Method for determining content of unhydrated water in hydrate based on nuclear magnetic signal intensity

Abstract

The invention relates to a method for determining the content of unhydrated water in hydrate based on nuclear magnetic signal intensity, which comprises the following steps: (1) taking a mixture with main components of 1H2O and 2H2O as a standard sample, and constructing the porosity of the standard sample by using 2H2O; (2) establishing a relational expression that the nuclear magnetic signal intensity of the standard sample with the porosity of 30% changes along with the temperature; (3) measuring and calculating the volume and porosity of the sand sample by taking sand with different particle sizes as a porous medium; (4) carrying out a methane hydrate formation experiment in the porous medium; (5) collecting a nuclear magnetic signal of the unhydrated water, and simultaneously obtaining a T2 relaxation distribution diagram of the unhydrated water; (6) calculating the content of unhydrated water; (7) calculating the mass of the methane hydrate; and (8) calculating the methane hydrate saturation Sh. The dynamic change characteristics of porous medium hydrate formation are directly, effectively and accurately analyzed on the basis of the perspective of unhydrated water, and the method has important theoretical research significance on exploration and prediction of natural gas hydrate mineral reserves, commercial exploitation and exploitation technology research and development in the future.

Description

technical field

[0001] The invention relates to the fields of energy and chemical industry, in particular to a method for determining the content of unhydrated water in hydrates based on the intensity of nuclear magnetic signals. Background technique

[0002] The conditions of hydrate occurrence areas in nature are generally more complex, and most of them are gas hydrate-bearing deposits. Due to the large specific surface area of ​​porous media, the interfacial phenomenon is extremely prominent, and often exhibits strong interfacial tension and capillary condensation, which makes the formation of gas hydrate in porous media very different from that in free planes. Therefore, porous media The formation characteristics and distribution of natural gas hydrates in China have also become one of the main research contents of natural gas hydrates.

[0003] In the past few decades, many scholars have conducted research on the kinetics of hydrate formation in sediments, focusing on ...

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