Method for measuring hydrogen index of crude oil by nuclear magnetic resonance

Abstract

The invention relates to a method for measuring a hydrogen index of crude oil by nuclear magnetic resonance. The method comprises the following steps of S1, measuring and fitting a pure water sample signal, using a functional equation with a single e index for fitting, and thus acquiring a saturation magnetization vector and a longitudinal relaxation time of a pure water sample; S2, measuring andfitting an crude oil sample signal, using a functional equation with dual e indexes for fitting, and thus acquiring a saturation magnetization vector of a crude oil sample and a longitudinal relaxation time of each component; and S3, building an equation set, and computing a relative volume and the hydrogen index of the crude oil sample. The invention provides the new method for measuring the hydrogen index of the crude oil by nuclear magnetic resonance, which can be applied to online measurement without sampling and without installing a gradient coil system. Specifically, the method providedby the invention adopts a reverse recovery pulse sequence to collect the signal, and is clear in principle, convenient to operate, high in accuracy of measurement result and good in repeatability; andthe method provided by the invention is also applicable to fluid of which an oil-water mixture cannot be significantly layered.

Description

technical field [0001] The invention belongs to the technical field of fluid measurement, and in particular relates to a method for measuring the hydrogen content index of crude oil by nuclear magnetic resonance. Background technique [0002] Hydrogen index (HI) is an inherent characteristic of hydrogen-containing fluids, which is defined as the ratio of the number of hydrogen atoms per unit volume of fluid to the number of hydrogen atoms per unit volume of pure water under standard conditions. The hydrogen content index is very important for NMR experiments: in the NMR logging evaluation, the hydrogen content index determines the value of the effective porosity of the formation, and the effective porosity is directly related to the reserves of the reservoir; In the field of fluid measurement, the hydrogen content index involves the calculation of the proportion of each phase composition of oil, water and gas mixed fluid, and the result directly affects the evaluation of oil...

AI Technical Summary

Problems solved by technology

However, conventional laboratory measurement methods are too cumbersome and require separate sampling, which is time-consuming and laborious, and the timeliness and cost-effectiveness are not high

The existing online measurement method needs to increase the gradient coil system to measure, which not only increases the cost, volume and weight of the instrument, but also increases the cost of maintenance; especially for fluids where the oil-water mixture cannot be clearly stratified, this method is difficult Individually and accurately measure the hydrogen index of crude oil components

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