Nuclear magnetic resonance laboratory measuring method for heavy oil and asphaltene cores

Abstract

The invention discloses a nuclear magnetic resonance laboratory measuring method for heavy oil and asphaltene cores and belongs to the technical field of automatic control. The method comprises: firstly, measuring the nuclear magnetic resonance attenuation signals of a core in a dry state, a core in a saturated brine state, and a core in a centrifugal state, secondly, obtaining the T2 distributionspectrum of cores in each state by inversion; thirdly, obtaining the corrected T2 distribution spectrum through the difference spectrum processing; further, obtaining a T2 distribution cumulative curve of a core in the saturated brine state and a T2 distribution cumulative curve of a core in the centrifugal state; obtaining total porosity, effective porosity, bound water saturation, and T2 cutoffvalue by calculating the above results. The calculated results are more realistic and accurate, and eliminate the influence of nuclear magnetic resonance attenuation signals in the dry state. The method is specially designed for unconventional cores containing heavy oil and asphaltenes, and has broad application prospects in the field of unconventional oil and gas nuclear magnetic logging.

Description

technical field [0001] The invention belongs to the technical field of petroleum exploration, in particular to a nuclear magnetic resonance laboratory measurement method for heavy oil and asphaltic rock cores. Background technique [0002] At present, NMR logging is mainly used in conventional oil and gas formations, and has achieved good application results in sandstone formations. Conventional experimental methods believe that the cores in the dried state do not have NMR attenuation signals. The resonance attenuation signal is not measured, the laboratory directly measures the nuclear magnetic resonance attenuation signal of the core, and the T 2 Distribution spectrum for calculation of total porosity, effective porosity, irreducible water saturation and T 2 cutoff, etc. [0003] However, in the field of unconventional oil and gas, NMR logging has encountered new challenges. Dry cores containing heavy oil and asphaltenic carbonate rocks have NMR attenuation signals. Inv...

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Problems solved by technology

[0003] However, in the field of unconventional oil and gas, NMR logging has encountered new challenges. Dry cores containing heavy oil and asphaltenic carbonate rocks have NMR attenuation signals. Inversion calculation after direct measurement will ignore the influence of the NMR attenuation signal of the dry state core, and will affect the effective porosity, centrifugal saturation and T 2 The cut-off value will have a great impact, making the measurement results far from the actual, which cannot meet the needs of production and development. Therefore, the NMR laboratory measurement method of conventional cores cannot be applied to unconventional cores containing heavy oil and asphaltenes. More targeted NMR laboratory measurements need to be established to address new issues in heavy oil, bituminous cores

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