Measuring method and device for underground thick oil molecule chain length

Abstract

The invention provides a measuring method and device for the underground thick oil molecule chain length. The method comprises the steps that a three-dimensional nuclear magnetic resonance pulse sequence is emitted into a probe of a nuclear magnetic resonance fluid analyzer filled with a thick oil sample, wherein the three-dimensional nuclear magnetic resonance pulse sequence contains three independent windows used for editing information of the longitudinal relaxation time T<1>, information of the diffusion coefficient D and information of the transverse relaxation time T<2> respectively; echo data is collected; inversion is performed on the echo data by adopting a fast inversion algorithm, and a joint probability distribution function about the longitudinal relaxation time T<1>, the diffusion coefficient D and the transverse relaxation time T<2> is calculated; a probability distribution function of the molecule chain length of all components in the thick oil sample is solved according to a pre-established model of the relation between the longitudinal relaxation time T<1> and the molecule chain length of all the components in the thick oil sample or a pre-established model of the relation between the diffusion coefficient D and the molecule chain length of all the components in the thick oil sample or a pre-established model of the relation between the transverse relaxation time T<2> and the molecule chain length of all the components in the thick oil sample.

Description

technical field [0001] The embodiments of the present invention relate to the technical field of heavy oil analysis, in particular to a method and device for measuring the molecular chain length of downhole heavy oil. Background technique [0002] Heavy oil is a kind of underground reservoir fluid with extremely complex composition, which has the characteristics of high viscosity, high density, difficult to be extracted and transported. The production value of heavy oil has received more and more attention. Understanding the crude oil components inside heavy oil is an important step in improving the efficiency of heavy oil production and utilization during actual production, even decomposition, refining and migration. [0003] At present, the commonly used crude oil components and molecular chain length analysis methods are mainly carried out in the laboratory, mainly including gas chromatography analysis methods, chemical shift methods and nuclear magnetic resonance method...

AI Technical Summary

Problems solved by technology

However, for heavy oil, it is difficult to convert the heavy components from liquid or semi-solid phase to gas phase for analysis, which also makes gas chromatography analysis method unable to obtain all the component information of heavy oil

Even for the chemical shift method, although the precise chemical composition and internal molecular structure of the sample can be obtained, it is difficult to interpret it due to the complexity of the heavy oil composition and the highly overlapping chemical spectrum distribution

For the NMR method, by editing the diffusion coefficient D, the longitudinal relaxation time T 1 , the transverse relaxation time T 2 , directly use the three-dimensional inverse Laplace transform to obtain the three-dimensional joint probability distribution function, resulting in slow data processing

[0004] On the other hand, the analysis method of crude oil components and molecular chain length is carried out in the laboratory. During the process of crude oil sampling from the downhole and transporting to the ground laboratory, due to changes in the external environment temperature and pressure, the physical parameters of the sample will also change. , individual heavy components may precipitate, which is not conducive to the accurate measurement of heavy oil components

Images