Evaluation method of blowout preventer rubber core under extreme high and low temperature and corrosive environment conditions

Abstract

The invention discloses a method for evaluating a blowout preventer rubber core under extreme high and low temperature and corrosive environment conditions, and belongs to the technical field of methods for evaluating the quality and reliability of the blowout preventer rubber core, and the method comprises the following steps: 1) researching the physical properties of the blowout preventer rubber core in a normal temperature state, evaluating the quality and performance parameters, and obtaining the basic data of the blowout preventer rubber core; 2) researching the change conditions of various performance indexes of the rubber core of the blowout preventer under the conditions of extreme high temperature and extreme low temperature, and performing structural analysis; 3) researching the aging performance of the blowout preventer rubber core in a high-temperature environment and an alternating environment from high temperature to limit low temperature; 4, four drilling and production corrosive environments are set, the aging performance and the aging service life of the nitrile rubber material for the blowout preventer rubber core are studied, and the performance control standard of the nitrile rubber material for the blowout preventer rubber core in the extreme high and low temperature environment is determined by combining the performance index for ensuring the normal use function of the blowout preventer rubber core and the actual detection condition and cooperating with experiments.

Description

Technical Field

[0001] The present invention belongs to the technical field of evaluation methods for the quality and reliability of blowout preventer rubber cores in drilling well control equipment, and specifically relates to an evaluation method for blowout preventer rubber cores under extreme high and low temperature and corrosive environmental conditions. Background Art

[0002] A blowout preventer is a key well control equipment for exploring and developing high-pressure oil and gas wells, preventing blowout accidents and balanced-pressure drilling. The performance of the rubber core is directly related to the success or failure of the entire well control system. Under the existing oil and gas exploitation environment and requirements, especially in high-cold regions such as western China and Central Asia, and high-sulfur natural gas wells in Sichuan and Chongqing regions of China, the quality and effective life of blowout preventer rubber cores are severely tested.

[0003] Currently, in the international community, for non-metallic parts of blowout preventers, there are only hardness test methods specified in ASTM D 2240:1997 or ASTM D 1415:1994; normal stress-strain performance test methods specified in ASTM D 412:1998 or ASTM D 1414:1994; compression deformation tests carried out as specified in ASTM D 395:1998 or ASTM D 1414:1994; immersion tests carried out as specified in ASTM D 471:1998 or ASTM D 1414:1994. However, all of these standards are only method test standards, and there are no specific control standards for the quality of blowout preventer rubber cores. ASTM is the abbreviation of the American Society for Testing and Materials.

[0004] In the requirements for blowout preventer materials in the national standard GB / T 20174-2006, relevant technical indicators are specified for metal materials. However, for the rubber core sealing material, the core component of the blowout preventer, there are no clear specific technical indicators. Only the application temperature grade is divided, and the specific performance requirements that should be met at each temperature grade are not specified. Therefore, in the actual operation process, this phenomenon makes it difficult to have a basis for and quantify specific quality and safety monitoring. Although domestic enterprises in China have carried out the localization work of blowout preventers, the research on the key quality control indicators of the key component rubber cores of blowout preventers is not deep enough, resulting in uneven product quality. There is still a large gap compared with foreign similar products. At the same time, for the application field, testing institutions lack basic data and evaluation methods for performance, reliability and life under relevant extreme conditions.

[0005] The Chinese patent with the publication number CN104034867A and the publication date of September 10, 2014 discloses an evaluation method for nitrile rubber materials used in blowout preventer rubber cores under extreme high and low temperature conditions. The characteristics are as follows: study the physical properties of nitrile rubber materials used in blowout preventer rubber cores at room temperature, conduct quality and performance parameter evaluations, and obtain the basic data of nitrile rubber materials used in blowout preventer rubber cores; study the changes in various performance indicators of nitrile rubber materials used in blowout preventer rubber cores under extreme high temperature and extreme low temperature conditions and conduct structural analysis. Combine the performance indicators to ensure the normal use function of the blowout preventer rubber core and the actual detection situation, and cooperate with experiments to determine the performance control standards of nitrile rubber materials used in blowout preventer rubber cores under extreme high and low temperature environments; study the aging performance of nitrile rubber materials used in blowout preventer rubber cores in high temperature environments and high temperature to extreme low temperature alternating environments, measure the changes and laws of various performance indicators of nitrile rubber materials used in blowout preventer rubber cores during the aging process, determine the aging resistance performance that meets the performance requirements of the blowout preventer rubber core, and determine the experimental method and quality control standards. However, this patent can only evaluate the quality of the blowout preventer rubber core under extreme high and low temperature conditions and cannot meet the environments encountered by the blowout preventer rubber core in actual production, that is, the quality assessment of the blowout preventer rubber core under extreme high and low temperature and corrosive environments. Summary of the Invention

[0006] The object of the present invention is to establish an evaluation method for blowout preventer rubber cores under extreme high and low temperature and corrosive environment conditions, aiming at the quality assessment of blowout preventer rubber cores in environments that cannot be met in actual production in the prior art.

[0007] The object of the present invention is achieved by the following technical solutions: An evaluation method for blowout preventer rubber cores under extreme high and low temperature and corrosive environment conditions, comprising the following steps: 1) Study the physical properties of nitrile rubber materials used in blowout preventer rubber cores at room temperature, conduct quality and performance parameter evaluations, and obtain the basic data of nitrile rubber materials used in blowout preventer rubber cores; 2) Study the changes in various performance indicators of nitrile rubber materials used in blowout preventer rubber cores under extreme high temperature and extreme low temperature conditions and conduct structural analysis. Combine the performance indicators to ensure the normal use function of the blowout preventer rubber core and the actual detection situation, and cooperate with experiments to determine the performance control standards of nitrile rubber materials used in blowout preventer rubber cores under extreme high and low temperature environments; 3) Study the aging performance of nitrile rubber materials used in blowout preventer rubber cores in high temperature environments and high temperature to extreme low temperature alternating environments, measure the changes and laws of various performance indicators of nitrile rubber materials used in blowout preventer rubber cores during the aging process, determine the aging resistance performance that meets the performance requirements of the blowout preventer rubber core, and determine the experimental method and quality control standards for extreme high and low temperatures; 4) With reference to NACE 0187 "Standard Test Methods for Elastic Materials in Sour Gas Environments", four drilling and production corrosive environments were set up to study the aging performance of nitrile rubber materials used in BOP rubber cores. The aging cycle was 4 days, and samples were taken every 1 day to evaluate the changes in various mechanical properties and conduct molecular structure change analysis; based on the key mechanical parameters of the rubber core, the aging life of the BOP rubber core under high temperature was calculated in combination with the Arrhenius equation; combined with the performance indicators and actual test conditions to ensure the normal use of the BOP rubber core, the performance control standards of nitrile rubber materials used in BOP rubber cores under extreme high and low temperature environments were determined in conjunction with experiments.

[0008] The specific extreme high and low temperature evaluation method is as follows: for the nitrile rubber material used in the blowout preventer rubber core, first use calorimetric analysis, dynamic mechanical analysis and infrared analysis to characterize the microstructure; then, in combination with the macroscopic performance parameters of hardness, tension, tearing, compression, compression permanent deformation and resistance to liquid mass volume change, the glass transition temperature, molecular chain structure, mechanical properties and medium resistance of the nitrile rubber material used in the blowout preventer rubber core are studied by temperature level, and finally, the changes in glass transition temperature, molecular chain structure, mechanical properties and medium resistance are linked to the application performance of the blowout preventer, and the key technical indicators of the nitrile rubber material used in the blowout preventer rubber core at each temperature level are established, thereby forming an extreme high and low temperature evaluation method.

[0009] Preferably, the extreme high temperature specifically refers to the maximum temperature grade G of non-metallic sealing materials determined to be 177°C according to the record in the standard GB / T 20174-2006.

[0010] Preferably, the extreme low temperature specifically refers to the low temperature grade A of non-metallic sealing materials determined to be -26°C according to the record in the standard GB / T 20174-2006.

[0011] Preferably, the high temperature environment refers to a closed space filled with hot air at 120°C.

[0012] Preferably, the high temperature to extreme low temperature alternating environment specifically refers to treating the nitrile rubber material for the blowout preventer rubber core from -26℃→120℃→-26℃→120℃, then treating it from 120℃→-26℃→120℃→-26℃, then treating it from -26℃→120℃→-26℃→120℃, and finally treating it from 120℃→-26℃→120℃→-26℃. During each treatment, each temperature value is placed for 12 hours and samples are taken to analyze and evaluate various properties of the material.

[0013] Preferably, the evaluation method under corrosive environments is as follows: For the nitrile rubber material used in the blowout preventer rubber core, first, a differential scanning calorimeter, a dynamic thermomechanical analyzer, a thermogravimetric analyzer, and a Fourier transform infrared spectrometer are used for microstructure analysis and characterization. Then, combined with macroscopic performance parameters such as hardness, tensile strength, tear strength, resilience, abrasion, compression, compression set, and change in mass-volume of resistance to liquids, a simulated drilling and production corrosive environment is set up to study the changes in the mechanical properties and microstructure of the nitrile rubber material used in the blowout preventer rubber core. Finally, the changes in the glass transition temperature, molecular chain structure, mechanical properties, and resistance to media are related to the application performance of the blowout preventer, and the key technical indicators of the nitrile rubber material used in the blowout preventer rubber core under various corrosive environments are established, thereby forming an evaluation method under corrosive environments.

[0014] Preferably, the four drilling and production corrosive environments are as follows: a), Pressure: 7 MPa, Temperature: 121 °C, Gas phase components: 20% H2S + 5% CO2 + 75% N2, Liquid phase components: 25% n-hexane + 20% n-octane + 50% n-decane + 5% toluene; b), Pressure: 35 MPa, Temperature: 121 °C, Gas phase components: 20% H2S + 5% CO2 + 75% N2, Liquid phase components: 25% n-hexane + 20% n-octane + 50% n-decane + 5% toluene; c), Pressure: 35 MPa, Temperature: 121 °C, Gas phase components: 5% H2S + 20% CO2 + 75% N2, Liquid phase components: 25% n-hexane + 20% n-octane + 50% n-decane + 5% toluene; d), Pressure: 35 MPa, Temperature: 177 °C, Gas phase components: 5% H 2 S + 20% CO 2 + 75% N 2 , Liquid phase components: 25% n-hexane + 20% n-octane + 50% n-decane + 5% toluene.

[0015] The beneficial effects of this technical solution are as follows: 1. The evaluation method for the blowout preventer rubber core provided by the present invention under extreme high and low temperature and corrosive environment conditions will improve the quality control indicators and evaluation system of the blowout preventer rubber core material under extreme high and low temperature environment and corrosive environment conditions, put forward clear specific technical indicators for the rubber core sealing material of the blowout preventer core component, divide its application temperature grade, and clarify the specific performance requirements that should be met at each temperature grade. This will effectively ensure the use safety of the blowout preventer and ensure the effective development of well control work. In the actual operation process, the establishment and implementation of this method enable specific quality and safety monitoring to be based on evidence and quantified.

[0016] II. The evaluation method for the blowout preventer rubber core provided by the present invention under extreme high and low temperature and corrosive environmental conditions. By applying modern analytical and testing techniques, the physical property changes and aging process of the nitrile rubber material used for the blowout preventer rubber core at different temperature levels are studied. The key technical indicators and their evaluation methods for the nitrile rubber material used for the blowout preventer rubber core at each temperature level are established. The performance indicators of the blowout preventer rubber core in Appendix C of the existing SY / T5053.1-2000 "Surface Blowout Preventers and Surface Equipment" standard are divided into temperature levels, covering the entire temperature range (-26°C to 177°C) applicable to all blowout preventer rubber core materials, filling the gap in this field.

[0017] III. The evaluation method for the blowout preventer rubber core provided by the present invention under extreme high and low temperature and corrosive environmental conditions. Through the simulation of the corrosive drilling environment, the aging process, physical properties and structural changes of the nitrile rubber material used for the blowout preventer rubber core under different concentrations, temperatures and pressures of hydrogen sulfide are studied. A rapid aging experimental simulation method and detection control standard for predicting the service life of the nitrile rubber material used for the blowout preventer rubber core in a hydrogen sulfide corrosion environment are established. Through rapid experimental simulation, the performance tracking curves of domestic rubber core materials under different pressures (7 MPa, 35 MPa, 70 MPa), temperatures (121°C, 177°C) and hydrogen sulfide concentrations (5%, 20%) are obtained. The basic data of the performance changes of the blowout preventer rubber core material in a hydrogen sulfide corrosion environment and its life prediction method are obtained, filling the domestic gap. Detailed implementation manners

[0018] The present invention will be further described in detail below in conjunction with embodiments, but the implementation manners of the present invention are not limited thereto. Embodiment

[0019] The present embodiment provides an evaluation method for the blowout preventer rubber core under extreme high and low temperature and corrosive environmental conditions, including the following steps: 1) Study the physical properties of the nitrile rubber material used for the blowout preventer rubber core at room temperature, evaluate the quality and performance parameters, and obtain the basic data of the nitrile rubber material used for the blowout preventer rubber core; 2) Study the changes in various performance indicators of the nitrile rubber material used for the blowout preventer rubber core under extreme high temperature and extreme low temperature conditions and conduct structural analysis. Combining the performance indicators to ensure the normal use function of the blowout preventer rubber core and the actual detection situation, and cooperating with experiments, determine the performance control standards of the nitrile rubber material used for the blowout preventer rubber core in extreme high and low temperature environments; 3) Study the aging performance of the nitrile rubber material used for the blowout preventer rubber core in a high temperature environment and a high temperature to extreme low temperature alternating environment, measure the changes and laws of various performance indicators of the nitrile rubber material used for the blowout preventer rubber core during the aging process, determine the aging resistance performance that meets the performance requirements of the blowout preventer rubber core, and determine the extreme high and low temperature experimental methods and quality control standards; 4) Refer to NACE 0187 "Standard Test Method for Elastomeric Materials in Sour Gas Environments", set up four corrosive drilling and production environments, study the aging performance of nitrile rubber materials used for blowout preventer rubber cores, with an aging cycle of 4 days, sampling once every 1 day, evaluate the changes in various mechanical properties, and conduct molecular structure change analysis; based on the key mechanical parameters of the rubber core, combine with the Arrhenius equation to calculate the aging life of the blowout preventer rubber core at high temperatures; combine with the performance indicators to ensure the normal use function of the blowout preventer rubber core and the actual detection situation, and cooperate with experiments to determine the performance control standards of nitrile rubber materials used for blowout preventer rubber cores in extreme high and low temperature environments.

[0020] The specific method for evaluating extreme high and low temperatures is as follows: For nitrile rubber materials used for blowout preventer rubber cores, first conduct microscopic structure characterization using calorimetric analysis, dynamic mechanical analysis, and infrared analysis; then, combined with macroscopic performance parameters such as hardness, tensile strength, tear strength, compression, compression set, and mass-volume change resistance to liquids, study the changes in the glass transition temperature, molecular chain structure, mechanical properties, and medium resistance properties of nitrile rubber materials used for blowout preventer rubber cores by temperature grades. Finally, link the changes in the glass transition temperature, molecular chain structure, mechanical properties, and medium resistance properties with the application performance of the blowout preventer to establish the key technical indicators of nitrile rubber materials used for blowout preventer rubber cores at each temperature grade, thus forming a method for evaluating extreme high and low temperatures.

[0021] Preferably, the extreme high temperature specifically refers to determining that the highest temperature grade G of non-metallic sealing materials is 177 °C according to the records in Standard GB / T 20174-2006.

[0022] Preferably, the extreme low temperature specifically refers to determining that the low temperature grade A of non-metallic sealing materials is -26 °C according to the records in Standard GB / T 20174-2006.

[0023] Preferably, the high temperature environment refers to filling a closed space with hot air at 120 °C.

[0024] Preferably, the alternating environment of high temperature to extreme low temperature specifically refers to treating nitrile rubber materials used for blowout preventer rubber cores in a temperature environment of -26 °C → 120 °C → -26 °C → 120 °C, then treating them in a temperature environment of 120 °C → -26 °C → 120 °C → -26 °C, then treating them in a temperature environment of -26 °C → 120 °C → -26 °C → 120 °C, and finally treating them in a temperature environment of 120 °C → -26 °C → 120 °C → -26 °C. During each treatment, place them at each temperature value for 12 h and sample to analyze and evaluate the various properties of the material.

[0025] Preferably, the evaluation method in a corrosive environment is as follows: For the nitrile rubber material used for the blowout preventer rubber core, first, a differential scanning calorimeter, a dynamic thermomechanical analyzer, a thermogravimetric analyzer, and a Fourier transform infrared spectrometer are used for microstructure analysis and characterization. Then, combined with macroscopic performance parameters such as hardness, tensile strength, tear strength, resilience, abrasion, compression, compression set, and change in mass-volume of the liquid resistance, a simulated drilling and production corrosive environment is set up to study the changes in the mechanical properties and microstructure of the nitrile rubber material used for the blowout preventer rubber core. Finally, the changes in the glass transition temperature, molecular chain structure, mechanical properties, and medium resistance properties are related to the application performance of the blowout preventer, and the key technical indicators of the nitrile rubber material used for the blowout preventer rubber core in each corrosive environment are established, thus forming an evaluation method in a corrosive environment.

[0026] Preferably, the four drilling and production corrosive environments are as follows: a), Pressure: 7 MPa, Temperature: 121 °C, Gas phase components: 20% H2S + 5% CO2 + 75% N2, Liquid phase components: 25% n-hexane + 20% n-octane + 50% n-decane + 5% toluene; b), Pressure: 35 MPa, Temperature: 121 °C, Gas phase components: 20% H2S + 5% CO2 + 75% N2, Liquid phase components: 25% n-hexane + 20% n-octane + 50% n-decane + 5% toluene; c), Pressure: 35 MPa, Temperature: 121 °C, Gas phase components: 5% H2S + 20% CO2 + 75% N2, Liquid phase components: 25% n-hexane + 20% n-octane + 50% n-decane + 5% toluene; d), Pressure: 35 MPa, Temperature: 177 °C, Gas phase components: 5% H 2 S + 20% CO 2 + 75% N 2 , Liquid phase components: 25% n-hexane + 20% n-octane + 50% n-decane + 5% toluene.

[0027] The establishment and implementation of this method will establish and improve the quality control indicators and evaluation system for the blowout preventer rubber core material under extreme high and low temperatures and corrosive environments, put forward clear specific technical indicators for the rubber core sealing material of the blowout preventer core component, divide its application temperature grade, clarify the specific performance requirements to be met at each temperature grade, and determine the type of corrosive environment. This will effectively ensure the use safety of the blowout preventer and ensure the effective development of well control work. In the actual operation process, the establishment and implementation of this method enable specific quality and safety monitoring to be based on evidence and quantified.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate, rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. Evaluation method of BOP rubber core under extreme high and low temperature and corrosive environment conditions, characterized by: The following steps are involved: 1) Study the physical properties of nitrile rubber materials used in BOP rubber cores at room temperature, evaluate the quality and performance parameters, and obtain the basic data of nitrile rubber materials used in BOP rubber cores; 2) Study the changes in various performance indicators of nitrile rubber materials used in BOP rubber cores under extreme high and low temperature conditions and conduct structural analysis. Combined with the performance indicators and actual test results to ensure the normal use of the BOP rubber core, and in conjunction with experiments, determine the performance control standards of nitrile rubber materials used in BOP rubber cores under extreme high and low temperature environments; 3) Study the aging performance of nitrile rubber materials used in BOP rubber cores in high temperature environments and in alternating environments from high temperature to extremely low temperature, measure the changes and laws of various performance indicators of nitrile rubber materials used in BOP rubber cores during the aging process, determine the aging resistance that meets the performance requirements of BOP rubber cores, and determine the extreme high and low temperature test methods and quality control standards; 4) With reference to NACE 0187 "Standard Test Methods for Elastic Materials in Sour Gas Environments", four drilling and production corrosive environments were set up to study the aging performance of nitrile rubber materials used in BOP rubber cores. The aging period was 4 days, and samples were taken every 1 day to evaluate the changes in various mechanical properties and conduct molecular structure change analysis. The aging life of the BOP rubber core under high temperature was calculated based on the key mechanical parameters of the rubber core and the Arrhenius equation. The performance indicators and actual test conditions that ensure the normal use of the BOP rubber core were combined with experiments to determine the performance control standards of the nitrile rubber materials used in the BOP rubber core under extreme high and low temperature environments.

2. The method for evaluating the BOP rubber core under extreme high and low temperature and corrosive environmental conditions according to claim 1 is characterized by: The specific extreme high and low temperature evaluation method is as follows: for the nitrile rubber material used in the blowout preventer core, calorimetric analysis, dynamic mechanical analysis and infrared analysis are first used to characterize the microstructure; then, in combination with the macroscopic performance parameters of hardness, tension, tearing, compression, compression permanent deformation and resistance to liquid mass volume change, the glass transition temperature, molecular chain structure, mechanical properties and medium resistance of the nitrile rubber material used in the blowout preventer core are studied according to temperature levels. Finally, the changes in glass transition temperature, molecular chain structure, mechanical properties and medium resistance are linked to the application performance of the blowout preventer, and the key technical indicators of the nitrile rubber material used in the blowout preventer core at each temperature level are established, thereby forming: the extreme high and low temperature evaluation method.

3. The method for evaluating the BOP rubber core under extreme high and low temperature and corrosive environmental conditions according to claim 2 is characterized by: The extreme high temperature specifically refers to the maximum temperature grade G of non-metallic sealing materials determined to be 177°C according to the record in the standard GB / T 20174-2006.

4. The method for evaluating the BOP rubber core under extreme high and low temperature and corrosive environmental conditions according to claim 3 is characterized by: The extreme low temperature specifically refers to the low temperature grade A of non-metallic sealing materials determined as -26°C according to the record in the standard GB / T 20174-2006.

5. The method for evaluating the BOP rubber core under extreme high and low temperature and corrosive environmental conditions according to claim 4 is characterized in that: The high temperature environment refers to a closed space filled with hot air at 120°C.

6. The method for evaluating the BOP rubber core under extreme high and low temperature and corrosive environmental conditions according to claim 5 is characterized in that: The high temperature to extreme low temperature alternating environment specifically refers to treating the nitrile rubber material for the blowout preventer rubber core in a temperature environment of -26°C → 120°C → -26°C → 120°C, then treating it in a temperature environment of 120°C → -26°C → 120°C → -26°C, then treating it in a temperature environment of -26°C → 120°C → -26°C → 120°C, and finally treating it in a temperature environment of 120°C → -26°C → 120°C → -26°C, and in each treatment, each temperature value is placed for 12 hours and samples are taken to analyze and evaluate various properties of the material.

7. The method for evaluating the BOP rubber core under extreme high and low temperature and corrosive environmental conditions according to claim 6 is characterized by: The specific evaluation method under corrosive environment is as follows: For the nitrile rubber material used in the core of the blowout preventer, the differential scanning calorimeter, dynamic thermomechanical analyzer, thermogravimetric analyzer and Fourier transform infrared spectrometer are first used to perform microstructural analysis and characterization. Then, combined with macroscopic performance parameters such as hardness, tensile strength, tearing, rebound, wear, compression, compression permanent deformation and resistance to liquid mass volume change, a simulated drilling and production corrosive environment is set up to study the mechanical properties and microstructural changes of the nitrile rubber material used in the core of the blowout preventer. Finally, the changes in glass transition temperature, molecular chain structure, mechanical properties and medium resistance are linked to the application performance of the blowout preventer, and the key technical indicators of the nitrile rubber material used in the core of the blowout preventer in various corrosive environments are established, thereby forming an evaluation method under corrosive environment.

8. The method for evaluating the rubber core of a blowout preventer under extreme high and low temperature and corrosive environmental conditions according to claim 7 is characterized in that: The four types of drilling corrosive environments are: a) Pressure: 7MPa, temperature: 121℃, gas phase composition: 20%H2S+5%CO2+75%N2, liquid phase composition: 25%n-ethane+20%n-octane+50%n-decane+5%toluene; b) Pressure: 35MPa, temperature: 121℃, gas phase composition: 20%H2S+5%CO2+75%N2, liquid phase composition: 25%n-ethane+20%n-octane+50%n-decane+5%toluene; c), pressure: 35MPa, temperature: 121℃, gas phase composition: 5%H2S+20%CO2+75%N2, liquid phase composition: 25%n-ethane+20%n-octane+50%n-decane+5%toluene; d), pressure: 35MPa, temperature: 177℃, gas phase components: 5%H2S+20%CO2+75%N2, liquid phase components: 25%n-ethane+20%n-octane+50%n-decane+5%toluene.