Blockage removal method by using pressure fluctuation of well bottom

Abstract

The invention discloses a method for removing blockage by utilizing pressure fluctuation of a shaft bottom, and particularly relates to the field of oilfield exploitation, and the method specifically comprises the following steps of S1, equipment installation, S2, high-pressure fluid injection, S3, pressure fluctuation excitation, S4, blockage dredging and S5, monitoring and adjustment. Blockage removal is conducted through pressure fluctuation of the shaft bottom, chemical agents do not need to be added, and the problem of secondary pollution is avoided; compared with a traditional plug removal method, the operation is convenient, the cost input is reduced, secondary precipitation is not generated, and secondary precipitation caused by conventional measures is eliminated; through periodical pressure fluctuation and instantaneous negative pressure flowback action, the self-excited pressure wave is small in frequency and large in amplitude, can generate continuous fluctuation action on an oil layer, weakens the liquid resistance effect, effectively dredges a blocked channel, improves the water injection efficiency and the oil extraction yield, and is suitable for solving the blocking problem of various types of oil-water wells such as water injection wells and oil wells.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield exploitation, and more particularly to a method for removing blockages by utilizing the inherent pressure fluctuation at the bottom of a well. Background Art

[0002] In the process of oil and gas field development, blockage and secondary pollution have always been important problems affecting production efficiency and environmental protection. In order to solve these problems, the research background is divided into two major directions: physical method and chemical method:

[0003] Physical methods mainly include technologies such as ultrasound, high-pressure water rotating jets, high-energy gas fracturing, electric pulses and hydraulic shock waves. The principle of these methods is to use high-energy effects generated by physical means to break and discharge the blockage, thereby restoring the patency of the channel. For example, ultrasound can loosen the blockage through sound wave vibrations; high-pressure water rotating jets use high-pressure water flow to impact the blockage; and high-energy gas fracturing creates cracks through the instantaneous release of high-pressure gas to discharge the blockage. However, these physical methods may face the problem of the blockage not being able to be completely discharged in actual applications;

[0004] Chemical methods mainly include soil acid, organic soil acid, temporary plugging acidification and various slow-rate acids. The chemical method uses chemical agents to react with blockages to achieve the purpose of dissolving and loosening blockages. For example, soil acid can react with minerals in blockages, and organic soil acid increases the penetration capacity of acid through organic components. Temporary plugging acidification technology uses temporary plugging agents during the acidification process to selectively block certain channels to improve the utilization efficiency of acid. However, these methods may also cause secondary pollution problems, requiring further environmental protection measures.

[0005] In the process of oilfield exploitation, blockage of oil and water wells is one of the key factors restricting production efficiency. Traditional unblocking methods such as chemical unblocking and mechanical dredging have problems such as high cost, secondary pollution, and short-term effect. Therefore, it is particularly important to develop an efficient, environmentally friendly and sustainable unblocking method. Summary of the invention

[0006] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a method for unblocking by utilizing the inherent pressure fluctuation at the bottom of a well. The technical problem to be solved by the present invention is: how to solve the problems of high cost of unblocking of oil and water wells, short-lasting effect, and easy generation of secondary pollution, so as to improve water injection efficiency and oil production.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for removing blockage by utilizing the natural pressure fluctuation at the bottom of a well, specifically comprising the following steps:

[0008] Step S1, installing equipment: installing the self-excited pressure pulse control device and the self-excited pressure generating device on the wellhead valve, ensuring that the device is connected to the wellbore fluid passage;

[0009] Step S2, injecting high-pressure fluid: using a high-pressure pump truck to inject high-pressure fluid into the wellbore, and when the pressure of the fluid reaches a preset required value, maintaining the pressure supply so that the fluid in the wellbore reaches a balanced state;

[0010] Step S3, exciting pressure fluctuations: a self-excited pressure pulse control device is used to cause periodic pressure pulse waves to the wellbore fluid, so that the fluid in the wellbore experiences pressure fluctuations; a relatively high pulse pressure acts on the formation near the wellbore, and the fluid entering the formation impacts the cracks and formation pores;

[0011] Step S4, unblocking: under the action of the self-excited pressure wave of the self-excited pressure generating device, the cementing materials and mechanical impurities on the surface of the rock pores are damaged and gradually broken and peeled off under fatigue stress, thereby unblocking the liquid flow channel; at the same time, the blocking particles are effectively removed by utilizing the instantaneous negative pressure backflow effect;

[0012] Step S5, monitoring and adjustment: according to the changes in the wellbore and formation pressure, the frequency and amplitude of the self-excited pressure pulse are adjusted in a timely manner to achieve the best unblocking effect.

[0013] In a preferred embodiment, in step S4, when the self-excitation pressure generating device is activated, a layer of liquid in the wellbore is pushed to stop flowing instantaneously within an infinitesimal time Δt; the volume of this part of the liquid is AΔs, and its mass is ρAΔs, wherein the self-excitation pressure calculation formula is:

[0014]

[0015] Among them, in the formula: c-pressure propagation speed; c 0 - speed of sound in the liquid; D- diameter of the tube; E 0 -Elastic coefficient of the pipe; E-elastic coefficient of the liquid; e-thickness of the pipe wall.

[0016] In a preferred embodiment, the preset value of the fluid pressure in step S2 is set to an oil pressure less than 20 MPa, and the casing internal pressure resistance strength is not less than 90 MPa.

[0017] In a preferred embodiment, the pulse wave of the ultrasonic oscillation generated by the self-excited pressure pulse control device in step S3 has a corresponding frequency spectrum range of 20-40kHz and a radiation power range of 50-80W·cm -2 .

[0018] In a preferred embodiment, the water pressure range of the high-pressure water rotating jet in step S2 is set to 200-350 MPa and the water flow range is 15-25 L·min -1 .

[0019] Technical effects and advantages of the present invention:

[0020] 1. The present invention establishes a dual-channel unblocking operation mode by combining self-excited pressure pulses with instantaneous negative pressure backflow, and uses the inherent pressure fluctuations at the bottom of the well to unblock, without adding chemical agents, thus avoiding the problem of secondary pollution. Compared with the traditional unblocking method, the present invention is convenient to operate, reduces the cost investment, does not produce secondary precipitation, and excludes the secondary precipitation caused by conventional measures. Through the periodic pressure fluctuations and instantaneous negative pressure backflow, the self-excited pressure wave has a small frequency and a large amplitude, which can produce a continuous fluctuation effect on the oil layer, weaken the liquid resistance effect, effectively dredge the blocked channel, improve the water injection efficiency and oil production, and is suitable for various types of oil and water well blockage problems such as water injection wells and oil wells.

[0021] 2. The present invention generates pressure pulses through self-excitation downhole. The self-excited pressure wave has positive and negative directions, which can reciprocate and impact and release the blockage at the bottom of the well, and oscillate and break the blockage. It has higher pertinence and efficiency, and will provide important technical support for the efficient and environmentally friendly development of oil and gas fields, and more effectively solve the blockage and pollution problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the principle model of the wellbore structure of the present invention.

[0023] Figure 2 This is a working principle diagram of the self-excited pressure pulse generator of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment 1:

[0026] The present invention provides a method for removing blockage by utilizing the natural pressure fluctuation at the bottom of a well, which specifically comprises the following steps:

[0027] Step S1, installing equipment: installing the self-excited pressure pulse control device and the self-excited pressure generating device on the wellhead valve, ensuring that the device is connected to the wellbore fluid passage;

[0028] Step S2, injecting high-pressure fluid: Use a high-pressure pump truck to inject high-pressure fluid into the wellbore. The water pressure range of the high-pressure water rotating jet is set to 200-350MPa and the water flow range is 15-25L·min -1 When the fluid pressure reaches the preset required value, the pressure supply is maintained to make the fluid in the wellbore reach a balanced state; the preset value of the fluid pressure is set to oil pressure less than 20MPa, and the casing internal pressure resistance strength is not less than 90MPa;

[0029] Step S3, exciting pressure fluctuations: a self-excited pressure pulse control device is used to cause periodic pressure pulse waves to the wellbore fluid. The corresponding spectrum range of the pulse wave is set to 20-40kHz, and the radiation power range is set to 50-80W·cm -2 , causing pressure fluctuations in the wellbore; the self-excited pressure pulse generator emits pulse pressure waves to the fluid in the wellbore at the wellhead, which are instantly transmitted to the formation through the wellbore fluid, generating a superposition of multiple pulse waves in the formation, forming a shock wave oscillation field, and establishing an oscillation field in the formation, which produces a vibration effect on the rock porous medium with strong alternating pressure; a relatively high pulse pressure acts on the near-wellbore formation, and the fluid entering the formation impacts the cracks and formation pores. Under the action of the self-excited pressure wave, the cement and mechanical impurities on the surface of the rock pores are damaged under fatigue stress and gradually broken, peeled off, and the liquid flow channel is unblocked, which plays a role in increasing permeability;

[0030] Step S4, unblocking: under the action of the self-excited pressure wave of the self-excited pressure generating device, the cementing materials and mechanical impurities on the surface of the rock pores are damaged under fatigue stress and gradually broken and peeled off, thereby unblocking the liquid flow channel; at the same time, the blocking particles are effectively removed by utilizing the instantaneous negative pressure backflow effect, and the self-excited pressure wave will affect the physical properties and flow state of the oil layer fluid, and can change the dynamics of the solid-liquid-gas interface; it mainly destroys or changes the balance of the capillary force in the micropores, thereby weakening the liquid resistance effect;

[0031] When the self-excited pressure generating device occurs, within the infinitesimal Δt moment, a layer of liquid in the wellbore is pushed to stop flowing instantly; then the volume of this part of the liquid is AΔs, and its mass is ρAΔs, where the self-excited pressure calculation formula is:

[0032]

[0033] Among them, in the formula: c-pressure propagation speed; c 0 - speed of sound in the liquid; D- diameter of the tube; E 0 -Elastic coefficient of the pipe; E-elastic coefficient of the liquid; e-thickness of the pipe wall;

[0034] Step S5, monitoring and adjustment: according to the changes in the wellbore and formation pressure, the frequency and amplitude of the self-excited pressure pulse are adjusted in a timely manner to achieve the best unblocking effect.

[0035] Among them, in the water injection wells:

[0036] The injection volume can be reached in the early stage, but as time goes by, the injection volume of the well decreases rapidly, and it is urgent to increase the injection volume;

[0037] Wells with low initial injection pressure and a rapid increase in injection pressure as the production time increases need to urgently reduce the wellhead injection pressure;

[0038] In the oil well:

[0039] The near-wellbore area is mainly blocked by inorganic substances, such as mechanical impurities, bridging particles in cementing materials, and blockage of well-killing fluid and mud solid particles caused by human operation, resulting in reduced production of production wells.

[0040] Self-excited pressure plugging removal technology can also be used for oil and water well flushing to achieve the effect of shock well flushing;

[0041] Specifically in this embodiment: Figure 1 As shown, the model built in this embodiment is a water injection vertical well with a well depth of 1000m, a casing length of 1000m, a tubing length of 950m, and a packer for isolation, which belongs to a vertical well casing perforation completion; a self-excited pressure pulse generator controls the frequency of pressure generation at the wellhead, and the pressure is transmitted to the bottom of the well through the fluid in the well to act on the formation without passing through the annulus;

[0042] The self-excited pressure pulse oscillation unblocking is applied to the area near the wellbore. The wellbore and the area near the wellbore model are as follows: Figure 2 shown.

[0043] Experimental effect proof and case analysis: Taking a water well as an example, the oil pressure before the measure was 22MPa, the casing pressure was 22MPa, and the daily injection was 18m 3 , daily water injection 0m 3 ,Currently the oil pressure is 19MPa, casing pressure is 19MPa, and the daily injection is 16m 3 , daily water injection 16m 3 As of the end of the day, the cumulative injection volume is 1973m 3 , valid for 105 days;

[0044] In summary: For the blockage problem of a water injection well, the method described in the present invention is used to remove the blockage. First, the self-excited pressure pulse control device and the self-excited pressure generating device are installed, and then the high-pressure fluid is injected to the preset pressure value. By adjusting the frequency and amplitude of the self-excited pressure pulse, the natural pressure fluctuation at the bottom of the well is stimulated. After a period of time, the changes in the wellbore and formation pressure are observed, and it is found that the blocked channel is effectively unblocked, and the water injection efficiency is significantly improved.

[0045] Embodiment 2:

[0046] The present invention provides a method for removing blockage by utilizing the natural pressure fluctuation at the bottom of a well, which specifically comprises the following steps:

[0047] Step S1, installing equipment: installing the self-excited pressure pulse control device and the self-excited pressure generating device on the wellhead valve, ensuring that the device is connected to the wellbore fluid passage;

[0048] Step S2, injecting high-pressure fluid: Use a high-pressure pump truck to inject high-pressure fluid into the wellbore. The water pressure range of the high-pressure water rotating jet is set to 200-350MPa and the water flow range is 15-25L·min -1 When the fluid pressure reaches the preset required value, the pressure supply is maintained to make the fluid in the wellbore reach a balanced state; the preset value of the fluid pressure is set to oil pressure less than 20MPa, and the casing internal pressure resistance strength is not less than 90MPa;

[0049] Step S3, exciting pressure fluctuations: a self-excited pressure pulse control device is used to cause periodic pressure pulse waves to the wellbore fluid. The corresponding spectrum range of the pulse wave is set to 20-40kHz, and the radiation power range is set to 50-80W·cm -2 , causing pressure fluctuations in the wellbore; the self-excited pressure pulse generator emits pulse pressure waves to the fluid in the wellbore at the wellhead, which are instantly transmitted to the formation through the wellbore fluid, generating a superposition of multiple pulse waves in the formation, forming a shock wave oscillation field, and establishing an oscillation field in the formation, which produces a vibration effect on the rock porous medium with strong alternating pressure; a relatively high pulse pressure acts on the near-wellbore formation, and the fluid entering the formation impacts the cracks and formation pores. Under the action of the self-excited pressure wave, the cement and mechanical impurities on the surface of the rock pores are damaged under fatigue stress and gradually broken, peeled off, and the liquid flow channel is unblocked, which plays a role in increasing permeability;

[0050] Step S4, unblocking: under the action of the self-excited pressure wave of the self-excited pressure generating device, the cementing materials and mechanical impurities on the surface of the rock pores are damaged under fatigue stress and gradually broken and peeled off, thereby unblocking the liquid flow channel; at the same time, the blocking particles are effectively removed by utilizing the instantaneous negative pressure backflow effect, and the self-excited pressure wave will affect the physical properties and flow state of the oil layer fluid, and can change the dynamics of the solid-liquid-gas interface; it mainly destroys or changes the balance of the capillary force in the micropores, thereby weakening the liquid resistance effect;

[0051] When the self-excited pressure generating device occurs, within the infinitesimal Δt moment, a layer of liquid in the wellbore is pushed to stop flowing instantly; then the volume of this part of the liquid is AΔs, and its mass is ρAΔs, where the self-excited pressure calculation formula is:

[0052]

[0053] Among them, in the formula: c-pressure propagation speed; c 0- speed of sound in the liquid; D- diameter of the tube; E 0 -Elastic coefficient of the pipe; E-elastic coefficient of the liquid; e-thickness of the pipe wall;

[0054] Step S5, monitoring and adjustment: according to the changes in the wellbore and formation pressure, the frequency and amplitude of the self-excited pressure pulse are adjusted in a timely manner to achieve the best unblocking effect.

[0055] Among them, in the water injection wells:

[0056] The injection volume can be reached in the early stage, but as time goes by, the injection volume of the well decreases rapidly, and it is urgent to increase the injection volume;

[0057] Wells with low initial injection pressure and a rapid increase in injection pressure as the production time increases need to urgently reduce the wellhead injection pressure;

[0058] In the oil well:

[0059] The near-wellbore area is mainly blocked by inorganic substances, such as mechanical impurities, bridging particles in cementing materials, and blockage of well-killing fluid and mud solid particles caused by human operation, resulting in reduced production of production wells.

[0060] Self-excited pressure plugging removal technology can also be used for oil and water well flushing to achieve the effect of shock well flushing;

[0061] Specifically in this embodiment: Figure 1 As shown, the model built in this embodiment is a water injection vertical well with a well depth of 1000m, a casing length of 1000m, a tubing length of 950m, and a packer for isolation, which belongs to a vertical well casing perforation completion; a self-excited pressure pulse generator controls the frequency of pressure generation at the wellhead, and the pressure is transmitted to the bottom of the well through the fluid in the well to act on the formation without passing through the annulus;

[0062] The self-excited pressure pulse oscillation unblocking is applied to the area near the wellbore. The wellbore and the area near the wellbore model are as follows: Figure 2 shown.

[0063] Experimental effect proof and case analysis: Taking a water well as an example, the oil pressure before the measure was 22MPa, the casing pressure was 22MPa, and the daily injection was 18m 3 , daily water injection 0m 3 ,Currently the oil pressure is 19MPa, casing pressure is 19MPa, and the daily injection is 16m 3 , daily water injection 16m 3 As of the end of the day, the cumulative injection volume is 1973m 3 , valid for 105 days;

[0064] In summary, the inorganic blockage problem in the vicinity of a certain oil well was solved by the method of the present invention. After the blockage-removing treatment, the oil well production volume increased significantly, and the normal production capacity was restored.

[0065] Embodiment 4:

[0066] The oil wells were cleaned by using the plugging removal methods using the bottom hole pressure fluctuations described in the above Examples 1-2, and compared by using the method of dynamic backwashing of the wells using the co-solvent and active water, and the following data were obtained:

[0067] Dynamic backwashing of wells with co-solvent and activated water

[0068]

[0069] Self-excited pressure pulse oscillation blockage removal + solvent treatment

[0070]

[0071] It can be seen from the above table that the dual-channel unblocking operation mode established by self-excited pressure pulse plus instantaneous negative pressure return has a better oil and water well unblocking effect than the dynamic backwashing of wells with co-solvent and active water. It uses the bottom hole's own pressure fluctuation to unblock. Through the periodic pressure fluctuation and instantaneous negative pressure return, the self-excited pressure wave has a small frequency and a large amplitude, which can produce a continuous fluctuation effect on the oil layer, weaken the liquid resistance effect, effectively dredge the blocked channel, and effectively solve the problems of high cost, secondary pollution, and short-term effect of traditional unblocking methods.

[0072] Finally, a few points should be explained: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, which may refer to mechanical connection or electrical connection, or internal communication between two components, or direct connection. "upper", "lower", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may change;

[0073] Secondly: In the drawings of the embodiments disclosed in the present invention, only the structures related to the embodiments disclosed in the present invention are involved, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other;

[0074] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for removing blockage by utilizing the natural pressure fluctuation at the bottom of a well, characterized in that: The specific steps include: Step S1, installing equipment: installing the self-excited pressure pulse control device and the self-excited pressure generating device on the wellhead valve, ensuring that the device is connected to the wellbore fluid passage; Step S2, injecting high-pressure fluid: using a high-pressure pump truck to inject high-pressure fluid into the wellbore, and when the pressure of the fluid reaches a preset required value, maintaining the pressure supply so that the fluid in the wellbore reaches a balanced state; Step S3, exciting pressure fluctuations: a self-excited pressure pulse control device is used to cause periodic pressure pulse waves to the wellbore fluid, so that the fluid in the wellbore experiences pressure fluctuations; a relatively high pulse pressure acts on the formation near the wellbore, and the fluid entering the formation impacts the cracks and formation pores; Step S4, unblocking: under the action of the self-excited pressure wave of the self-excited pressure generating device, the cementing materials and mechanical impurities on the surface of the rock pores are damaged and gradually broken and peeled off under fatigue stress, thereby unblocking the liquid flow channel; at the same time, the blocking particles are effectively removed by utilizing the instantaneous negative pressure backflow effect; Step S5, monitoring and adjustment: according to the changes in the wellbore and formation pressure, the frequency and amplitude of the self-excited pressure pulse are adjusted in a timely manner.

2. A method for removing blockage by utilizing the natural pressure fluctuation at the bottom of a well according to claim 1, characterized in that: In step S4, when the self-excitation pressure generating device is activated, a layer of liquid in the wellbore is pushed to stop flowing instantaneously within an infinitesimal time Δt; the volume of this part of liquid is AΔs, and its mass is ρAΔs, wherein the self-excitation pressure calculation formula is: Among them, in the formula: c-pressure propagation speed; c0-speed of sound in liquid; D-diameter of the pipe; E0-elastic coefficient of the pipe; E-elastic coefficient of the liquid; e-thickness of the pipe wall.

3. The method for removing blockage by utilizing the natural pressure fluctuation at the bottom of a well according to claim 1, characterized in that: The preset value of the fluid pressure in step S2 is set to be oil pressure less than 20 MPa, and the casing internal pressure resistance strength is not less than 90 MPa.

4. The method for removing blockage by utilizing the natural pressure fluctuation at the bottom of a well according to claim 1, characterized in that: The pulse wave of ultrasonic oscillation generated by the self-excited pressure pulse control device in step S3 corresponds to a frequency spectrum range of 20-40kHz and a radiation power range of 50-80W·cm -2 .

5. The method for removing blockage by utilizing the natural pressure fluctuation at the bottom of a well according to claim 1, characterized in that: The water pressure range of the high-pressure water rotating jet in step S2 is set to 200-350 MPa, and the water flow range is 15-25 L·min -1 .

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