Calculation method for pressure drop of water ring oil pipeline

Abstract

The invention discloses a water ring oil pipeline pressure drop calculation method, and belongs to the technical field of oil and gas pipelines. Comprising the following steps: collecting water ring oil pipeline data and oil-water density parameters; fitting the collected starting and ending point pressure difference, the oil-water apparent velocity, the pipe diameter, the pipe length, the oil-water two-phase density and the viscosity to obtain a relational expression of the starting and ending point pressure difference of the water ring conveying pipeline about the oil-water apparent velocity, the pipe diameter, the pipe length, the oil-water two-phase density and the viscosity; and the actual pressure drop of the water ring oil pipeline can be calculated by inputting the oil-water apparent velocity, the pipe diameter, the pipe length, the oil-water two-phase density and the viscosity which are actually measured on the water ring oil transportation site according to the relational expression. The method for calculating the pressure drop of the water ring oil conveying pipeline has the advantage of being easy to operate, and the obtained fitting relational expression can be conveniently and rapidly used for pressure drop calculation on a water ring oil conveying site.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas pipelines and relates to a method for calculating the pressure drop of a water ring oil pipeline. Background Art

[0002] Crude oil has high viscosity and is difficult to transport. The use of water ring drag reduction technology can significantly save energy consumption in the pump station system. When using this technology to transport oil, the oil and water phases in the pipe can form an annular flow. Water, as a lubricant for the core oil phase, separates the oil from the pipe wall, greatly reducing the resistance to oil transportation. However, when implementing this technology, the density of oil is often less than that of water. The density difference between the oil and water phases is likely to cause the oil core to float, the water film to sink, and the core annular flow to evolve into an eccentric annular flow, thereby affecting the pipeline pressure drop.

[0003] At present, the pressure drop of water ring drag reduction pipeline is mostly obtained by establishing pipeline geometric model and multiphase flow theory. This method is limited to the condition that the oil and water two phases strictly form a core annular flow and the oil core has no eccentricity. Therefore, the pressure drop prediction results are generally low, and the adaptability in the field of oil pipeline is poor, which is not conducive to the safe operation of the pipeline. Therefore, it is urgent to develop a water ring oil pipeline pressure drop calculation method that can be applied on site. Summary of the invention

[0004] The present invention aims to solve the problem of poor accuracy in calculating the pressure drop of a water ring oil pipeline. The present invention proposes a method of collecting pipeline data and oil-water density of oil transported by a water ring technology, fitting the pressure difference between the starting and ending points of the pipeline, the apparent oil-water flow rate, the pipe diameter, the pipe length and the oil-water-two-phase density, and obtaining two fitting parameters and a relational expression. The pressure drop of a water ring oil pipeline under different oil-water apparent flow rates, pipe diameters, pipe lengths and oil-water-two-phase densities can be quickly obtained through the relational expression.

[0005] The present invention is achieved through the following technical solutions:

[0006] Step 1, collecting water ring oil pipeline data and oil-water two-phase parameters that need to be calculated for pressure drop;

[0007] Step 2, select a pipeline for oil transportation using water ring drag reduction technology, fit the starting and ending pressures of the pipeline, the apparent flow velocity of the oil and water phases, the pipe diameter, the pipe length, the density and viscosity of the oil and water phases, and obtain the relationship between the starting and ending pressure difference of the water ring pipeline and the apparent flow velocity of the oil and water phases, the pipe diameter, the pipe length, the density and viscosity of the oil and water phases;

[0008] Step 3, using the relationship, inputting the measured oil-water apparent flow velocity, pipe diameter, pipe length, oil-water two-phase density and viscosity data of the oil field where the water ring drag reduction technology is implemented, the pressure drop of the water ring oil pipeline can be calculated.

[0009] In step 1, water ring oil pipeline data and oil-water two-phase parameters are collected, including the following:

[0010] The starting and ending pressure difference of the water ring oil pipeline, the apparent flow velocity of the oil and water phases, the pipe diameter, the pipe length, the density and viscosity of the oil and water phases.

[0011] In step 2, a pipeline that uses water ring drag reduction technology to transport oil is selected, and the pressure difference between the starting and ending points of the pipeline, the apparent flow rate of oil and water, the pipe diameter, the pipe length, the density and viscosity of the oil and water two phases are fitted to obtain the relationship between the pressure difference between the starting and ending points of the water ring pipeline and the apparent flow rate of oil and water two phases, the pipe diameter, the pipe length, the density and viscosity of oil and water two phases, including the following contents:

[0012] The collected pipeline start-end pressure difference, oil-water two-phase apparent flow velocity, pipe diameter, pipe length, oil-water two-phase density and viscosity are fitted in the form of formula (1) to (3);

[0013]

[0014] ρ m =ρ o (1-H w )+ρ w H w (3)

[0015] In the formula, Δp is the pressure difference between the start and end of the pipeline, L is the length of the pipeline, D is the diameter of the pipeline, and ρ o , w , m are the density of oil, water and the density of oil-water mixture, J o and J w are the superficial flow rates of oil and water, respectively, H w is the water holding capacity, μ w is the viscosity of water, a and b are the coefficients obtained after fitting.

[0016] In step 3, the fitted relationship is used to input the oil-water two-phase apparent flow rate J measured by the water ring drag reduction transport in the oil field. o and J w , pipe diameter D, pipe length L, oil-water two-phase density ρ o , w and viscosity μ w The pressure difference Δp between the starting and ending points of the pipeline can be calculated.

[0017] The present invention adopts the above technical solution to achieve the following beneficial effects:

[0018] (1) The present invention proposes a method for calculating the pressure drop of a water ring oil pipeline. By collecting the oil pipeline data using the water ring technology and the oil-water density parameters, the pipeline start-end pressure difference, the oil-water apparent flow velocity, the oil-water two-phase density, the pipe diameter and the pipe length are fitted to obtain a relationship for calculating the pressure drop of the water ring oil pipeline.

[0019] (2) The method for calculating the pressure drop of a water ring oil pipeline proposed in the present invention can save the cost of real-time monitoring of the pressure drop of the pipeline system. The operation is simple, and the obtained fitting relationship has good applicability and high accuracy for the water ring oil pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a step diagram of a method for calculating pressure drop of a water ring oil pipeline proposed by the present invention. DETAILED DESCRIPTION

[0021] In order to make the technical solution of the present invention more clear, the technical solution of the present invention is further described in conjunction with the accompanying drawings and the following embodiments, but the present invention is not limited to these examples.

[0022] like Figure 1 As shown, a method for calculating the pressure drop of a water ring oil pipeline comprises the following steps:

[0023] Step 1, collecting water ring oil pipeline data and oil-water two-phase parameters;

[0024] Step 2, select a pipeline for oil transportation using water ring drag reduction technology, fit the pressure difference between the starting and ending points of the pipeline, the apparent flow velocity of the oil and water phases, the pipe diameter, the pipe length, the density and viscosity of the oil and water phases, and obtain the relationship between the pressure difference between the starting and ending points of the water ring pipeline and the apparent flow velocity of the oil and water phases, the pipe diameter, the pipe length, the density and viscosity of the oil and water phases;

[0025] Step 3, using the relationship, inputting the oil-water two-phase apparent flow velocity, pipe diameter, pipe length, oil-water two-phase density and viscosity data measured on site in the oil field where the water ring drag reduction technology is implemented, the pressure drop of the water ring oil pipeline can be calculated.

[0026] Example

[0027] Now, according to the method of the present invention, the pressure drop of a pipeline in a certain oil field that uses water ring technology to transport oil is calculated, and the implementation steps are as follows:

[0028] Step 1: Collect water ring oil pipeline data and oil-water density parameters. The results are shown in Table 1:

[0029] Table 1 Water ring oil pipeline data and oil-water parameters

[0030]

[0031] Step 2, combining the pipeline start-end pressure difference, oil-water apparent flow rate, pipe diameter, pipe length and oil-water-two-phase density to fit, and obtain the relationship between the start-end pressure difference of the water ring transmission pipeline and the oil-water apparent flow rate, pipe diameter, pipe length and oil-water-two-phase density, as shown below:

[0032]

[0033] ρm =ρ o (1-H w )+ρ w H w (3)

[0034] In the formula, Δp is the pressure difference between the start and end of the pipeline, L is the length of the pipeline, D is the diameter of the pipeline, and ρ o , w , m are the density of oil, water and the density of oil-water mixture, J o and J w are the superficial flow rates of oil and water, respectively, H w is the water holding capacity, μ w is the viscosity of water.

[0035] Step 3, using equations (1) to (3), the pressure difference between the start and end points of the pipeline, the apparent flow rate of the oil-water two-phase, the pipe diameter, the pipe length, the density and viscosity of the oil-water two-phase can be calculated to obtain the pressure difference between the start and end points of the water ring conveying pipeline. The calculation results are shown in Table 2:

[0036] Table 2 Calculation results of pressure drop of water ring oil pipeline

[0037]

[0038] The present invention discloses a method for calculating the pressure drop of a water ring oil pipeline. The above is only a preferred embodiment of the present invention. Any modifications, equivalent substitutions and improvements made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the pressure drop of a water ring oil pipeline, characterized in that: The following steps are involved: Step 1, collecting water ring oil pipeline data and oil-water two-phase parameters that need to be calculated for pressure drop; Step 2, select a pipeline for oil transportation using water ring drag reduction technology, fit the pipeline start-end pressure difference, oil-water two-phase apparent flow velocity, pipe diameter, pipe length, oil-water two-phase density and viscosity, and obtain the relationship between the start-end pressure difference of the water ring pipeline and the oil-water apparent flow velocity, pipe diameter, pipe length, oil-water two-phase density and viscosity; Step 3, using the relationship, inputting the oil-water apparent flow velocity, pipe diameter, pipe length, and oil-water two-phase density and viscosity measured on site in the oil field where the water ring drag reduction technology is implemented, the pressure drop of the water ring oil pipeline can be calculated.

2. A method for calculating pressure drop of a water ring oil pipeline as claimed in claim 1, characterized in that: The collection of water ring oil pipeline data and oil-water two-phase parameters in step 1 includes the following contents: The starting and ending pressure difference of the water ring oil pipeline, the apparent flow velocity of the oil and water phases, the pipe diameter, the pipe length, the density and viscosity of the oil and water phases are collected.

3. A method for calculating pressure drop of a water ring oil pipeline as claimed in claim 1, characterized in that: In the step 2, a pipeline for transporting oil using the water ring drag reduction technology is selected, and the pressure difference between the start and end points of the pipeline, the apparent flow velocity of the oil and water phases, the pipe diameter, the pipe length, the density and viscosity of the oil and water phases are fitted to obtain the relationship between the pressure difference between the start and end points of the water ring transport pipeline and the apparent flow velocity of the oil and water phases, the pipe diameter, the pipe length, the density and viscosity of the oil and water phases, including the following contents: The collected pipeline start-end pressure difference, oil-water two-phase apparent flow velocity, pipe diameter, pipe length, oil-water two-phase density and viscosity are fitted according to formulas (1) to (3): r m =ρ o (1-H w )+r w H w (3) In the formula, Δp is the pressure difference between the start and end of the pipeline, L is the length of the pipeline, D is the diameter of the pipeline, and ρ o , w , m are the density of oil, water and the density of oil-water mixture, J o and J w are the superficial flow rates of oil and water, respectively, H w is the water holding capacity, μ w is the viscosity of water, a and b are the coefficients obtained after fitting.

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