Pressure control well cementation annulus return pressure calculation method and device based on annulus return displacement

Abstract

The invention relates to the technical field of pressure control well cementation, in particular to a pressure control well cementation annulus return pressure calculation method and device based on annulus return displacement. Determining hydrostatic column pressure generated by the annulus fluid in combination with wellhead annulus return displacement; determining annulus friction pressure loss by combining the wellhead annulus return displacement; determining the wellbore pressure by combining the annulus friction resistance pressure loss and the hydrostatic column pressure generated by the annulus fluid; and according to the pressure-controlled well cementation annulus return pressure value range condition, the pressure-controlled well cementation annulus return pressure value range is determined. The pressure control well cementation annulus return pressure is calculated in combination with the real-time wellhead annulus return displacement, so that the obtained pressure control well cementation annulus return pressure better conforms to the real-time working condition and is more accurate, it is ensured that the wellhead pressure is within the controllable range so as to ensure the stability of the wellhead pressure, and the method has the advantages of being high in precision, monitoring in real time, adapting to the complex working condition and the like; and the method has important guiding significance on field well cementation operation and has great popularization potential at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of controlled pressure cementing, in particular to a method and a device for calculating annular back pressure of controlled pressure cementing based on annular return displacement. Background Art

[0002] Controlled pressure cementing is an important process in the field of cementing in petroleum engineering. It effectively prevents adverse effects such as wellbore wall rupture and environmental pollution caused by wellbore overflow and leakage by controlling the pressure during cementing construction. In actual operation, controlled pressure cementing involves the adjustment and control of many parameters, among which the most important parameter is the annular back pressure. In the process of controlled pressure cementing construction, the accuracy and real-time calculation of the annular back pressure are key, because it can help engineers adjust the control parameters and prevent dangerous situations during the construction process.

[0003] Traditional annular space back pressure calculation methods are usually based on design data, and cannot be calculated through real-time collected data. Therefore, there are inaccurate annular space back pressure and poor real-time performance, which can easily lead to inaccurate adjustment of control parameters and dangerous situations during construction. Therefore, traditional annular space back pressure calculation methods are not suitable for complex working conditions. Summary of the invention

[0004] The present invention provides a method and device for calculating the annulus back pressure of a pressure-controlled cementing well based on the annulus return displacement, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems of the existing annulus back pressure calculation method that the annulus back pressure is calculated based on design data and the annulus return displacement collected in real time cannot be used for calculation, which easily leads to inaccurate annulus back pressure calculation and poor real-time performance.

[0005] One of the technical solutions of the present invention is achieved by the following measures: a method for calculating annular back pressure of pressure-controlled cementing based on annular return displacement, comprising:

[0006] Obtain real-time collection of wellhead annulus return displacement;

[0007] Combined with the wellhead annulus return displacement, the dynamic height of various cementing working fluids after entering the annulus is determined, and combined with the dynamic height of various cementing working fluids after entering the annulus, the static liquid column pressure generated by the annular fluid is calculated. The dynamic height calculation formula of various cementing working fluids after entering the annulus is as follows:

[0008]

[0009] Where H is the well depth; i is the type of fluid in the annulus; n is the total type of cementing fluid; D o is the average open hole diameter; D w D is the outer diameter of the casing; in is the inner diameter of the casing; t is the construction time; Q is the wellhead annulus return displacement collected in real time; Vi is the volume of the i-th cementing working fluid;

[0010] The annular flow rate is determined in combination with the wellhead annular return displacement, and the annular friction pressure loss is calculated in combination with the annular flow rate and the dynamic height of various cementing working fluids after entering the annular space. The annular flow rate calculation formula is as follows:

[0011]

[0012] Where v is the annular velocity; Q is the wellhead annular return displacement collected in real time; D o is the average open hole diameter; D w is the outer diameter of the casing;

[0013] The wellbore pressure is determined by combining the annular friction pressure loss and the hydrostatic column pressure generated by the annular fluid;

[0014] Set the controlled pressure cementing annulus back pressure value range conditions, and determine the controlled pressure cementing annulus back pressure value range according to the controlled pressure cementing annulus back pressure value range conditions, where the controlled pressure cementing annulus back pressure value range conditions are as follows:

[0015] (P p -P)<P Back <(P b -P)

[0016] Among them, P Back P is the annular back pressure of the controlled pressure cementing; p is the formation pore pressure; P b is the formation fracture pressure; P is the wellbore pressure.

[0017] The following are further optimizations and / or improvements to the above technical solutions:

[0018] The above formula is combined with the dynamic height of various cementing working fluids after entering the annulus to calculate the static liquid column pressure generated by the annulus fluid:

[0019]

[0020] Among them, ρ1 is the density of the i-th cementing fluid; g is the gravitational acceleration.

[0021] The above calculation of annular friction and pressure loss is based on the annular flow rate and the dynamic height of various cementing fluids after entering the annular space, including:

[0022] Determine the Reynolds number of each cementing fluid at annular flow velocity;

[0023] Substitute the Reynolds number into the preset flow state discrimination condition to determine the flow state of the cementing working fluid, where the flow state discrimination condition is as follows:

[0024] When Re<3250-1150×n, the flow state is laminar flow;

[0025] When 3250-1150×n<Re, the flow state is turbulent flow;

[0026] Calculate the corresponding friction coefficient according to the flow pattern;

[0027] The annular friction pressure loss is determined based on the friction coefficient and the dynamic height of various cementing working fluids after entering the annular space.

[0028] The above Reynolds numbers include the Reynolds numbers of the Bingham mode, the power law mode, and the Herbach mode, which are as follows:

[0029] Bingham mode Reynolds number calculation formula:

[0030]

[0031] The formula for calculating the Reynolds number in power-law mode is:

[0032]

[0033] The formula for calculating the Reynolds number of the Herbach mode is:

[0034]

[0035] Among them, μ p is the plastic viscosity of the Bingham fluid; τ0 is the yield stress of the fluid; n is the fluidity index of the fluid; k is the consistency coefficient of the fluid.

[0036] The above-mentioned annular friction pressure loss is determined based on the friction coefficient and the dynamic height of various cementing working fluids after entering the annular space, as follows:

[0037]

[0038] Among them, p f is the annular friction pressure loss; H is the well depth; i is the type of fluid in the annular space; n is the total type of cementing working fluid; D o is the average open hole diameter; D w is the outer diameter of the casing; Q is the real-time collected wellhead annulus return displacement; ρ1 is the density of the i-th cementing working fluid; f1 is the friction coefficient of the i-th flow state; h i (t) is the dynamic height of various cementing fluids after entering the annulus.

[0039] The second technical solution of the present invention is achieved by the following measures: a pressure-controlled cementing annulus back pressure calculation device based on annulus return displacement, characterized in that it includes:

[0040] An acquisition unit is used to acquire the wellhead annulus return displacement collected in real time;

[0041] The first intermediate quantity calculation unit determines the dynamic height of various cementing working fluids after entering the annulus in combination with the wellhead annulus return displacement, and calculates the static liquid column pressure generated by the annulus fluid in combination with the dynamic height of various cementing working fluids after entering the annulus. The calculation formula for the dynamic height of various cementing working fluids after entering the annulus is as follows:

[0042]

[0043] Where H is the well depth; i is the type of fluid in the annulus; n is the total type of cementing fluid; D o is the average open hole diameter; D w D is the outer diameter of the casing; in is the inner diameter of the casing; t is the construction time; Q is the wellhead annulus return displacement collected in real time; V i is the volume of the i-th cementing working fluid;

[0044] The second intermediate quantity calculation unit determines the annular flow rate in combination with the wellhead annular return displacement, and calculates the annular friction pressure loss in combination with the annular flow rate and the dynamic height of various cementing working fluids after entering the annular space. The annular flow rate calculation formula is as follows:

[0045]

[0046] Where v is the annular velocity; Q is the wellhead annular return displacement collected in real time; D o is the average open hole diameter; D w is the outer diameter of the casing;

[0047] The third intermediate quantity calculation unit determines the wellbore pressure by combining the annular friction pressure loss and the hydrostatic column pressure generated by the annular fluid;

[0048] The annular back pressure selection unit sets the value range conditions of the annular back pressure of the controlled pressure cementing well. The value range of the annular back pressure of the controlled pressure cementing well is determined according to the value range conditions of the annular back pressure of the controlled pressure cementing well. The value range conditions of the annular back pressure of the controlled pressure cementing well are as follows:

[0049] (P p -P)<P Back <(P b -P)

[0050] Among them, P Back P is the annular back pressure of the controlled pressure cementing; p is the formation pore pressure; P b is the formation fracture pressure; P is the wellbore pressure.

[0051] The following are further optimizations and / or improvements to the above technical solutions:

[0052] The second intermediate quantity calculation unit comprises:

[0053] Reynolds number generation module, to determine the Reynolds number of each cementing fluid at the annular flow velocity;

[0054] The flow state discrimination module brings the Reynolds number into the preset flow state discrimination conditions to determine the flow state of the cementing working fluid, where the flow state discrimination conditions are as follows:

[0055] When Re<3250-1150×n, the flow state is laminar flow;

[0056] When 3250-1150×n<Re, the flow state is turbulent flow;

[0057] The friction coefficient generating unit calculates the corresponding friction coefficient according to the flow state;

[0058] The friction and pressure loss generating unit determines the annular space friction and pressure loss according to the friction coefficient and the dynamic height of various cementing working fluids after entering the annular space.

[0059] The present invention calculates the controlled pressure cementing annulus back pressure in combination with the real-time wellhead annulus return displacement, so that the obtained controlled pressure cementing annulus back pressure is more in line with the real-time working conditions and more accurate, ensuring that the wellhead pressure is within a controllable range to ensure the stability of the wellhead pressure. Compared with the traditional method of calculating the controlled pressure cementing annulus back pressure based on design data, the present invention has the advantages of high accuracy, real-time monitoring, and adaptability to complex working conditions, etc., and has important guiding significance for on-site cementing operations, and also has great promotion potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Attached Figure 1 The figure is a flow chart of the method of the present invention.

[0061] Attached Figure 2 The present invention is a flowchart of a method for determining annular friction pressure loss in an embodiment of the present invention.

[0062] Attached Figure 3 It is a schematic diagram of the device structure of the present invention.

[0063] Attached Figure 4 Schematic diagram of the structure of the second intermediate quantity calculation unit in an embodiment of the present invention. DETAILED DESCRIPTION

[0064] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0065] The present invention will be further described below in conjunction with embodiments and drawings:

[0066] Embodiment 1: As attached Figure 1 As shown, the embodiment of the present invention discloses a method for calculating annular back pressure of controlled pressure cementing based on annular return displacement, which is characterized by comprising:

[0067] Step S101, obtaining the wellhead annulus return displacement collected in real time;

[0068] Step S102, combining the wellhead annulus return displacement, determining the dynamic height of each type of cementing working fluid after entering the annulus, and calculating the static liquid column pressure generated by the annular fluid based on the dynamic height of each type of cementing working fluid after entering the annulus, wherein the dynamic height calculation formula of each type of cementing working fluid after entering the annulus is as follows:

[0069]

[0070] Where H is the well depth, m; i is the type of fluid in the annulus; n is the total type of cementing fluid; D o is the average open hole diameter, m; D w is the outer diameter of the casing, m; D in is the inner diameter of the casing, m; t is the construction time, min; Q is the real-time collected wellhead annulus return displacement, m 3 / min; V i is the volume of the i-th cementing fluid, m 3 ;

[0071] Step S103, the annular flow rate is determined in combination with the wellhead annular return displacement, and the annular friction pressure loss is calculated in combination with the annular flow rate and the dynamic height of various cementing working fluids after entering the annular space, wherein the annular flow rate calculation formula is as follows:

[0072]

[0073] Where v is the annular velocity; Q is the wellhead annular return displacement collected in real time, m3 / min; D o is the average open hole diameter, m; D w is the outer diameter of the casing, m;

[0074] Step S104, determining the wellbore pressure by combining the annular friction pressure loss and the hydrostatic column pressure generated by the annular fluid;

[0075] Step S105, setting the controlled pressure cementing annulus back pressure value range conditions, and determining the controlled pressure cementing annulus back pressure value range according to the controlled pressure cementing annulus back pressure value range conditions, wherein the controlled pressure cementing annulus back pressure value range conditions are as follows:

[0076] (P p -P)<P Back <(P b -P)

[0077] Among them, P Back P is the annular back pressure of the controlled pressure cementing; p is the formation pore pressure, MPa; P bis the formation fracture pressure, MPa; P is the wellbore pressure.

[0078] The present invention discloses a method for calculating the annulus back pressure of a pressure-controlled cementing well based on the annulus return displacement, which collects the wellhead annulus return displacement in real time, uses the wellhead annulus return displacement to determine the hydrostatic column pressure and the annulus friction pressure loss generated by the annulus fluid, and obtains the value range of the annulus back pressure of the pressure-controlled cementing well based on the hydrostatic column pressure and the annulus friction pressure loss. Based on this, the present invention combines the real-time wellhead annulus return displacement to make the obtained pressure-controlled cementing well annulus back pressure more in line with the real-time working condition and more accurate, ensuring that the wellhead pressure is within a controllable range to ensure the stability of the wellhead pressure. Compared with the traditional method of calculating the annulus back pressure of the pressure-controlled cementing well based on design data, the method has the advantages of high precision, real-time monitoring, and adaptability to complex working conditions, etc., and has important guiding significance for on-site cementing operations, and also has great promotion potential.

[0079] Embodiment 2: As attached Figure 1 , 2 As shown, an embodiment of the present invention discloses a method for calculating annular back pressure of controlled pressure cementing based on annular return displacement, comprising:

[0080] Step S201, obtaining the wellhead annulus return displacement collected in real time.

[0081] Step S202, combining the wellhead annulus return displacement, determining the dynamic height of various cementing working fluids after entering the annulus, and calculating the static liquid column pressure generated by the annulus fluid based on the dynamic height of various cementing working fluids after entering the annulus, including:

[0082] (1) Combined with the wellhead annulus return displacement, determine the dynamic height of various cementing working fluids after entering the annulus. The formula is as follows:

[0083]

[0084] Among them, ρ1 is the density of the i-th cementing fluid; g is the gravitational acceleration.

[0085] (2) The static liquid column pressure generated by the annular fluid is calculated based on the dynamic height of various cementing working fluids after entering the annular space. The dynamic height calculation formula of various cementing working fluids after entering the annular space is as follows:

[0086]

[0087] Where H is the well depth, m; i is the type of fluid in the annulus; n is the total type of cementing fluid; D o is the average open hole diameter, m; D w is the outer diameter of the casing, m; D in is the inner diameter of the casing, m; t is the construction time, min; Q is the real-time collected wellhead annulus return displacement, m 3 / min; V i is the volume of the i-th cementing fluid, m 3 .

[0088] Step S203, determining the annular flow rate in combination with the wellhead annular return displacement, and calculating the annular friction pressure loss in combination with the annular flow rate and the dynamic height of various cementing working fluids after entering the annular space, including:

[0089] (1) Determine the annular flow rate based on the wellhead annular return displacement. The annular flow rate calculation formula is as follows:

[0090]

[0091] Where v is the annular velocity; Q is the wellhead annular return displacement collected in real time, m3 / min; D o is the average open hole diameter, m; D w is the outer diameter of the casing, m.

[0092] (2) As attached Figure 2 As shown in the figure, the annular friction pressure loss is calculated by combining the annular flow velocity and the dynamic height of various cementing working fluids after entering the annular space, including:

[0093] Step 301, determining the Reynolds number of each cementing working fluid at the annular flow velocity, the Reynolds number includes Bingham mode, power law mode, and Herbach mode, which are as follows:

[0094] Bingham mode Reynolds number calculation formula:

[0095]

[0096] The formula for calculating the Reynolds number in power-law mode is:

[0097]

[0098] The formula for calculating the Reynolds number of the Herbach mode is:

[0099]

[0100] Among them, μ p is the plastic viscosity of the Bingham fluid, Pa·s; τ0 is the yield stress of the fluid, Pa; n is the fluidity index of the fluid, dimensionless; k is the consistency coefficient of the fluid, Pa·sn.

[0101] Step 302, the Reynolds number is brought into a preset flow state discrimination condition to determine the flow state of the cementing working fluid, wherein the flow state discrimination condition is as follows:

[0102] When Re<3250-1150×n, the flow state is laminar flow;

[0103] When 3250-1150×n<Re, the flow state is turbulent flow.

[0104] Step 303, calculating the corresponding friction coefficient according to the flow state;

[0105] In this step, calculating the corresponding friction coefficient according to the flow state is a conventional setting. This embodiment provides a method for calculating the friction coefficient of the power-law mode fluid, and the rest will not be repeated.

[0106] When Re<3250-1150×n, the flow state is laminar flow, and the friction coefficient calculation formula is:

[0107]

[0108] When 3250-1150×n<Re, the flow state is turbulent flow, and the friction coefficient calculation formula is:

[0109]

[0110] Among them, f s is the laminar flow friction coefficient; f is the turbulent flow friction coefficient; ρ i is the density of the i-th cementing fluid, Kg / m 3 .

[0111] Step 304, the annular friction pressure loss is determined according to the friction coefficient and the dynamic height of various cementing working fluids after entering the annular space, as follows:

[0112]

[0113] Among them, p f is the annular friction pressure loss; H is the well depth; i is the type of fluid in the annular space; n is the total type of cementing working fluid; D o is the average open hole diameter; D w is the outer diameter of the casing; Q is the real-time collected wellhead annulus return displacement; ρ1 is the density of the i-th cementing working fluid; f1 is the friction coefficient of the i-th flow state; h i (t) is the dynamic height of various cementing fluids after entering the annulus.

[0114] Step S204, combining the annular friction pressure loss and the hydrostatic column pressure generated by the annular fluid, determines the wellbore pressure, as follows:

[0115] P=P al +P f

[0116] Among them, P al P is the hydrostatic column pressure generated by the annular fluid; f is the annular friction pressure loss.

[0117] Step S205, setting the controlled pressure cementing annulus back pressure value range conditions, and determining the controlled pressure cementing annulus back pressure value range according to the controlled pressure cementing annulus back pressure value range conditions, wherein the controlled pressure cementing annulus back pressure value range conditions are as follows:

[0118] (P p -P)<P Back <(P b -P)

[0119] Among them, P Back P is the annular back pressure of the controlled pressure cementing; p is the formation pore pressure; P b is the formation fracture pressure; P is the wellbore pressure.

[0120] The controlled pressure cementing annulus back pressure in this step is the controlled pressure cementing annulus back pressure compensation value, which is the controlled pressure cementing annulus back pressure that needs to be applied.

[0121] Embodiment 3: As attached Figure 3 As shown, the embodiment of the present invention discloses a pressure-controlled cementing annulus back pressure calculation device based on annulus return displacement, comprising:

[0122] An acquisition unit is used to acquire the wellhead annulus return displacement collected in real time;

[0123] The first intermediate quantity calculation unit determines the dynamic height of various cementing working fluids after entering the annulus in combination with the wellhead annulus return displacement, and calculates the static liquid column pressure generated by the annulus fluid in combination with the dynamic height of various cementing working fluids after entering the annulus. The calculation formula for the dynamic height of various cementing working fluids after entering the annulus is as follows:

[0124]

[0125] Where H is the well depth; i is the type of fluid in the annulus; n is the total type of cementing fluid; D o is the average open hole diameter; D w D is the outer diameter of the casing; in is the inner diameter of the casing; t is the construction time; Q is the wellhead annulus return displacement collected in real time; V i is the volume of the i-th cementing working fluid;

[0126] The second intermediate quantity calculation unit determines the annular flow rate in combination with the wellhead annular return displacement, and calculates the annular friction pressure loss in combination with the annular flow rate and the dynamic height of various cementing working fluids after entering the annular space. The annular flow rate calculation formula is as follows:

[0127]

[0128] Where v is the annular velocity; Q is the wellhead annular return displacement collected in real time; D ois the average open hole diameter; D w is the outer diameter of the casing;

[0129] The third intermediate quantity calculation unit determines the wellbore pressure by combining the annular friction pressure loss and the hydrostatic column pressure generated by the annular fluid;

[0130] The annular back pressure selection unit sets the value range conditions of the annular back pressure of the controlled pressure cementing well. The value range of the annular back pressure of the controlled pressure cementing well is determined according to the value range conditions of the annular back pressure of the controlled pressure cementing well. The value range conditions of the annular back pressure of the controlled pressure cementing well are as follows:

[0131] (P p -P)<P Back <(P b -P)

[0132] Among them, P Back P is the annular back pressure of the controlled pressure cementing; p is the formation pore pressure; P b is the formation fracture pressure; P is the wellbore pressure.

[0133] Further, as attached Figure 4 As shown, the second intermediate quantity calculation unit in the above embodiment includes:

[0134] Reynolds number generation module, to determine the Reynolds number of each cementing fluid at the annular flow velocity;

[0135] The flow state discrimination module brings the Reynolds number into the preset flow state discrimination conditions to determine the flow state of the cementing working fluid, where the flow state discrimination conditions are as follows:

[0136] When Re<3250-1150×n, the flow state is laminar flow;

[0137] When 3250-1150×n<Re, the flow state is turbulent flow;

[0138] The friction coefficient generating unit calculates the corresponding friction coefficient according to the flow state;

[0139] The friction and pressure loss generating unit determines the annular space friction and pressure loss according to the calculated friction coefficient and the dynamic height of various cementing working fluids after entering the annular space.

[0140] Embodiment 4: The embodiment of the present invention discloses a storage medium, on which a computer program readable by a computer is stored, and the computer program is configured to execute a method for calculating annulus back pressure of a pressure-controlled cementing well based on annulus return displacement when running.

[0141] The above storage medium may include, but is not limited to: a USB flash drive, a read-only memory, a mobile hard disk, a magnetic disk or an optical disk, and other media that can store computer programs.

[0142] Embodiment 5: The embodiment of the present invention discloses an electronic device, including a processor and a memory, wherein the memory stores a computer program, and the computer program is loaded and executed by the processor to implement a method for calculating annulus back pressure of controlled pressure cementing based on annulus return displacement.

[0143] The processor may be a central processing unit (CPU), a general purpose processor, a digital signal processor (DSP), an ASIC, an FPGA or other programmable logic device, a transistor logic device, a hardware component or any combination thereof. It may implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. It may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, and the like. The memory may include, but is not limited to, various media that can store computer programs, such as a USB flash drive, a read-only memory, a mobile hard disk, a magnetic disk or an optical disk.

[0144] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0145] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0146] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0147] The above technical features constitute the best embodiment of the present invention, which has strong adaptability and best implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A method for calculating annular back pressure of controlled pressure cementing based on annular return displacement, characterized in that: include: Obtain real-time collection of wellhead annulus return displacement; Combined with the wellhead annulus return displacement, the dynamic height of various cementing working fluids after entering the annulus is determined, and combined with the dynamic height of various cementing working fluids after entering the annulus, the static liquid column pressure generated by the annular fluid is calculated. The dynamic height calculation formula of various cementing working fluids after entering the annulus is as follows: Where H is the well depth; i is the type of fluid in the annulus; n is the total type of cementing fluid; D o is the average open hole diameter; D w D is the outer diameter of the casing; in is the inner diameter of the casing; t is the construction time; Q is the wellhead annulus return displacement collected in real time; V i is the volume of the i-th cementing working fluid; The annular flow rate is determined in combination with the wellhead annular return displacement, and the annular friction pressure loss is calculated in combination with the annular flow rate and the dynamic height of various cementing working fluids after entering the annular space. The annular flow rate calculation formula is as follows: Where v is the annular velocity; Q is the wellhead annular return displacement collected in real time; D o is the average open hole diameter; D w is the outer diameter of the casing; The wellbore pressure is determined by combining the annular friction pressure loss and the hydrostatic column pressure generated by the annular fluid; Set the controlled pressure cementing annulus back pressure value range conditions, and determine the controlled pressure cementing annulus back pressure value range according to the controlled pressure cementing annulus back pressure value range conditions, where the controlled pressure cementing annulus back pressure value range conditions are as follows: (P p -P)<P Back <(P b -P) Among them, P Back P is the annular back pressure of the controlled pressure cementing; p is the formation pore pressure; P b is the formation fracture pressure; P is the wellbore pressure.

2. The method for calculating annular back pressure of controlled pressure cementing based on annular return displacement according to claim 1, characterized in that: The static liquid column pressure generated by the annular fluid is calculated by combining the dynamic height of various cementing working fluids after entering the annular space through the following formula: Among them, ρ1 is the density of the i-th cementing fluid; g is the gravitational acceleration.

3. The method for calculating annular back pressure of controlled pressure cementing based on annular return displacement according to claim 1 or 2, characterized in that: The annular friction pressure loss is calculated by combining the annular flow rate and the dynamic height of various cementing working fluids after entering the annular space, including: Determine the Reynolds number of each cementing fluid at annular flow velocity; Substitute the Reynolds number into the preset flow state discrimination condition to determine the flow state of the cementing working fluid, where the flow state discrimination condition is as follows: When Re<3250-1150×n, the flow state is laminar flow; When 3250-1150×n<Re, the flow state is turbulent flow; Calculate the corresponding friction coefficient according to the flow pattern; The annular friction pressure loss is determined based on the friction coefficient and the dynamic height of various cementing working fluids after entering the annular space.

4. The method for calculating annular back pressure of controlled pressure cementing based on annular return displacement according to claim 3, characterized in that: The Reynolds number includes the Reynolds number of Bingham mode, power law mode, and Herbach mode, which are as follows: Bingham mode Reynolds number calculation formula: The formula for calculating the Reynolds number in power law mode is: The Herbach mode Reynolds number calculation formula is: Among them, μ p is the plastic viscosity of the Bingham fluid; τ0 is the yield stress of the fluid; n is the fluidity index of the fluid; k is the consistency coefficient of the fluid.

5. The method for calculating annular back pressure of controlled pressure cementing based on annular return displacement according to claim 3, characterized in that: The annular friction pressure loss is determined according to the friction coefficient and the dynamic height of various cementing working fluids after entering the annular space, as follows: Among them, p f is the annular friction pressure loss; H is the well depth; i is the type of fluid in the annular space; n is the total type of cementing working fluid; D o is the average open hole diameter; D w is the outer diameter of the casing; Q is the real-time collected wellhead annulus return displacement; ρ1 is the density of the i-th cementing working fluid; f1 is the friction coefficient of the i-th flow state; h i (t) is the dynamic height of various cementing fluids after entering the annulus.

6. A device for calculating annular back pressure of controlled pressure cementing based on annular return displacement using the method as claimed in any one of claims 1 to 5, characterized in that: include: An acquisition unit is used to acquire the wellhead annulus return displacement collected in real time; The first intermediate quantity calculation unit determines the dynamic height of various cementing working fluids after entering the annulus in combination with the wellhead annulus return displacement, and calculates the static liquid column pressure generated by the annulus fluid in combination with the dynamic height of various cementing working fluids after entering the annulus. The calculation formula for the dynamic height of various cementing working fluids after entering the annulus is as follows: Where H is the well depth; i is the type of fluid in the annulus; n is the total type of cementing fluid; D o is the average open hole diameter; D w D is the outer diameter of the casing; in is the inner diameter of the casing; t is the construction time; Q is the wellhead annulus return displacement collected in real time; V i is the volume of the i-th cementing working fluid; The second intermediate quantity calculation unit determines the annular flow rate in combination with the wellhead annular return displacement, and calculates the annular friction pressure loss in combination with the annular flow rate and the dynamic height of various cementing working fluids after entering the annular space. The annular flow rate calculation formula is as follows: Where v is the annular velocity; Q is the wellhead annular return displacement collected in real time; D o is the average open hole diameter; D w is the outer diameter of the casing; The third intermediate quantity calculation unit determines the wellbore pressure by combining the annular friction pressure loss and the hydrostatic column pressure generated by the annular fluid; The annular back pressure selection unit sets the value range conditions of the annular back pressure of the controlled pressure cementing well. The value range of the annular back pressure of the controlled pressure cementing well is determined according to the value range conditions of the annular back pressure of the controlled pressure cementing well. The value range conditions of the annular back pressure of the controlled pressure cementing well are as follows: (P p -P)<P Back <(P b -P) Among them, P Back P is the annular back pressure of the controlled pressure cementing; p is the formation pore pressure; P b is the formation fracture pressure; P is the wellbore pressure.

7. The device for calculating annular back pressure of controlled pressure cementing based on annular return displacement according to claim 6, characterized in that: The second intermediate quantity calculation unit comprises: Reynolds number generation module, to determine the Reynolds number of each cementing fluid at the annular flow velocity; The flow state discrimination module brings the Reynolds number into the preset flow state discrimination conditions to determine the flow state of the cementing working fluid, where the flow state discrimination conditions are as follows: When Re<3250-1150×n, the flow state is laminar flow; When 3250-1150×n<Re, the flow state is turbulent flow; The friction coefficient generating unit calculates the corresponding friction coefficient according to the flow state; The friction and pressure loss generating unit determines the annular space friction and pressure loss according to the friction coefficient and the dynamic height of various cementing working fluids after entering the annular space.

8. A storage medium, characterized in that: The storage medium stores a computer program that can be read by a computer, and the computer program is configured to execute the method for calculating annular back pressure of controlled pressure cementing based on annular return displacement as claimed in any one of claims 1 to 5 when running.

9. An electronic device, characterized in that: The method comprises a processor and a memory, wherein a computer program is stored in the memory, and the computer program is loaded and executed by the processor to implement the method for calculating the annulus back pressure of the pressure-controlled cementing based on the annulus return displacement as claimed in any one of claims 1 to 5.

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