Element yield and thermal neutron count ratio combined porosity measurement method

Abstract

The invention discloses an element yield and thermal neutron count ratio combined porosity measurement method. According to the method, a three-detector pulsed neutron instrument is adopted for measurement, and the formation porosity is evaluated by combining a thermal neutron counting ratio obtained by a thermal neutron detector and element yields extracted by an inelastic scattering gamma-ray energy spectrum and a capture gamma-ray energy spectrum measured by a gamma-ray detector. The method comprises the following steps: determining a relationship between neutron porosity and thermal neutron counting ratio under a standard condition by using a measurement result of an instrument under a standard limestone scale well group, establishing a numerical simulation model according to a specified well, and simulating to obtain element yields under different lithology and mineral composition conditions; and performing nonlinear regression analysis on the actually measured element yield and the simulated element yield to obtain the relationship among the lithology factor, the thermal neutron count ratio and the formation porosity. According to the method, the lithologic factors are determined by utilizing the stratum element yield, the influence of lithology and mineral composition on the neutron porosity is eliminated, and the accuracy of evaluating the porosity in the unconventional complex lithologic reservoir is improved.

Description

technical field [0001] The invention belongs to the technical field of mine geophysical well logging, and in particular relates to a porosity measurement method combining element yield and thermal neutron count ratio. Background technique [0002] With the development of the petroleum industry and the massive exploitation of conventional oil and gas resources, unconventional oil and gas resources have become the main source of global fossil energy. Since 1990, the global unconventional oil and gas reserves have increased by 24.1 billion tons of oil equivalent, accounting for 16.7% of the global new reserves. In 2019, global unconventional oil and gas production accounted for 12.1% and 29.8% of the world's total oil and gas production, respectively. It can be seen that the exploration and development of unconventional oil and gas resources has become the main direction of future oil industry development. [0003] Unconventional oil and gas resources mainly include fractured-...

AI Technical Summary

Problems solved by technology

After years of development, neutron porosity logging technology has been very mature, but because neutron porosity logging is greatly affected by the borehole and formation environment, especially when the formation lithology and mineral composition are relatively complex, neutron porosity logging The measurement results of the degree of deviation are very large, resulting in inaccurate conclusions about the qualitative interpretation of the reservoir

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