Pressure cracking plugging method for chemical flooding injection low-efficiency well of middle-shallow sandstone thin and poor oil layer

Abstract

The invention relates to the technical field of oil production engineering, in particular to a fracturing and plugging method for a chemical flooding injection low-efficiency well of a middle-shallow sandstone thin and poor oil layer. The method comprises the steps that a target fractured well is determined, historical fracturing data and dynamic profile test data of the target fractured well are collected, and a fracturing plugging target layer is determined; according to historical fracturing data analysis and an ASP flooding core blockage rule experiment, the fracture radius of a target layer, the ASP flooding reservoir blockage radius, the reservoir physical property and fracturing scheme of the target layer, the lower limit of the quality-divided injection permeability of the target layer and the damage degree caused by fracturing residues of the target layer are obtained; the method comprises the following steps: sequentially acquiring the dosage of a blocking remover for chemical blocking removal of a target layer, slug combination parameters, fracture parameters of a fractured position, a post-fracturing quality-divided injection process and post-fracturing injection mode combination, performing fracturing blocking removal on the target layer according to the acquired data, and collecting fracturing blocking removal effect data in real time. According to the method, the operation efficiency is improved, and meanwhile the construction cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil production engineering, and particularly relates to a fracturing and plugging method for a low-efficiency well of a chemical flooding injection in a middle-shallow sandstone thin and poor oil layer. BACKGROUND

[0002] With the development, the chemical flooding development object gradually turns to the three types of oil layers of 'thin, low, narrow and poor', and compared with the second type of oil layer, the pore throat radius of the third type of oil layer is reduced by 29.7-50.9%, the overall physical property characteristics are poor, the injection well plugging problem is more serious, the implementation difficulty of the conventional acidification, fracturing and other reservoir reconstruction technologies is large, the measure cost is high, and the measure effect is poor; the conventional acidification plugging control range is limited, and only the near wellbore plugging can be removed, and the injection and production end is difficult to establish an effective displacement relationship; the conventional fracturing plugging low-efficiency well proportion is high, the measure effective period is short, and the production urgently needs to remove the fracture plugging after the fracturing failure to restore the 'highway' flow conductivity; the thin and poor reservoir has strong heterogeneity and large physical property difference, and the post-fracturing general injection leads to the difficulty in developing part of the thin and poor layers. In summary, the single conventional general plugging or fracturing plugging cannot solve the problem of the chemical flooding injection in the thin and poor reservoir of the low-efficiency well. SUMMARY

[0003] (I) Technical problem to be solved

[0004] The present application provides a fracturing and plugging method for a low-efficiency well of a chemical flooding injection in a middle-shallow sandstone thin and poor oil layer to overcome the problem that the conventional technology generally adopts a single measure general plugging, a single measure multi-fracture, ordinary fracturing, post-fracturing general injection and post-fracturing regular well washing, and the integration idea of the fracturing and plugging is imperfect.

[0005] (II) Technical scheme

[0006] In order to solve the above problems, the present application provides a fracturing and plugging method for a low-efficiency well of a chemical flooding injection in a middle-shallow sandstone thin and poor oil layer, which comprises the following steps:

[0007] Step one: determining a target fracturing well, collecting historical fracturing data and dynamic profile test data of the target fracturing well;

[0008] Step two: determining a target layer of fracturing and plugging according to the historical fracturing data and the dynamic profile test data of the target fracturing well;

[0009] Step three: obtaining the fracture radius of the target layer, the three-component composite flooding reservoir plugging radius, the reservoir property of the target layer, the fracturing scheme of the target layer, the lower limit of the quality injection permeability of the target layer and the damage degree caused by the fracturing residue of the target layer according to the historical fracturing data analysis and the three-component composite flooding core plugging law experiment;

[0010] Step four: obtain the amount of chemical plugging remover and slug combination parameters of the chemical plugging of the target layer according to the crack radius of the target layer and the plugging radius of the ternary combination drive reservoir, obtain the crack parameters of the fracturing layer of the target layer according to the reservoir property and fracturing scheme of the target layer, obtain the post-fracturing stratified injection process of the target layer according to the lower limit of the stratified injection permeability of the target layer, and obtain the post-fracturing injection mode combination of the target layer according to the degree of damage caused by the fracturing residue of the target layer;

[0011] Step five: according to the amount of chemical plugging remover and slug combination parameters, crack parameters of the fracturing layer, post-fracturing stratified injection process and post-fracturing injection mode combination, implement fracturing and plugging removal of the target layer, and collect real-time effect data of fracturing and plugging removal.

[0012] Preferably, the content of the historical fracturing data and dynamic profile test data includes historical fracturing layer, fracturing mode, logging curve gamma, permeability, effective thickness and previous isotope profile test data.

[0013] Preferably, the historical fracturing data and dynamic profile test data are the basis for determining whether the last fracturing operation of the fracturing target well is a single segment single card fracturing or a layer position of multi-segment combined pressure.

[0014] Preferably, the single segment single card fracturing determination basis is the old layer that has been fractured, and the multi-segment combined pressure layer determination basis is the qualitative judgment of whether the cracks of each layer are opened.

[0015] Preferably, the type of the target layer for fracturing and plugging removal includes a fracturing target layer, a plugging removal target layer and a non-measured layer, the fracturing target layer is a new layer that has not been fractured or an old layer that has been fractured and the old layer shows no water absorption in previous isotopes, the plugging removal target layer is an old layer that has been fractured, and the non-measured layer is a layer position that shows water absorption in the latest isotope data.

[0016] Preferably, the method for obtaining the amount of chemical plugging remover and slug combination parameters of the chemical plugging of the target layer comprises: determining the fractured small layer and sanding amount according to the qualitative judgment result of the multi-crack pressure opening small layer; based on the core plugging rule experiment of ternary combination drive, establishing a reservoir plugging radius derivation calculation method, and designing plugging removal parameters and the last plugging area range through the calculation method; calculating the amount of plugging remover according to the determined crack radius of the fractured layer, the effective thickness of the fracturing layer position, the porosity of the fracturing layer position and the last fracturing sanding amount according to the last plugging area range; optimizing the proportion parameters of the plugging remover according to the component content analysis of the injection well flowback, and performing targeted plugging removal measures.

[0017] Preferably, the fracture parameter acquisition method of the fracturing interval of the target layer comprises: calculating the fracture radius of the current repeated fracturing interval and the new fracturing interval according to the last plugging area range and the different sand body chemical flooding injection well penetration ratio template in the target fracturing well research area respectively; and establishing a fracturing model according to the reservoir physical property and the fracturing scheme, and selecting the fracture conductivity capacity matched with the reservoir by the injection amount prediction result of different schemes and the calculated fracture radius, in cooperation with the post-fracturing balanced production of each interval.

[0018] Preferably, the judgment method of the post-fracturing quality-based injection process of the target layer comprises: post-fracturing sub-dividing the injection interval based on the reservoir physical property; determining the lower limit value of the quality-based injection permeability according to the core permeability and polymer molecular weight relationship chart; and determining that the layer section needs to adopt the quality-based injection process when the number of intervals with permeability lower than the lower limit value and the effective thickness proportion in each injection interval are both more than 50%.

[0019] Preferably, the determination method of the post-fracturing injection mode combination of the target layer comprises: determining the first injection mode combination after fracturing for the well condition that a small amount of fracturing residues cause damage after fracturing; determining the second injection mode combination after fracturing for the well condition that a large amount of fracturing residues cause serious damage after fracturing; determining the third injection mode combination after fracturing for the well condition that a large amount of fracturing residues cause serious damage after fracturing and part of the intervals cannot inject the oil displacement agent; and determining the fourth injection mode combination after fracturing for the injection plugging well after fracturing.

[0020] Preferably, the first injection mode combination is: after fracturing, first injecting clean water for a period of time, and then injecting the ternary liquid; the second injection mode combination is: after fracturing, first injecting clean water for a period of time, then unblocking once, then injecting clean water for a period of time, and finally injecting the ternary liquid; the third injection mode combination is: after fracturing, first injecting clean water for a period of time, then unblocking once, then injecting clean water for a period of time, and then injecting the ternary liquid; and the fourth injection mode combination is: after fracturing, injecting clean water for a period of time, and when the post-fracturing daily injection increment decreases by 50-70%, the fracture appears obvious blockage but has not been blocked yet.

[0021] (Three) beneficial effects

[0022] The fracturing and unblocking method of the chemical flooding injection low-efficiency well of the middle-shallow layer sandstone thin and poor oil layer provided by the application integrates the fracturing reconstruction, chemical unblocking, post-fracturing quality-based injection and the injection mode combination of different displacement media, has a reliable basic principle, organically combines the fracturing, unblocking and injection, realizes the integrated operation of the fracturing, chemical unblocking and injection, improves the operation efficiency, and simultaneously reduces the construction cost. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1A flow chart of the fracturing and plugging removal method for the low-efficiency well of the chemical flooding injection in the shallow sandstone thin and poor oil layer in the embodiment of the present application is shown in the figure.

[0024] Figure 2 A standard diagram for selecting the fracturing and plugging removal layer in the embodiment of the present application is shown in the figure.

[0025] Figure 3 A dosage design diagram for the plugging removal of the fractured layer in the embodiment of the present application is shown in the figure.

[0026] Figure 4 A fracturing data and analysis result diagram of Well A in September 2021 in the embodiment of the present application is shown in the figure.

[0027] Figure 5 A layer selection diagram for the fracturing and plugging removal measures of Well A in the embodiment of the present application is shown in the figure.

[0028] Figure 6 A core permeability and polymer molecular weight relationship diagram in the embodiment of the present application is shown in the figure.

[0029] Figure 7 A chemical flooding fracturing and plugging removal comprehensive treatment field test curve diagram in the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] Figure 1 A flow chart of the fracturing and plugging removal method for the low-efficiency well of the chemical flooding injection in the shallow sandstone thin and poor oil layer in the embodiment of the present application is shown in the figure. Figure 1 The present application provides a fracturing and plugging removal method for the low-efficiency well of the chemical flooding injection in the shallow sandstone thin and poor oil layer, specifically including:

[0032] Step one: determine the target fracturing well, and collect the historical fracturing data and dynamic profile test data of the target fracturing well;

[0033] Step two: determine the target layer for fracturing and plugging removal according to the obtained historical fracturing data and dynamic profile test data of the target fracturing well;

[0034] Step three: obtain the fracture radius of the target layer, the plugging radius of the ternary compound flooding reservoir, the reservoir physical property of the target layer, the fracturing scheme of the target layer, the lower limit of the quality injection permeability of the target layer, and the damage degree caused by the fracturing residue of the target layer according to the analysis of the collected historical fracturing data and the core plugging law experiment of the ternary compound flooding;

[0035] Step four: obtain the amount of chemical deblocking agent and slug combination parameters of the chemical deblocking of the target layer according to the crack radius of the target layer and the plugging radius of the reservoir of the ternary combination flooding, obtain the crack parameters of the fracturing horizon of the target layer according to the reservoir property and the fracturing scheme of the target layer, obtain the post-fracturing stratified injection process of the target layer according to the lower limit of the stratified injection permeability of the target layer, and obtain the post-fracturing injection mode combination of the target layer according to the degree of damage caused by the fracturing residue of the target layer;

[0036] Step five: implement the fracturing deblocking of the target layer according to the amount of chemical deblocking agent and slug combination parameters, the crack parameters of the fracturing horizon, the post-fracturing stratified injection process and the post-fracturing injection mode combination, and collect the effect data of the fracturing deblocking in real time.

[0037] In the fracturing deblocking method, the historical fracturing data and the dynamic profile test data include the historical fracturing horizon, the fracturing mode, the logging curve gamma, the permeability, the effective thickness and the isotope profile test data of previous times. In actual application, the historical fracturing data and the dynamic profile test data are the basis for judging whether the last fracturing construction of the fracturing target well is the horizon of single-segment single-pad fracturing or multi-segment combined pressure. The single-segment single-pad fracturing is determined according to the old layer that has been fractured, and the horizon of multi-segment combined pressure is determined according to the qualitative judgment of whether the cracks of each layer are opened.

[0038] It should be noted that the priority order of determining whether the cracks of each layer are opened is that the lower the logging curve gamma value, the higher the permeability value and the greater the effective thickness, the easier the cracks are to open. The number of old layers that have been fractured is the number of wax ball injections plus 1.

[0039] In actual application, the types of the target layer for fracturing deblocking include the fracturing target layer, the deblocking target layer and the non-measured layer. The fracturing target layer is a new layer that has not been fractured or an old layer that has been fractured and the old layer shows no water absorption in the isotope profile of previous times. The deblocking target layer is an old layer that has been fractured. The non-measured layer is the horizon that shows water absorption in the isotope data of the last time.

[0040] In the fracturing deblocking method, the method for obtaining the amount of chemical deblocking agent and the slug combination parameters of the chemical deblocking of the target layer includes: determining the fractured small layer and the sand amount according to the qualitative judgment result of the multi-crack pressure opening of the small layer; based on the core plugging law experiment of the ternary combination flooding, establishing a reservoir plugging radius derivation and calculation method, and designing deblocking parameters and the last plugging area range through the calculation method; calculating the amount of deblocking agent according to the determined crack radius of the fractured layer, the effective thickness of the fracturing horizon, the porosity of the fracturing horizon and the last fracturing sand amount, according to the last plugging area range; optimizing the deblocking agent proportion parameters according to the component content analysis of the flowback material of the injection well, and performing targeted deblocking measures.

[0041] In practical application, the volume method and PT software are respectively used to calculate and inversely calculate the fracture radius of the fractured layer, and the larger value is selected as the fracture radius of the fractured layer to ensure the effect of augmented injection. In addition, the effective rate of the design of the plugging removal parameter and the last plugging area is 85.2%.

[0042] In the fracturing and plugging removal method, the method for obtaining the fracture parameters of the fracturing layer of the target layer comprises the following steps: the fracture radius of the repeated fracturing layer and the fracture radius of the new layer are calculated according to the last plugging area range and the different sand body chemical flooding injection well penetration ratio template in the research area of the target fracturing well; a fracturing model is established according to the reservoir properties and the fracturing scheme, the injection amount prediction results of different schemes and the calculated fracture radius are used to select the fracture conductivity that matches the reservoir by balancing the production of each layer after fracturing.

[0043] In practical application, the larger value is selected to ensure the effect of augmented injection, and the fracture radius of the new layer is selected to be similar to the fracture radius of the repeated fracturing layer to realize the balanced production of each layer.

[0044] In the fracturing and plugging removal method, a fracturing model is established according to the reservoir properties and the fracturing scheme, the injection amount prediction results of different schemes are used to select the fracture conductivity that matches the reservoir according to the optimized fracture radius, and the fracture conductivity is optimized by considering the balanced production of each layer after fracturing.

[0045] In practical application, the judgment method of the post-fracturing separate quality injection process of the target layer comprises the following steps: the injection layer is divided based on the reservoir properties after fracturing; the lower limit value of the separate quality injection permeability is determined according to the relationship between the core permeability and the polymer molecular weight; the number of layers and the effective thickness ratio of the layers with permeability lower than the lower limit value in each injection layer are counted, and if one of the two ratios is more than 50%, it is determined that the layer needs to use the separate quality injection process.

[0046] In the fracturing and plugging removal method, the determination method of the post-fracturing injection mode combination of the target layer comprises the following steps: the first injection mode combination is determined for the well condition with a little fracturing residue causing damage after fracturing; the second injection mode combination is determined for the well condition with a large amount of fracturing residue causing serious damage after fracturing; the third injection mode combination is determined for the well condition with a large amount of fracturing residue causing serious damage and part of the layer position being unable to inject the oil displacement agent; and the fourth injection mode combination is determined for the well with injection plugging after fracturing.

[0047] In practical application, the first injection mode combination: after fracturing, first inject clean water for a period of time, and then inject the ternary liquid; the second injection mode combination: after fracturing, first inject clean water for a period of time, then unblock once, then inject clean water for a period of time, and finally inject the ternary liquid; the third injection mode combination: after fracturing, first inject clean water for a period of time, then unblock once, inject clean water for a period of time, and then inject the ternary liquid; the fourth injection mode combination: after fracturing, inject clean water for a period of time, when the post-fracturing daily injection rate decreases by 50-70%, the fracture appears obvious blockage but has not been blocked.

[0048] The present application provides a fracturing and unblocking method for a low-efficiency injection well of a chemical flooding in a middle-shallow sandstone thin and poor oil layer, and the method is a comprehensive treatment method for the low-efficiency injection well of the chemical flooding, which combines fracturing, chemical unblocking, post-fracturing injection of different qualities, and injection mode combination of different displacement media, has a reliable basic principle, organically combines fracturing, unblocking and injection, realizes integrated operation of fracturing, chemical unblocking and injection, improves operation efficiency, and reduces construction cost.

[0049] Reference Figures 2 to 7 The working process of the fracturing and unblocking method for the low-efficiency injection well of the chemical flooding in the middle-shallow sandstone thin and poor oil layer will be described below:

[0050] In this embodiment, well A is a low-efficiency injection well of a chemical flooding in a thin and poor oil layer of a sandstone reservoir in an old area of an oilfield, is currently in a ternary main plug stage, has a polymer molecular weight of 16 million, was fractured and put into production in September 2021, and was unblocked once in November 2022.

[0051] In practical application, first, a target fracturing well is determined, historical fracturing data and dynamic profile test data of the target fracturing well are collected, and the target layer for fracturing and unblocking is determined according to the historical fracturing data and the dynamic profile test data of the target fracturing well.

[0052] In this embodiment, the curve gamma, the permeability and the effective thickness comprehensively determine that 9 small layers are fractured and opened, and the layer positions are SII12 layer, SII11(1) layer, SII10(1) layer, SII8(2) layer, SII7 layer, SII4(1) layer, SII21(1), SII21(2) and SII1.

[0053] In practical application, the fractured target layer is a new layer which has not been fractured or an old layer which has been fractured and the old layer shows no water absorption in previous isotopic data, and five small layers are fractured, wherein the new layer which has not been fractured is Sa II 22+3 layer, Sa II 8(1) layer and Sa II 6 layer, and the old layer which has been fractured and shows no water absorption in previous isotopic data is Sa II 7 layer and Sa II 8(2) layer; the deblocking target layer is an old layer which has been fractured, and four small layers are deblocked, which are Sa II 21 layer, Sa II 7 layer, Sa II 8(2) layer and Sa II 10 layer; and the non-measured layer is a layer which shows water absorption in the latest isotopic data, which is Sa II 11 layer, Sa II 12 layer, Sa II 4 layer and Sa II 1 layer.

[0054] In the embodiment, the fracture radius of the target layer and the plugging radius of the reservoir of the ternary complex flooding, the reservoir property and the fracturing scheme of the target layer, the lower limit of the injection permeability of the target layer and the damage degree caused by the fracturing residue of the target layer are obtained according to the analysis of the collected historical fracturing data and the core plugging rule experiment of the ternary complex flooding; in practical application, the dosage of the deblocking agent and the slug combination parameters of the chemical deblocking of the target layer are obtained according to the fracture radius of the target layer and the plugging radius of the reservoir of the ternary complex flooding, the fracture parameters of the fracturing layer of the target layer are obtained according to the reservoir property and the fracturing scheme of the target layer, the post-fracturing injection process of the target layer is obtained according to the lower limit of the injection permeability of the target layer, and the injection mode combination of the target layer after fracturing is obtained according to the damage degree caused by the fracturing residue of the target layer.

[0055] In practical application, the dosage of the deblocking agent and the slug combination parameters of the chemical deblocking of the fractured layer are determined according to the fracture radius of the fractured layer and the plugging radius of the reservoir of the ternary complex flooding, and the details are as follows:

[0056] Firstly, the fractured layer and the sanding amount are determined according to the qualitative judgment result of the multi-fracture pressure opening small layer, the fracture radius of the fractured layer is calculated by using the volume method and the PT software to perform the initial fracturing construction curve inversion, and the larger value of the two is selected as the fracture radius of the fractured layer, which is 12-20m, so as to ensure the injection effect;

[0057] Secondly, the injection wells are divided into unfractured injection wells and fractured injection wells, wherein the unfractured injection well is plugged in the 1.0-9.0m area near the wellbore, the plugging is most serious in about 4.0m, and the deblocking radius is 4.0m; the fractured injection well is plugged in the 4.0m area outside the fracture radius and inside the fractured fracture, and the deblocking radius is 16-24m;

[0058] Then, the dosage of the deblocking agent (V) is calculated according to the determined fracture radius (R1) of the fractured layer, the effective thickness (H) of the fracturing layer, the porosity (φ) of the fracturing layer and the sanding amount (V1) of the last fracturing, and the plugging exists in the 4.0m formation outside the last fracturing radius and in the fracture, and the calculation formula is as follows:

[0059] V={π(R1+4.0)2 -πR1 2}×H×Φ+V1;

[0060] The total amount of the plugging removal agent is determined by calculation 351m 3 ;

[0061] Finally, according to the component content analysis of the flowback material of the injection well, the proportion parameters of the plugging removal agent are optimized, and the proportion of the plugging removal agent includes degradation + descaling, wherein the permeation agent is 15%, the main function of which is to swell and loosen the plugging material, and to change the physical property of the rock surface, so that the plugging material is more easily separated from the rock surface; the plugging removal agent is 80%, the main function of which is to dissolve the polymer and plugging material in the near wellbore zone, to remove the pollution of the oil layer, to maintain a low pH environment, and to prevent secondary pollution and clay swelling and migration; and the anti-deposition agent is 5%, the main function of which is to preferentially adsorb on the rock surface, so that the surface of the pore channel becomes smooth, the formation of scale and polymer plugging material is slowed down, the effective period of the treatment is prolonged, and the plugging removal treatment is performed in a targeted manner.

[0062] In this embodiment, according to the reservoir property and the fracturing optimization scheme, the fracture parameters of the fracturing layer are determined, and the specific parameters are as follows:

[0063] Firstly, the fracture radius of the repeated fracturing layer is calculated according to the injection well penetration ratio optimization template of the chemical flooding of the different sand bodies of the oil production plant and 4m outside the fracture radius of the last fracturing, and the larger value of the two is taken to ensure the effect of the augmented injection; in order to realize the balanced production of each sublayer, the fracture radius of the new layer is selected to be similar to the fracture radius of the repeated fracturing layer with similar permeability, and the fracture radius of the optimized design in this case is 18-24m;

[0064] Then, the reservoir permeability of the test well is mainly concentrated in 42-303mD, according to the reservoir property and the fracturing optimization scheme, the fracturing model is established, the injection amount prediction results of different schemes are referred to, the fracture conductivity of 25-35um 2 .cm that is matched with the reservoir is selected according to the optimized fracture radius, and the fracture conductivity of 30um 2 .cm is optimized considering the balanced production of each sublayer after fracturing.

[0065] In actual application, the fracturing post-subquality injection process is determined according to the lower limit of the subquality injection permeability, and the specific parameters are as follows:

[0066] Firstly, well A is an injection well of general injection before fracturing, and the injection layer is subdivided based on the reservoir property after fracturing, wherein the partial 1 section is Sa II 1-6 layer, and the partial 2 section is Sa II 7-12 layer.

[0067] Secondly, according to the core permeability and polymer molecular weight relationship chart, the 1600 million molecular weight polymer can pass through the oil layer with permeability greater than 100 mD, and the lower limit value of the permeability of the injection quality is determined to be 100 mD. The number of layers of the partial 1 section with permeability lower than 100 mD accounts for 71.0% of the well, and the effective thickness accounts for 66.7%. In order to realize effective injection, the partial 1 section needs to be injected downhole with different qualities, and the injection molecular weight is appropriately reduced.

[0068] In the embodiment, the injection mode combination after fracturing is determined according to the degree of damage caused by fracturing residues. In actual application, the fourth injection mode combination after fracturing is adopted, that is, after fracturing, clear water is injected for a period of time, and when the daily injection increment after fracturing is reduced by 50-70%, chemical deblocking measures are carried out before the fracture is obviously blocked but not completely blocked, so as to avoid complete blockage of the fracture and prolong the effective period of the fracture.

[0069] In actual application, the fracturing deblocking is carried out on the target layer according to the deblocking agent dosage and slug combination parameters obtained by chemical deblocking, the fracture parameters of the fracturing layer, the fracturing quality injection process after fracturing and the injection mode combination after fracturing, and the effect data of the fracturing deblocking is collected in real time.

[0070] In the embodiment, after the comprehensive treatment of the fracturing deblocking of the well, the initial injection pressure is reduced by 3.7 MPa, the daily injection increment is 28 m 3 , the effective period is increased by 113 days compared with the conventional fracturing, and good reconstruction effect is obtained.

[0071] The fracturing deblocking method of the low-efficiency well for chemical flooding injection of the middle-shallow layer sandstone thin and poor oil layer provided by the present application is a comprehensive treatment method of the low-efficiency injection well for chemical flooding, which integrates fracturing reconstruction, chemical deblocking, fracturing quality injection after fracturing and injection mode combination of different displacement media. The basic principle is reliable. The thin and poor reservoir is finely layered and fractured to improve the overall reservoir percolation capacity, and the chemical deblocking agent is injected into the fractured layer to remove the blockage in the internal part of the fractured layer and the area 4.0 meters outside the fracturing radius. After fracturing, the quality injection mode is adopted to realize balanced injection of each layer. After fracturing, the injection mode combination of different displacement media is adopted to realize the purpose of prolonging the effective period of the injection measures. The fracturing, deblocking and injection are organically combined to realize the integrated operation of fracturing, chemical deblocking and injection, improve the operation efficiency, and reduce the construction cost.

[0072] The above embodiments are only used to illustrate the present application, and are not intended to limit the present application. Those skilled in the related technical field can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions also belong to the scope of the present application, and the patent protection scope of the present application should be defined by the claims.

Claims

1. A fracturing and plugging method for low-efficiency wells of chemical flooding in middle-shallow sandstone thin and poor oil layers, characterized in that, The method comprises the following steps: Step 1: determining a target fracturing well, collecting historical fracturing data and dynamic profile test data of the target fracturing well; Step 2: determining a fracturing unblocking target layer according to the historical fracturing data and dynamic profile test data of the target fracturing well; Step 3: obtaining a fracture radius of the target layer, a ternary complex drive reservoir plugging radius, reservoir properties of the target layer, a fracturing scheme, a lower limit of a separate quality injection permeability of the target layer and a degree of damage caused by fracturing residues of the target layer according to historical fracturing data analysis and ternary complex drive core plugging law experiments; Step 4: obtaining a chemical unblocking agent dosage and slug combination parameters of the target layer according to the fracture radius of the target layer and the ternary complex drive reservoir plugging radius, obtaining fracture parameters of a fracturing layer of the target layer according to the reservoir properties of the target layer and the fracturing scheme, obtaining a separate quality injection process after fracturing of the target layer according to the lower limit of the separate quality injection permeability of the target layer, and obtaining an injection mode combination after fracturing of the target layer according to the degree of damage caused by the fracturing residues of the target layer; Step 5: implementing fracturing unblocking of the target layer according to the chemical unblocking agent dosage and the slug combination parameters, the fracture parameters of the fracturing layer, the separate quality injection process after fracturing and the injection mode combination after fracturing, and collecting effect data of the fracturing unblocking in real time.

2. The method according to claim 1, wherein the method is characterized in that, The historical fracturing data and dynamic profile test data include historical fracturing layer, fracturing method, logging curve gamma, permeability, effective thickness and previous isotope profile test data.

3. The method according to claim 2, wherein the historical fracturing data and dynamic profile test data are used as a basis for judging whether the last fracturing operation of the target well is a single-stage single-pad fracturing or a multi-stage combined fracturing.

4. The method according to claim 3, wherein the single-stage single-pad fracturing is determined according to an old layer that has been fractured, and the multi-stage combined fracturing is determined according to a qualitative judgment of whether the fractures of each layer are open.

5. The method according to claim 1, wherein the method is characterized in that, The fracturing unblocking target layer includes a fracturing target layer, an unblocking target layer and a non-measured layer, the fracturing target layer is a new layer that has not been fractured or an old layer that has been fractured and shows no water absorption in previous isotopes, the unblocking target layer is an old layer that has been fractured, and the non-measured layer is a layer that shows water absorption in the latest isotope data.

6. The method according to claim 1, wherein the method is characterized in that, The method for obtaining the chemical unblocking agent dosage and the slug combination parameters of the target layer comprises the following steps: determining fractured layers and sanding amounts according to a qualitative judgment result of multi-fracture pressure opening of small layers; establishing a reservoir plugging radius derivation calculation method based on ternary complex drive core plugging law experiments, and designing unblocking parameters and a last plugging area range through the calculation method; calculating the unblocking agent dosage according to the fracture radius of the determined fractured layer, the effective thickness of the fracturing layer, the porosity of the fracturing layer and the last fracturing sanding amount, and according to the last plugging area range; optimizing the unblocking agent proportion parameters according to the component content analysis of the injection well flowback material, and performing targeted unblocking measures.

7. The method according to claim 1, wherein the method is characterized in that, The method for obtaining the fracture parameters of the fracturing interval of the target layer comprises: calculating the fracture radius of the current repeated fracturing interval and the new fracturing interval according to the last plugging area range and the different sand body chemical flooding injection well penetration ratio template in the target fracturing well research area respectively; and establishing a fracturing model according to the reservoir physical properties and the fracturing scheme, and selecting the fracture conductivity capacity matched with the reservoir by the injection amount prediction results of different schemes, the calculated fracture radius and the balanced performance of each layer after fracturing.

8. The method according to claim 1, wherein the method is characterized in that, The method for determining the post-fracturing quality-based injection process of the target layer comprises: post-fracturing based on the reservoir physical properties to subdivide the water injection interval; determining the lower limit value of the quality-based injection permeability according to the core permeability and polymer molecular weight relationship chart; and counting the number of layers and the effective thickness proportion of the layers with permeability lower than the lower limit value in each injection interval, and determining that the interval needs to use the quality-based injection process when one of the two proportions exceeds 50%.

9. The method according to claim 1, wherein the method is characterized in that, The method for determining the post-fracturing injection mode combination of the target layer comprises: determining the first injection mode combination after fracturing for the well condition with a little fracturing residue causing damage after fracturing; determining the second injection mode combination after fracturing for the well condition with a large amount of fracturing residue causing serious damage after fracturing; determining the third injection mode combination after fracturing for the well condition with a large amount of fracturing residue causing serious damage and part of the layers being unable to inject the oil displacement agent; and determining the fourth injection mode combination after fracturing for the injection plugging well after fracturing.

10. The method according to claim 9, wherein the method is characterized in that, The first injection mode combination: after fracturing, first inject clean water for a period of time, and then inject the ternary liquid; the second injection mode combination: after fracturing, first inject clean water for a period of time, then unplug once, then inject clean water for a period of time, and finally inject the ternary liquid; the third injection mode combination: after fracturing, first inject clean water for a period of time, then unplug once, then inject clean water for a period of time, and then inject the ternary liquid; and the fourth injection mode combination: after fracturing, inject clean water for a period of time, and when the post-fracturing daily injection amount decreases by 50-70%, the fracture appears obvious plugging but has not been blocked.

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