CN-121997788-A - Non-metal pipeline oil-water two-phase stratified flow friction resistance pressure drop calculation method

CN121997788ACN 121997788 ACN121997788 ACN 121997788ACN-121997788-A

Abstract

The invention discloses a method for calculating the friction resistance pressure drop of oil-water two-phase stratified flow of a nonmetallic pipeline, which comprises the steps of 1) obtaining related parameters of oil-water two-phase stratified flow in the nonmetallic pipeline, 2) obtaining a friction resistance coefficient calculation model under the influence of wetting characteristics, 3) obtaining related parameters of oil-water two-phase stratified flow of the nonmetallic pipeline, 4) calculating the wet cycle length of the oil-water two-phase in a two-phase flow pipeline according to the water content of the oil-water two-phase stratified flow in the nonmetallic pipeline by referring to a double-fluid model, 5) establishing a friction resistance coefficient prediction model of the nonmetallic pipeline under the influence of wetting according to the friction resistance coefficient calculation value under the influence of the wetting characteristics and the wet cycle length of the oil-water two-phase in the two-phase flow pipeline by referring to the double-fluid model, and deducing an oil-water two-phase stratified flow friction resistance pressure drop calculation value to obtain a final friction resistance pressure drop calculation value. The invention belongs to the technical field of oil-water two-phase flow along-path friction pressure drop, and the accuracy of a calculation result is obviously improved.

Inventors

HU BING
SUN YINJUAN
ZHANG FENGXI
QIAO WENBO
HU JIANGUO
ZHANG JIANXIAO
PANG YONGLI
ZHU GUOCHENG
WANG RONGMIN
HUO FUYONG
DU XIN
ZHANG DEXIN

Assignees

长庆工程设计有限公司
中国石油天然气集团有限公司

Dates

Publication Date: 20260508
Application Date: 20241107

Claims (8)

1. The method for calculating the friction drag pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline is characterized by comprising the following steps of: step 1, acquiring relevant parameters of oil and water single-phase flow in a nonmetallic pipeline; Step 2, obtaining a friction coefficient calculation value under the influence of the wetting characteristic of the nonmetallic pipeline; step 3, obtaining relevant parameters of oil-water two-phase layered flow of the nonmetallic pipeline; step 4, calculating the wet cycle length of the oil-water two-phase in the two-phase flow pipeline according to the water content of the oil-water two-phase layered flow in the nonmetallic pipeline by referring to the two-fluid model; And 5, according to the friction coefficient calculated value under the influence of the wetting characteristic of the nonmetallic pipeline and the wet cycle length of the oil-water two-phase flow pipeline, referring to the two-fluid model, establishing a friction coefficient prediction model of the nonmetallic pipeline under the influence of the wetting characteristic, and deducing an oil-water two-phase stratified flow friction pressure drop calculated formula to obtain a final friction pressure drop calculated value.
2. The method for calculating the friction drag and pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline according to claim 1, wherein in the step 1, the specific process is as follows: the method comprises the steps of measuring the flow and the temperature of an oil-water single-phase flow pipeline in a nonmetallic pipeline and the contact angles of an oil phase, a water phase and the nonmetallic pipeline, wherein the data are respectively obtained by measuring one set of data of the oil phase and the water phase.
3. The method for calculating the friction drag and pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline according to claim 1, wherein in the step 2, the specific process is as follows: And calculating the friction coefficient of the nonmetallic pipeline under the influence of the wetting characteristic according to the contact angle of the oil and water single phase and the nonmetallic pipeline to obtain the friction coefficient calculation value under the influence of the wetting characteristic of the nonmetallic pipeline.
4. The method for calculating the friction drag and pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline according to claim 1, wherein in the step 3, the specific process is as follows: the flow, temperature and water content of the oil-water two-phase layered flow pipeline of the nonmetallic pipeline are obtained, and the data are obtained through measurement respectively, and are a set of data due to the oil-water layered flow.
5. The method for calculating the friction drag and pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline according to claim 1, wherein in the step 4, the derivation process of the wet cycle length is as follows: According to the geometric parameters of the section of the oil-water laminar flow pipeline, when the oil-water two phases flow in the pipeline, the wet cycle length of the oil phase and the water phase in the pipeline in which the oil-water two phases flow in a layered manner is obtained, and the wet cycle length is respectively shown as the formula (2) and the formula (3): (2) (3) Wherein S W represents the wet cycle length of the oil phase, S 0 represents the wet cycle length of the aqueous phase, D represents the diameter of an oil-water two-phase pipeline, and the unit is m; a is one half width of the oil phase; h w is the global height of the aqueous phase; Assuming that the flow rate of the oil phase and the flow rate of the water phase in the pipeline are equal, the section water content and the volume water content of the oil-water two-phase pipeline are equal, and the flow area of the oil phase and the water phase in the pipeline is represented by the water content, the relationship between the wet circumferences of the oil phase and the water phase in the two-phase pipeline and the water content is shown as the following formula (4) and formula (5): (4) (5) Wherein Ɛ W represents the water content, and is dimensionless.
6. The method for calculating the friction drag pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline according to the claim 1, wherein in the step 5, according to the obtained friction drag coefficient calculation value and the wet cycle length, referring to a double fluid model, a friction drag coefficient prediction model considering the wetting characteristic and the slip characteristic is constructed, and the specific process is as follows: When water flows through the experimental pipe, the head loss is reduced compared with the slip-free boundary condition due to the existence of the slip velocity, and the head loss reduced due to the slip boundary condition is expressed as formula (6) according to darcy's formula: (6) Wherein h f represents the head loss in the slip-free boundary pipeline, and the unit is m; h f-ps represents the head loss in the positive slip boundary pipeline, and the unit is m; Lambda represents friction coefficient, dimensionless; lambda ps represents the friction coefficient with consideration of wetting, dimensionless; L represents the length of the pipeline, and the unit is m; R represents the radius of the pipeline, and the unit is m; g represents gravitational acceleration in m/s2; v av represents the average velocity of the tube flow in m/s; therefore, the friction coefficient prediction model under the condition of considering the wetting characteristic is as shown in formula (7): (7) Wherein, theta a represents the contact angle of the liquid drop on the rough solid wall surface, and the unit is degree; θ 0 represents the contact angle of the droplet on the smooth solid wall surface in degrees; reynolds number, dimensionless.
7. The method for calculating the friction drag pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline according to claim 1, wherein in the step 5, the calculation formula of the friction drag pressure drop of the oil-water two-phase stratified flow in the pipeline is determined, and the final calculation value of the friction drag pressure drop is obtained, and the specific process is as follows: the prediction object in the step is oil-water two-phase stratified flow in a pipeline, and the relationship between the friction pressure drop of the oil-water laminar flow in the pipeline and the pressure drop of the independent water delivery and oil delivery of the pipeline is shown as the formula (8) assuming that the inter-phase interaction of the oil phase and the water phase does not exist, namely the inter-phase loss is not considered: (8) Wherein, the Represents the pressure drop of the oil and water laminar flow unit pipe length in the pipeline, Pa/m; The pressure drop of the whole water phase pipeline per unit pipe length is expressed, and the unit is Pa/m; the pressure drop of the unit pipe length of the oil phase pipeline is expressed, and the unit is Pa/m; obtaining a calculation formula of oil-water two-phase layered flow friction pressure drop in the pipeline, as shown in formula (9): (9) wherein, theta w-a represents the contact angle of water drop on the rough solid wall surface, and the unit is degree; θ w-0 represents the contact angle of a water drop on a smooth solid wall surface, and the unit is DEG; θ o-a represents the contact angle of an oil drop on a rough solid wall surface, and the unit is DEG; θ o-0 represents the contact angle of an oil drop on a smooth solid wall surface in degrees.
8. The method for calculating the friction drag pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline according to claim 1 is characterized in that the method is based on the principle of a Cassie model and the principle of a Navier linear sliding model, wherein the Cassie model comprehensively considers acting force and a coarse structure between a solid surface and liquid and has double influences on liquid infiltration characteristics, and the Navier linear sliding model is used for describing a simplified model of sliding behavior of fluid near the solid surface.

Description

Non-metal pipeline oil-water two-phase stratified flow friction resistance pressure drop calculation method Technical Field The invention belongs to the technical field of oil-water two-phase flow along-process friction pressure drop, and relates to a method for calculating oil-water two-phase stratified flow friction pressure drop of a nonmetallic pipeline. Background In recent years, as many large-scale oil fields gradually enter the middle and later stages of development, part of blocks enter the high water content stage, and the application prospect of the oil-water two-phase gathering and conveying pipeline is wider. However, the produced liquid also has the problems of high mineralization degree, sand content, increased proportion of corrosive gas and the like, so that the gathering pipeline on the oilfield site has serious corrosion perforation, scaling and cracking phenomena. In order to solve the problems, nonmetallic pipelines are introduced into the oilfield site for off-site oil gathering and transportation pipelines, so that the corrosion problem of the pipelines is effectively solved, the on-site operation maintenance workload is reduced, and the operation reliability of the on-site oil gathering and transportation pipelines is improved. The nonmetallic pipeline has the advantages of strong corrosion resistance, smooth inner wall of the pipeline, small fluid resistance, lighter weight, quick and simple installation, good temperature resistance, low installation cost, good comprehensive economic benefit and the like, and is widely applied to the field pipeline of the oil field. However, in the high water content period, the oil-water two-phase flow is arranged in the gathering and conveying pipeline, and as for the laminar flow of oil and water, the influence of wettability on friction is not considered in the traditional friction pressure drop calculation method, if the traditional friction pressure drop calculation method is directly adopted to predict the friction pressure drop of the nonmetallic pipeline, the error is larger generally. Therefore, a new method is needed to be developed, and an oil-water two-phase layered flow pressure drop prediction model is established based on a solid-liquid wetting theory so as to provide theoretical guidance for application of nonmetallic pipelines in an oil-water two-phase gathering pipeline. Disclosure of Invention The invention aims to provide a method for calculating the friction resistance pressure drop of oil-water two-phase stratified flow of a non-metal pipeline, which solves the problem that the prior art adopts the traditional friction resistance pressure drop calculation method, and the influence of the wetting characteristic of the wall surface of the non-metal pipeline on the friction resistance pressure drop is not considered, so that the calculation result error is larger. The technical scheme adopted by the invention is that the method for calculating the friction resistance pressure drop of the oil-water two-phase stratified flow of the nonmetallic pipeline is implemented according to the following steps: step 1, acquiring relevant parameters of oil and water single-phase flow in a nonmetallic pipeline; Step 2, obtaining a friction coefficient calculation value under the influence of the wetting characteristic of the nonmetallic pipeline; step 3, obtaining relevant parameters of oil-water two-phase layered flow of the nonmetallic pipeline; step 4, calculating the wet cycle length of the oil-water two-phase in the two-phase flow pipeline according to the water content of the oil-water two-phase layered flow in the nonmetallic pipeline by referring to the two-fluid model; And 5, according to the friction coefficient calculated value under the influence of the wetting characteristic of the nonmetallic pipeline and the wet cycle length of the oil-water two-phase flow pipeline, referring to the two-fluid model, establishing a friction coefficient prediction model of the nonmetallic pipeline under the influence of the wetting characteristic, and deducing an oil-water two-phase stratified flow friction pressure drop calculated formula to obtain a final friction pressure drop calculated value. The invention has the beneficial effects that the wall wetting theory and the wall sliding theory are combined, the influence of the non-metal pipeline wall wetting characteristic on the friction pressure drop is fully considered, the oil-water two-phase stratified flow friction pressure drop of the non-metal pipeline is accurately predicted and calculated, and further theoretical guidance is provided for the application of the non-metal pipeline in the oil-water two-phase gathering pipeline. Drawings FIG. 1 is a schematic representation of a Cassie wetting model employed in the method of the present invention; FIG. 2 is a schematic diagram of a Navier linear slip model employed in the method of the present invention; FIG. 3 is a schematic diagram of an o