Construction method for reconstructing gas storage from karst cave-penetrating waste oil and gas well

Abstract

The invention discloses a construction method for reconstructing a gas storage from a karst cave-penetrating waste oil-gas well, and belongs to the field of natural gas storage. Comprising the following steps: determining a communication position of the abandoned oil and gas well and a karst cave reservoir body according to historical drilling leakage accident processing data of the abandoned oil and gas well, and determining upper and lower leakage horizon positions of the karst cave reservoir body; blocking the bottom of the waste oil and gas well until the bottom surface is flush with the bottom of the carbonate rock salt reservoir; accurate perforation is carried out on the upper and lower leakage layers of the casing pipe of the abandoned oil and gas well to obtain upper and lower cluster perforations; a packer is put between the upper cluster perforation and the lower cluster perforation of the casing pipe, and an oil pipe of the abandoned oil and gas well penetrates through the packer from a wellhead to be communicated with the lower cluster perforation; evaluating the gas storage volume of the karst cave reservoir body; stored gas is injected from a wellhead of the oil sleeve annulus, and under the gas injection pressure, original fluid at the bottom of the karst cave reservoir body is discharged out of the lower cluster perforation and flows back to the ground through an oil pipe. The reconstructed gas storage has the advantages of being low in construction cost, good in sealing performance and stability, large in effective gas storage volume and the like.

Description

Technical Field

[0001] The present application relates to the technical field of natural gas storage, and in particular to a construction method for converting abandoned oil and gas wells through karst caves into gas storage facilities. Background Art

[0002] As a "container" for storing natural gas, underground gas storage is an important facility for strategic natural gas reserves and peak-shaving supply. The existing types of underground gas storage mainly include depleted oil and gas reservoir gas storage, aquifer gas storage, salt cavern gas storage and abandoned mine pit gas storage.

[0003] Depleted oil reservoir gas storage can realize the reuse of original ground equipment, but its construction period is long and the assessment fee is high, resulting in high construction cost. Depleted gas reservoir gas storage has the advantages of high safety and reliability, high utilization rate of injected gas, and short construction period, but depleted gas reservoir gas storage has high requirements for sealing and injected gas type. The structure of aquifer gas storage is complete, and drilling and completion can be completed in one go, but the survey, research and selection of storage are difficult, the risk is high, and the investment and operation cost is high. Salt cavern gas storage is formed by dissolving salt in underground salt layers. The gas injection time is short, but the effective gas storage volume for storing natural gas is small, drilling and completion are difficult, and the construction cost is high. Abandoned mine pit gas storage has a wide source, but its original wellbore is difficult to seal, there is a risk of gas leakage to the ground, and the stability is poor.

[0004] From the above, it can be seen that the existing underground gas storage has the problems of high construction cost, poor sealing and stability, and small effective gas storage volume. Summary of the invention

[0005] The embodiment of the present application provides a construction method for converting abandoned oil and gas wells through caves into gas storage facilities, which can solve the problems of existing underground gas storage facilities such as high construction cost, poor sealing and stability, and small effective gas storage capacity.

[0006] In order to achieve the above object, the technical solution of the embodiment of the present invention is:

[0007] The embodiment of the present invention provides a construction method for converting an abandoned oil and gas well through a karst cave into a gas storage reservoir, comprising:

[0008] Determine the location of the abandoned oil and gas well and the cave reservoir according to the data of historical drilling leakage accident treatment of the abandoned oil and gas well, and determine the upper leakage layer and the lower leakage layer of the cave reservoir, the upper leakage layer is located close to the ground, and the abandoned oil and gas well passes through the carbonate formation;

[0009] The bottom of the abandoned oil and gas well is sealed until the bottom surface is flush with the bottom of the carbonate salt reservoir;

[0010] Precisely perforating the upper leakage layer from the casing of the abandoned oil and gas well to obtain upper cluster perforations, wherein the upper cluster perforations penetrate the casing and are connected with the karst cave reservoir;

[0011] Precisely perforating from the casing to the lower leakage layer to obtain lower cluster perforations, wherein the lower cluster perforations penetrate the casing and are connected to the karst cave reservoir;

[0012] A packer is placed between the upper cluster hole and the lower cluster hole of the casing, and the oil pipe of the abandoned oil and gas well passes through the packer from the wellhead and is connected to the lower cluster hole;

[0013] Assessing the gas storage capacity of the cave reservoir;

[0014] The stored gas is injected from the wellhead of the oil casing annulus between the casing and the oil pipe. Under the gas injection pressure, the original fluid at the bottom of the cave reservoir is discharged from the lower cluster perforations and returned to the ground through the oil pipe.

[0015] In a possible implementation, plugging the bottom of the abandoned oil and gas well includes:

[0016] The bottom of the abandoned oil and gas well is injected with cement slurry, and plugging is achieved after the cement slurry solidifies.

[0017] In a possible implementation, the perforating method for connecting the casing and the cave reservoir includes perforating bullet perforating or water jet perforating.

[0018] In a possible implementation, the evaluating the gas storage capacity of the cave reservoir includes:

[0019] Liquid is injected from the wellhead of the casing annulus, and the gas storage volume of the cave reservoir is calculated by constant flow injection pressure test, wherein the calculation formula is:

[0020] Where V is the volume of the cave reservoir, is the injection pressure at time t, is the injection pressure at the initial moment, c is the compressibility coefficient of the liquid, Q is the flow rate of the liquid, and t is the injection time.

[0021] In a possible implementation, the storage gas is injected from the wellhead of the casing annulus between the casing and the tubing, and under the gas injection pressure, the original fluid at the bottom of the cave reservoir is discharged from the lower cluster perforations and returned to the ground through the tubing, including:

[0022] The stored gas is repeatedly injected and then released from the wellhead of the oil casing annulus.

[0023] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0024] The construction method for converting abandoned oil and gas wells through caves into gas storage provided by an embodiment of the present invention first determines the location of the abandoned oil and gas wells and the cave reservoir based on the data of historical drilling leakage accidents of the abandoned oil and gas wells, and determines the upper leakage layer and the lower leakage layer of the cave reservoir. Then, the bottom of the abandoned oil and gas well is sealed until the bottom surface is flush with the bottom of the carbonate salt reservoir. Then, the upper cluster perforations are accurately perforated from the casing of the abandoned oil and gas well upward to the leakage layer, and the upper cluster perforations penetrate the casing and are connected to the cave reservoir. The lower cluster perforations are accurately perforated from the casing downward to the leakage layer to obtain the lower cluster perforations, and the lower cluster perforations penetrate the casing and are connected to the cave reservoir. Then, a packer is lowered between the upper cluster perforations and the lower cluster perforations of the casing, and the oil pipe of the abandoned oil and gas well passes through the packer from the wellhead and is connected to the lower cluster perforations. Then, the gas storage capacity of the cave reservoir is evaluated. According to the assessed gas storage capacity of the karst cave reservoir, the stored gas is finally injected from the wellhead of the casing annulus between the casing and the tubing. Since the packer is located between the upper cluster perforations and the lower cluster perforations, the packer divides the casing annulus into two sub-annuli. Under the gas injection pressure, the stored gas enters the upper sub-annulus and flows downward, and then enters the inner cavity of the karst cave reservoir along the upper cluster perforations. With the input of stored gas, the fluid in the karst cave reservoir is discharged from the lower cluster perforations to the lower sub-annulus, and then flows through the gap between the bottom end of the tubing and the bottom surface of the casing, and then flows into the bottom of the tubing and is discharged back to the ground through the tubing, thus realizing the reconstruction of a gas storage reservoir from abandoned oil and gas wells in karst caves.

[0025] The embodiment of the present application utilizes existing abandoned oil and gas wells that pass through carbonate formations to rebuild gas storage reservoirs, which is convenient and fast, has a short construction period, low construction cost, can provide a large gas storage capacity, and also has good sealing and stability. In addition, the gas storage reservoir rebuilt from abandoned oil and gas wells that pass through karst caves in the embodiment of the present application can dynamically adjust the gas injection volume and exhaust volume according to demand, and has relatively good flexibility. The construction method for rebuilding a gas storage reservoir from abandoned oil and gas wells that pass through karst caves provided in the embodiment of the present application can not only be used as a method for providing important energy reserves, but also the transformation of abandoned oil and gas wells that pass through carbonate formations can realize the effective application of geological resources, improve economic benefits, optimize resource allocation, and provide a new means for energy storage and management. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0027] Figure 1The present invention is a structural schematic diagram of a construction method for converting abandoned oil and gas wells in carbonate reservoirs into gas storage facilities using an embodiment of the present application.

[0028] Icons: 1- tubing; 2- casing; 3- cave reservoir; 4- upper cluster perforation; 5- lower cluster perforation; 6- packer. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] In the relevant description of this embodiment, the terms "including, containing, having" and the like are open terms and are generally understood to include but not limited to. In the following description of this embodiment, the terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms of "a" and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0031] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of the sequence numbers does not mean the order of execution, some or all of the steps can be executed in parallel or in sequence, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. Unless otherwise specified, the technical / scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the present application belongs.

[0032] The embodiment of the present invention provides a construction method for converting an abandoned oil and gas well through a karst cave into a gas storage reservoir, comprising the following steps 1 to 8, wherein the numbers after the steps do not represent the order of execution.

[0033] Step 1: Determine the location of the abandoned oil and gas well and the cave reservoir 3 based on the data of historical drilling leakage accidents of abandoned oil and gas wells, as well as the upper leakage layer and lower leakage layer of the cave reservoir 3. The upper leakage layer is located close to the ground, and the abandoned oil and gas well passes through the carbonate formation. In addition, the size of the cave reservoir 3 is preliminarily determined by exploration methods such as the lowering of the detector array. The abandoned oil and gas well had a serious leakage during the early drilling process and is used as a potential gas storage well.

[0034] The leakage layer refers to the rock layer position where the flushing fluid (such as mud, water, etc.) is partially or completely lost due to complex formation conditions such as cracks, caves, loose fracture zones, etc. during the drilling process. It is a layer that potentially stores a large amount of fluid. The determination of the leakage layer can facilitate the subsequent perforation at the corresponding position to obtain the upper cluster perforation hole 4 or the lower cluster perforation hole 5.

[0035] Step 2: Seal the bottom of the abandoned oil and gas well until the bottom surface is flush with the bottom of the carbonate salt reservoir.

[0036] Specifically, cement slurry is used to perfuse the bottom of the abandoned oil and gas well, and plugging is achieved after the cement slurry solidifies. The bottom of the casing 2 is plugged with cement slurry, and the plugging effect is good, there is no gap at the bottom, and it is not easy to leak.

[0037] Step 3: The upper cluster perforations 4 are obtained by accurately perforating upward from the casing 2 of the abandoned oil and gas well to the leakage layer. The upper cluster perforations 4 penetrate the casing 2 and are connected with the karst cave reservoir 3, forming the upper connection point between the casing 2 and the karst cave reservoir 3.

[0038] The perforating method for connecting the casing 2 and the karst reservoir 3 includes perforating bullet perforating or water jet perforating.

[0039] Perforating charges are explosives used to penetrate the casing 2 and the formation during the perforating process. Shaped charge perforating charges are the most widely used perforating charges and are also the most efficient perforating charges. Water jets are high-speed water streams of different shapes formed by the nozzle, and the flow rate of the jet depends on the pressure drop before and after the nozzle outlet section. Water jets are the simplest form of energy conversion and application. Usually, a power-driven pump completes a suction and discharge process for water, pumps a certain amount of water to a high-pressure pipeline, and makes it reach the nozzle with a certain energy. The aperture of the nozzle is much smaller than the diameter of the high-pressure pipeline, so a certain amount of water reaching the nozzle is accelerated to condense and form a jet when it flows out of the nozzle hole. When the jet reaches the inner wall of the casing 2, the energy formed by the jet's speed is converted into impact pressure to act on the casing 2 for precise perforation to obtain an upper cluster perforation hole 4 or a lower cluster perforation hole 5.

[0040] Step 4: accurately perforate the leakage layer downward from the casing 2 to obtain the lower cluster perforations 5. The lower cluster perforations 5 penetrate the casing 2 and are connected with the cave reservoir 3, forming the lower connection point between the casing 2 and the cave reservoir 3, so as to facilitate the discharge of the liquid in the cave reservoir 3 from the lower cluster perforations 5.

[0041] Step 5: a packer 6 is lowered between the upper shower hole 4 and the lower shower hole 5 of the casing 2 , and the oil pipe 1 of the abandoned oil and gas well passes through the packer 6 from the wellhead and is connected to the lower shower hole 5 .

[0042] Step 6: Evaluate the gas storage capacity of cave reservoir 3.

[0043] Specifically, step 6 includes: injecting liquid from the wellhead of the casing annulus between the casing 2 and the oil pipe 1, and calculating the gas storage volume of the cave reservoir 3 by constant flow injection pressure test, wherein the calculation formula is:

[0044] Where V is the volume of the cave reservoir 3, is the injection pressure at time t, is the injection pressure at the initial moment, c is the compressibility coefficient of the liquid, Q is the flow rate of the liquid, and t is the injection time.

[0045] The method for evaluating the gas storage capacity of the cave reservoir body 3 in the embodiment of the present application is simple, fast, environmentally friendly and emission-reducing, and provides a new way for energy storage and management.

[0046] Step 7: Inject storage gas from the wellhead of the casing annulus between the casing 2 and the tubing 1. Under the gas injection pressure, the original fluid at the bottom of the cave reservoir 3 is discharged from the lower cluster perforations 5 and returned to the ground through the tubing 1.

[0047] The fluid may be the liquid originally stored in the cave reservoir 3. If the gas storage capacity of the cave reservoir 3 is evaluated by constant displacement water injection, the fluid is water.

[0048] Step 8: Repeat the process of injecting and then releasing the stored gas from the wellhead in the casing annulus to evaluate the stability and gas output rate of the reconstructed gas storage. Stability refers to the ability to store natural gas and keep it from leaking.

[0049] The construction method for converting an abandoned oil and gas well through a cave into a gas storage reservoir provided by an embodiment of the present invention first determines the location of the abandoned oil and gas well and the cave reservoir 3 based on the data of the historical drilling leakage accident treatment of the abandoned oil and gas well, and determines the upper leakage layer and the lower leakage layer of the cave reservoir 3. Then the bottom of the abandoned oil and gas well is blocked until the bottom surface is flush with the bottom of the carbonate salt reservoir. Then, the upper cluster perforation 4 is obtained by accurately perforating the upper leakage layer from the casing 2 of the abandoned oil and gas well, and the upper cluster perforation 4 penetrates the casing 2 and is connected to the cave reservoir 3. The lower cluster perforation 5 is obtained by accurately perforating the lower leakage layer from the casing 2, and the lower cluster perforation 5 penetrates the casing 2 and is connected to the cave reservoir 3. Then, a packer 6 is lowered between the upper cluster perforation 4 and the lower cluster perforation 5 of the casing 2, and the oil pipe 1 of the abandoned oil and gas well passes through the packer 6 from the wellhead and is connected to the lower cluster perforation 5. Then, the gas storage volume of the cave reservoir 3 is evaluated. According to the assessed gas storage capacity of the karst cave reservoir 3, the stored gas is finally injected from the wellhead of the oil-casing annulus between the casing 2 and the oil pipe 1. Since the packer 6 is located between the upper cluster hole 4 and the lower cluster hole 5, the packer 6 divides the oil-casing annulus into two sub-annuli. Under the gas injection pressure, the stored gas enters the upper sub-annulus and flows downward, and then is input into the inner cavity of the karst cave reservoir 3 along the upper cluster hole 4. With the input of the stored gas, the fluid in the karst cave reservoir 3 is discharged from the lower cluster hole 5 to the lower sub-annulus, and then flows through the gap between the bottom end of the oil pipe 1 and the bottom surface of the casing 2, and then flows into the bottom of the oil pipe 1 and is discharged back to the ground through the oil pipe 1, that is, the abandoned oil and gas well through the karst cave is converted into a gas storage reservoir.

[0050] The embodiment of the present application utilizes existing abandoned oil and gas wells that pass through carbonate formations to rebuild gas storage reservoirs, which is convenient and fast, has a short construction period, low construction cost, can provide a large gas storage capacity, and also has good sealing and stability. In addition, the gas storage reservoir rebuilt from abandoned oil and gas wells that pass through karst caves in the embodiment of the present application can dynamically adjust the gas injection volume and exhaust volume according to demand, and has relatively good flexibility. The construction method for rebuilding a gas storage reservoir from abandoned oil and gas wells that pass through karst caves provided in the embodiment of the present application can not only be used as a method for providing important energy reserves, but also the transformation of abandoned oil and gas wells that pass through carbonate formations can realize the effective application of geological resources, improve economic benefits, optimize resource allocation, and provide a new means for energy storage and management.

[0051] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0052] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the present application. Although the present application is described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A construction method for converting abandoned oil and gas wells through karst caves into gas storage reservoirs. It is characterized in that include: Determine the location of the abandoned oil and gas well and the cave reservoir according to the data of historical drilling leakage accident treatment of the abandoned oil and gas well, and determine the upper leakage layer and the lower leakage layer of the cave reservoir, the upper leakage layer is located close to the ground, and the abandoned oil and gas well passes through the carbonate formation; The bottom of the abandoned oil and gas well is sealed until the bottom surface is flush with the bottom of the carbonate salt reservoir; Precisely perforating the upper leakage layer from the casing of the abandoned oil and gas well to obtain upper cluster perforations, wherein the upper cluster perforations penetrate the casing and are connected with the karst cave reservoir; Precisely perforating from the casing to the lower leakage layer to obtain lower cluster perforations, wherein the lower cluster perforations penetrate the casing and are connected to the karst cave reservoir; A packer is placed between the upper cluster hole and the lower cluster hole of the casing, and the oil pipe of the abandoned oil and gas well passes through the packer from the wellhead and is connected to the lower cluster hole; Assessing the gas storage capacity of the cave reservoir; The stored gas is injected from the wellhead of the oil casing annulus between the casing and the oil pipe. Under the gas injection pressure, the original fluid at the bottom of the cave reservoir is discharged from the lower cluster perforations and returned to the ground through the oil pipe.

2. The construction method for converting abandoned oil and gas wells through karst caves into gas storage according to claim 1, It is characterized in that The method of plugging the bottom of the abandoned oil and gas well comprises: The bottom of the abandoned oil and gas well is injected with cement slurry, and plugging is achieved after the cement slurry solidifies.

3. The construction method for converting abandoned oil and gas wells through karst caves into gas storage according to claim 1, It is characterized in that The perforating method for connecting the casing and the cave reservoir includes perforating bullet perforating or water jet perforating.

4. The construction method for converting abandoned oil and gas wells through karst caves into gas storage according to claim 1, It is characterized in that The step of evaluating the gas storage capacity of the cave reservoir comprises: Liquid is injected from the wellhead of the casing annulus, and the gas storage volume of the cave reservoir is calculated by constant flow injection pressure test, wherein the calculation formula is: Where V is the volume of the cave reservoir, is the injection pressure at time t, is the injection pressure at the initial moment, c is the compressibility coefficient of the liquid, Q is the flow rate of the liquid, and t is the injection time.

5. The construction method for converting abandoned oil and gas wells through karst caves into gas storage according to claim 1, It is characterized in that The method comprises: injecting stored gas from the wellhead of the casing annulus between the casing and the oil pipe, and discharging the original fluid at the bottom of the cave reservoir from the lower cluster perforations under the gas injection pressure and returning to the ground through the oil pipe, comprising: The stored gas is repeatedly injected and then released from the wellhead of the oil casing annulus.

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