Identification method for desorbed gas and free gas in shale output gas

Abstract

The invention belongs to the field of natural gas extraction and relates to an identification method for desorbed gas and free gas in shale output gas. The identification method comprises the following steps: firstly, before experiment, sampling volume V of a sample, metering the mass m, calibrating V, and setting the temperature T of a thermostat as experimental temperature; secondly, closing a valve I and opening a valve III; thirdly, after the pressure of a system is stabilized, recording initial pressure p by a pressure sensor; and closing the valve III; fourthly, setting a high-precisionplunger pump as a constant-pressure mode, and setting pump pressure as a first experimental pressure value; at the moment, starting to retreat the pump, and clearing the volume of accumulated producedgas of the high-precision plunger pump to zero; fifthly, opening the valve III and continuously retreating the pump; sixthly, when a pressure value reaches a first experimental pressure value set bythe high-precision plunger pump and is balanced, recording the pressure P', closing the valve III, and repeating the fourth step to the fifth step. According to the method, the contents of the desorbed gas and the free gas in the output gas can be identified and the reliability of a test result is ensured.

Description

technical field [0001] The invention relates to the technical field of natural gas exploitation, and more specifically, to a method for identifying desorbed gas and free gas in shale gas produced gas. Background technique [0002] At present, the exploration and development of shale gas in my country is in its infancy. Laboratory experiments are mostly based on petrological analysis, geochemical analysis, and gas-bearing analysis. Development physical simulation research focuses on the determination of physical parameters, pore structure characteristics, adsorption experiments, and seepage. In terms of characteristics, etc., there are few studies on dynamic physical simulation such as the identification of free gas and desorbed gas in the process of gas production, and the gas production characteristics of different development stages are very important for the prediction of shale gas production. [0003] Patent document CN201420640699.3 discloses a shale property tester, whi...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a method for identifying desorbed gas and free gas in shale gas output gas, aiming at the problem that existing shale gas adsorption and desorption devices cannot carry out gas production rules. When carrying out mining simulation experiments, by establishing The experimental data processing method can identify the content of desorbed gas and free gas in the produced gas, and obtain the production change characteristics of desorbed gas and free gas under different production pressures, so as to provide support for the optimization of production methods, production capacity prediction and dynamic analysis

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