A method and device for establishing a flow rate and pressure model of injection fluid in a coal seam U-type well

Abstract

The application discloses a method and device for establishing a coal seam U-shaped well injection fluid flow and pressure model. The method comprises the following steps: determining a coal seam U-shaped well oxygen injection flow and pressure model and a nitrogen injection flow and pressure model according to a gas injection flow and pressure model, wherein the oxygen injection flow and pressure model represents the relationship among the oxygen injection flow, the injection pressure and the oxygen cavity pressure at the well bottom of the U-shaped well, and the nitrogen injection flow and pressure model represents the relationship among the nitrogen injection flow, the injection pressure and the nitrogen cavity pressure at the well bottom of the U-shaped well; and determining a U-shaped well water injection flow and pressure model according to a hydraulic friction formula of the annular water injection, wherein the water injection flow and pressure model represents the relationship among the water injection flow, the injection pressure and the water pressure at the well bottom of the U-shaped well. The method can reasonably determine the relationship among the oxygen injection flow, the nitrogen injection flow, the water injection flow, the injection pressure and the well bottom pressure of the U-shaped well, and provides guidance data for the effective development of the underground coal gasification.

Description

Technical Field

[0001] This invention relates to the field of coal resource development technology, and in particular to a method and apparatus for establishing a model of fluid flow and pressure in a U-shaped well in a coal seam. Background Technology

[0002] Underground coal gasification involves creating suitable in-situ process conditions for the controlled combustion of underground coal. Through pyrolysis and a series of chemical reactions involving coal, oxygen, and water vapor, combustible gases such as hydrogen, carbon monoxide, and methane are produced. Advances in horizontal well and coiled tubing controlled back-injection technology have facilitated the development of modern underground coal gasification technology.

[0003] The underground gasification concentric coiled pipe is one of the key pieces of equipment for the successful underground coal gasification mining. During production, ignition fluid is intermittently injected into the underground gasification chamber through the concentric coiled pipe, while pure oxygen is continuously injected. Simultaneously, clean water or formation water is injected into the underground gasification chamber through the annulus between the concentric coiled pipe and the outer combustible pipe. Additionally, the concentric coiled pipe needs to carry cables for testing temperature or pressure. When injecting water, oxygen, and nitrogen into the coal seam through the inner and outer pipes of the concentric coiled pipe and the annulus between the coiled pipe and the outer combustible pipe, the injection pressure, flow rate, and velocity of the injected fluids must be strictly controlled. Therefore, simulation studies of the injection flow field in the underground gasification concentric coiled pipe are of great significance. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a method and apparatus for establishing a model of injection fluid flow rate and pressure in a coal seam U-shaped well to overcome or at least partially solve the above problems, which can reasonably determine the relationship between the injection flow rate, injection pressure and bottom hole pressure of oxygen, nitrogen and water in a coal seam U-shaped well.

[0005] In a first aspect, embodiments of the present invention provide a method for establishing a model of injection fluid flow and pressure in a coal seam U-shaped well, comprising performing at least one of the following:

[0006] Based on the gas injection flow rate and pressure model, the oxygen injection flow rate and pressure model for a coal seam U-shaped well is determined. The oxygen injection flow rate and pressure model characterizes the relationship between the injection flow rate and pressure of oxygen in the U-shaped well and the pressure of the oxygen chamber at the bottom of the well. The gas injection flow rate and pressure model is obtained based on the gas state equation, the gas continuity equation, and the gas motion equation.

[0007] Based on the gas injection flow rate and pressure model, the nitrogen injection flow rate and pressure model for the U-shaped well is determined. The nitrogen injection flow rate and pressure model characterizes the relationship between the nitrogen injection flow rate, injection pressure and nitrogen chamber pressure at the bottom of the well in the U-shaped well.

[0008] Based on the hydraulic friction formula for water in the annulus, a model for the injection flow rate and pressure of water in a U-shaped well is determined. The model characterizes the relationship between the injection flow rate, injection pressure, and water pressure at the bottom of the well. The hydraulic friction formula is derived from fluid mechanics.

[0009] Secondly, embodiments of the present invention provide a device for establishing a flow rate and pressure model of injected fluid in a coal seam U-shaped well, comprising at least one of the following modules:

[0010] The oxygen injection flow rate and pressure model establishment module is used to determine the oxygen injection flow rate and pressure model of the coal seam U-shaped well based on the gas injection flow rate and pressure model. The oxygen injection flow rate and pressure model characterizes the relationship between the oxygen injection flow rate, injection pressure and oxygen chamber pressure at the bottom of the well in the U-shaped well. The gas injection flow rate and pressure model is obtained based on the gas state equation, the gas continuity equation and the gas motion equation.

[0011] The nitrogen injection flow rate and pressure model establishment module is used to determine the nitrogen injection flow rate and pressure model of the U-shaped well based on the gas injection flow rate and pressure model. The nitrogen injection flow rate and pressure model characterizes the relationship between the nitrogen injection flow rate, injection pressure and nitrogen chamber pressure at the bottom of the well in the U-shaped well.

[0012] The water injection flow rate and pressure model establishment module is used to determine the U-shaped well water injection flow rate and pressure model based on the hydraulic friction formula of water in the annulus. The water injection flow rate and pressure model characterizes the relationship between the injection flow rate, injection pressure and water pressure at the bottom of the U-shaped well. The hydraulic friction formula is obtained from fluid mechanics.

[0013] Thirdly, embodiments of the present invention provide a computer program product, including a computer program / instruction, wherein the computer program / instruction, when executed by a processor, implements the above-mentioned method for establishing the flow rate and pressure model of injected fluid in a U-shaped coal seam.

[0014] Fourthly, this disclosure provides a server, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-mentioned method for establishing the flow rate and pressure model of injected fluid in a U-shaped coal seam.

[0015] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0016] The method for establishing injection flow rate and pressure models for coal seam U-shaped wells provided in this invention derives gas injection flow rate and pressure models based on the gas state equation, gas continuity equation, and gas motion equation. These gas injection flow rate and pressure models are then used to determine oxygen and nitrogen injection flow rate and pressure models for the coal seam U-shaped wells. A hydraulic friction formula is derived from fluid mechanics to further determine the water injection flow rate and pressure model for the U-shaped well. By fully utilizing theoretical knowledge from relevant disciplines, the method establishes the relationships between the injection flow rate, injection pressure, and bottom hole pressure of oxygen, nitrogen, and water in coal seam U-shaped wells, providing guiding data for the effective implementation of underground coal gasification and ensuring its smooth operation.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 This is a schematic diagram of a U-shaped well structure in a coal seam.

[0021] Figure 2 This is a flowchart of the method for establishing the flow rate and pressure model of injected fluid in a U-shaped well in a coal seam according to Embodiment 1 of the present invention;

[0022] Figure 3 for Figure 1 The detailed implementation flowchart of step S23 is shown below;

[0023] Figure 4 A schematic diagram showing the positional relationship between the outer pipe and the combustible sleeve of the underground gasification concentric continuous pipe;

[0024] Figure 5A A side view of a schematic diagram of an underground gasification concentric continuous pipe structure;

[0025] Figure 5B A top view of a schematic diagram of an underground gasification concentric continuous pipe structure;

[0026] Figure 6 This is a schematic diagram of the device for establishing the flow rate and pressure model of injected fluid in a U-shaped well in a coal seam according to an embodiment of the present invention. Detailed Implementation

[0027] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0028] Reference Figure 1 The diagram shows a schematic of a U-shaped coal seam well. A U-shaped coal seam well consists of a horizontal well drilled at one end of the coal seam as an injection well for the gasifying agent, and a vertical well drilled at the other end, its diameter connected to the end of the horizontal section of the horizontal well as a crude coal gas production well. The shape of the connected horizontal and vertical wells is U-shaped, hence the name U-shaped well. In this embodiment of the invention, the U-shaped well refers specifically to its injection well portion. Typically, oxygen is injected into the annulus between the outer and inner pipes of the underground gasification concentric continuous tubing (oil tubing) within the wellbore, nitrogen is injected into the inner pipe, and water is injected into the annulus between the outer pipe and the combustible casing of the outer concentric continuous tubing.

[0029] To address the problem of simulating the injection flow field pressure in U-shaped coal seams, this invention provides a method and apparatus for establishing a model of injection fluid flow rate and pressure in U-shaped coal seams, which can reasonably determine the relationship between the injection flow rate, injection pressure and bottom hole pressure of oxygen, nitrogen and water in U-shaped coal seams.

[0030] Example 1

[0031] Embodiment 1 of the present invention provides a method for establishing a model of injection fluid flow rate and pressure in a U-shaped coal seam well, including executing... Figure 2 At least one of the steps shown:

[0032] Step S21: Based on the gas injection flow rate and pressure model, determine the oxygen injection flow rate and pressure model for the coal seam U-shaped well. The oxygen injection flow rate and pressure model characterizes the relationship between the oxygen injection flow rate, injection pressure and oxygen chamber pressure at the bottom of the well in the U-shaped well.

[0033] Step S22: Based on the gas injection flow rate and pressure model, determine the nitrogen injection flow rate and pressure model for the U-shaped well. The nitrogen injection flow rate and pressure model characterizes the relationship between the nitrogen injection flow rate, injection pressure and nitrogen chamber pressure at the bottom of the well in the U-shaped well.

[0034] The gas injection flow rate and pressure model is derived from the gas state equation, the gas continuity equation, and the gas motion equation, specifically as shown in the following formula (1):

[0035] (1)

[0036] In formula (1), m is the mass flow rate of the injected gas at the wellhead, kg / s; The injection pressure of the gas at the wellhead is expressed in Pa. The pressure in the gas chamber at the bottom of the injected well, in Pa; The local gravitational acceleration is in m / s². 2 Z is the compressibility coefficient of the gas, which is dimensionless; R is the gas constant. M is the molar mass of the gas, m 2 / (s 2 .K); T is the temperature of the gas, K; L and D are the length and equivalent inner diameter of the gas injection channel in the injection well, respectively, m; The height difference, in meters, is the difference between the end of the injection channel and the wellhead. This is the coefficient of friction of the gas in the injection channel. , without dimension.

[0037] Since the gas temperature does not change much along the injection channel, the gas flow in the continuous tube is simplified to a frictional isothermal flow with a constant cross-section. The relationship between the mass flow rate and pressure drop of the isothermal flow is obtained by using the ideal gas law, process equation, continuity equation, and momentum equation. Based on this, the gas pressure at the inlet and outlet of the gas injection channel is calculated.

[0038] Using the above gas injection flow rate and pressure model, the relevant parameters of oxygen injection and oxygen injection channel in the U-shaped well are substituted into the above formula (1) to establish the oxygen injection flow rate and pressure model of the coal seam U-shaped well; the relevant parameters of nitrogen injection and nitrogen injection channel in the U-shaped well are substituted into the above formula (1) to establish the nitrogen injection flow rate and pressure model of the coal seam U-shaped well.

[0039] Furthermore, based on the inner diameter of the outer tube and the outer diameter of the inner tube of the underground gasification concentric continuous tube in the coal seam U-shaped well, the equivalent inner diameter of the first annulus between the outer and inner tubes of the concentric continuous tube is determined, which serves as the equivalent inner diameter of the oxygen injection channel in the concentric continuous tube; based on the equivalent inner diameter of the oxygen injection channel and the gas injection flow rate and pressure model, the oxygen injection flow rate and pressure model of the U-shaped well is determined. The oxygen injection flow rate and pressure model is as follows: (2)

[0040] (2)

[0041] In formula (2), , These represent the injected oxygen mass flow rate and injection pressure at the wellhead of the U-shaped coal seam, respectively. This refers to the oxygen chamber pressure at the bottom of the U-shaped well. For local gravitational acceleration, is the compressibility coefficient of oxygen. Let be the gas constant of oxygen. , Here is the molar mass of oxygen. The temperature of oxygen, , These are the pipe length of the underground gasification concentric continuous pipe in the U-shaped well and the equivalent inner diameter of the oxygen injection channel (the cross street area of ​​the first annulus is equal to the area of ​​a circle with the equivalent inner diameter as its diameter). The height difference between the end of the concentric coiled tubing and the wellhead. This is the coefficient of friction of oxygen in the oxygen injection channel. .

[0042] The inner diameter of the concentric continuous tube for underground gasification in the U-shaped coal seam well is taken as the equivalent inner diameter of the nitrogen injection channel in the concentric continuous tube. Based on the equivalent inner diameter of the nitrogen injection channel and the gas injection flow rate and pressure model, the nitrogen injection flow rate and pressure model for the U-shaped well is determined. The nitrogen injection flow rate and pressure model is shown in the following formula (3):

[0043] (3)

[0044] In formula (3), , These represent the injection mass flow rate and injection pressure of nitrogen at the wellhead of the U-shaped coal seam, respectively. This refers to the nitrogen chamber pressure at the bottom of the U-shaped well. For local gravitational acceleration, Let be the compressibility coefficient of nitrogen. Let be the gas constant of nitrogen. , Here is the molar mass of nitrogen. The temperature of nitrogen gas, The equivalent inner diameter of the nitrogen injection channel in the underground gasification concentric continuous pipe in the U-shaped well. The friction coefficient of nitrogen gas in the nitrogen injection channel. .

[0045] Typically, the oxygen injection flow rate and pressure model for the U-shaped well described above represents the first annular airborne oxygen injection flow rate and pressure model between the outer and inner pipes of the underground gasification concentric continuous pipe in the U-shaped well; the nitrogen injection flow rate and pressure model for the U-shaped well represents the nitrogen injection flow rate and pressure model within the inner pipe of the concentric continuous pipe; and the water injection flow rate and pressure model for the U-shaped well represents the second annular airborne water injection flow rate and pressure model between the combustible casing and the outer pipe of the underground gasification concentric continuous pipe in the U-shaped well.

[0046] Optionally, the oxygen and nitrogen injection channels can be interchanged. The establishment of the specific injection flow rate and pressure model is similar to the method described above, and will not be repeated here.

[0047] Step S23: Based on the hydraulic friction formula of water in the annulus, determine the U-shaped well water injection flow rate and pressure model. The water injection flow rate and pressure model characterizes the relationship between the injection flow rate, injection pressure and water pressure at the bottom of the U-shaped well.

[0048] The formula for the hydraulic friction of water in the annulus is derived from fluid mechanics.

[0049] Reference Figure 3 As shown, establishing a water injection flow rate and pressure model can include the following steps:

[0050] Step S231: Determine the Reynolds number of the second annular water in the coal seam U-shaped well based on the injection flow rate of the second annular water between the combustible casing and the outer pipe of the underground gasification concentric continuous pipe.

[0051] Based on the water injection flow rate in the second annulus between the combustible casing and the outer pipe of the underground gasification concentric continuous pipe in the coal seam U-shaped well. The Reynolds number of the water in the second ring air is determined by the following formula (4). :

[0052] (4)

[0053] In formula (4), The inner diameter of the combustible sleeve is in meters (m). The outer diameter of the concentric continuous tube is in meters (m). and The density of the injected water (kg / m³) 3 ) and viscosity (mpa.s); The injection flow rate of water in the second ring air is m 3 / s; The injection velocity of water in the second ring air is given in m / s. .

[0054] If Re If Re > 2000, the fluid is considered to be in a laminar flow state; if Re > 2000, the fluid is considered to be in a turbulent flow state.

[0055] Step S232: Based on the determined Reynolds number and the hydraulic friction formula for water in the annulus, determine the relationship between the injection flow rate of water in the second annulus and the hydraulic friction of water in the second annulus.

[0056] Based on the determined Reynolds number and the hydraulic friction formula for water in the annulus, the injection flow rate of water in the second annulus is determined. Hydraulic friction with water in the second ring The relationship between them is shown in the following formula (5):

[0057] (5)

[0058] In formula (5), The length of the concentric continuous pipe. This is the eccentricity correction factor for the outer tube of the concentric continuous tube.

[0059] Eccentricity correction factor for concentric continuous tube outer tube It is determined in advance by the following formula (6):

[0060] (6)

[0061] In formula (6), , The eccentricity of the outer tube of the concentric continuous tube is denoted by .

[0062] Since the eccentricity of the outer tube of the concentric coiled tubing cannot be accurately determined (the eccentricity δ cannot be accurately determined), Ec cannot be accurately determined and an approximate value can be used in the calculation. If the outer tube of the concentric coiled tubing is exactly centered in the wellbore, then Ec=0 and Cef=1; if the outer wall of the outer tube of the concentric coiled tubing is close to the inner wall of the wellbore, then Ec=1 and the value of Cef is the smallest. For a near-vertical outer coiled tubing annulus, the value of Ec ranges from 0.5 to 0.75.

[0063] See Figure 4 The diagram shown illustrates the positional relationship between the outer tube of the concentric continuous tube and the combustible sleeve. Figure 5A and Figure 5B These are side and top views of a schematic diagram of an underground gasification concentric continuous pipe structure.

[0064] Step S233: Based on the relationship between the injection flow rate of water in the second annulus and the hydraulic friction of water in the second annulus, obtain the U-shaped well water injection flow rate and pressure model.

[0065] Based on the relationship between the injection flow rate of water in the second annulus and the hydraulic friction of water in the second annulus, the injection flow rate and pressure model of U-shaped well water can be obtained through the following formula (7):

[0066] (7)

[0067] In formula (7), This refers to the liquid column pressure of the water column in the second ring. , The injection pressure for water in the second ring air. This refers to the water pressure at the bottom of the second ring well.

[0068] The steps S21-S23 above are not sequential.

[0069] The method for establishing injection flow rate and pressure models for coal seam U-shaped wells provided in Embodiment 1 of this invention derives gas injection flow rate and pressure models based on the gas state equation, gas continuity equation, and gas motion equation. These gas injection flow rate and pressure models are then used to determine oxygen and nitrogen injection flow rate and pressure models for the coal seam U-shaped wells. A hydraulic friction formula is derived from fluid mechanics to further determine the water injection flow rate and pressure model for the U-shaped wells. By fully utilizing theoretical knowledge from relevant disciplines, the method establishes the relationships between the injection flow rates, injection pressures, and bottom hole pressures of oxygen, nitrogen, and water in coal seam U-shaped wells, providing guiding data for the effective implementation of underground coal gasification and ensuring its smooth operation.

[0070] In some embodiments, it may further include:

[0071] Based on the oxygen chamber pressure at the bottom of the U-shaped well in the coal seam, the oxygen flow rate at the bottom of the U-shaped well is determined using the following formula (8). :

[0072] (8);

[0073] Based on the nitrogen chamber pressure at the bottom of the U-shaped well in the coal seam, the nitrogen flow rate at the bottom of the U-shaped well is determined using the following formula (9). :

[0074] (9)

[0075] In formulas (8) and (9), Atmospheric pressure under standard conditions, 101325 Pa; , These are the volumetric flow rates of oxygen and nitrogen under standard conditions, respectively, in Nm³. 3 / h; , These are the oxygen chamber pressure and nitrogen chamber pressure at the bottom of the coal seam U-shaped well, respectively, in Pa; , These are the equivalent inner diameters, in meters, of the oxygen injection channel and nitrogen injection channel in the U-shape, respectively.

[0076] Based on the inner diameter of the outer tube and the outer diameter of the inner tube of the concentric continuous tube in the underground gasification system of the coal seam U-shaped well, the equivalent inner diameter of the first annulus between the outer and inner tubes of the concentric continuous tube is determined, and used as the equivalent inner diameter of the oxygen injection channel in the concentric continuous tube. The inner diameter of the concentric continuous tube for underground gasification in a U-shaped coal seam well is used as the equivalent inner diameter of the nitrogen injection channel in the concentric continuous tube. .

[0077] In some embodiments, it may further include:

[0078] Based on the oxygen injection pressure of the U-shaped well in the coal seam Oxygen chamber pressure at the bottom of the well and tool export pressure reduction The frictional resistance along the oxygen injection channel in the concentric continuous tube for underground gasification in a U-shaped well is determined by the following formula (10). :

[0079] (10)

[0080] In formula (10), The pressure of the air column in the oxygen injection channel. , The density of oxygen, This represents the height difference between the end of the concentric continuous tubing and the wellhead.

[0081] Based on the nitrogen injection pressure of the U-shaped well in the coal seam Nitrogen chamber pressure at the bottom of the well and tool export pressure reduction The frictional resistance along the nitrogen injection channel in the underground gasification concentric continuous tube of the U-shaped well is determined by the following formula (11). :

[0082] (11)

[0083] In formula (11), The pressure of the gas column in the nitrogen injection channel. , The density of nitrogen gas is given.

[0084] The process of deriving the gas injection flow rate and pressure model based on the gas state equation, gas continuity equation, and gas motion equation is as follows:

[0085] For an ideal gas, in all states...

[0086] (12)

[0087] For real gases, introducing a correction factor yields the following gas law:

[0088] (13)

[0089] In the formula, The pressure is the gas pressure, in Pa. is the compressibility coefficient of the gas, which is dimensionless; The density of the gas is kg / m³. 3 ; The gas constant is 8314.3 / the molar mass of the gas, m 2 / (s 2.K); Let K be the temperature of the gas.

[0090] If we disregard changes in the pipe cross-section, according to the law of conservation of mass, the gas flow continuity equation is:

[0091] (13)

[0092] In the formula, The density of the gas is kg / m³. 3 ; The velocity of the gas is expressed in m / s. Let 's' be the time variable, 's'. The depth is measured in meters (m) along the length of the wellbore, i.e., the well depth.

[0093] For steady flow, the flow parameters do not change with time, and the first term on the left side of the above equation is 0. Therefore, the continuity equation is:

[0094] (14)

[0095] According to Newton's second law, the equations of motion for a gas established by fluid mechanics can be written as follows:

[0096] :15)

[0097] In the formula, The density of the gas is kg / m³. 3 ; The velocity of the gas is expressed in m / s. Let 's' be the time variable, 's'. The depth is measured along the length of the wellbore, i.e., the well depth, in meters (m). The local gravitational acceleration is in m / s². 2 ; The angle between the wellbore and the horizontal plane, i.e., the well inclination angle, is expressed in rad. The coefficient of hydraulic friction is dimensionless. Let be the inner diameter of the pipe, in meters (m). Let be the gas pressure in the pipeline, in Pa.

[0098] For steady flow, the first term on the left-hand side of the above equation is 0. Considering the continuity equation, we get:

[0099] (16)

[0100] From the continuity equation and the gas law, we can obtain:

[0101] (17)

[0102] Combining the continuity equation, the gas state equation, and the equation of motion, we can obtain:

[0103] (18)

[0104] Right now

[0105] (19)

[0106] By rearranging and combining terms, we get:

[0107] (20)

[0108] Transformed into:

[0109] (twenty one)

[0110] In the formula, The injection pressure of the gas at the wellhead, in Pa; The pressure in the gas chamber at the end of the pipe, in Pa; The mass flow rate of the gas is kg / s; The height difference, in meters, is the difference between the end of the pipe at the bottom of the well and the wellhead.

[0111] set up

[0112] (twenty two)

[0113] (twenty three)

[0114] Substituting a and b into equation 1.11, then

[0115] (twenty four)

[0116] or

[0117] (25)

[0118] To simplify the above formula, let the formula contain... Expand the terms into a power series form:

[0119] (26)

[0120] because Therefore, the above series converges quickly, so we only need to take the first one or two terms of the series; the other terms can be ignored because their values ​​are very small. Substituting, we get:

[0121] (27)

[0122] Substituting b into the formula yields the gas injection flow rate and pressure model for the injection well, i.e., the formula (1) above.

[0123] The above formula for the hydraulic friction of water in the annulus is determined through the following steps:

[0124] The frictional pressure loss (hydraulic friction) of a Newtonian fluid in the wellbore annulus can be calculated using the following formula:

[0125] (28)

[0126] flow If based on traffic Replace speed Then the above formula can be transformed into:

[0127] (29)

[0128] In the formula, is the annular eccentricity correction factor; f is the friction coefficient of the liquid flowing in the pipe; D is the wellbore diameter (m); D is the outer diameter of the concentric coiled tubing (outer tube) (m); ρ is the density of water (kg / m³). 3 Q represents the water flow rate, in meters. 3 / s; L is the pipe length (i.e., well depth), in meters.

[0129] The coefficient of friction of a fluid flowing in the annulus of a wellbore can be expressed as:

[0130] (30)

[0131] In the formula, when the fluid in the pipe is laminar, c=16, d=1; when the fluid in the pipe is turbulent, c=0.07875, d=0.25; f is the friction coefficient.

[0132] The simulation model for the injection fluid flow rate and pressure in the injection well is as follows:

[0133] When the fluid inside the pipe is in a laminar flow state

[0134] (31)

[0135] When the fluid inside the pipe is in a turbulent state

[0136] (32)

[0137] In the formula, Re is the frictional pressure loss in the annulus of the wellbore; Re is the Relow number; Cef is the annulus eccentricity correction factor; Dw is the wellbore diameter (m); D is the outer diameter of the concentric coiled tubing (outer tube) (m); ρ is the density of water (kg / m³). 3 Q represents the water flow rate, in meters. 3 / s; L is the pipe length (i.e., well depth), in meters.

[0138] Example 2

[0139] This invention provides a specific application of a method for establishing a flow rate and pressure model for injected fluid in a U-shaped coal seam well. The fluid conditions for an underground gasification concentric continuous pipe are as follows: continuous pipe length 2200m, including a vertical section of 1000m and a horizontal section of 1200m; maximum oxygen delivery pressure 20MPa, oxygen mass flow rate 30~70t / d; normal operating pressure of the gasifier 5~10MPa, assumed pressure drop at tools and outlet 4MPa; maximum injection pressure of annular water in the continuous pipe and combustible casing 14MPa. In the calculation, the outer diameter of the ignition fluid injection pipe is 25.4mm, the outer diameter of the temperature measuring cable armor is 4mm, the outer diameter of the concentric continuous pipe is 73.0mm, and the wellbore diameter is 97.18mm. The underground gasification concentric continuous pipe structure adopts a two-pipe parallel scheme, with the ignition fluid injection pipe and temperature measuring cable parallel inside the oxygen injection pipe, facilitating pipe layout. Its structure is as follows... Figure 5A and Figure 5B As shown.

[0140] like Figure 1 As shown, as a transitional stage of the downhole ignition process, after switching the manifold process to the ignition condition, nitrogen is continuously injected downhole to ensure the bottom hole pressure and prepare for the subsequent injection ignition operation.

[0141] After the gasification starts smoothly, adjust the oxygen and water injection rates until the crude gas composition meets the standards and the gasification operates stably.

[0142] During the gasification operation phase, cooling water is injected into the annulus of the injection well casing, nitrogen is injected under controlled pressure inside the concentric continuous tubing, and oxygen is injected into the annulus of both the inner and outer tubing of the concentric continuous tubing. Cooling water is injected into the spray pipe of the production well, and crude coal gas is discharged from the annulus of the production tubing and spray pipe.

[0143] The tool outlet pressure drop during nitrogen and oxygen injection in concentric coiled tubing is 4 MPa, and the gas chamber pressure is 5-10 MPa.

[0144] The flow rates, velocities, and pressures of water injection into the annulus, oxygen injection into the outer tube of the concentric coiled tubing, and nitrogen injection into the inner tube of the concentric coiled tubing under the gasification operation conditions at a well depth of 2200m are shown in Tables 1, 2, and 3.

[0145] Table 1. Water flow rate, velocity, and pressure in the annulus at a well depth of 2200m.

[0146]

[0147] Table 2. Oxygen injection flow rate, velocity, and pressure in the outer tubing of the concentric coiled tubing at a well depth of 2200m.

[0148]

[0149] Table 3. Nitrogen injection flow rate, velocity, and pressure inside concentric coiled tubing at a well depth of 2200m.

[0150]

[0151] Based on the inventive concept of this invention, embodiments of this invention also provide a device for establishing a model of injection fluid flow and pressure in a U-shaped coal seam well. The structure of this device is as follows: Figure 6 ( Figure 6 As shown in the example (which includes all three modules), it includes at least one of the following modules:

[0152] The oxygen injection flow rate and pressure model establishment module 61 is used to determine the oxygen injection flow rate and pressure model of the coal seam U-shaped well based on the gas injection flow rate and pressure model. The oxygen injection flow rate and pressure model characterizes the relationship between the injection flow rate and injection pressure of oxygen in the U-shaped well and the pressure of the oxygen chamber at the bottom of the well. The gas injection flow rate and pressure model is obtained based on the gas state equation, the gas continuity equation and the gas motion equation.

[0153] The nitrogen injection flow rate and pressure model establishment module 62 is used to determine the nitrogen injection flow rate and pressure model of the U-shaped well based on the gas injection flow rate and pressure model. The nitrogen injection flow rate and pressure model characterizes the relationship between the nitrogen injection flow rate, injection pressure and nitrogen chamber pressure at the bottom of the well in the U-shaped well.

[0154] The water injection flow rate and pressure model establishment module 63 is used to determine the U-shaped well water injection flow rate and pressure model based on the hydraulic friction formula of water in the annulus. The water injection flow rate and pressure model characterizes the relationship between the injection flow rate, injection pressure and water pressure at the bottom of the U-shaped well. The hydraulic friction formula is obtained from fluid mechanics.

[0155] Regarding the apparatus in the above embodiments, the specific manner in which each module performs its operation has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0156] Based on the inventive concept of the present invention, embodiments of the present invention also provide a computer program product, including a computer program / instruction, wherein the computer program / instruction, when executed by a processor, implements the above-mentioned method for establishing the flow rate and pressure model of injected fluid in a U-shaped coal seam.

[0157] Unless otherwise specifically stated, terms such as processing, calculation, operation, determination, display, etc., may refer to the actions and / or processes of one or more processing or computing systems or similar devices that represent the manipulation and conversion of data representing physical (e.g., electronic) quantities within the registers or memory of the processing system into other data similarly representing physical quantities within the memory, registers, or other such information storage, transmission, or display devices of the processing system. Information and signals can be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0158] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0159] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0160] Those skilled in the art will also understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments herein can be implemented as electronic hardware, computer software, or a combination thereof. To clearly illustrate the interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps described above are generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in alternative ways for each specific application; however, such implementation decisions should not be construed as departing from the scope of this disclosure.

[0161] The steps of the methods or algorithms described in conjunction with the embodiments herein can be directly embodied in hardware, software modules executed by a processor, or a combination thereof. The software modules can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal. Alternatively, the processor and storage medium can exist as discrete components in the user terminal.

[0162] For software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described in this application. This software code can be stored in memory units and executed by a processor. The memory units can be implemented within the processor or outside the processor; in the latter case, they are communicatively coupled to the processor via various means, as is well known in the art.

[0163] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term “comprising” as used in the specification or claims is interpreted in a manner similar to the term “including,” as it is understood when used as a conjunction in the claims. Additionally, the use of any term “or” in the specification of the claims is intended to mean “non-exclusive or.” The terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

Claims

1. A method for establishing a model of fluid flow rate and pressure in a U-shaped coal seam well, characterized in that, Includes performing at least one of the following: Based on the gas injection flow rate and pressure model, the oxygen injection flow rate and pressure model for a coal seam U-shaped well is determined. The oxygen injection flow rate and pressure model characterizes the relationship between the injection flow rate and pressure of oxygen in the U-shaped well and the pressure of the oxygen chamber at the bottom of the well. The gas injection flow rate and pressure model is obtained based on the gas state equation, the gas continuity equation, and the gas motion equation. Based on the gas injection flow rate and pressure model, the nitrogen injection flow rate and pressure model for the U-shaped well is determined. The nitrogen injection flow rate and pressure model characterizes the relationship between the nitrogen injection flow rate, injection pressure and nitrogen chamber pressure at the bottom of the well in the U-shaped well. Based on the water injection flow rate in the second annulus between the combustible casing and the outer pipe of the underground gasification concentric continuous pipe in the coal seam U-shaped well. The Reynolds number of the water in the second annulus is determined by the following formula (1). : （1）； In formula (1), The inner diameter of the combustible sleeve, The outer diameter of the concentric continuous tube is given. and These are the density and viscosity of the injected water, respectively. Based on the determined Reynolds number and the hydraulic friction formula for water in the annulus, the relationship between the injection flow rate and the hydraulic friction of water in the second annulus is determined; based on the relationship between the injection flow rate and the hydraulic friction of water in the second annulus, the U-shaped well water injection flow rate and pressure model is obtained. The water injection flow rate and pressure model characterizes the relationship between the injection flow rate, injection pressure, and water pressure at the bottom of the U-shaped well, and the hydraulic friction formula is derived from fluid mechanics; the oxygen injection flow rate and pressure model for the U-shaped well is the first annular airborne oxygen injection flow rate and pressure model between the outer and inner tubes of the underground gasification concentric continuous pipe in the U-shaped well; the nitrogen injection flow rate and pressure model for the U-shaped well is the nitrogen injection flow rate and pressure model in the inner tube of the concentric continuous pipe; the water injection flow rate and pressure model for the U-shaped well is the second annular airborne water injection flow rate and pressure model between the combustible casing and the outer tube of the underground gasification concentric continuous pipe in the U-shaped well.

2. The method as described in claim 1, characterized in that, The gas injection flow rate and pressure model is given by the following formula (2): （2）； In formula (2), m, These represent the injected mass flow rate and injection pressure of the gas in the injection well, respectively. This refers to the gas chamber pressure at the bottom of the injected well. Let Z be the acceleration due to gravity, Z be the compressibility of the gas, and R be the gas constant. M is the molar mass of the gas, T is the temperature of the gas, and L and D are the length and equivalent inner diameter of the gas injection channel in the injection well, respectively. The height difference between the end of the injection channel and the wellhead of the injection well. The friction coefficient of the gas in the injection channel. .

3. The method as described in claim 2, characterized in that, The determination of the oxygen injection flow rate and pressure model for a coal seam U-shaped well based on the gas injection flow rate and pressure model specifically includes: Based on the inner diameter of the outer tube and the outer diameter of the inner tube of the underground gasification concentric continuous tube in the coal seam U-shaped well, the equivalent inner diameter of the first annulus between the outer tube and the inner tube of the concentric continuous tube is determined, and used as the equivalent inner diameter of the oxygen injection channel in the concentric continuous tube. Based on the equivalent inner diameter of the oxygen injection channel and the gas injection flow rate and pressure model, the oxygen injection flow rate and pressure model of the U-shaped well is determined.

4. The method as described in claim 2, characterized in that, The step of determining the nitrogen injection flow rate and pressure model for the U-shaped well based on the gas injection flow rate and pressure model specifically includes: The inner diameter of the concentric continuous underground gasification pipe in the coal seam U-shaped well is taken as the equivalent inner diameter of the nitrogen injection channel in the concentric continuous pipe. Based on the equivalent inner diameter of the nitrogen injection channel and the gas injection flow rate and pressure model, the nitrogen injection flow rate and pressure model for the U-shaped well is determined.

5. The method as described in claim 1, characterized in that, Also includes: Based on the oxygen chamber pressure at the bottom of the U-shaped well in the coal seam, the oxygen flow rate at the bottom of the U-shaped well is determined using the following formula (3). : (3)； Based on the nitrogen pressure at the bottom of the U-shaped well in the coal seam, the nitrogen flow rate at the bottom of the U-shaped well is determined by the following formula (4). : (4)； In formulas (3) and (4), Atmospheric pressure under standard conditions , These are the volumetric flow rates of oxygen and nitrogen under standard conditions, respectively. , These are the oxygen chamber pressure and nitrogen chamber pressure at the bottom of the U-shaped coal seam well, respectively. , These are the equivalent inner diameters of the oxygen injection channel and nitrogen injection channel in the U-shape, respectively.

6. The method as described in claim 5, characterized in that, Also includes: Based on the inner diameter of the outer tube and the outer diameter of the inner tube of the underground gasification concentric continuous tube in the coal seam U-shaped well, the equivalent inner diameter of the first annulus between the outer and inner tubes of the concentric continuous tube is determined, and used as the equivalent inner diameter of the oxygen injection channel in the concentric continuous tube. ; The inner diameter of the concentric continuous pipe for underground gasification in the U-shaped coal seam well is taken as the equivalent inner diameter of the nitrogen injection channel in the concentric continuous pipe. .

7. The method as described in claim 1, characterized in that, Also includes: Based on the oxygen injection pressure of the U-shaped well in the coal seam Oxygen chamber pressure at the bottom of the well and tool export pressure reduction The frictional resistance along the oxygen injection channel in the concentric continuous tube for underground gasification in a U-shaped well is determined by the following formula (5). : (5)； In formula (5), The pressure of the air column in the oxygen injection channel. , The density of oxygen, This is the height difference between the end of the concentric continuous tubing and the wellhead. Based on the nitrogen injection pressure of the U-shaped well in the coal seam Nitrogen chamber pressure at the bottom of the well and tool export pressure reduction The frictional resistance along the nitrogen injection channel in the underground gasification concentric continuous pipe of the U-shaped well is determined by the following formula (6). : (6)； In formula (6), The pressure of the gas column in the nitrogen injection channel. , The density of nitrogen gas is given.

8. The method as described in claim 1, characterized in that, The process of determining the relationship between the injection flow rate of the second annular water and the hydraulic friction of the second annular water, based on the determined Reynolds number and the hydraulic friction formula for water in the annulus, specifically includes: Based on the determined Reynolds number and the hydraulic friction formula for water in the annulus, the injection flow rate of water in the second annulus is determined. Hydraulic friction with water in the second annulus The relationship between them is shown in the following formula (7): (7)； In formula (7), The length of the concentric continuous pipe is given. The eccentricity correction coefficient for the outer tube of the concentric continuous tube; The eccentricity correction factor of the outer tube of the concentric continuous tube It is determined in advance by the following formula (8): （8）； In formula (8), , The eccentricity of the outer tube of the concentric continuous tube is given.

9. The method as described in claim 8, characterized in that, The model for U-shaped well water injection flow rate and pressure is derived based on the relationship between the injection flow rate and the hydraulic friction of the water in the second annulus. Specifically, it includes: Based on the relationship between the injection flow rate of the water in the second annulus and the hydraulic friction of the water in the second annulus, the injection flow rate and pressure model of the U-shaped well are obtained through the following formula (9): （9）； In formula (9), This is the liquid column pressure of the water in the second annulus. , The injection pressure of water in the second annulus. This refers to the water pressure at the bottom of the second annular well.

10. A device for establishing a model of injection fluid flow rate and pressure in a U-shaped coal seam well, characterized in that, Includes at least one of the following modules: The oxygen injection flow rate and pressure model establishment module is used to determine the oxygen injection flow rate and pressure model of the coal seam U-shaped well based on the gas injection flow rate and pressure model. The oxygen injection flow rate and pressure model characterizes the relationship between the oxygen injection flow rate, injection pressure and oxygen chamber pressure at the bottom of the well in the U-shaped well. The gas injection flow rate and pressure model is obtained based on the gas state equation, the gas continuity equation and the gas motion equation. The nitrogen injection flow rate and pressure model establishment module is used to determine the nitrogen injection flow rate and pressure model of the U-shaped well based on the gas injection flow rate and pressure model. The nitrogen injection flow rate and pressure model characterizes the relationship between the nitrogen injection flow rate, injection pressure and nitrogen chamber pressure at the bottom of the well in the U-shaped well. The water injection flow rate and pressure model building module is used to establish the water injection flow rate in the second annulus between the combustible casing and the outer pipe of the underground gasification concentric continuous pipe in the coal seam U-shaped well. The Reynolds number of the water in the second annulus is determined by the following formula. : ,in, The inner diameter of the combustible sleeve, The outer diameter of the concentric continuous tube is given. and The density and viscosity of the injected water are respectively determined. Based on the determined Reynolds number and the hydraulic friction formula for water in the annulus, the relationship between the injected flow rate and the hydraulic friction of the water in the second annulus is determined. Based on this relationship, a U-shaped well water injection flow rate and pressure model is obtained. This model characterizes the relationship between the injected flow rate, injection pressure, and water pressure at the bottom of the well. The hydraulic friction formula is derived from fluid mechanics. The U-shaped well oxygen injection flow rate and pressure model is the first annulus oxygen injection flow rate and pressure model between the outer and inner pipes of the underground gasification concentric continuous pipe in the U-shaped well. The U-shaped well nitrogen injection flow rate and pressure model is the nitrogen injection flow rate and pressure model in the inner pipe of the concentric continuous pipe. The U-shaped well water injection flow rate and pressure model is the second annulus water injection flow rate and pressure model between the combustible casing and the outer pipe of the underground gasification concentric continuous pipe in the U-shaped well.

11. A computer program product, comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the method for establishing the flow rate and pressure model of injected fluid in a coal seam U-shaped well as described in any one of claims 1 to 9.

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