Gas reservoir density calculation method based on density, neutron and nuclear magnetic resonance logging

Abstract

The invention discloses a gas reservoir density calculation method based on density, neutron and nuclear magnetic resonance logging, comprising the specific steps of S1, acquiring three logging curves, to be specific, applying neutron logging-while-drilling, density logging and nuclear magnetic resonance logging to the same best measurement, and alternatively, applying cable neutron logging, density logging and nuclear magnetic resonance logging to the same measurement, thereby ensuring that an object reservoir under measurement gains time unification and invasion depth approximation; S2, applying an equation that is shown in the description to density logging measurement information; S3, applying an equation that is shown in the description to neutron logging measurement information; S4,applying an equation that is shown in the description to nuclear magnetic resonance logging measurement information; S5, through simultaneous equations of neutron, density and nuclear magnetic resonance, calculating three unknown numbers: true total porosity phi of the gas reservoir, gas saturation (1-S<xo>) and gas reservoir density rho h; S6, outputting calculation results. The method herein helps provide logging evaluation for gas reservoirs, provides precise reliable total porosity, flushed zone gas saturation and gas density, provides improved geological evaluation accuracy, has accuratemodel calculation results and is widely applicable.

Description

technical field [0001] The invention relates to the technical field of fluid identification, porosity, and fluid density measurement of gas-bearing reservoirs, in particular to a gas layer density calculation method based on density, neutron, and nuclear magnetic resonance logging. Background technique [0002] In gas field logging reservoir evaluation, it has always been a difficult problem to accurately calculate the true total porosity, gas density and gas saturation of the flushing zone; The hydrogen content index and the electron density index determine the response of neutron logging and density logging, and they are related to each other. The relationship is established by the existence of hydrogen, and the neutron density logging response is related to the rock volume density, so These two kinds of logging information can be used to calculate porosity and identify fluids; however, the reliability of solving three unknowns by using two equations is very poor, so the p...

AI Technical Summary

Problems solved by technology

[0002] In gas field logging reservoir evaluation, it has always been a difficult problem to accurately calculate the true total porosity, gas density and gas saturation of the flushing zone; The hydrogen content index and the electron density index determine the response of neutron logging and density logging, and they are related to each other. The relationship is established by the existence of hydrogen, and the neutron density logging response is related to the rock volume density, so These two kinds of logging information can be used to calculate porosity and identify fluids; however, the reliability of solving three unknowns by using two equations is very poor, so the priori gas density parameters are often substituted. The gas density value is generally obtained from formation test data, and the cost It is relatively expensive, and lacks the possibility that the gas density of each well may change, so the joint calculation method of neutron density has always been flawed in the application of quantitatively obtaining the parameters of gas saturation and gas density in the flushing zone

Images