Method for carbon dioxide flooding of deep sandstone conglomerate low permeability reservoirs

Abstract

The present application provides a kind of deep sand gravel low permeability reservoir carbon dioxide drive production method, the deep sand gravel low permeability reservoir carbon dioxide drive production method includes: step 1, determine the miscibility pressure of reservoir crude oil;Step 2, determine the miscibility ability and carbon dioxide gas source of the block at present reservoir;Step 3, based on gas source and miscibility ability, according to short-term with or without carbon dioxide gas source design specific production process;Step 4, according to the process to carry out field test injection and formal injection;Step 5, carry out tracking adjustment research, according to the design process to implement control.The deep sand gravel low permeability reservoir carbon dioxide drive production method improves the success rate of deep sand gravel low permeability reservoir carbon dioxide drive implementation, realizes effective displacement, improves development effect, and provides a more accurate production method for the implementation of deep sand gravel low permeability reservoir carbon dioxide drive development plan.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil reservoir development, in particular to a carbon dioxide flooding production method for deep sandstone and conglomerate low permeability oil reservoirs. BACKGROUND

[0002] Deep sandstone and conglomerate low permeability oil reservoirs in China are rich in reserves and have great development potential, but they are generally characterized by complex reservoir connectivity, poor reservoir properties, strong heterogeneity, weak natural energy, and poor natural energy and water flooding development effect. Due to the large burial depth, high formation pressure and good oil properties of deep sandstone and conglomerate reservoirs, the carbon dioxide has strong miscibility and high oil displacement efficiency. Laboratory experiments and field practices have shown that under the same conditions, the carbon dioxide injection capacity of low permeability reservoirs is generally more than three times that of water injection capacity. Therefore, carbon dioxide miscible flooding is an effective development method for deep sandstone and conglomerate low permeability reservoirs and has a wide application prospect. Due to the influence of burial depth, poor reservoir properties, strong heterogeneity and complex reservoir connectivity of deep sandstone and conglomerate low permeability reservoirs, which are nearshore underwater fan or fan delta deposits, and due to the shortage of domestic carbon dioxide gas sources and the lack of practical experience of carbon dioxide flooding for deep sandstone and conglomerate low permeability reservoirs, there is a lack of effective technical guidance on the gas absorption capacity, gas drive characteristics and risk prevention and control of gas channeling of deep sandstone and conglomerate low permeability reservoirs during implementation.

[0003] The miscibility capacity of carbon dioxide miscible flooding is the main factor affecting the development effect of deep sandstone and conglomerate reservoirs, but due to the limitation of domestic carbon dioxide gas sources and the differences in development status of different blocks, the carbon dioxide miscibility capacity of the reservoirs is greatly different during gas injection, and the miscibility capacity of the original oil in the formation needs to be considered during the implementation of the scheme.

[0004] Due to the poor properties of deep sandstone and conglomerate low permeability reservoirs, the natural productivity is low, and large-scale fracturing is generally required for production wells, and fracturing is also required for water injection wells. However, due to the strong injection capacity and strong seepage capacity of carbon dioxide, gas channeling is easy to occur after reservoir fracturing. Therefore, in order to avoid the injection of carbon dioxide along the fractures and cause gas channeling in production wells during the implementation of carbon dioxide flooding, the response strategies under different production modes of injection and production wells need to be considered.

[0005] The reservoir connectivity of deep sandstone and conglomerate low permeability reservoirs is complex and the heterogeneity is strong, which leads to differences in gas drive speed and effect in different directions. Therefore, whether there is gas channeling needs to be considered in advance for different conditions during the implementation of the carbon dioxide flooding development scheme.

[0006] Currently, the carbon dioxide flooding production method for deep sand-gravel low permeability reservoirs mainly adopts the carbon dioxide flooding production method for conventional low permeability reservoirs. In the actual implementation process, there is a lack of effective plan for the problems that may be encountered in the carbon dioxide flooding of deep sand-gravel reservoirs, and it is difficult to adapt to the injection-production characteristics of the carbon dioxide flooding of deep sand-gravel low permeability reservoirs. At present, there is a lack of carbon dioxide flooding production method for deep sand-gravel low permeability reservoirs controlled by multiple factors such as gas source, injection-production capacity, and connectivity.

[0007] We analyzed the reservoir characteristics of deep sand-gravel low permeability reservoirs and the current carbon dioxide miscible capacity of the reservoirs, and found that there are problems such as uncertain miscible capacity, uncertain injection capacity of injection wells and production capacity of production wells under different completion methods, uncertain interwell injection-production connectivity characteristics, and uncertain injection-production control measures in the injection-production process of carbon dioxide miscible flooding.

[0008] In the Chinese patent application with the application number CN201810263005.1, a process for mixed oil displacement using natural gas and carbon dioxide is involved, which includes: perfecting the injection-production well pattern of the gas injection well, adopting the well pattern of straight well gas injection and new drilled horizontal well oil production, and carrying out steam huff and puff oil production in the new drilled horizontal well for 1-2 years; installing equipment for injecting carbon dioxide and natural gas at the wellhead of the gas injection well, installing oil production equipment at the wellhead of the new drilled horizontal well, and online measuring the casing gas oxygen content of the gas injection well and the new drilled horizontal well, when the casing gas oxygen content of the gas injection well is higher than the explosion point, injecting carbon dioxide gas into the gas injection well; continuously injecting the mixed gas of natural gas and carbon dioxide into the gas injection well, driving the crude oil in the oil layer to the surrounding new drilled horizontal well, and intermittently opening and producing and shutting down the surrounding new drilled horizontal wells.

[0009] In the Chinese patent application with the application number CN201611243994.5, an air injection and carbon dioxide assisted steam huff and puff oil production method is involved. The method includes: step one, setting injection-production wells and adjacent wells, and online measuring the casing gas oxygen content of the injection-production wells and the adjacent wells; step two, when the casing gas oxygen content of the injection-production well is higher than the explosion point, injecting nitrogen and / or carbon dioxide gas into the injection-production well, and taking the casing gas oxygen content of the injection-production well being lower than the explosion point as the injection end point; step three, injecting the mixed gas of air and carbon dioxide until the total amount reaches the designed amount, after which carbon dioxide slug is used for well killing, and then steam is injected; or, injecting the mixed gas slug of air and carbon dioxide, then injecting the steam slug, and then continuously cyclically injecting the mixed gas slug and the steam slug alternately, until the total amount of the mixed gas slug injection reaches the designed amount, after which carbon dioxide slug is used for well killing after the cyclic injection is completed; step four, huff and puff until the well pressure reaches the normal pressure, and then blowout production.

[0010] In the Chinese patent application with the application number CN201710435296.3, a downhole self-generating mixed-phase thermal fluid huff and puff oil production method is related to the oil field oil production technical field. The method comprises: performing well completion operation on the target huff and puff well, arranging the downhole mixed-phase thermal fluid generator and the matching ground supply system in the downhole after well completion, producing and injecting the mixed-phase thermal fluid in the downhole into the oil layer, and shutting in the well after the injection amount reaches the preset range, and performing oil production operation after the shut-in time reaches the preset range.

[0011] The above prior art is quite different from the present application, and cannot solve the technical problems we want to solve. Therefore, we have invented a new carbon dioxide flooding production method for deep sand gravel low permeability reservoirs. SUMMARY

[0012] The purpose of the present application is to provide a carbon dioxide flooding production method for deep sand gravel low permeability reservoirs, which can improve the success rate of carbon dioxide flooding implementation for deep sand gravel low permeability reservoirs, realize effective displacement, and improve the development effect.

[0013] The purpose of the present application can be achieved by the following technical measures: a carbon dioxide flooding production method for deep sand gravel low permeability reservoirs, which comprises:

[0014] Step 1, determining the oil reservoir crude oil miscibility pressure;

[0015] Step 2, determining the miscibility ability of the current oil reservoir and the carbon dioxide gas source of the implementation block;

[0016] Step 3, based on the gas source and the miscibility ability, designing a specific production process according to whether there is a carbon dioxide gas source in the short term;

[0017] Step 4, carrying out field test injection and formal gas injection according to the process;

[0018] Step 5, carrying out tracking adjustment research, and implementing control according to the designed process.

[0019] The purpose of the present application can also be achieved by the following technical measures:

[0020] In step 1, representative formation crude oil samples of the target block are selected, and the minimum miscibility pressure of the target block oil reservoir crude oil is determined through carbon dioxide phase characteristic experiment and minimum miscibility pressure test.

[0021] In step 2, comprehensive geological research and oil reservoir dynamic analysis research are carried out to determine the reservoir physical property, heterogeneity, predict the possible connectivity between different wells, and determine the current oil reservoir pressure and miscibility ability.

[0022] In step 2, according to the reservoir characteristics drilled by the test well, the first section is tested according to the segmented and variable density perforation mode, if the injection capacity can meet the design without fracturing, all well sections are betted according to the perforation mode without fracturing; the production well is perforated according to the perforation mode of segmented and clustered, the first section is put into production according to the conventional perforation mode, if the oil production capacity can meet the design without fracturing, all well sections are put into production according to the perforation mode without fracturing, if the production capacity cannot meet the design, the production well is put into production according to the mode of small-scale multi-stage fracturing; the supply time, daily supply amount and total supply amount of carbon dioxide gas source are determined according to the carbon dioxide gas source around the block; the specific production process is designed according to the carbon dioxide gas source.

[0023] In step 3, if there is a stable carbon dioxide gas source, the implementation process with carbon dioxide gas source is implemented, the specific implementation process is as follows:

[0024] Step 31a, select the test injection well to test carbon dioxide injection; according to the vertical heterogeneity of the test injection well, the variable density perforation mode is preferred for perforating well section; at least three different injection rates are tested, each injection rate is adjusted to the next injection rate after stable injection, and the injection pressure monitoring, dynamic monitoring and tracking research of the production well are done;

[0025] Step 31b, if the test injection well has poor gas absorption capacity, the test injection well is fractured according to the small-scale fracturing design to form a network of fractures near the wellbore, and at least three different injection rates are tested, each injection rate is adjusted to the next injection rate after stable injection, and the injection pressure monitoring, dynamic monitoring and tracking research of the production well are done.

[0026] Step 31a includes:

[0027] ①If the test injection well is injected normally and no gas channeling occurs, the injection well is normally injected according to the design parameters, the production well is put into production by using the cluster perforation completion, and the conditions for later fracturing are provided; if the production well reaches the design production capacity, the production well is normally put into production; if the production well does not reach the design production capacity, the production well is put into production by using the small-scale carbon dioxide stimulation fracturing;

[0028] ②If the test injection well is injected normally and the production well has gas channeling, the reason for gas channeling is analyzed, if the gas channeling is controllable, the injection mode is optimized, including segmented injection and production, coupled injection and production, gas-water alternation and foam flooding; the production well is put into production by using the cluster perforation completion, and the conditions for later fracturing are provided; if the production well reaches the design production capacity, the production well is normally put into production; if the production well does not reach the design production capacity, the production well is put into production by using the small-scale carbon dioxide stimulation fracturing;

[0029] ③ If the injection of the test injection well is normal and the gas channeling in the production well is uncontrollable, it indicates that the block is not suitable for carbon dioxide flooding development, and all the wells are converted into large-scale fracturing natural energy development.

[0030] Step 31b includes:

[0031] ① If the injection of the test injection well is normal and no gas channeling occurs, the new injection well is fractured in the near wellbore zone according to a small-scale fracturing design, and the injection is performed according to the design parameters, and the new production well is completed by cluster perforation and put into production; if the production well reaches the designed production capacity, the production well is normally put into production; if the production well does not reach the designed production capacity, the production well is put into production by carbon dioxide stimulation small-scale fracturing;

[0032] ② If the injection of the test injection well is normal and the gas channeling in the production well exists, the reason for the gas channeling is analyzed; if the gas channeling is controllable, the new injection well is fractured in the near wellbore zone according to a small-scale fracturing design, and the injection mode is optimized, including segmented injection and production, coupled injection and production, gas-water alternation, and foam flooding; the new production well is completed by cluster perforation and put into production to provide conditions for later fracturing; if the production well reaches the designed production capacity, the production well is normally put into production; if the production well does not reach the designed production capacity, the production well is put into production by carbon dioxide stimulation small-scale fracturing;

[0033] ③ If the injection of the test injection well is normal and the gas channeling in the production well is uncontrollable, it indicates that the block is not suitable for carbon dioxide flooding development, and all the wells are converted into large-scale fracturing natural energy development.

[0034] In step 3, if there is no stable carbon dioxide gas source in the short term, the implementation process without carbon dioxide gas source is implemented, and the specific implementation process is as follows:

[0035] Step 32a, the new production well is put into production by carbon dioxide stimulation small-scale fracturing and multi-stage fracturing;

[0036] Step 32b, the test injection well is selected for carbon dioxide injection test, and according to the vertical heterogeneity of the test injection well, the variable density perforation method is used for perforation; at least three different injection rates are tested, and each injection rate is stabilized before adjusting to the next injection rate, and the injection pressure monitoring, dynamic monitoring and tracking research of all production wells are performed;

[0037] Step 32c, if a stable carbon dioxide gas source can be obtained before the formation pressure drops to 1.3MMP, the injection well is normally injected according to the design, and the injection pressure monitoring, dynamic monitoring and tracking research of all production wells are performed;

[0038] Step 32d, if the stable carbon dioxide gas source is obtained after the formation pressure drops to 1.3MMP, the formation pressure recovery is carried out according to the actual situation of pressure depletion, preferably by injecting gas or water, until the formation pressure is recovered to more than 1.3MMP, the gas injection well is put into normal gas injection according to the design, and the monitoring of the injection pressure, the dynamic monitoring and tracking research of all production wells are well done.

[0039] Step 32b includes:

[0040] ①If the injection of the test injection well is normal and no gas channeling occurs or the gas channeling is controllable, stop injection, and convert to normal gas injection after the gas source is settled; if the gas channeling of the production well is uncontrollable, the carbon dioxide of the gas injection well is introduced, large-scale segmented fracturing is carried out, and the whole area is developed by natural energy.

[0041] ②If the gas absorption capacity of the test injection well is poor, the well section of the test injection well is fractured according to the small-scale fracturing design to fracture the near-wellbore zone, and then the test injection is carried out according to the above method, and the monitoring of the injection pressure, the dynamic monitoring and tracking research of all production wells are well done; if no gas channeling occurs or the gas channeling is controllable, stop injection, and convert to normal gas injection after the gas source is settled; if the gas channeling of the production well is uncontrollable, the carbon dioxide of the gas injection well is introduced, large-scale segmented fracturing is carried out, and the whole area is developed by natural energy.

[0042] Step 32c includes:

[0043] ①If the injection of the gas injection well is normal and no gas channeling occurs, the well is put into production according to the design parameters and the tracking control research is carried out;

[0044] ②If the injection of the gas injection well is normal, the production well has gas channeling, the reason for the gas channeling is analyzed, if the gas channeling is controllable, the injection mode is optimized, including segmented injection and production, coupled injection and production, gas-water alternation, foam flooding, etc., the well is put into production normally, and the tracking control research is carried out; if the gas channeling of the production well is uncontrollable, the carbon dioxide of the gas injection well is introduced, large-scale segmented fracturing is carried out, and the whole area is developed by natural energy.

[0045] Step 32d includes:

[0046] ①If the injection of the gas injection well is normal and no gas channeling occurs, the well is put into production according to the design parameters and the tracking control research is carried out;

[0047] ②If the injection of the gas injection well is normal, the production well has gas channeling, the reason for the gas channeling is analyzed, if the gas channeling is controllable, the injection mode is optimized, including segmented injection and production, coupled injection and production, gas-water alternation, foam flooding, etc., the well is put into production normally, and the tracking control research is carried out; if the gas channeling of the production well is uncontrollable, the carbon dioxide of the gas injection well is introduced, large-scale segmented fracturing is carried out, and the whole area is developed by natural energy.

[0048] In step 4, according to the carbon dioxide gas source, the on-site implementation work is carried out, and the injection pressure and injection volume of the gas injection well are monitored and data are recorded; the liquid production, oil production, gas-oil ratio, carbon dioxide content and pressure of the production well are detected and data are recorded.

[0049] In step 5, the follow-up adjustment research is carried out, and real-time control is carried out based on the actual situation and the design process; comprehensive research is carried out according to the on-site monitoring data, and real-time control is carried out throughout the process according to the actual situation and the implementation process of the design, so as to ensure the success of the scheme implementation and the implementation effect of the block.

[0050] The carbon dioxide flooding production method for deep sand gravel low permeability reservoirs in the application considers the carbon dioxide flooding production method for deep sand gravel low permeability reservoirs, is used for the design and production implementation of the carbon dioxide miscible flooding development scheme for deep sand gravel low permeability reservoirs, and can improve the success rate of the carbon dioxide flooding implementation for deep sand gravel low permeability reservoirs, realize effective displacement, and improve the development effect of deep sand gravel low permeability reservoirs.

[0051] Through analysis of the reservoir characteristics of deep sand gravel low permeability reservoirs and the current carbon dioxide miscibility capacity of the reservoirs, it is found that there are problems such as uncertain miscibility capacity in the carbon dioxide miscible flooding injection and production process, uncertain injection capacity of injection wells and production capacity of production wells under different completion methods, uncertain interwell injection and production connection characteristics, and uncertain injection and production control measures. Based on this finding, we consider the carbon dioxide flooding production method for deep sand gravel low permeability reservoirs. Through the new method, the success rate of the carbon dioxide flooding implementation for deep sand gravel low permeability reservoirs is improved, effective displacement is realized, and the development effect is improved. The carbon dioxide flooding development scheme for deep sand gravel low permeability reservoirs provides a more accurate production method. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The flowchart of a specific embodiment of the carbon dioxide flooding production method for deep sand gravel low permeability reservoirs of the application;

[0053] Figure 2 The implementation flowchart in the case of carbon dioxide gas source in a specific embodiment of the application;

[0054] Figure 3 The implementation flowchart in the case of no carbon dioxide gas source in a specific embodiment of the application. DETAILED DESCRIPTION

[0055] It should be pointed out that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the application belongs.

[0056] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used in this description, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0057] The method for carbon dioxide flooding production of deep sandstone and conglomerate low-permeability reservoirs of the present application comprises the following steps:

[0058] (1) determining the crude oil miscibility pressure of the reservoir;

[0059] (2) determining the miscibility capacity of the current reservoir of the implementation block and the carbon dioxide gas source;

[0060] (3) designing a specific production process;

[0061] (4) carrying out field test injection and formal gas injection according to the process;

[0062] (5) carrying out follow-up adjustment research and implementing control according to the designed process.

[0063] The following are several specific embodiments of the application.

[0064] Embodiment 1:

[0065] In a specific embodiment 1 of the application, as shown in Figure 1 , it is a flow chart of the method for carbon dioxide flooding production of deep sandstone and conglomerate low-permeability reservoirs provided by the present application. The specific implementation steps of the method are as follows:

[0066] Step 101, representative formation crude oil samples of the target block are selected, and the minimum miscibility pressure (MMP) of the crude oil of the target block reservoir is determined through the implementation of carbon dioxide phase property experiment and minimum miscibility pressure test.

[0067] Step 102, carry out geological comprehensive research and reservoir dynamic analysis research, determine reservoir physical property, heterogeneity, predict possible connectivity between different wells, and determine current reservoir pressure and miscibility capacity. According to the characteristics of the reservoir drilled by the test injection well, first, test injection of the first section according to the segmented and variable density perforation method, if the injection capacity can meet the design without fracturing, then all well sections are bet according to the non-fracturing perforation method. The production well is perforated according to the segmented and clustered perforation method, first, the first section is put into production according to the conventional perforation method, if the oil production capacity can meet the design without fracturing, then all well sections are put into production according to the non-fracturing perforation method, if the production capacity cannot meet the design value, then the small-scale multi-stage fracturing method is used to put into production. Through the investigation of the carbon dioxide gas source around the block, the carbon dioxide gas source supply time, daily supply amount and total supply amount are determined. According to the carbon dioxide gas source, the specific production process is designed.

[0068] Step 103, based on the gas source and miscibility capacity, the specific production process is designed according to whether there is carbon dioxide gas source in a short period.

[0069] Step 104, carry out field test injection and formal injection according to the process. According to the carbon dioxide gas source, carry out field implementation, monitor and record the injection pressure and injection amount of the injection well; monitor and record the liquid production, oil production, gas-oil ratio, carbon dioxide content, pressure and other data of the production well.

[0070] Step 105, carry out tracking adjustment research, and carry out real-time control based on the actual situation and the designed process. According to the monitoring data, carry out comprehensive research, and carry out real-time control according to the actual situation and the designed process, to ensure the success of the scheme implementation and the implementation effect of the block.

[0071] Embodiment 2

[0072] In a specific embodiment 2 of the application, as shown in Figure 2 if there is a stable carbon dioxide gas source, the implementation process with carbon dioxide gas source is implemented, and the specific implementation process is as follows:

[0073] (1) Select a test injection well to test injection of carbon dioxide. According to the vertical heterogeneity of the test injection well, the variable density perforation method is used for perforation; at least three different injection speeds are tested, and each injection speed is adjusted to the next injection speed after stable injection, while monitoring the injection pressure, monitoring and tracking research in the production well.

[0074] ①If the injection of the test injection well is normal and no gas channeling occurs, the injection gas well is injected normally according to the design parameters, and the new production well is put into production by using the cluster perforation completion, so as to provide the condition for the later fracturing; if the production well reaches the design production capacity, the production well is normally put into production; if the production well does not reach the design production capacity, the production well is put into production by using the carbon dioxide induced small-scale fracturing.

[0075] ②If the injection of the test injection well is normal and the gas channeling occurs in the production well, the reason of the gas channeling is analyzed; if the gas channeling is controllable, the injection mode is optimized, including the segmented injection and production, the coupled injection and production, the gas-water alternation, the foam flooding and the like; the new production well is put into production by using the cluster perforation completion, so as to provide the condition for the later fracturing; if the production well reaches the design production capacity, the production well is normally put into production; if the production well does not reach the design production capacity, the production well is put into production by using the carbon dioxide induced small-scale fracturing.

[0076] ③If the injection of the test injection well is normal and the gas channeling in the production well is uncontrollable, it is indicated that the block is not suitable for the carbon dioxide flooding development, and all the wells are converted into the large-scale fracturing natural energy development.

[0077] (2)If the gas absorption capacity of the test injection well is poor, the near-wellbore network fracturing is performed on the injection well segment of the test injection well according to the small-scale fracturing design, and the injection is tested at least at three different injection rates; it is required that each injection rate is stable before being adjusted to the next injection rate for testing, and the injection pressure monitoring, the dynamic monitoring and the tracking research of the production well are well performed.

[0078] ①If the injection of the test injection well is normal and no gas channeling occurs, the near-wellbore network fracturing is performed on the new injection gas well according to the small-scale fracturing design, and the injection gas is injected according to the design parameters; the new production well is put into production by using the cluster perforation completion; if the production well reaches the design production capacity, the production well is normally put into production; if the production well does not reach the design production capacity, the production well is put into production by using the carbon dioxide induced small-scale fracturing.

[0079] ②If the injection of the test injection well is normal and the gas channeling occurs in the production well, the reason of the gas channeling is analyzed; if the gas channeling is controllable, the near-wellbore network fracturing is performed on the new injection gas well according to the small-scale fracturing design, and the injection mode is optimized, including the segmented injection and production, the coupled injection and production, the gas-water alternation, the foam flooding and the like; the new production well is put into production by using the cluster perforation completion, so as to provide the condition for the later fracturing; if the production well reaches the design production capacity, the production well is normally put into production; if the production well does not reach the design production capacity, the production well is put into production by using the carbon dioxide induced small-scale fracturing.

[0080] ③If the injection of the test injection well is normal and the gas channeling in the production well is uncontrollable, it is indicated that the block is not suitable for the carbon dioxide flooding development, and all the wells are converted into the large-scale fracturing natural energy development.

[0081] Example 3:

[0082] In a specific embodiment 3 of the application, as shown in Figure 3 If there is no stable carbon dioxide gas source in the short term, the implementation process without carbon dioxide gas source is implemented, and the specific implementation process is as follows:

[0083] (1) A new well is implemented with carbon dioxide induced small-scale fracturing, and multi-stage fracturing is used for one-time production.

[0084] (2) A test injection well is selected for carbon dioxide test injection. According to the vertical heterogeneity of the test injection well, the variable density perforation method is used for perforation; at least three different injection rates are tested, and each injection rate is adjusted to the next injection rate after stable injection, and the injection pressure monitoring, dynamic monitoring and tracking research of all production wells are done well.

[0085] ①If the test injection well is injected normally and there is no gas channeling or the gas channeling is controllable, stop injection, and convert to normal gas injection after the gas source is settled. If the production well gas channeling is uncontrollable, the carbon dioxide injection of the injection well is induced by large-scale staged fracturing, and the whole area is developed by natural energy.

[0086] ②If the test injection well has poor gas absorption capacity, the injection well section is designed according to the small-scale fracturing design to fracture the near wellbore network, and then tested according to the above method, and the injection pressure monitoring, dynamic monitoring and tracking research of all production wells are done well. If there is no gas channeling or the gas channeling is controllable, stop injection, and convert to normal injection after the gas source is settled. If the production well gas channeling is uncontrollable, the carbon dioxide injection of the injection well is induced by large-scale staged fracturing, and the whole area is developed by natural energy.

[0087] (3) If stable carbon dioxide gas source can be obtained before the formation pressure drops to 1.3MMP, the injection well is put into normal injection according to the design, and the injection pressure monitoring, dynamic monitoring and tracking research of all production wells are done well.

[0088] ①If the injection well is injected normally and there is no gas channeling, the injection well is put into normal injection and tracking control research according to the design parameters.

[0089] ②If the injection well is injected normally, the production well has gas channeling, and the reason for the gas channeling is analyzed. If the gas channeling is controllable, the injection mode is optimized, including segmented injection and production, coupled injection and production, gas-water alternation, foam flooding, etc. Normal investment is put into production, and tracking control research is carried out. If the production well gas channeling is uncontrollable, the carbon dioxide injection of the injection well is induced by large-scale staged fracturing, and the whole area is developed by natural energy.

[0090] (4) If the stable carbon dioxide gas source is obtained after the formation pressure drops to 1.3MMP, according to the actual situation of pressure depletion, gas injection or water injection is preferred to restore the formation pressure until the formation pressure is restored to 1.3MMP or more, and the gas injection well is put into normal gas injection according to the design scheme, while the monitoring of injection pressure, dynamic monitoring and tracking research of all production wells are done well.

[0091] ① If the gas injection well is injected normally and there is no gas channeling, it is put into normal production and tracking research according to the design parameters.

[0092] ② If the gas injection well is injected normally and there is gas channeling in the production well, the cause of gas channeling is analyzed, if the gas channeling is controllable, the injection mode is optimized, including segmented injection and production, coupled injection and production, gas-water alternation, foam flooding and other ways to put into normal production, and tracking research is carried out. If the gas channeling of the production well is uncontrollable, the carbon dioxide injection effect of the gas injection well is large, the full-area natural energy development is put into production.

[0093] Finally, it should be pointed out that the above is only the preferred embodiment of the present application and is not intended to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced equivalently. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0094] In addition to the technical features described in the specification, they are known to those skilled in the art.

Claims

1. A method for carbon dioxide flooding of a deep, sandy, low permeability reservoir, characterized in that, The method for carbon dioxide flooding of the deep sandstone low-permeability reservoir comprises the following steps: Step 1, determining the miscibility pressure of crude oil in the reservoir; Step 2, determining the miscibility capacity of the reservoir and the carbon dioxide gas source of the implementation block; Step 3, based on the gas source and the miscibility capacity, designing a specific production process in a short term with or without the carbon dioxide gas source; If there is a stable carbon dioxide gas source, the implementation process with the carbon dioxide gas source is implemented, and the specific implementation process is as follows: Step 31a, selecting a test injection well for carbon dioxide test injection; according to the longitudinal heterogeneity of the test injection well, the perforation interval is perforated by using the variable density perforation method; at least three different injection rates are tested, and each injection rate is required to be stable before adjusting to the next injection rate for testing, while the injection pressure monitoring, dynamic monitoring and tracking research of the production well are performed; Step 31a comprises: ①If the test injection well is injected normally and no gas channeling occurs, the injection well is normally injected according to the design parameters, and the new production well is completed and put into production by using the cluster perforation, so as to provide conditions for the later fracturing; if the production well reaches the designed production capacity, the production well is normally put into production; if the production well does not reach the designed production capacity, the production well is put into production by using the carbon dioxide induced small-scale fracturing; ②If the test injection well is injected normally and the production well has gas channeling, the reason for the gas channeling is analyzed; if the gas channeling is controllable, the injection mode is optimized, including the segmented injection and production, coupled injection and production, gas-water alternation and foam flooding; the new production well is completed and put into production by using the cluster perforation, so as to provide conditions for the later fracturing; if the production well reaches the designed production capacity, the production well is normally put into production; if the production well does not reach the designed production capacity, the production well is put into production by using the carbon dioxide induced small-scale fracturing; ③If the test injection well is injected normally and the production well has uncontrollable gas channeling, it is indicated that the block is not suitable for carbon dioxide flooding development, and all the wells are converted into large-scale fracturing natural energy development; Step 31b, if the test injection well has poor gas absorption capacity, the injection interval of the test injection well is perforated by using the near-wellbore network fracturing design of the small-scale fracturing, and at least three different injection rates are tested, and each injection rate is required to be stable before adjusting to the next injection rate for testing, while the injection pressure monitoring, dynamic monitoring and tracking research of the production well are performed; Step 31b comprises: ①If the test injection well is injected normally and no gas channeling occurs, the new injection well is perforated by using the near-wellbore network fracturing design of the small-scale fracturing, and is injected according to the design parameters, and the new production well is completed and put into production by using the cluster perforation; if the production well reaches the designed production capacity, the production well is normally put into production; if the production well does not reach the designed production capacity, the production well is put into production by using the carbon dioxide induced small-scale fracturing; If the injection is normal in the test injection well, and gas channeling exists in the production well, analyze the cause of the gas channeling; if the gas channeling is controllable, the new injection well is fractured in the near wellbore zone according to a small-scale fracturing design, and the injection mode is optimized, including segmented injection and production, coupled injection and production, gas-water alternation, and foam flooding; the new production well is completed by cluster perforation, to provide conditions for later fracturing; if the production well reaches the designed production capacity, the production well is put into normal production; if the production well does not reach the designed production capacity, the production well is fractured by carbon dioxide stimulation and small-scale fracturing, and put into production; If the injection is normal in the test injection well, and the gas channeling in the production well is uncontrollable, it indicates that the block is not suitable for carbon dioxide flooding development, and all the wells are converted into large-scale fracturing and natural energy development; If there is no stable carbon dioxide gas source in the short term, the implementation process without carbon dioxide gas source is implemented, and the specific implementation process is as follows: Step 32a, the new production well is fractured by carbon dioxide stimulation and small-scale fracturing, and is put into production at one time by multi-stage fracturing; Step 32b, the test injection well is selected for carbon dioxide injection test, the well section is perforated by variable density perforation according to the vertical heterogeneity of the test injection well; at least three different injection rates are tested, and each injection rate is stabilized before adjusting to the next injection rate; at the same time, the injection pressure is monitored, and the dynamic monitoring and tracking research of all production wells are carried out; Step 32b includes: If the injection is normal in the test injection well and there is no gas channeling or the gas channeling is controllable, stop injection, and convert to normal injection after the gas source is settled; if the gas channeling in the production well is uncontrollable, the injection well is fractured by carbon dioxide stimulation and large-scale staged fracturing, and the whole area is developed by natural energy production; If the injection is normal in the test injection well and there is no gas channeling or the gas channeling is controllable, stop injection, and convert to normal injection after the gas source is settled; if the gas channeling in the production well is uncontrollable, the injection well is fractured by carbon dioxide stimulation and large-scale staged fracturing, and the whole area is developed by natural energy production; Step 32c, if the stable carbon dioxide gas source can be obtained before the formation pressure drops to 1.3MMP, the injection well is put into normal injection according to the design, and the injection pressure is monitored, and the dynamic monitoring and tracking research of all production wells are carried out; Step 32c includes: If the injection is normal in the test injection well and there is no gas channeling or the gas channeling is controllable, stop injection, and convert to normal injection after the gas source is settled; if the gas channeling in the production well is uncontrollable, the injection well is fractured by carbon dioxide stimulation and large-scale staged fracturing, and the whole area is developed by natural energy production; If the injection is normal in the test injection well and there is no gas channeling or the gas channeling is controllable, stop injection, and convert to normal injection after the gas source is settled; if the gas channeling in the production well is uncontrollable, the injection well is fractured by carbon dioxide stimulation and large-scale staged fracturing, and the whole area is developed by natural energy production; Step 32d, if the formation pressure drops to 1.3MMP and stable carbon dioxide gas source is obtained, according to the actual situation of pressure depletion, gas injection or water injection is carried out to restore the formation pressure until the formation pressure is restored to more than 1.3MMP, the gas injection well is put into normal injection according to the design, and the monitoring of gas injection pressure, dynamic monitoring and tracking research of all production wells are done; Step 4, carry out field test injection and formal gas injection according to the process; Step 5, carry out tracking adjustment research, and implement control according to the design process.

2. The method for carbon dioxide flooding of deep, sandy, glutenite, low permeability reservoirs according to claim 1, characterized in that, In step 1, representative formation crude oil samples are selected from the target block, and the minimum miscibility pressure of the crude oil in the target block is determined by carrying out carbon dioxide phase characteristic experiment and minimum miscibility pressure test.

3. The method for carbon dioxide flooding of deep, sandy, glutenite, low permeability reservoirs according to claim 1, characterized in that, In step 2, comprehensive geology research and reservoir dynamic analysis research are carried out to determine the reservoir property, heterogeneity, and possible connectivity between different wells, and to determine the current reservoir pressure and miscibility capacity.

4. The method for carbon dioxide flooding of deep, sandy, glutenite, low permeability reservoirs according to claim 3, characterized in that, In step 2, according to the characteristics of the reservoir drilled by the test injection well, the first section is tested by segmenting and variable density perforating, if the injection capacity of the design can be met without fracturing, all well sections are betted by non-fracturing perforating; the production well is perforated by segmenting and clustering, the first section is put into production by conventional perforating, if the oil production capacity of the design can be met without fracturing, all well sections are put into production by non-fracturing perforating, if the production capacity cannot meet the design value, the small-scale multi-stage fracturing is used to put into production; through investigation of carbon dioxide gas sources around the block, the supply time, daily supply amount and total supply amount of carbon dioxide gas source are determined; the specific production process is designed according to the carbon dioxide gas source.

5. The method for carbon dioxide flooding of deep, sandy, glutenite, low permeability reservoirs according to claim 1, characterized in that, Step 32d includes: ①If the gas injection well is normally injected and there is no gas channeling, the tracking control research is carried out according to the normal injection and production of the design parameters; ②If the gas injection well is normally injected and the production well has gas channeling, the reason for gas channeling is analyzed, if the gas channeling is controllable, the injection mode is optimized, including segmented injection and production, coupled injection and production, gas-water alternation, foam flooding, and the like, and the tracking control research is carried out; if the gas channeling of the production well is uncontrollable, carbon dioxide injection of the gas injection well, large-scale segmented fracturing, and full-area natural energy development are used to put into production.

6. The method for carbon dioxide flooding of deep, sandy, glutenite, low permeability reservoirs according to claim 1, characterized in that, In step 4, according to the carbon dioxide gas source, field implementation is carried out, and the monitoring and data recording of the injection pressure and injection amount of the gas injection well, and the detection and data recording of the liquid production, oil production, gas-oil ratio, carbon dioxide content and pressure of the production well are done.

7. The method for CO2 flooding of deep, sandy, glutenite, low permeability reservoirs according to claim 1, characterized in that, In step 5, tracking adjustment research is carried out, and real-time control is carried out based on the actual situation and the design process; According to the field monitoring data, comprehensive research is carried out, and real-time control is carried out throughout the process according to the actual situation and the design implementation process, so as to ensure the success of the scheme implementation and the implementation effect of the block. According to the field monitoring data, comprehensive research is carried out, and real-time control is carried out throughout the process according to the actual situation and the design implementation process, so as to ensure the success of the scheme implementation and the implementation effect of the block.

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