Steam drive one-furnace multi-injection-well flow monitoring method

Abstract

The invention relates to a steam drive one-furnace multi-injection-well flow monitoring method, and belongs to the technical field of thick oil steam injection well flow testing. Theoretical modeling comprises the following steps that S1, steam pressure drop is theoretically calculated; s2, calculating the relationship between steam density and dryness; s3, the wellhead steam flow is calculated; and S4, determining the friction resistance coefficient. According to the method, flow data of a single well is calculated by recording several simple parameters of a wellhead, a theoretical model of steam pressure, dryness and flow is constructed, and friction resistance coefficients in the theoretical model are determined by recording actual measurement data of the flow; and the single well flow is calculated according to the actually measured wellhead pressure and dryness data. The technical achievement can be popularized and applied to flow monitoring of multiple injection wells in one furnace. The method has the characteristics of simplicity and convenience in operation, practical technology and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of flow rate testing of heavy oil steam injection wells, and in particular relates to a method for monitoring flow rates of multiple injection wells in a steam-driven boiler. Background Art

[0002] The steam injection process of steam drive generally adopts a one-boiler-multiple-injection steam injection method, that is, a boiler uses multiple pipes to inject steam into multiple wells at the same time. Since steam is affected by friction and heat loss in the process of passing through the ground pipeline, wellbore, and oil layer, the resistance along the steam changes dynamically, which leads to changes in the steam injection volume of a single well, resulting in deviations between the designed steam injection volume and the actual steam injection volume, and the deviation of some wells is 2-3 times. The phenomenon of steam injection deviation in the injection wells has a serious impact on the dynamic analysis of the reservoir and the evaluation of production indicators. It is of great significance to carry out flow monitoring of multiple injection wells in one boiler.

[0003] In order to accurately measure the flow rate of a single well, the current method is to install a single well flow meter to directly monitor the steam flow rate. The advantage of this method is that it can accurately obtain monitoring data and adjust the steam injection parameters in a timely manner. The disadvantage is that a flow meter must be installed in each well, which increases equipment investment and requires regular maintenance. In order to alleviate the high cost of heavy oil hot injection, the development of simple and economical steam flow monitoring technology has always been the goal pursued by the majority of scientific and technological workers. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes: a method for monitoring flow rates of multiple injection wells in a steam drive furnace, the theoretical modeling steps are as follows:

[0005] S1. Theoretical calculation of steam pressure drop;

[0006] S2. Calculate the relationship between steam density and dryness;

[0007] S3, calculate the wellhead steam flow;

[0008] S4. Determine the friction coefficient.

[0009] Furthermore, in step S1, a mathematical model of the pressure drop of wet steam flowing in the ground pipeline is established, and the following assumptions are made:

[0010] 1) The steam parameters at the boiler outlet or wellhead remain unchanged, including steam injection rate, pressure, temperature and dryness;

[0011] 2) Horizontal layout of ground pipelines;

[0012] 3) The flow of wet steam in the ground pipeline is a one-dimensional stable flow.

[0013] Furthermore, the boiler / steam distribution room is taken as the coordinate origin, the steam flow direction along the wellbore is the Z-axis direction, and the control equation of the steam pressure drop gradient in the wellbore is established according to the principle of conservation of momentum, and the steam injection surface pipeline network is connected.

[0014] Furthermore, the total pressure gradient is composed of the gravity gradient, the friction gradient, and the acceleration gradient, namely:

[0015]

[0016]

[0017]

[0018] p g =ρ m gsinθ (4)

[0019] Where: p f —Frictional resistance loss per unit length, Pa;

[0020] f m — Friction coefficient of wet steam fluid, dimensionless;

[0021] ρ m —Density of wet steam fluid, kg / m 3 ;

[0022] v m —average velocity of wet steam fluid m / s;

[0023] D—inner diameter of oil pipe, m;

[0024] p a —Acceleration pressure drop gradient loss, Pa;

[0025] A—flow cross-sectional area, m 2 ;

[0026] G—mass flow rate of wet steam fluid, kg / s;

[0027] p a —pressure loss per unit length due to gravity;

[0028] θ—ground pipeline, θ=0°;

[0029] For the surface pipeline θ=0°, equation (1) is expressed as:

[0030]

[0031] The kinetic energy term is only considered in the mist flow. For the mist flow, the gas volume flow rate is much larger than the liquid volume flow rate, and the ideal gas law is applied; formula (6):

[0032]

[0033] Where: Q—steam volume flow rate, m 3 / s;

[0034] The steam flow rate and volume flow rate are calculated according to formulas (7) and (8) respectively:

[0035]

[0036]

[0037] Therefore, for the mist flow, the pressure drop calculation formula for the steam-water two-phase flow is:

[0038]

[0039] Furthermore, the whole wellbore is divided into several sections by numerical method, each section is of length Δz, and equation (9) is integrated in each section to obtain the formula for calculating the steam pressure at the outlet of each section:

[0040]

[0041] Furthermore, in step S2, the step of calculating the relationship between steam density and dryness is as follows:

[0042] The relationship between steam density and dryness is shown in formula (11):

[0043]

[0044] ρ l =3786.31-37.2487×(T+273.15)+0.196246×(T+273.15) 2 -5.04708×10 -4 ×(T+273.15) 3 +6.29368×10 -7 ×(T+273.15) 4 -3.0848×10 -10 ×(T+273.15) 5 (12)

[0046] lnρ g =-93.7072+0.833941×(T+273.15)-0.00320809×(T+273.15) 2 +6.57652×10 -6 ×(T+273.15) 3 -6.93747×10 -9×(T+273.15) 4 +2.97203×10 -12 ×(T+273.15) 5 (13)

[0048] Where: g —Density of saturated steam, kg / m 3 ;

[0049] ρ l —Density of saturated water, kg / m 3 .

[0050] Furthermore, in step S3, the steps of calculating the wellhead steam flow are as follows:

[0051] Combining formulas (7), (10) and (11), we can get

[0052]

[0053] The single wellhead steam flow rate is calculated according to formula (14).

[0054] Furthermore, in step S4, the friction coefficient is determined by using a flow meter to test the wellhead flow data of a well, and using formula (14) to calculate the pipeline friction coefficient.

[0055] The beneficial effects of the present invention are as follows: the present invention is easy to operate, low in cost, and suitable for monitoring the flow rate of multiple injection wells in a steam-driven boiler; the present invention obtains the flow rate data of a single well by recording several simple parameters at the wellhead (steam pressure, dryness), and the present invention has the characteristics of easy operation, practical technology, and low cost. The present invention constructs a theoretical model of steam pressure, dryness and flow rate, and determines the friction coefficient in the theoretical model by recording the measured flow rate data; the flow rate of a single well is calculated according to the measured wellhead pressure and dryness data. The technical achievement can be promoted and applied to monitoring the flow rate of multiple injection wells in a single boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Attached Figure 1 This is a schematic diagram of the steam injection surface pipeline network. DETAILED DESCRIPTION

[0057] A method for monitoring the flow rate of multiple injection wells in a steam-driven boiler is provided. The single well flow rate data is calculated by recording several simple parameters at the wellhead (steam pressure, dryness). The invention has the characteristics of simple operation, practical technology and low cost. A theoretical model of steam pressure, dryness and flow rate is constructed. The friction coefficient in the theoretical model is determined by recording the measured flow rate data; the single well flow rate is calculated based on the measured wellhead pressure and dryness data. The technical achievement can be extended to the monitoring of the flow rate of multiple injection wells in a boiler.

[0058] Theoretical modeling:

[0059] (1) Steam pressure drop calculation theory

[0060] In order to establish a mathematical model of the pressure drop of wet steam flowing in the ground pipeline, the following assumptions are made:

[0061] 1) The steam parameters at the boiler outlet or wellhead (steam injection rate, pressure, temperature and dryness) remain unchanged;

[0062] 2) Horizontal layout of ground pipelines;

[0063] 3) The flow of wet steam in the ground pipeline is a one-dimensional stable flow.

[0064] Take the boiler / steam distribution room as the coordinate origin, the steam flow direction along the wellbore as the Z-axis direction, and establish the control equation of the steam pressure drop gradient in the wellbore based on the principle of conservation of momentum. The surface pipe network for steam injection is shown in the attached Figure 1 The total pressure gradient is composed of the gravity gradient, friction gradient and acceleration gradient, namely:

[0065]

[0066]

[0067]

[0068] p g =ρ m gsinθ (4)

[0069] Where: p f —Frictional resistance loss per unit length, Pa;

[0070] f m — Friction coefficient of wet steam fluid, dimensionless;

[0071] ρ m —Density of wet steam fluid, kg / m 3 ;

[0072] v m —average velocity of wet steam fluid m / s;

[0073] D—inner diameter of oil pipe, m;

[0074] p a —Acceleration pressure drop gradient loss, Pa;

[0075] A—flow cross-sectional area, m 2 ;

[0076] G—mass flow rate of wet steam fluid, kg / s;

[0077] pa —pressure loss per unit length due to gravity;

[0078] θ—ground pipeline, θ=0°.

[0079] Since the surface pipeline θ = 0°, equation (1) can be expressed as:

[0080]

[0081] The kinetic energy (acceleration) term is only considered in the mist flow. For the mist flow, the gas volume flow is much larger than the liquid volume flow, so the ideal gas law can be approximately applied. Therefore, formula (6) can be obtained:

[0082]

[0083] Where: Q—steam volume flow rate, m 3 / s.

[0084] The steam flow rate and volume flow rate can be calculated according to formulas (7) and (8) respectively:

[0085]

[0086]

[0087] Therefore, for the mist flow, the pressure drop calculation formula for the steam-water two-phase flow is:

[0088]

[0089] The whole wellbore is divided into several sections by numerical method, each section is Δz long, and equation (9) is integrated in each section to obtain the formula for calculating the steam pressure at the outlet of each section:

[0090]

[0091] (2) Calculation of the relationship between steam density and dryness

[0092] The relationship between steam density and dryness is shown in formula (11):

[0093]

[0094]

[0095]

[0096] Where: g —Density of saturated steam, kg / m 3 ;

[0097] ρ l —Density of saturated water, kg / m3 .

[0098] Wellhead steam flow calculation

[0099] Combining formulas (7), (10) and (11), we can get

[0100]

[0101] According to formula (14), the steam flow rate at the wellhead of a single well can be calculated.

[0102] Determination of friction coefficient

[0103] Since the friction coefficient of the steam injection surface pipeline is difficult to determine, in order to solve this problem, a flow meter is used to test the wellhead flow data, and the pipeline friction coefficient is calculated using formula (14).

[0104] (II) On-site data collection and application

[0105] (1) On-site data collection

[0106] First, record the pressure, dryness and flow data of the steam in the boiler or steam distribution room; secondly, record the pressure and dryness data of the steam at the wellhead of each well.

[0107] (2) Data application calculation

[0108] Using the basic data collected, combined with the above theoretical derivation formula, first use the collected pressure, dryness and flow data of the boiler or steam distribution room steam to calculate the friction coefficient; then use the collected pressure and dryness data of the wellhead steam to calculate the single well flow value. The following is an example, the basic data are shown in Tables 1 and 2, and the single well flow calculation results are shown in Table 3.

[0109] Table 1 Pressure, dryness and flow data of boiler / steam distribution room steam

[0110] Steam injection method Steam pressure (MPa) Steam dryness (%) Steam displacement (t / h) One furnace 3 wells 5 76.2 13.6

[0111] Table 2 Single wellhead steam pressure and dryness data

[0112] well name Steam pressure (MPa) Steam dryness (%) Length of ground pipeline (m) Well 1# 3.425 71.07 240 Well 2# 3.227 68.29 170 Well 3# 2.878 68.14 410

[0113] Table 3 Comparison of single well flow calculation results and measured results

[0114] well name Well 1# Well 2# Well 3# Calculated displacement (t / h) 4.4 5.5 3.7 Measured displacement (t / h) 4.2 5.6 3.8 Relative error (%) 4.5 1.8 2.7

[0115] The displacement calculated by this method has a small error with the actual displacement, which fully meets the requirements of actual production applications.

[0116] 1. Borrowing technology

[0117] Calculation method for steam pipe flow pressure drop; calculation method for the relationship between steam density and dryness.

[0118] 2. Original technology

[0119] A technical method is proposed to obtain the single well steam flow rate by constructing a theoretical model and using the measured steam pressure and dryness data.

[0120] 3. Difficulties and key points of the invention

[0121] Difficulty: Determine the friction coefficient by recording the flow rate and related measured data.

[0122] Key points: Construct a theoretical model of steam pressure, dryness and flow rate.

[0123] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for monitoring flow rates of multiple injection wells in a steam drive furnace, characterized in that: The theoretical modeling steps are as follows: S1. Theoretical calculation of steam pressure drop; S2. Calculate the relationship between steam density and dryness; S3, calculate the wellhead steam flow; S4. Determine the friction coefficient.

2. The method for monitoring flow rates of multiple injection wells in a steam drive furnace as claimed in claim 1, characterized in that: In step S1, a mathematical model of the pressure drop of wet steam flowing in the ground pipeline is established, and the following assumptions are made: 1) The steam parameters at the boiler outlet or wellhead remain unchanged, including steam injection rate, pressure, temperature and dryness; 2) Horizontal layout of ground pipelines; 3) The flow of wet steam in the ground pipeline is a one-dimensional stable flow.

3. The method for monitoring flow rates of multiple injection wells in a steam drive furnace as claimed in claim 2, characterized in that: Take the boiler / steam distribution room as the coordinate origin, the steam flow direction along the wellbore as the Z-axis direction, establish the control equation of the steam pressure drop gradient in the wellbore based on the principle of conservation of momentum, and connect the steam injection surface pipeline network.

4. The method for monitoring flow rates of multiple injection wells in a steam drive furnace as claimed in claim 3, characterized in that: The total pressure gradient is composed of the gravity gradient, the friction gradient, and the acceleration gradient, namely: p g =ρ m gsinθ (4) Where: p f —Frictional resistance loss per unit length, Pa; f m —Friction coefficient of wet steam fluid, dimensionless; ρ m —Density of wet steam fluid, kg / m 3 ; v m —average velocity of wet steam fluid m / s; D—inner diameter of oil pipe, m; p a —Acceleration pressure drop gradient loss, Pa; A—flow cross-sectional area, m 2 ; G—mass flow rate of wet steam fluid, kg / s; p a —pressure loss per unit length due to gravity; θ—ground pipeline, θ=0°; For the surface pipeline θ=0°, equation (1) is expressed as: The kinetic energy term is only considered in the mist flow. For the mist flow, the gas volume flow rate is much larger than the liquid volume flow rate, and the ideal gas law is applied; formula (6): Where: Q—steam volume flow, m 3 / s; The steam flow rate and volume flow rate are calculated according to formulas (7) and (8) respectively: Therefore, for the mist flow, the pressure drop calculation formula for the steam-water two-phase flow is:

5. The method for monitoring flow rates of multiple injection wells in a steam drive furnace as claimed in claim 4, characterized in that: The whole wellbore is divided into several sections by numerical method, each section is Δz long, and equation (9) is integrated in each section to obtain the formula for calculating the steam pressure at the outlet of each section:

6. The method for monitoring flow rates of multiple injection wells in a steam drive furnace as claimed in claim 1, characterized in that: In step S2, the steps of calculating the relationship between steam density and dryness are as follows: The relationship between steam density and dryness is shown in formula (11): ρ l =3786.31-37.2487×(T+273.15)+0.196246×(T+273.15) 2 -5.04708×10 -4 ×(T+273.15) 3 +6.29368×10 -7 ×(T+273.15) 4 -3.0848×10 -10 ×(T+273.15) 5 (12) lnρ g =-93.7072+0.833941×(T+273.15)-0.00320809×(T+273.15) 2 +6.57652×10 -6 ×(T+273.15) 3 -6.93747×10 -9 ×(T+273.15) 4 +2.97203×10 -12 ×(T+273.15) 5 (13) Where: g —Density of saturated steam, kg / m 3 ; ρ l —Density of saturated water, kg / m 3 .

7. The method for monitoring flow rates of multiple injection wells in a steam drive furnace as claimed in claim 1, characterized in that: In step S3, the steps of calculating the wellhead steam flow are as follows: Combining formulas (7), (10) and (11), we can get The single wellhead steam flow rate is calculated according to formula (14).

8. The method for monitoring flow rates of multiple injection wells in a steam drive furnace as claimed in claim 7, characterized in that: In step S4, the friction coefficient is determined by using a flow meter to test the wellhead flow data of a well, and using formula (14) to calculate the pipeline friction coefficient.

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