CN105257279A

CN105257279A - Method for measuring working fluid level of pumping well

Info

Publication number: CN105257279A
Application number: CN201510702552.1A
Authority: CN
Inventors: 李少甫; 唐庆; 韩岐清; 冯国强; 马晓雁; 金满库; 卢晨
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2015-10-26
Filing date: 2015-10-26
Publication date: 2016-01-20

Abstract

The invention discloses a method for measuring the working fluid level of an oil pumping well, which comprises the following steps of calculating a model according to a resistance coefficient to obtain the resistance coefficient; acquiring displacement parameters and load parameters of the sucker rod string at different depth positions according to the resistance coefficient, the sucker rod string displacement motion model and the sucker rod string load calculation model; thereby obtaining the displacement parameter and the load parameter of the pump; acquiring a pump work diagram of the pump according to the displacement parameter and the load parameter of the pump; and acquiring the working fluid level parameter of the pumping well according to the pump diagram, the sinking pressure calculation model and the fluid physical property calculation model. The method for measuring the working fluid level of the pumping well can effectively improve the timeliness of the method under the condition of ensuring the calculation precision, and can be applied to an oil well for controlling casing pressure production, so that the error of the calculated working fluid level is reduced.

Description

Method for measuring working fluid level of pumping well

Technical Field

The invention relates to the technical field of petroleum, in particular to a method for measuring the working fluid level of an oil pumping well.

Background

The dynamic liquid level of the pumping well is an important parameter for knowing the liquid supply condition of the oil well, diagnosing the fault of the oil well and evaluating and optimizing the adaptability of the oil extraction process. At present, the main testing method of the working fluid level of the oil well is a sound wave reflection method, and the method has the main problems that: the method includes the steps of relying on manual operation of workers; certain unsafe factors exist in the wellhead sound generating device; the change of the working fluid level cannot be tracked on line by testing once a month; and for an oil well with the working fluid level depth larger than 1000 m, the oil well is easily influenced by other working conditions, and the test error is relatively large.

In recent years, due to the development of indicator diagram testing means, the technology for calculating the working fluid level according to the indicator diagram is changed from theory to application, the change trend tracking technology of the working fluid level is gradually established and continuously improved, however, when the working fluid level of an oil well is calculated by surveying, mapping and actually measuring the static load indicator diagram, the influence of factors such as inertial load, vibration load, friction load and the like can be effectively eliminated, the calculation result precision is relatively high, meanwhile, the acquisition of the upper static load and the lower static load is relatively complex and tedious, the checking is difficult, once the working condition of the oil well changes, the static load indicator diagram also needs to be corrected, the timeliness is poor, and when the working fluid level of the oil well is calculated by adopting the method, the influence of casing pressure is not considered, and the calculated working fluid level has the problem of relatively high error for an oil well for controlling casing pressure production.

Disclosure of Invention

The invention provides a method for measuring the working fluid level of an oil pumping well, which can effectively improve the timeliness of the method under the condition of ensuring the calculation precision, and can be applied to an oil well for controlling casing pressure production, so that the error of the calculated working fluid level is reduced.

The embodiment of the invention provides a method for measuring the working fluid level of an oil pumping well, which comprises the following steps:

acquiring a resistance coefficient corresponding to the pumping well according to the resistance coefficient calculation model;

acquiring the displacement parameter of the sucker rod string according to the resistance coefficient and the sucker rod string displacement motion model; and

acquiring a load parameter of the sucker rod string according to the resistance coefficient and a sucker rod string load calculation model;

acquiring the displacement parameter of a pump at the lower part of the sucker rod string according to the displacement parameter of the sucker rod string; acquiring the load parameter of the pump according to the load parameter of the sucker rod string;

acquiring a pump work diagram of the pump according to the displacement parameter of the pump and the load parameter of the pump;

acquiring a sinking pressure parameter of a suction inlet of the pump according to the pump diagram;

obtaining fluid physical property parameters of the shaft according to the temperature distribution of the shaft of the pumping well and a fluid physical property calculation model;

acquiring pressure distribution parameters in an annular space between an oil pipe and a casing of the pumping well according to the sinking pressure parameters of the suction inlet and the physical property parameters of the fluid;

and acquiring the working fluid level parameter of the pumping well according to the pressure distribution parameter.

Optionally, the resistance coefficient calculation model specifically includes:

C = \frac{2 π μ}{ρ_{r} A_{r}} {\frac{1}{\ln m} + \frac{4}{B_{2}} (B_{1} + 1) {B_{1} + \frac{2}{\frac{ω L}{a} \frac{1}{s i n \frac{ω l}{a}} + c o s \frac{ω l}{a}}}};

wherein,

m = \frac{D_{t}}{D_{r}}, B_{1} = \frac{m^{2} - 1}{2 \ln m} - 1, B_{2} = m^{4} - 1 - \frac{{(m^{2} - 1)}^{2}}{\ln m}

wherein μ represents the liquid viscosity; rho_rThe density of the sucker rod is shown; a. the_rThe sectional area of the sucker rod is shown; d_tRepresents the tubing diameter; d_rThe diameter of the sucker rod is shown; l represents the sucker rod length; c represents a drag coefficient.

Optionally, the obtaining of the displacement parameter of the sucker rod string according to the resistance coefficient and the sucker rod string displacement motion model specifically includes:

substituting the resistance coefficient into the sucker rod string displacement motion model to obtain the displacement parameter of the sucker rod string, wherein the sucker rod string displacement motion model specifically comprises the following steps:

\frac{\partial U (x, t)}{\partial t^{2}} = a^{2} \frac{\partial^{2} (x, t)}{\partial x^{2}} - c \frac{\partial U (x, t)}{\partial t}

in the formula:

u (x, t) represents the displacement of the sucker rod string at the x section at time t;

a represents the speed of sound wave propagation in the rod string.

Optionally, the obtaining a load parameter of the rod string according to the resistance coefficient and the rod string load calculation model specifically includes:

and substituting the resistance coefficient into the sucker rod string load calculation model to obtain the load parameters of the sucker rod string, wherein the sucker rod string load calculation model comprises a sucker rod gravity calculation model, a liquid string load calculation model, a fluid through valve hole resistance calculation model, a sucker rod string inertia load calculation model, a liquid string inertia load calculation model, a pump barrel and plunger friction load calculation model, a sucker rod and liquid friction load calculation model, a pipe liquid friction load calculation model and a sucker rod string uplift force calculation model.

Optionally, the obtaining a sinking pressure parameter of a suction port of the pump according to the pump diagram specifically includes:

selecting upper and lower load points in the pump diagram;

and acquiring sinking pressure parameters of the suction inlet according to the upper and lower load points and a model for calculating the sinking pressure of the suction inlet of the pump.

Optionally, the pump suction inlet submergence pressure calculation model specifically includes:

P_{n} = \frac{2 P_{h} (f_{p} - f_{r})}{f_{p}} + 2 Δ P + \frac{W_{l}}{f_{p}},

wherein Δ P represents the amount of oil production fluid passing through the fixed valve and the traveling valve holePressure drop; w_lRepresenting the well fluid column load.

By one embodiment or a plurality of embodiments, the invention has the following advantages or advantages:

according to the method for measuring the dynamic liquid level of the pumping well, displacement parameters of the sucker rod string and load parameters of the sucker rod string are obtained according to a resistance coefficient calculation model, a sucker rod string displacement motion model and a sucker rod string load calculation model; acquiring the displacement parameter of a pump at the lower part of the sucker rod string according to the displacement parameter of the sucker rod string; acquiring the load parameter of the pump according to the load parameter of the sucker rod string; acquiring a pump work diagram of the pump according to the displacement parameter of the pump and the load parameter of the pump; acquiring a sinking pressure parameter of a suction inlet of the pump according to the pump diagram; obtaining fluid physical property parameters of the shaft according to the temperature distribution of the shaft of the pumping well and a fluid physical property calculation model; acquiring pressure distribution parameters in an annular space between an oil pipe and a casing of the pumping well according to the sinking pressure parameters of the suction inlet and the physical property parameters of the fluid; according to the pressure distribution parameters, obtaining the working fluid level parameters of the pumping well, so that the influence of inertia, vibration and friction load can be eliminated through a resistance coefficient calculation model, a sucker rod string displacement motion model and a sucker rod string load calculation model, the static load of a pump work diagram can be solved, the accuracy of the obtained static load of the pump work diagram is higher, the accuracy of the working fluid level parameters obtained through working fluid level calculation according to the static load of the pump work diagram is improved, and the working fluid level parameters can be obtained in real time through the calculation model, so that the timeliness of the working fluid level parameters can be effectively improved, and the measuring method provided by the application can be used for obtaining the working fluid level parameters according to the pressure distribution parameters in the annular space, so that the measuring method provided by the application can also be applied to an oil well for controlling casing pressure production, so that the error of the calculated working fluid level is reduced.

Drawings

FIG. 1 is a schematic diagram of the operation of a pump in an embodiment of the present invention;

FIG. 2 is a wellbore fluid profile in an embodiment of the invention.

The relevant reference numbers in the figures are as follows:

10-pump cylinder, 11-plunger, 12-traveling valve, 13-fixed valve, 14-sucker rod, 20-gas column section, 21-gas-containing oil column section, 22-mixed liquid section.

Detailed Description

In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.

Before describing the method for measuring the working fluid level of the rod-pumped well of the present invention, it is necessary to understand the working principle of the pump, specifically, referring to fig. 1, the pump includes a pump barrel 10, a plunger 11, a traveling valve 12, a fixed valve 13 and a sucker rod 14, during the operation of the pump, the pressure P (t) in the pump barrel 10 changes with the moving direction of the plunger, and the pressure P (t) is measured by the suction pressure P_iIs raised to the discharge pressure P_POr from P_PDown to P_iThe plunger 11 completes unloading or loading: when the fixed valve 13 is opened, the liquid is sucked into the pump cavity through the hole of the fixed valve 13, and P (t) ═ P_iWhen the plunger 11 is loaded, the pump load is kept unchanged; when the traveling valve 12 is opened, the liquid is discharged out of the pump chamber through the hole of the traveling valve 12, and P (t) ═ P at this time_PThe unloading of the plunger 11 is completed and the pumping load remains unchanged.

If the inertial force of the plunger and the liquid is neglected, the equilibrium equation acting on the plunger should be:

an upstroke:

F_p(t)＝P_p·(f_p-f_r)-P(t)·f_p+W_p+ f formula 1

A down stroke:

F_p(t)＝P_p·f_r-P(t)·f_p+W_p-f equation 2

In formula 1 and formula 2, F_p(t) represents the load of the pump, in units: n; p_pPressure at the top of the traveling valve 12 is expressed in units: pa; p (t) represents the pressure in the pump barrel 10 in units of: pa; w_pRepresents the weight of the plunger 11, unit: n; f represents the frictional resistance between the plunger 11 and the pump cylinder 10, in units: n; f. of_pThe cross-sectional area of the plunger 11 is expressed in units: m is²；f_rRepresents the cross-sectional area of the sucker rod 14, in units: m is²。

The measuring method is used for obtaining the sinking pressure parameter of the pump suction inlet and the pressure distribution parameter so as to obtain the working fluid level surface parameter, and the working fluid level surface parameter comprises the depth of the working fluid level surface.

The invention provides a method for measuring the working fluid level of an oil pumping well, which comprises the following steps:

step 100: and obtaining a resistance coefficient corresponding to the pumping well according to the resistance coefficient calculation model.

In the implementation, the actual stroke of the pump can be obtained by the pump diagram, however, the resistance coefficient must be known before the pump diagram is accurately calculated. In this case, the resistance coefficient may be obtained by a gibbs resistance coefficient calculation model, where the gibbs resistance coefficient calculation model specifically includes:

C = \frac{2 π μ}{ρ_{r} A_{r}} {\frac{1}{\ln m} + \frac{4}{B_{2}} (B_{1} + 1) {B_{1} + \frac{2}{\frac{ω L}{a} \frac{1}{s i n \frac{ω l}{a}} + c o s \frac{ω l}{a}}}}

formula (II)3

m = \frac{D_{t}}{D_{r}}

B_{1} = \frac{m^{2} - 1}{2 \ln m} - 1

B_{2} = m^{4} - 1 - \frac{{(m^{2} - 1)}^{2}}{\ln m}

In equation 3, μ represents the liquid viscosity in units: pa · s; rho_rDensity, unit: kg/m³；A_rCross-sectional area, unit, of sucker rod: m is²；D_tRepresents tubing diameter, in units: m; d_rRepresenting sucker rod diameter, unit: m; l represents sucker rod length, unit: m; a represents the propagation speed of sound waves in the sucker rod string (the propagation speed of sound waves in carbon steel is approximately 4900 m/s); ω represents crank angular velocity; m represents the ratio of the inner diameter of the oil pipe to the diameter of the sucker rod.

Specifically, the formula 3 is only a single-stage sucker rod string calculation model, and is only suitable for a single-stage sucker rod string, the multi-stage sucker rod string can divide the solution into multi-stage calculation, and the tail data of each stage is used as the boundary condition of the next stage of calculation to perform multi-stage solution, so that the multi-stage calculation can be obtained.

Step 101: and obtaining the displacement parameters of the sucker rod string according to the resistance coefficient and the sucker rod string displacement motion model.

In the specific implementation process, the displacement motion model of the sucker rod column can be described by a damped wave equation, which is as follows:

\frac{\partial U (x, t)}{\partial t^{2}} = a^{2} \frac{\partial^{2} (x, t)}{\partial x^{2}} - c \frac{\partial U (x, t)}{\partial t}

equation 4

In equation 4, U (x, t) represents the displacement of the sucker rod string at x section at time t; a represents the propagation speed of sound waves in the sucker rod string (the propagation speed of sound waves in carbon steel is approximately 4900 m/s); thus, after the value of c is obtained in step 100, the value of c is substituted into the sucker rod string displacement motion model, and the displacement parameters of the sucker rod string obtained may be specifically represented by U (x, t).

The boundary conditions of formula 4 are a suspension point dynamic load function d (t) and a polished rod displacement function u (t), and both equations are given by the formula in a truncated fourier series manner:

D (t) = \frac{σ_{0}}{2} + Σ_{n = 1}^{\overset{&OverBar;}{n}} (σ_{n} \cos n ω t + τ_{n} \sin n ω t)

equation 5

U (t) = \frac{ν_{0}}{2} + Σ_{n = 1}^{\overset{&OverBar;}{n}} (ν_{n} \cos n ω t + δ_{n} \sin n ω t)

Equation 6

Because the sucker rod string gravity is not considered in equation 4, the actual dynamic load function D (t) should be the suspension point load minus the sucker rod gravity and the dynamic load function is used as the boundary condition for the model. Fourier coefficient σ of D (t) and U (t)₀、σ_n、τ_nAnd v₀、ν_n、_nThe solution equation is as follows:

σ_{n} = \frac{ω}{π} {&Integral;}_{0}^{T} D (t) \cos n ω t d t, (n = 0, 1, 2 ... ... \overset{&OverBar;}{n})

equation 7

τ_{n} = \frac{ω}{π} {&Integral;}_{0}^{T} D (t) \sin n ω t d t, (n = 0, 1, 2 ... ... \overset{&OverBar;}{n})

Equation 8

v_{n} = \frac{ω}{π} {&Integral;}_{0}^{T} U (t) \cos n ω t d t (n = 0, 1, 2 ... ... \overset{&OverBar;}{n})

Equation 9

δ_{n} = \frac{ω}{π} {&Integral;}_{0}^{T} U (t) \sin n ω t d t, (n = 0, 1, 2 ... ... \overset{&OverBar;}{n})

Equation 10

Wherein in the above formula, ω represents a crank angular velocity; t represents the pumping period.

Specifically, in actual work, d (t) and u (t) are given in the form of indicator diagram data points, and can be determined by area integration of available fourier coefficients, the maximum value of the fourier series n can be 6, and the integral solution is performed by dividing an integral image into 144 blocks of equal width by a dividing method. The equation is simplified and solved by a method of separating variables, and the displacement change relation of the sucker rod string at the x section at the time t is obtained as shown in the following formula:

U (x, t) = \frac{σ}{2 {EA}_{r}} x + \frac{ν_{0}}{2} + Σ_{n = 1}^{\overset{&OverBar;}{n}} [O_{n} (x) \cos n ω t + P_{n} (x) \sin n ω t]

equation 46

the change relation of the dynamic load function at the x section of the sucker rod string at the time t is shown as the following formula:

F (x, t) = {EA}_{r} [\frac{σ_{0}}{2 {EA}_{r}} + Σ_{n = 1}^{\overset{&OverBar;}{n}} [\frac{\partial O_{n} (x)}{\partial x} \cos n ω t + \frac{\partial P_{n} (x)}{\partial x} \sin n ω t]

equation 47

At time t, the total load on the x-section of the rod string, F (x, t) + the weight of the rod string below the x-section of the rod string, is modeled as follows:

O_n(x)＝(K_nchβ_nx+_nshβ_nx)sina_nx+(μ_nshβ_nx+ν_nchβ_nx)cosa_nx equation 48

P_n(x)＝(K_nshβ_nx+_nchβ_nx)cosa_nx+(μ_nchβ_nx+ν_nshβ_nx)sina_nx equation 49

α_{n} = \frac{n ω}{a \sqrt{2}} \sqrt{1 + \sqrt{1 + {(\frac{C}{n ω})}^{2}}}

β_{n} = \frac{n ω}{a \sqrt{2}} \sqrt{- 1 + \sqrt{+ {(\frac{C}{n ω})}^{2}}}

K_{n} = \frac{σ_{n} α_{n} + τ_{n} β_{n}}{{EA}_{r} ({α^{2}}_{n} + β_{n}^{2})}

μ_{n} = \frac{σ_{n} β_{n} - τ_{n} α_{n}}{{EA}_{r} (α_{n}^{2} + β_{n}^{2})}

Step 102: and acquiring the load parameter of the sucker rod string according to the resistance coefficient and the sucker rod string load calculation model.

In a specific implementation process, the resistance coefficient is substituted into the sucker rod string load calculation model to obtain the load parameters of the sucker rod string, wherein the sucker rod string load calculation model comprises a sucker rod gravity calculation model, a liquid column load calculation model, a resistance calculation model of fluid passing through a valve hole, a sucker rod string inertia load calculation model, a liquid column inertia load calculation model, a pump cylinder and plunger friction load calculation model, a sucker rod and liquid friction load calculation model, a pipe-liquid friction load calculation model and a sucker rod string uplift force calculation model.

Specifically, the sucker rod gravity model is used for eliminating the influence of the gravity of the sucker rod string, and the gravity of the sucker rod string with the corresponding length is directly subtracted from the suspension point load calculated in a sectional mode, wherein the calculation model is as follows:

F_r＝q_rgL equation 11

In the formula 11, F_rRepresents the gravity of the sucker rod string in air, unit: n; l represents sucker rod string length in units: m; q. q.s_rRepresents the mass per meter of the rod string, in units: kg/m.

Specifically, the liquid column load calculation model specifically includes:

F_l＝(A_p-A_m)×P_out-A_p×P_inequation 12

In the formula 12, F_lRepresents the liquid column load acting on the plunger, in units: n; a. the_mThe sectional area of the pumping rod at the lowest stage is shown in unit: m 2; a. the_pRepresents the cross-sectional area of the oil pump piston, m 2; p_outRepresenting the pressure at the pump discharge in units: pa; p_inRepresents the pressure at the pump suction, in units: pa.

Specifically, the model for calculating the resistance of the fluid passing through the valve hole is

F_{v} = \frac{1.5 \times 2 \times ρ_{l}}{729 \times μ^{2}} \times \frac{A_{p}^{3}}{f_{0}^{2}} \times {(S_{p} \times N)}^{2}

Equation 13

In the formula 13, F_vRepresents the resistance of the fluid through the valve orifice, in units: n; rho_lDenotes the fluid density, kg/m³；f₀Represents the flow area of the valve orifice, in units: m is²；S_pRepresents the effective stroke of the piston, in units: m; n represents the number of impulses, unit: rpm; μ denotes an experimentally determined valve flow coefficient, calculated by the following formula:

\{\begin{matrix} μ = 0.225 + 0.325 \times {({lgN}_{Re} - 4)}^{1.7} & N_{Re} &GreaterEqual; 10^{4} \\ μ = 0.225 \times {({lgN}_{Re} - 3)}^{0.6} & N_{Re} < 10^{4} \end{matrix}

equation 14

N_{Re} = \frac{d_{V o} \times A_{p} \times S_{p} \times N \times ρ_{l}}{19 \times f_{0} \times μ_{l}}

Equation 15

In equations 14 and 15, d_v0Denotes the valve hole diameter, unit: m; mu.s_lDenotes the fluid viscosity, in units: Pa.S.

Specifically, the calculation model of the inertial load of the sucker rod string is as follows:

equation 16

Equation 17

In equations 16 and 17, F_riRepresenting the rod string inertial load, in units: n; s represents stroke, unit: m; r represents the beam-pumping unit crank radius, in units: m; l represents the pumping unit connecting rod length, unit: and m is selected.

Specifically, the liquid column inertial load calculation model specifically includes:

F_{l i} = \frac{F_{l} \times S \times N^{2}}{1790} \times (1 + r / l) \times \frac{A_{p} - A_{r}}{A_{t} - A_{r}}

equation 18

In the formula 18, F_liRepresents the liquid column inertial load, in units: n; a. the_tRepresents the oil pipe cross-sectional area, unit: m is²。

Specifically, the calculation model of the friction load of the pump cylinder and the plunger specifically comprises the following steps:

F_{p} = 0.94 \times \frac{d_{p}}{d_{e}} - 140

equation 19

In the formula 19, F_pIndicating pump barrelFriction load with plunger, unit: n; d_pRepresents the pump plunger diameter, in units: m; d_eClearance of the plunger from the bushing is expressed in units: m;

specifically, the friction load calculation model of the sucker rod and the liquid specifically is as follows:

F_{r l} = 2 π^{2} {SNμ}_{l} L [\frac{m^{2} - 1}{(m^{2} + 1) \ln (m) - (m^{2} - 1)}]

equation 20

In the formula 20, F_rlRepresents the rod fluid friction load, in units: n; l represents sucker rod length, unit: m; m represents the ratio of the inner diameter of the oil pipe to the diameter of the sucker rod,d_trepresents the tubing inside diameter, in units: m; d_rRepresents the sucker rod inner diameter, in units: and m is selected.

Specifically, the pipe fluid friction load calculation model is

F_{t l} = \frac{F_{r l}}{1.3}

Equation 21

In the formula 21, F_tlRepresents the tube fluid friction load, in units: and N is added.

Specifically, the calculation model of the uplift force of the sucker rod string is

F_rxj＝P_j×(A_rj-A_rj+1) (j ═ 1,2,. m) formula 22

In the formula 22, F_rxjThe hydraulic lifting force of the lower end face of the j-th-level sucker rod is expressed by the following unit: n; p_jThe unit of the fluid pressure borne by the lower end face of the j-th-stage sucker rod is as follows: pa; a. the_rjThe sectional area of the j-th sucker rod is expressed by unit: m is²；A_rj+1Represents the sectional area of the sucker rod of the j +1 th level, unit: m is²(ii) a m represents the number of pumping rod stages.

Step 103: and acquiring the displacement parameter of the pump at the lower part of the sucker rod string according to the displacement parameter of the sucker rod string.

In the specific implementation process, since the displacement parameter of the rod string corresponds to the displacement parameter of the pump, the displacement parameter of the pump can be obtained according to the displacement parameter of the rod string after the displacement parameter of the rod string is obtained in step 101, wherein the displacement parameter of the rod string is the same as the displacement parameter of the pump.

Step 104: and acquiring the load parameters of the pump according to the load parameters of the sucker rod string.

In the specific implementation process, since the load parameter of the rod string corresponds to the load parameter of the pump, after the load parameter of the rod string is obtained in step 102, the load parameter of the pump can be obtained according to the load parameter of the rod string, wherein the load parameter of the rod string is the same as the load parameter of the pump.

Step 105: and acquiring a pump work diagram of the pump according to the displacement parameter of the pump and the load parameter of the pump.

In a specific implementation process, after the displacement parameter of the pump and the load parameter of the pump are obtained, the pump work diagram of the pump can be obtained directly according to the displacement parameter of the pump and the load parameter of the pump.

Specifically, the mathematical model is established for calculation, so that the influences of dynamic load of the sucker rod, expansion and contraction of a rod column and the like are eliminated, and the pump diagram which is regular in shape and can accurately reflect the actual working condition of the pump is obtained. The pump diagram data are used for calculation, so that the influences of dynamic load of the sucker rod, expansion and contraction of the rod column, frictional resistance of the rod column and the like can be effectively eliminated, calculation errors can be effectively reduced, and the dynamic liquid level parameters calculated according to the pump diagram are more accurate.

Step 106: and acquiring a sinking pressure parameter of a suction inlet of the pump according to the pump diagram.

In the specific implementation process, selecting upper and lower load points in the pump diagram; and acquiring sinking pressure parameters of the suction inlet according to the upper and lower load points and a model for calculating the sinking pressure of the suction inlet of the pump.

Specifically, an upper load point and a lower load point in the pump diagram are selected, the sinking pressure parameter of the suction inlet is calculated according to the pump suction inlet sinking pressure calculation model, and the produced fluid of the oil reservoir generates a pressure drop Δ P when passing through a fixed valve and a traveling valve hole, wherein the pump suction inlet sinking pressure calculation model specifically comprises:

Δ P = \frac{1}{729} \cdot \frac{ρ_{l}}{ξ^{2}} \cdot {(\frac{f_{p}}{f_{o}})}^{2} \cdot {(s \cdot n)}^{2}

equation 23

In equation 23: rho_lDensity, unit: kg/m³ξ shows the valve flow coefficient (clear functional relationship with valve hole diameter, liquid viscosity and liquid flow rate, which can be calculated from the functional relationship) f_oRepresents the cross-sectional area of the valve hole, unit: m is²。

N_{Re} = \frac{d_{o} V_{f}}{ν}

Equation 24

In the formula 24, N_ReRepresents the Reynolds number; d_oDenotes the valve pore diameter, unit: m; v_fExpressing the flow velocity, unit: m/s; ν denotes the kinematic viscosity of the liquid, in units: m is²/s。

Wherein the pressure P of the upper part of the travelling valve_pThe calculation model is as follows:

P_p＝P_h+ρ_lgL equation 25

The calculation model of the load of the upstroke pump can be known from formula 3 to formula 22, and specifically includes:

P(t)＝P_n- Δ P equation 26

F_pu＝P_p·(f_p-f_r)-(P_n-ΔP)·f_p+W_p+ f equation 27

The load on the pump after the downstroke of the traveling valve is opened and before it is closed can be calculated by the following equation:

P(t)＝P_n+ Δ P equation 28

F_pd＝P_p·f_r-(P_p+ΔP)·f_p+W_p-f equation 29

From equations 28 and 29, the suction inlet submergence pressure parameter can be obtained as follows:

P_{n} = \frac{2 P_{p} (f_{p} - f_{r})}{f_{p}} + 2 Δ P + \frac{2 f}{f_{p}} - \frac{f_{p u} - f_{p d}}{f_{p}}

equation 30

Neglecting the frictional resistance f, f between the plunger and the pump barrel_pu-f_pdI.e. the oil well fluid column load W_lThe suction inlet sinking pressure parameter can be obtained by indicator diagram data, and specifically comprises:

P_{n} = \frac{2 P_{h} (f_{p} - f_{r})}{f_{p}} + 2 Δ P + \frac{W_{l}}{f_{p}}

equation 31

Obtaining oil well liquid column load W according to oil well indicator diagram_lThe suction inlet sinking pressure parameter can be calculated by using the formula 31.

Step 107: and acquiring fluid physical property parameters of the shaft according to the temperature distribution of the shaft of the pumping well and a fluid physical property calculation model.

In the specific implementation process, since the underground temperature and pressure may have a certain influence on the physical parameters of the wellbore fluid, the influence of the temperature and pressure on the physical parameters of the wellbore fluid and the wellbore temperature gradient distribution must be considered in the calculation process as the temperature distribution parameters.

Wherein, the density calculation model of the crude oil is as follows:

ρ_{o} = \frac{1000 (γ_{o} + 1.206 \times 10^{- 3} R_{s} γ_{g})}{B_{o}}

equation 32

In the formula 32, ρ_oThe density of crude oil at average pressure and average temperature is expressed in units: kg/m³；γ_oRepresents the relative density of crude oil at surface conditions; gamma ray_gRepresents the relative density of the gas at surface conditions; r_sRepresents the dissolved gas-oil ratio under average pressure and average temperature conditions, in units of: m is³/m³；B_oThe volume coefficient of crude oil under the conditions of average pressure and average temperature is shown.

Specifically, the calculation model of the crude oil API degree is as follows:

γ_{A P I} = \frac{141.5}{γ_{o}} - 131.5

equation 33

Specifically, the volume coefficient of the crude oil is specifically as follows:

B_o＝0.972+0.000147F^1.175equation 34

Wherein:

F = 5.615 R_{s} \sqrt{\frac{γ_{g}}{γ_{o}}} + 2.25 T + 40

equation 35

Wherein, the dissolved gas-oil ratio:

R_{s} = \frac{γ_{g} {(1.404 \times 10^{- 4} p)}^{1.0937}}{27.64} \times 10^{\frac{11.172 γ_{A P I}}{1.8 T + 32 + 459.67}} (γ_{A P I} \leq 30)

equation 36

R_{s} = \frac{γ_{g} {(1.404 \times 10^{- 4} p)}^{1.0937}}{56.06} \times 10^{\frac{10.393 γ_{A P I}}{1.8 T + 32 + 459.67}} (γ_{A P I} > 30)

Equation 37

In equations 36 and 37, T represents the average temperature in units of: DEG C; p represents the average pressure, in units: pa.

Specifically, the density of the oil-water mixed liquid is as follows:

ρ_l＝ρ_o(1-f_w)+ρ_wf_wequation 38

In the formula 38, f_wWater content by volume, unit: % of the total weight of the composition.

Specifically, the density of the natural gas is specifically:

ρ_{g} = 3.4844 \times 10^{- 3} \times \frac{γ_{g} p}{Z (T + 273.15)}

equation 39

In equation 39, ρ_gDenotes the density of natural gas at given temperature and pressure conditions, in units: kg/m³。

Specifically, the wellbore temperature field calculation model is as follows:

because the formation temperature changes with the change of the depth, and the change of the temperature can cause the change of the physical parameters of the fluid in the well bore, the formation temperature at different positions must be calculated in the design, the physical parameters of the fluid in the formation are determined according to the temperature, and the temperature distribution along the well bore can be calculated according to an empirical formula:

G = \frac{Q_{l} \times 1000}{24}

equation 40

K_{P} = \frac{1}{1.1573 + 5.246 \times e^{- \frac{G}{1000}}}

Equation 41

B_{A T A} = \frac{2 {πK}_{P}}{G (1 + f_{w})}

Equation 42

t = t_{0} + \frac{t_{r} - t_{0}}{B_{A T A} H} [B_{A T A} L + 1 - e^{- B_{A T A} (H - L)}]

Equation 43

In equations 40, 41, 42, and 43, Q_lRepresents the amount of oil well produced, unit: t/d; f. of_wExpressed mass water content, unit: percent; t is t₀Represents the temperature of the earth's surface constant temperature layer, unit: DEG C; t is t_rRepresents the reservoir temperature, unit: DEG C; h represents the mid-reservoir depth in units: m; l represents the calculated point depth, in units: and m is selected.

Step 108: and acquiring pressure distribution parameters in an annular space between an oil pipe and a casing of the pumping well according to the sinking pressure parameters of the suction inlet and the physical property parameters of the fluid.

In practice, and referring to fig. 2, the fluid in the annulus between the tubing and the casing is differentiated by gravity, generally forming three sections: the gas column section 20, the gas-oil column section 21 and the mixed liquid section 22 for mixing oil, gas and water, wherein the sinking pressure parameter of the suction inlet is the sum of the two pressure sections of the gas column section 20 and the gas-oil column section 21:

P_n＝P_D+ΔP_oequation 44

In formula 44, P_nRepresents the suction inlet sinking pressure, unit: pa; p_DPressure at the meniscus, unit: pa; delta P_oRepresents the pressure generated by the liquid surface to the oil column at the pump, in units: pa.

WhereinAnnular gas column pressure P_DThe calculation method is as follows:

because the annular flow cross section of the rod-pumped well is relatively large, the air flow is generally not very large, and therefore the pressure loss caused by friction resistance and kinetic energy can be ignored. Considering that the density of the gas column changes with the pressure and temperature, the pressure at the meniscus is determined by the following equation:

P_{D} (X) = P_{s o} \exp (\frac{ρ_{g o} {gxT}_{0}}{P_{0} T_{a v} Z_{a v}})

equation 45

In equation 45, x represents depth from the wellhead in units: m; g represents the acceleration of gravity, unit: m/s 2; t is₀、P₀Denotes the temperature and pressure under standard conditions, in units: k and MPa; rho_g0Denotes the gas density under standard conditions, in units: kg/m 3; t is_avRepresents the gas compression factor at average temperature; z_avRepresents the gas compression factor at average temperature and pressure; p_soIndicating the well head casing pressure (taking its absolute value), singlyBit: MPa; p_D(x) Represents the gas column pressure at x (in its absolute value), in units: MPa.

Further, the pressure Δ P generated by the oil column at the pump from the working fluid level_oThe calculation method is as follows:

in particular, the pressure Δ P generated by the oil column at the pump from the working fluid level_oThe method can be obtained by calculating the pressure gradient distribution of the oil column in the air of the oil sleeve ring through a multiphase flow model.

Step 109: and acquiring the working fluid level parameter of the pumping well according to the pressure distribution parameter.

In the specific implementation process, an indicator diagram of the pumping well can be drawn; firstly, determining the liquid column load; then calculating a pump diagram and determining the liquid load; then calculating the inlet sinking pressure parameter; then calculating the pressure distribution parameter of the annular liquid column; and then calculating pressure distribution parameters in the annular space, and finally determining that the intersection point of the annular liquid column pressure distribution parameters and the pressure distribution parameters in the annular space is the working fluid level parameters, wherein the parameters in the application file can be represented by curves.

In the practical application process, the comparison table of the working fluid level parameter obtained by the measuring method of the application and the actual working fluid level depth is specifically shown in the following table 1.

TABLE 1

The method comprises the steps of establishing a dynamic liquid level prediction model of the pumping unit well, converting a ground indicator diagram into a pump indicator diagram, carrying out quantitative processing on the pump indicator diagram, and further calculating by combining basic data of an oil well and physical parameters of crude oil to obtain the dynamic liquid level of the oil well. Through field tests, the prediction precision is about 3%, the method has the advantages of high precision and good reliability, and the prediction can be carried out in real time, so that the prediction real-time performance is improved.

In the practical application process, taking a certain practical production oil well as an example, the dynamic liquid level depth of the oil well is measured by the measuring method, and relevant technical data of the oil well are firstly collected, wherein the relevant technical data comprise basic production data of normal production of the oil well, and data of polished rod stroke and stroke frequency of the oil pumping unit, pump diameter of the oil well pump, pump-down depth, crude oil density, water content and the like. The multi-stage sucker rod string combination system also comprises the diameter, the length and the steel grade information of each stage of sucker rod string, indicator diagram data is load displacement data, and specifically acquired oil well data are shown in tables 2 and 3.

Depth in oil layer/m	1921.95	Pump diameter/mm	44
				Relative density of gas	0.7	Pump depth/m	1696.3
Relative density of crude oil	0.9	Stroke/m	6
				Formation temperature/. degree.C	60	Number of strokes	1.8
Water content ratio	0.633	Fluid production amount/t	8.04
				viscosity/mPa.s of crude oil	640	Oil production/t	2.95
Production gasoline ratio	10	Oil pressure/MPa	0.86
				Oil pipe inner diameter/mm	62.0	Casing pressure/MPa	1.83
Inner diameter/mm of casing	139.7	Back pressure/MPa	0.83

TABLE 2

TABLE 3

Specifically, according to the data in tables 2 and 3, the oil well is measured by the measurement method of the present application, and the pump diagram data of the oil well is obtained as shown in table 4.

TABLE 4

Further, a load maximum value and a load minimum value are selected from a predicted pump diagram, namely from table 4, and then working fluid level prediction is carried out by combining basic data, wherein the load maximum value and the load minimum value of the pump diagram in table 4 are 24.1KN and-1.12 KN, the load difference is 25.22KN, the pressure of a pump suction inlet is calculated to be 0.13MPa, and then working fluid level parameters of the oil well are measured to be 1668m by combining the working diagram of the oil well, the actual working fluid level depth is 1680m, and the error is-0.714%.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for measuring the working fluid level of an oil pumping well is characterized by comprising the following steps:

acquiring the displacement parameter of a pump at the lower part of the sucker rod string according to the displacement parameter of the sucker rod string; and

acquiring the load parameter of the pump according to the load parameter of the sucker rod string;

2. The method according to claim 1, characterized in that the resistance coefficient calculation model is in particular:

C = \frac{2 π μ}{ρ_{r} A_{r}} {\frac{1}{\ln m} + \frac{4}{B_{2}} (B_{1} + 1) {B_{1} + \frac{2}{\frac{ω L}{a} \frac{1}{s i n \frac{ω l}{a}} + c o s \frac{ω l}{a}}}};

wherein,

m = \frac{D_{t}}{D_{r}}, B_{1} = \frac{m^{2} - 1}{2 \ln m} - 1, B_{2} = m^{4} - 1 - \frac{{(m^{2} - 1)}^{2}}{1 n m}

wherein μ represents the liquid viscosity; rho_rIndicating the density of the sucker rod；A_rThe sectional area of the sucker rod is shown; d_tRepresents the tubing diameter; d_rThe diameter of the sucker rod is shown; l represents the sucker rod length; c represents a drag coefficient.

3. The method of claim 2, wherein obtaining the displacement parameter of the sucker rod string based on the drag coefficient and the sucker rod string displacement motion model comprises:

\frac{\partial U (x, t)}{\partial t^{2}} = a^{2} \frac{\partial^{2} (x, t)}{\partial x^{2}} - c \frac{\partial U (x, t)}{\partial t}

in the formula:

a represents the speed of sound wave propagation in the rod string.

4. The method of claim 3, wherein obtaining the load parameter of the rod string from the model of the drag coefficient and the rod string load calculation comprises:

5. The method according to claim 4, wherein the obtaining a sinking pressure parameter of a suction port of the pump according to the pump diagram specifically comprises:

selecting upper and lower load points in the pump diagram;

6. The method of claim 5, wherein the pump intake submergence pressure calculation model is embodied as:

P_{n} = \frac{2 P_{h} (f_{p} - f_{r})}{f_{p}} + 2 Δ P + \frac{W_{l}}{f_{p}},

wherein, the delta P represents the pressure drop generated when the oil layer production liquid passes through the fixed valve and the moving valve hole; w_lRepresenting the well fluid column load.