Method for collecting light hydrocarbons in natural gas in laboratory, online circulating system and application

Abstract

The invention provides a method for collecting light hydrocarbons in natural gas in a laboratory as well as an online circulating system and application, and relates to the field of gas geochemical analysis. The method comprises the following steps: in a vacuum circulating system, enabling the natural gas repeatedly to flow through a pipeline filled with a molecular sieve, so that the light hydrocarbons in the natural gas are enriched in the molecular sieve; in a vacuum circulating system, heating the molecular sieve enriched with the light hydrocarbon, and collecting to obtain the light hydrocarbon released by the molecular sieve, wherein the light hydrocarbon is C5 hydrocarbon, C6 hydrocarbon, C7 hydrocarbon and C8 hydrocarbon. In the invention, the pure C5-C8 light hydrocarbon gas can be obtained from the natural gas with extremely low light hydrocarbon content by constructing a circulating system with a molecular sieve, so that the method is simple, low in cost, simple and convenient to operate and high in obtaining efficiency.

Description

technical field [0001] The invention relates to the field of gas geochemical analysis, in particular to a method and system for collecting light hydrocarbons in natural gas. Background technique [0002] Light hydrocarbons (C 5 -C 8 ) is one of the important components of natural gas, which contains extremely important and rich geochemical information. The geochemical indicators of light hydrocarbons can not only be used to determine the maturity of natural gas, identify gas reservoirs subjected to water washing or biodegradation, trace the source of natural gas, and The types of natural gas origin can be divided. [0003] Crude oil samples contain a large amount of volatile light hydrocarbon components, so gas chromatography or high performance liquid chromatography can be used to analyze light hydrocarbon components; however, the content of light hydrocarbon components in natural gas is extremely low, especially the methane content in "dry gas" is as high as More than 9...

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Problems solved by technology

The current gas elution method, thermal evaporation method, rock sealing extraction, rock low-boiling point light hydrocarbon extraction method, and adsorption-acidolysis hydrocarbon analysis method are only suitable for crude oil and source rock samples with high light hydrocarbon content. Xu Lian (1990) designed the pressurized sampling method, which is only suitable for the analysis of natural gas with high humidity, and needs to raise the temperature of the natural gas cylinder to 120°C, which has great potential safety hazards; Zhang Juhe et al. (1994) disclosed that the quartz tube is rich The amount of natural gas collected by the set method is limited, and the six-way valve part is prone to errors, and the light hydrocarbon components cannot be accurately detected

In recent years, some studies have used solid phase microextraction (SPME) technology to analyze light hydrocarbons in natural gas (Li et al. 2014), but the method is still immature, and the detection of light hydrocarbon components in natural gas cannot be realized at present

Wang Shunyu et al disclosed a natural gas C 3 -C 8 A new method for hydrocarbon enrichment analysis, which self-made C 3 -C 8 Hydrocarbon concentrator, but when testing, it is still necessary to elute the methane, ethane and other impurity gases in the concentrator

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