Testing device and evaluation method for stability and rheological property of pipeline foam fluid

Abstract

The invention discloses an experimental testing device and an evaluation method for stability and rheological property of pipeline foam fluid, the experimental testing device comprises a foam generating system and a visual rheological system, and the evaluation method comprises the steps of determining an evaluation range and an evaluation object, constructing an evaluation system, obtaining evaluation index data under different conditions and performing quantitative evaluation. According to the invention, foam pipe flow simulation tests under the conditions of different gas-liquid ratios, different mass foam concentrations, different temperatures and the like can be realized, and experimental results can be used for exploring rheological properties and stability of different types of foam fluids; the method is beneficial for deeply analyzing the foam stability, the rheological property and the correlation of each parameter and exploring the foam stability and rheological property control mechanism.

Description

Technical Field

[0001] The invention belongs to the technical field of foam fluid research, and in particular relates to a test device and an evaluation method for the stability and rheological properties of pipeline foam fluid. Background Art

[0002] Foam fluids have been widely used in oil and gas field development due to their special properties. For oil and gas field development, the technology of oil and gas recovery in the form of foam fracturing, foam flooding, foam drainage, etc. has become increasingly mature, but the foam generated by the gas-liquid phase is in an unstable state. Therefore, for the development of oil and gas fields, controlling the stability of bubbles and analyzing the collapse process of bubbles under complex working conditions are the main research directions of current foam technology. Since the stability of foam is related to rheology, a comprehensive analysis of the two is required.

[0003] The collapse of foam is mainly affected by three processes, including foam drainage, bubble coarsening and liquid film rupture. In these three processes: foam drainage determines the liquid content of the foam, which is a key parameter for bubble coarsening and merging, and is a dominant mechanism for the stability of the foam system, directly affecting the stability of the foam; coarsening and foam drainage are strongly coupled, and the coarsening process does not directly affect the foam life, but foam drainage strongly depends on the bubble size controlled by coarsening, so coarsening can control the foam life through the influence of foam drainage.

[0004] Among them, temperature, pressure, foam quality, foam texture, foaming agent properties, gas and liquid properties, bubble network interaction, and the type and concentration of surfactants used are important parameters that affect foam stability and rheology. These parameters affect the stability and rheology of foam by affecting the three processes of foam collapse. Since the three processes of foam drainage, bubble coarsening, and liquid film rupture are not independent, these important parameters will also be coupled, making it difficult to analyze the stability and rheology of foam.

[0005] The foam performance test method and test device disclosed in Chinese Patent No. 201010620889.5 are to test the anti-foaming and defoaming properties of a water-based processing fluid in a vertical transparent test tube. The test environment is quite different from the foam pipe flow state, so it is not suitable for the performance test of the foam in the pipeline; Chinese Patent No. 201510887385.2 discloses an online detection method for the performance of oil displacement foam, which uses a core foam flooding experiment, which is similar to its oil displacement environment, and can obtain the performance of the oil displacement foam, but this method is not suitable for the test of the foam flow performance under pipe flow conditions; Chinese Patent No. 201810871221 .4 discloses a high-temperature and high-pressure foam rheology test system and experimental method, which uses a high-temperature and high-pressure rheology measurement unit to test the rheology of foam, and obtains the rheological properties of foam under different pressure and temperature conditions. However, due to the lack of environmental conditions for pipe flow, its test results cannot be applied to multiphase flow containing foam; Chinese patent 201911067678.0 discloses an experimental device and method for testing foam fluid performance and defoaming separation effect, which uses a loop experimental device for gas-liquid two-phase flow, but the main body of its foam performance test module is an analysis tank. The test of foam performance in this environment is not carried out in the actual pipe flow process, so its test results may be different from the foam fluid performance in the actual flow. In summary, the existing foam performance test device and method are not suitable for foam performance testing under pipe flow conditions. Existing studies have studied foam stability and rheology separately, evaluated stability and rheology in isolation, and did not associate foam stability with rheology. In addition, the existing rheological model does not consider the situation of foam instability in foam pipe flow applications, and lacks the association between rheology and stability. Therefore, it is very necessary to develop an experimental test device and evaluation method for the stability and rheological properties of pipeline foam fluid. Summary of the invention

[0006] In order to solve the above technical problems, the first purpose of the present invention is to provide an experimental test device for pipeline foam fluid stability and rheology. By constraining the number of parameters, the foam stability and rheology in the pipeline are measured, and the foam rheology and stability are analyzed and studied through pipeline pressure drop, foam fluid shear rate, foam potential, foam quantity and size within a certain range and other data to explore the mechanism of action and the interaction between various important parameters.

[0007] The second object of the present invention is to provide a method for evaluating the stability and rheological properties of pipeline foam fluid.

[0008] The first object of the present invention is achieved by comprising a foam generating system and a visual rheology system; The foam generating system comprises a compressed gas storage tank, a foaming agent storage tank, a flow sensor, a one-way valve, a centrifugal pump, and a foam generating tube. The compressed gas storage tank is connected to a one-way main tube via a gas phase tube, the gas phase tube is provided with a one-way valve, the foaming agent storage tank is connected to a one-way main tube via a foaming agent tube, the foaming agent tube is provided with a centrifugal pump, the one-way main tube is connected to an inlet end of the foam generating tube, and the gas phase tube and the foaming agent tube are provided with flow sensors respectively; the foaming agent generates foam in the foam generating tube under gas phase impact, and flows into a visualized rheological testing system; The visualization rheology system includes a data monitoring center, a temperature sensor, a pressure sensor, a high-speed camera, a conductive probe, a rheological test tube, and a waste liquid tank. The rheological test tube is covered with an insulation layer for heat preservation. The outlet end of the foam generating tube is connected to the inlet end of the rheological test tube, and the outlet end of the rheological test tube is connected to the waste liquid tank through a drain pipe. The waste liquid tank is used to collect waste liquid discharged from the rheological test tube. A temperature sensor is arranged in the inlet end of the rheological test tube, and pressure sensors are arranged in the inlet and outlet ends of the rheological test tube respectively. Along the length direction of the rheological test tube, several rows of conductive probes are arranged at equal intervals in the rheological test tube. Each row of conductive probes is distributed along the circumference of the rheological test tube. The spacing between adjacent conductive probes in the same row is equal, and the conductive probes in different rows adjacent to each other are staggered. The high-speed camera faces the rheological test tube. The flow sensor, temperature sensor, pressure sensor, high-speed camera, and conductive probe are respectively connected to the monitoring center, which is used to receive and display data from the flow sensor, temperature sensor, pressure sensor, high-speed camera, and conductive probe. The connection relationship between the monitoring center and each component is a well-known technology in the art.

[0009] The foaming agent may be cocamidopropyl betaine (CAB-35); the gas phase pipeline, the foaming agent pipeline and the one-way main pipeline may be connected together by a tee piece well known to those skilled in the art.

[0010] The conductive probe uses a commercially available conductive probe and is connected to a data monitoring center to record changes in the conductivity of the foam fluid during the flow process. Through a ring-shaped staggered arrangement, the conductivity and changes of the foam fluid can be fully measured.

[0011] Preferably, the foaming agent storage tank is a constant temperature storage tank. Specifically, the constant temperature storage tank has a temperature adjustment function to meet different test requirements. The foam generating tube and the rheological test tube are both made of organic glass.

[0012] Preferably, a porous metal plate is provided in the inlet end of the rheological test tube, and the porous metal plate is used to produce fine, dense and uniform foam to eliminate the influence of differences in stability caused by inconsistent bubble sizes.

[0013] The second object of the present invention is achieved by comprising the following steps: S1. Determine the scope and object of evaluation: Conduct several foam fluid flow simulation experiments with different variables, select the measured data for analysis, and determine the scope and object of evaluation; S2. Construct an evaluation system: The gas phase is provided by the compressed gas storage tank 1, the foaming agent is loaded by the foaming agent storage tank 2, and the gas flow rate Q1 ( )、Frother flow Q2( ); the gas phase is input into the one-way main pipeline through the gas phase pipeline, and the foaming agent is transported to the one-way main pipeline through a centrifugal pump; the foaming agent generates foam in the foam generating tube under the impact of the gas phase, and the foaming agent flow rate Q2 is used to replace the foam fluid flow rate, and then the flow rate is obtained from the inner diameter of the tube D1 (mm) (m / s), through the formula The shear rate ; The foam fluid enters the rheological test tube for rheological testing, and the temperature sensor records the experimental temperature. (℃), record the pressure difference through the pressure sensors at the inlet and outlet of the rheological test tube (Pa), based on the test length L (mm), inner diameter D2 (mm), pipeline pressure drop By formula Shear stress (Pa), in order to facilitate engineering applications, the constitutive equation similar to Newtonian fluid is often used as the basic model: , from which the apparent viscosity is calculated (Pa·S), and then by the power law equation have to , and take the logarithm and plot Curve, get the viscosity index , rheological index and shear rate Apparent viscosity The relationship between the foam and the liquid is used to obtain the rheological properties of the foam fluid (shear thinning or shear thickening); at the same time, the high-speed camera takes pictures of the foam fluid, and the foam quantity and size (the size of the foam and the corresponding quantity) are obtained through imageJ software processing. The conductivity of the foam fluid is obtained through a conductive probe. Since the foam gas phase is not conductive and different manifolds have different conductivity characteristics, the foam liquid holding capacity is inverted through the change in conductivity, and the foam stability is evaluated by the foam quantity, size, and liquid holding capacity; specifically, the foam stability is mainly determined by the strength of the foam liquid film. Small and dense foams have stronger liquid films and better stability. Since the liquid film will drain, the foam will inevitably grow and merge, and the foam stability will deteriorate; the change in stability can be obtained through the changes in the foam quantity, size, and liquid holding capacity; S3. Obtaining evaluation index data under different conditions: using the test device for pipeline foam fluid stability and rheology to conduct pipeline simulation flow test on foam fluid, changing the gas-liquid ratio Q1 / Q2 by adjusting the compressed gas storage tank and the centrifugal pump, changing the temperature T by adjusting the temperature of the foaming agent storage tank, directly changing the concentration by changing the foaming agent concentration (mass concentration) in the foaming agent storage tank, observing the foam fluid flow, and obtaining the pipeline pressure drop. , foam quantity, size and conductivity; S4. Quantitative evaluation: under different conditions The curve, foam quantity, size, and conductivity are used to evaluate the effects of changes in gas-liquid ratio, temperature, and concentration on the stability and rheology of foam fluids. Specifically, by changing the foaming agent concentration, ambient temperature, and gas-liquid ratio, the results show that the foam fluid has a stable rheological property under different conditions. Curve and foam quantity, size, conductivity, and obtain the changes in rheology and stability of foam fluid under different conditions. Analyze the changes in foam rheology and stability through a single factor, compare the changes in rheology and stability through changes in conditions, quantify their relationship, and then expand to multi-factor analysis.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The device of the present invention can complete the study of the stability and rheological properties of foam fluids under different temperatures, concentrations, and gas-liquid ratios. Through the visualized rheological test section, it can not only realize the rheological test of the foam fluid, but also realize the visualized dynamic observation of the foam flow. The changes in the foam flow shape under different working conditions can be recorded in time, so as to study the morphological change law of the foam fluid and the corresponding rheological characteristics, and analyze and guide the pipe flow characteristics of the foam fluid under different working conditions; the device of the present invention has a simple structure, is easy to disassemble, and is easy to maintain and operate; flanges are used between the pipelines, and the organic glass tubes can be disassembled and cleaned separately, which is conducive to repeated experimental operations; 2. The evaluation method of the present invention constructs an evaluation system to obtain the changes in the rheology, stability and flow shape of the foam fluid under different working conditions, and analyzes and quantifies the influencing factors. The evaluation results provide a theoretical basis for the pipe flow characteristics and stability of the foam fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the device of the present invention; Figure 2 0.6wt%, 30℃, Q1=2 , Q2=0.1~0.5 hour curve; Figure 3 Q1=2 , Q2=0.1 Conductivity changes; Figure 4 Q1=2 , Q2=0.5 When the foam fluid flow state; Figure 5 Q1=2 , Q2=0.1 When the foam fluid flow state; In the figure: 1-compressed gas storage tank, 2-foaming agent storage tank, 3-flow sensor, 4-check valve, 5-centrifugal pump, 6-monitoring center, 7-temperature sensor, 8-foam generating tube, 9-pressure sensor, 10-high-speed camera, 11-conductive probe, 12-rheological test tube, 13-waste liquid tank, 14-porous metal plate. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with the accompanying drawings, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0017] Example 1 As attached Figure 1 The experimental test device for the stability and rheological properties of pipeline foam fluid in this embodiment shown includes a foam generation system and a visual rheological system; The foam generating system comprises a compressed gas storage tank 1, a foaming agent storage tank 2, a flow sensor 3, a one-way valve 4, a centrifugal pump 5, and a foam generating pipe 8. The compressed gas storage tank 1 is connected to a one-way main pipe through a gas phase pipe, and the gas phase pipe is provided with a one-way valve 4. The foaming agent storage tank 2 is connected to a one-way main pipe through a foaming agent pipe, and the foaming agent pipe is provided with a centrifugal pump 5. The one-way main pipe is connected to the inlet end of the foam generating pipe 8, and the gas phase pipe and the foaming agent pipe are respectively provided with flow sensors 3; The visualized rheology system includes a data monitoring center 6, a temperature sensor 7, a pressure sensor 9, a high-speed camera 10, a conductive probe 11, a rheological test tube 12, and a waste liquid tank 13. The rheological test tube 12 is covered with an insulation layer. The outlet end of the foam generating tube 8 is connected to the inlet end of the rheological test tube 12, and the outlet end of the rheological test tube 12 is connected to the waste liquid tank 13 through a drain pipe. The inlet end of the rheological test tube 12 is provided with a temperature sensor 7, and the inlet and outlet ends of the rheological test tube 12 are respectively provided with pressure sensors 9. Along the length direction of the rheological test tube 12, a plurality of rows of conductive probes 11 are arranged at equal intervals in the rheological test tube 12. Each row of conductive probes 11 is distributed along the circumference of the rheological test tube 12. The conductive probes 11 in the same row and adjacent to each other are at equal intervals, and the conductive probes 11 in different rows adjacent to each other are staggered. The high-speed camera 10 faces the rheological test tube 12. The flow sensor 3, temperature sensor 7, pressure sensor 9, high-speed camera 10, and conductive probe 11 are respectively connected to the monitoring center 6; The foaming agent storage tank 2 is a constant temperature storage tank, and the foam generating tube 8 and the rheological testing tube 12 are both made of organic glass.

[0018] Example 2 The method for evaluating the stability and rheological properties of pipeline foam fluid in this embodiment includes the following steps: S1. Determine the scope and object of evaluation: Conduct several foam fluid flow simulation experiments with different variables, select the measured data for analysis, and determine the scope and object of evaluation; S2. Construct an evaluation system: The gas phase is provided by the compressed gas storage tank 1, the foaming agent is loaded by the foaming agent storage tank 2, and the gas flow rate Q1 ( )、Frother flow Q2( ); the gas phase is input into the one-way main pipeline through the gas phase pipeline, and the foaming agent is transported to the one-way main pipeline through a centrifugal pump; the foaming agent generates foam in the foam generating tube under the impact of the gas phase, and the foaming agent flow rate Q2 is used to replace the foam fluid flow rate, and then the flow rate is obtained from the inner diameter of the tube D1 (mm) (m / s), through the formula The shear rate ; The foam fluid enters the rheological test tube for rheological testing, and the temperature sensor records the experimental temperature. (℃), record the pressure difference through the pressure sensors at the inlet and outlet of the rheological test tube (Pa), based on the test length L (mm), inner diameter D2 (mm), pipeline pressure drop By formula Shear stress (Pa), in order to facilitate engineering applications, the constitutive equation similar to Newtonian fluid is often used as the basic model: , from which the apparent viscosity is calculated (Pa·S), and then by the power law equation have to , and take the logarithm and plot Curve, get the viscosity index , rheological index and shear rate Apparent viscosity The relationship between the foam and the liquid is used to obtain the rheological properties of the foam fluid (shear thinning or shear thickening); at the same time, the high-speed camera takes pictures of the foam fluid, and the foam quantity and size (the size of the foam and the corresponding quantity) are obtained through imageJ software processing. The conductivity of the foam fluid is obtained through a conductive probe. Since the foam gas phase is not conductive and different manifolds have different conductivity characteristics, the foam liquid holding capacity is inverted through the change in conductivity, and the foam stability is evaluated by the foam quantity, size, and liquid holding capacity; specifically, the foam stability is mainly determined by the strength of the foam liquid film. Small and dense foams have stronger liquid films and better stability. Since the liquid film will drain, the foam will inevitably grow and merge, and the foam stability will deteriorate; the change in stability can be obtained through the changes in the foam quantity, size, and liquid holding capacity; S3. Obtaining evaluation index data under different conditions: Using the test device for the stability and rheological properties of pipeline foam fluid in Example 1, a pipeline simulation flow test under different conditions (gas-liquid ratio, temperature, and foaming agent concentration) is performed on the foam fluid. The gas-liquid ratio Q1 / Q2 is changed by adjusting the compressed gas storage tank 1 and the centrifugal pump 5. The temperature T is changed by adjusting the temperature of the foaming agent storage tank 2. The concentration is directly changed by changing the foaming agent concentration (mass concentration) in the foaming agent storage tank 2. The foam fluid flow rate is observed, and the pipeline pressure drop is obtained. , foam quantity, size and conductivity; S4. Quantitative evaluation: By changing the concentration of the foaming agent, the ambient temperature, and the gas-liquid ratio, the Curve and foam quantity, size, conductivity, and obtain the changes in rheology and stability of foam fluid under different conditions. Analyze the changes in foam rheology and stability through a single factor, compare the changes in rheology and stability through changes in conditions, quantify their relationship, and then expand to multi-factor analysis.

[0019] Example 3 (1) Prepare a bubbler solution with a concentration of 0.6 wt%, using cocopropylamide betaine (CAB-35) as the bubbler, and place it in a constant temperature water tank and heat it to 30 °C; (2) Turn on the air pump for a while, so that the target gas phase fills the entire device, and then turn off the air pump (if the gas phase is air, skip this step); (3) Turn on the centrifugal pump and set the gas phase flow rate Q1 to 2 ~10 , the foaming agent flow rate Q2 is 0.1 ~0.5 , D1=D2=50mm, and U=0.0141 s~0.0707 s, =2.256~11.312( ); (4) Records and through , , we can conclude and through , draw Curve, get the viscosity index , rheological index and shear rate Apparent viscosity The relationship between the conductivity and the foam is used to obtain the rheological properties of the foam fluid (shear thinning or shear thickening). At the same time, the conductivity change is monitored by a conductive probe, and the foam morphology is photographed by a high-speed camera. (5) From the data, we know that at a concentration of 0.6wt% and a temperature of 30°C, the fixed gas phase flow rate is 2 , and gradually increase the flow rate of the foaming agent by 0.1 ~0.5 , the foam fluid exhibits shear thinning characteristics; that is, as the shear rate increases, the fluid viscosity decreases; when the gas-liquid ratio is high, the foam fluid flow state will change to slug flow; As the pipe flow progresses, the conductivity of the foam fluid gradually increases (the rightmost electrode is No. 1). During the flow process, the foam becomes unstable to a certain extent, and as the flow rate of the foaming agent increases, the foam stability becomes worse; the decrease in viscosity causes the liquid film to drain faster and become more unstable; through the ratio of the conductivity of electrodes No. 1 and No. 8 to the conductivity of the foaming agent, it can be obtained that the foam fluid holdup changes from 92.2% to 84.5%; From the change in conductivity, it can be seen that the foam discharge is not uniform. The conductivity changes greatly in the section from electrode 4 to electrode 2, indicating that more liquid is discharged. At this time, the foam viscosity becomes smaller, the friction resistance becomes smaller, and the section from electrode 4 to electrode 1 has a larger pipeline pressure drop.

Claims

1. Test device for the stability and rheological properties of pipeline foam fluid, characterized by Including foam generation system and visual rheology system; The foam generating system comprises a compressed gas storage tank (1), a foaming agent storage tank (2), a flow sensor (3), a one-way valve (4), a centrifugal pump (5), and a foam generating pipe (8); the compressed gas storage tank (1) is connected to a one-way main pipe via a gas phase pipe, the gas phase pipe is provided with a one-way valve (4); the foaming agent storage tank (2) is connected to the one-way main pipe via a foaming agent pipe, the foaming agent pipe is provided with a centrifugal pump (5), the one-way main pipe is connected to an inlet end of the foam generating pipe (8), and the gas phase pipe and the foaming agent pipe are respectively provided with flow sensors (3); The visual rheological system comprises a data monitoring center (6), a temperature sensor (7), a pressure sensor (9), a high-speed camera (10), a conductive probe (11), a rheological test tube (12), and a waste liquid tank (13). The rheological test tube (12) is covered with a thermal insulation layer. The outlet end of the foam generating tube (8) is connected to the inlet end of the rheological test tube (12). The outlet end of the rheological test tube (12) is connected to the waste liquid tank (13) via a drain pipe. The inlet end of the rheological test tube (12) is provided with a temperature sensor. A sensor (7), a pressure sensor (9) is provided in the inlet and outlet of the rheological test tube (12), and a plurality of rows of conductive probes (11) are arranged at equal intervals in the rheological test tube (12) along the length direction of the rheological test tube (12). Each row of conductive probes (11) is distributed along the circumference of the rheological test tube (12), and the spacing between adjacent conductive probes (11) in the same row is equal, and the conductive probes (11) in different rows adjacent to each other are staggered. The high-speed camera (10) faces the rheological test tube (12); The flow sensor (3), temperature sensor (7), pressure sensor (9), high-speed camera (10), and conductive probe (11) are respectively connected to the monitoring center (6).

2. The test device for testing the stability and rheological properties of pipeline foam fluid according to claim 1, characterized in that The foaming agent storage tank (2) is a constant temperature storage tank, and the foam generating tube (8) and the rheological testing tube (12) are both made of organic glass.

3. The test device for testing the stability and rheological properties of pipeline foam fluid according to claim 1, characterized in that A porous metal plate (14) is provided in the inlet end of the rheological test tube (12).

4. Evaluation method of pipeline foam fluid stability and rheology, characterized by The following steps are involved: S1. Determine the scope and object of evaluation: Conduct several foam fluid flow simulation experiments with different variables, select the measured data for analysis, and determine the scope and object of evaluation; S2. Construct an evaluation system: The gas phase is provided by a compressed gas storage tank (1), and the foaming agent is loaded by a foaming agent storage tank (2). The gas flow Q1 and the foaming agent flow Q2 are displayed by a flow sensor (3); the gas phase is input into the one-way main pipeline through the gas phase pipeline, and the foaming agent is transported to the one-way main pipeline through a centrifugal pump (5); the foaming agent generates foam in the foam generating pipe (8) under the impact of the gas phase, and the foaming agent flow Q2 is used to replace the foam fluid flow, and the flow rate is obtained from the inner diameter D1 of the pipe. , through the formula The shear rate ; The foam fluid enters the rheological test tube (12) for rheological test, and the temperature sensor (7) records the experimental temperature. , the pressure difference is recorded through the pressure sensors (9) at the inlet and outlet of the rheological test tube (12). , based on the test length L, inner diameter D2, and pipeline pressure drop By formula Shear stress ,use , from which the apparent viscosity is calculated , and then from the power law equation have to , and take the logarithm and plot Curve, get viscosity index , rheological index and shear rate Apparent viscosity , and obtain the rheological properties of the foam fluid; at the same time, the high-speed camera (10) takes a picture of the morphology of the foam fluid, and obtains the amount and size of the foam after processing, and obtains the conductivity of the foam fluid through the conductive probe (11), and inverts the foam liquid holding capacity, and evaluates the foam stability based on the foam amount, size and liquid holding capacity; S3. Obtaining evaluation index data under different conditions: using the test device for pipeline foam fluid stability and rheology as described in any one of claims 1 to 3 to perform pipeline simulation flow test on the foam fluid, changing the gas-liquid ratio Q1 / Q2 by adjusting the compressed gas storage tank (1) and the centrifugal pump (5), changing the temperature T by adjusting the temperature of the foaming agent storage tank (2), directly changing the concentration by changing the foaming agent concentration in the foaming agent storage tank (2), observing the foam fluid flow rate, and obtaining the pipeline pressure drop , foam quantity, size and conductivity; S4. Quantitative evaluation: under different conditions Curve, foam quantity, size, and conductivity are used to evaluate the effects of changes in gas-liquid ratio, temperature, and concentration on the stability and rheology of foam fluids.

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