Tight sandstone permeability computing method based on nuclear magnetic resonance double-stop value

Abstract

The invention discloses a tight sandstone permeability computing method based on a nuclear magnetic resonance double-stop value. T2 spectrums are inverted by measuring nuclear magnetic resonance decay curves of tight sandstone in completely water-containing and irreducible water conditions, the nuclear magnetic resonance T2 spectrums in the two conditions are contrasted, and nuclear magnetic resonance stop values of absolutely movable water and absolutely non-movable water are determined. On the basis, the relation among the content of absolutely movable water, the content of absolutely non-movable water and the permeability is analyzed, and a permeability model based on the nuclear magnetic resonance double-stop value is established. The method takes the contribution of different pore components for interstifial flows into full consideration, so that the permeability prediction accuracy of tight sandstone is improved.

Description

technical field [0001] The invention belongs to the field of geophysical well logging, and in particular relates to a method for calculating the permeability of tight sandstone based on nuclear magnetic resonance double cut-off values. Background technique [0002] Since its development, nuclear magnetic resonance technology has been widely used in various fields of geophysics and geological research, and has become an important method to characterize reservoir microscopic pore structure, fluid properties and physical property parameters, and has achieved good application results in conventional reservoir evaluation. [0003] As a key parameter of reservoir evaluation, permeability plays a pivotal role in the exploration and development of oil and gas fields. At present, the method of calculating permeability with NMR data is mainly based on Timur-Coates formula and SDR model, by selecting NMR T 2 The cut-off value separates the mobile fluid from the bound fluid to obtain t...

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Problems solved by technology

However, these methods rely too much on petrophysical data, and the models built are obviously regional, and it is difficult to extend to other blocks

In addition, due to the essential difference between the pore-throat distribution obtained by capillary pressure and the pore distribution obtained by nuclear magnetic resonance, the existing improved model also has major theoretical flaws

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