and gel strength of the gel mother liquor system are mainly evaluated to measure the plugging effect. The gel mother liquor system includes acrylamide monomer (AM), a crosslinking agent and an initiator. Table 3 below shows the gelation time and gel strength of the gel mother liquor system with different components. In Table 3, the composition part shows the proportion of the components of the acrylamide monomer, the crosslinking agent and the initiator, and the remaining part is water. The gel strength is observed and evaluated by using the general "strength code method".

[0162] Table 3

[0163]

[0164]

[0165] In Table 3 above, the gel mother liquor system includes acrylamide monomer (AM), crosslinking agent and initiator, wherein the crosslinking agent is phenolic and the initiator is azo. Experiments were conducted on the gelation time and gelation strength under the following conditions: acrylamide monomer mass concentration of 3%-8%, crosslinking agent mass concentration of 0.5%-1%, and initiator mass concentration of 0.01%.

[0166] In the plugging application, a medium-to-low concentration gel mother liquor was used as slug 2 for plugging experiments. The medium-to-low concentration gel mother liquor included 3%-6% acrylamide monomer, 0.5%-1% crosslinking agent and 0.01% initiator by mass concentration. Experiments have shown that it can achieve better plugging effect.

[0167] Furthermore, a blocking experiment was conducted using a medium-to-low concentration gel mother liquor as slug 2 and a high concentration gel mother liquor as slug 4. The medium-to-low concentration gel mother liquor consisted of 3%-6% acrylamide monomer, 0.5%-1% crosslinking agent, and 0.01% initiator by mass concentration; the high concentration gel mother liquor consisted of 6%-8% acrylamide monomer, 0.5%-1% crosslinking agent, and 0.01% initiator by mass concentration, which resulted in better blocking performance.

[0168] Among them, medium and low concentration gel mother liquor can form gel in situ in the formation near the injection section, thereby further sealing and preventing gas channeling on the basis of the foaming system; high concentration gel mother liquor can form gel in situ, which is used to strengthen gas channeling sealing around the wellbore.

[0169] The gel mother liquor is prepared with fresh water, resulting in a low initial solution viscosity, which facilitates pumping and entry into high-permeability gas-channeling zones. Furthermore, the gelation time is typically 5 to 72 hours, and the timing is controllable. Figure 5 The upper part of the container shown is clearly demarcated, which is the state of the gel mother liquor of a certain system after gelation. It can be seen that the gel has high strength. After aging for 120 days under high temperature and high salinity conditions in the formation (temperature 120℃, mineralization 200000mg / L), the gel still exhibits strong adhesion and good elasticity compared to 60 days, and can be used for on-site gas channeling plugging.

[0170] The methods in the above embodiments can effectively solve the gas channeling problem in some production sections of horizontal wells, thereby solving the problem of small gas injection volume caused by gas channeling during gas injection development. It can reduce gas production without affecting oil production and effectively improve the oilfield development effect.

[0171] Example 6

[0172] This sixth embodiment provides a system for selectively plugging high-gas-producing sections in horizontal wells, the structure of which is as follows: Figure 6As shown, it comprises: a determining unit 01 and a plugging device 02.

[0173] The determining unit 01 is used for determining the plugging position of the high-yield gas section of the horizontal well;

[0174] The plugging device 02 is used for plugging the high-yield gas section of the horizontal well with a selected slug system at the determined plugging position; the slug system comprises: a slug 1, a slug 2, and a slug 3; the slug 1 is a foaming system, the foaming system comprises a foaming agent, or the foaming system comprises a foaming agent and a foam stabilizer; the slug 2 is a medium-low concentration gel mother liquor with an acrylamide monomer concentration less than 6%; and the slug 3 is water.

[0175] Unless specifically stated otherwise, terms such as processing, computing, calculating, determining, displaying, and the like, can refer to an action and / or process of one or more processing or computing systems, or similar devices, that manipulate and / or transform data represented as physical (e.g., electronic) quantities within the processing system's registers and / or memories into other data similarly represented as physical quantities within the processing system's memories, registers or other such information storage, transmission or display devices. The term "data" can refer to any demarcated representation of information used by the processing system. Information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0176] It should be understood that the specific order or hierarchy of steps in the processes disclosed is an example of exemplary approaches. Based upon design preferences, it should be understood that the specific order or hierarchy of steps in the processes can be re-arranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and as such the order is merely an example and is not intended to imply a requirement or particular order for the numerous steps. The various steps can be combined, rearranged, or otherwise re-arranged without departing from the scope of the disclosure.

[0177] In the above detailed description, various features are grouped together in single embodiments for the purpose of streamlining the disclosure. Such disclosed approaches should not be interpreted as reflecting an intention that the claimed subject matter requires more features than are explicitly recited in each claim. Rather, as the claims below reflect, inventive subject matter lies in fewer than all features of the disclosed subject matter. The claims below, therefore, are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate preferred embodiment. By way of example, an apparatus can be constructed comprising one but not each and every of the features recited in the claims.

[0178] Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0179] The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In the alternative, the processor and the storage medium can reside as discrete components in a user terminal.

[0180] For a software implementation, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes can be stored in memory units and executed by processors. The memory unit can be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is well known in the art.

[0181] The above description includes one or more examples of the embodiments. Of course, not all possible combinations of components or method steps described above can be claimed as embodiments. One of ordinary skill in the art can recognize that modifications and variations of the described embodiments are possible and are within the scope of the present disclosure. It is therefore intended that the embodiments described herein be considered in all respects as only illustrative and not restrictive. Specifically, the description of the embodiments should be considered to be illustrative and not exhaustive, and should be considered in the light of the claims. Further, the use of the term "comprise" in the specification is to be construed to be analogous to the term "include". Further, the use of the term "or" in the claims is to be construed as "non-exclusive or".

Claims

1. A method for selectively plugging high gas production sections of a horizontal well, characterized in that, The application relates to a method for plugging a high-yield gas section of a horizontal well. The method comprises the following steps: The plugging system comprises a plugging 1, a plugging 2 and a plugging 3: The plugging 1 is a foaming system, wherein the foaming system comprises a foaming agent or the foaming system comprises a foaming agent and a foam stabilizer; The plugging 2 is a medium-low concentration gel mother liquor with an acrylamide monomer concentration lower than 6%; The plugging 3 is water.

2. The method of claim 1, wherein, The foaming system comprises 0.1%-0.3% mass concentration of the foaming agent or the foaming system comprises 0.1%-0.3% mass concentration of the foaming agent and 0.1-0.2% mass concentration of the foam stabilizer.

3. The method of claim 1, wherein, The foaming agent comprises one or any combination of sodium alpha-olefin sulfonate, sodium lauryl sulfate and cocamidopropyl betaine; The foam stabilizer comprises one or any combination of carboxymethyl cellulose and magnesium lithium silicate.

4. The method of claim 1, wherein, The plugging system further comprises a plugging 4 between the plugging 2 and the plugging 3, wherein the plugging 4 is a high-concentration gel mother liquor with an acrylamide monomer concentration higher than 6%.

5. The method of claim 1 or 4, wherein, The medium-low concentration gel mother liquor comprises 3%-6% mass concentration of the acrylamide monomer, 0.5%-1% mass concentration of a crosslinking agent and 0.01% mass concentration of an initiator; The high-concentration gel mother liquor comprises 6%-8% mass concentration of the acrylamide monomer, 0.5%-1% mass concentration of the crosslinking agent and 0.01% mass concentration of the initiator.

6. The method of claim 5, wherein, The crosslinking agent comprises one or any combination of phenol formaldehyde, PEI and urotropine; The initiator comprises one or any combination of azo and ammonium persulfate.

7. The method of claim 1, wherein, The method for plugging the high-yield gas section of the horizontal well at the determined plugging position comprises the following steps: determining the position, length, physical property and gas production intensity of the high-yield gas section with a gas-oil ratio greater than a first threshold value in the horizontal well based on dynamic monitoring data of the horizontal well with a high gas-oil ratio; determining the injection position and injection amount of the selected plugging system based on the position, length, physical property and gas production intensity of the high-yield gas section; sequentially injecting the chemical reagents of each plugging section in the plugging system at the determined injection position of the plugging system according to the determined injection amount, and shutting down and waiting for plugging completion after the injection is completed.

8. The method of claim 7, wherein, The method for determining the injection position and injection amount of the plugging system based on the position, length, physical property and gas production intensity of the high-yield gas section comprises the following steps: determining the injection position of each plugging section in the plugging system based on the position of the high-yield gas section; determining the injection amount of each plugging section in the plugging system according to the position, length, physical property and gas production intensity of the high-yield gas section; the physical property comprises the porosity, temperature, pressure and flow rate of the high-yield gas section.

9. The method of claim 8, wherein, The method for determining the injection amount of the plugging system according to the length, physical property and gas production intensity of the high-yield gas section comprises the following steps: determining the treatment depth of the high-yield gas section according to the position and gas production intensity of the high-yield gas section; determining the injection amount of the plugging system based on the length, porosity and treatment depth of the high-yield gas section according to the following formula: wherein V is the total injection amount of the plugging system; alpha is a dosage coefficient, and the value range is 0.3-1.0; r i r is the processing depth for the i-th processing layer segment; h i L is the length of the i-th processing layer section; porosity of the ith treatment layer segment; the injection amount of each plugging section in the plugging system should be determined according to the position and gas production intensity of the high-yield gas section.

10. The method of claim 7, wherein, The method comprises the following steps of: injecting chemical reagents of each slug of a determined slug system into a determined injection position of the slug system according to a determined injection amount, and shutting down the well after the injection is completed to wait for plugging to be completed. The first injection stage: injecting a foaming system into a determined injection position of a slug 1 in the horizontal well to reach a designed injection amount, and the time length is 7-10 days; The second injection stage: injecting a medium-low concentration gel mother liquor into a determined injection position of a slug 2 in the horizontal well to reach a designed injection amount; The third injection stage: injecting formation water into a determined injection position of a slug 3 in the horizontal well to reach a designed injection amount; After the injection is completed, the well is shut down to wait for the slug system to gel, and the waiting time length is 3-5 days.

11. The method of claim 10, wherein, The method further comprises the following steps of: After the second injection stage is completed, a high-concentration gel mother liquor is injected into a determined injection position of a slug 4 in the horizontal well to reach a designed injection amount, and then the third injection stage is performed, and the total injection time length is 3-5 days.

12. The method of any one of claims 1-11, wherein, The method further comprises the following steps of: obtaining a gas production evaluation index of the horizontal well after plugging and a retention time of the gas production evaluation index; the gas production evaluation index comprises at least one of an average single-well gas production reduction and a gas-oil ratio of a production well; determining a plugging effect of a high-gas-production section of the horizontal well according to the gas production evaluation index, the retention time of the gas production evaluation index, and a corresponding relationship between the gas production evaluation index and the plugging effect.

13. The method of claim 12, wherein, If the gas production evaluation index is the average single-well gas production reduction, the method of determining the plugging effect of the high-gas-production section of the horizontal well according to the gas production evaluation index, the retention time of the gas production evaluation index, and the corresponding relationship between the gas production evaluation index and the plugging effect comprises the following steps of: if the average single-well gas production reduction of the horizontal well is greater than or equal to 20% and the retention time is 3 months or more, it is determined that the plugging effect is excellent; if the average single-well gas production reduction of the horizontal well is greater than or equal to 10% and less than 20% and the retention time is 2 months or more, it is determined that the plugging effect is good; if the average single-well gas production reduction of the horizontal well is greater than 3% and less than 10% and the retention time is 1 month or more, it is determined that the plugging effect is medium; if the average single-well gas production reduction of the horizontal well is less than or equal to 3%, it is determined that the plugging effect is poor.

14. Application of the method for selectively plugging a high-gas-production section of a horizontal well according to any one of claims 1-13 in a high-temperature and high-salinity reservoir.

15. The use of the method of selectively plugging high gas production sections of horizontal wells according to claim 14 in high temperature high salinity reservoirs, characterized in that, The formation temperature of the reservoir is not less than 120℃, and the salinity is not less than 200000 mg / L.

16. A system for selectively plugging a high gas production section of a horizontal well, characterized by, The method comprises the following steps of: determining a plugging position of a high-gas-production section of a horizontal well; plugging the high-gas-production section of the horizontal well with a selected slug system at the determined plugging position; the slug system comprises a slug 1, a slug 2, and a slug 3: the slug 1 is a foaming system, and the foaming system comprises a foaming agent or the foaming system comprises a foaming agent and a foam stabilizer; the slug 2 is a medium-low concentration gel mother liquor with an acrylamide monomer concentration less than 6%; the slug 3 is water.

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