Salt-cavern gas storage gas-liquid interface measurement method and system based on low-frequency electric signal

Abstract

The invention relates to a salt-cavern gas storage gas-liquid interface measurement method and system based on a low-frequency electric signal. The method comprises the steps of: applying a low-frequency current signal to a central tube by an excitation source; measuring the voltage of a central pipe below the insulating short section, and calculating the impedance Z lower at the lower end of the insulating short section according to the low-frequency current signal<lower>; according to the definition of the low-frequency current signal, the voltage of the central pipe below the insulation short section and the impedance Z<lower> of the lower end of the insulation short section, determining a calculation equation of the distance H between the insulation short section and a gas-liquid interface; and calculating the distance H between the insulating short section and the gas-liquid interface according to the impedance Z<lower> at the lower end of the insulating short section and the calculation equation. Measurement of a salt-cavern gas storage gas-liquid interface is realized by utilizing the property that the characteristic impedance of the central tube is far greater than that of saline water, and the gas-liquid interface is not prone to be influenced by an oil pollution environment and sound wave propagation attenuation; and the measuring system provided by the invention has recoverability, has small interference on the use of the salt-cavern gas storage, has good working stability, and effectively reduces the replacement frequency of underground equipment.

Description

technical field [0001] The invention belongs to the field of salt-cavern gas storage measurement, and in particular relates to a method and system for measuring the gas-liquid interface of a salt-cavern gas storage based on low-frequency electrical signals. Background technique [0002] In recent years, my country's natural gas consumption has grown rapidly, showing a trend of short supply. In order to reduce the peak load of natural gas pipelines and ensure the flexibility and reliability of natural gas supply, the construction of underground gas storage in major consumption areas along natural gas trunk lines has become the mainstream method to ensure the peak-shaving supply of natural gas. There are three main types of underground gas storage: depleted gas reservoir type, aquifer type and salt cavern type. As the name implies, a salt cavern refers to an underground cavity formed by dissolving salt rock in a salt-bearing formation or a salt dome by injecting a solvent suc...

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Problems solved by technology

[0005] In order to solve the problem that the existing gas-liquid interface measurement method of salt-cavern gas storage is easily affected by the environment and has measurement errors, in the first aspect of the present invention, a method for measuring the gas-liquid interface of salt-cavern gas storage based on low-frequency electrical signals is provided. Including: installing the insulating pup joint at the joint of the two sections of the central tube, installing the excitation source on the outer wall of the insulating pup joint, and the positive and negative poles of the excitation source are respectively connected to the center tube above the insulating pup joint and the center below the insulating pup joint. The outer wall of the tube is connected; the voltage measuring device is installed on the outer wall of the central tube under the insulating short joint, and is located above the highest height of the gas-liquid interface; the excitation source applies a low-frequency current signal to the central tube; measure the voltage of the central tube under the insulating joint , and calculate the impedance Z of the lower end of the insulation nipple according to the low-frequency current signal 下 ;According to the low-frequency current signal, the central tube voltage under the insulating pup and the impedance Z of the lower end of the insulating pup 下 The definition of the calculation equation to determine the distance H between the insulating pup and the gas-liquid interface; according to the impedance Z of the lower end of the insulating pup 下 and the calculation equation, calculate the distance H between the insulating pup joint and the gas-liquid interface

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