Crack body density quantitative calculation method based on neutron activation analysis self-shielding correction

Abstract

The invention discloses a crack body density quantitative calculation method based on neutron activation analysis self-shielding correction. The crack body density quantitative calculation method comprises the steps that tracer elements with high thermal neutron capture cross sections are added into a propping agent, capture gamma-ray energy spectra before and after fracturing construction are measured through a pulsed neutron instrument, and a measured value of fracture body density after fracturing is obtained; the capture gamma-ray energy spectra before and after fracturing are analyzed based on an instantaneous gamma neutron activation analysis technology; elements with invariable contents before and after fracturing are extracted and any one element from the elements is elected, and aself-shielding correction factor is calculated by utilizing a characteristic peak counting ratio before and after fracturing of the element; a true value of the self-shielding correction factor is determined by performing self-shielding correction on a measured value of characteristic peak counting of the tracing element; and numerical fitting is carried out on the true value of the characteristic peak count of the tracing element and the fracture body density to determine a fracture body density quantitative calculation formula. According to the crack body density quantitative calculation method based on the neutron activation analysis self-shielding correction, the saturation effect caused by self-shielding is eliminated, the crack response sensitivity is further improved, and the quantitative calculation of the crack body density is realized.

Description

technical field [0001] The invention belongs to the field of petroleum and natural gas development, in particular to a method for quantitatively calculating fracture body density based on neutron activation analysis and self-shielding correction. Background technique [0002] Hydraulic fracturing is a oil and gas stimulation technology widely used in the development of unconventional oil and gas reservoirs such as oil and gas, especially shale oil and gas. By impacting the rock with high-pressure fluid with proppant to break it, the proppant stays in the fracture to change the seepage capacity of the reservoir, thereby forming oil and gas seepage channels. Accurate evaluation of proppant position and quantitative evaluation of near-wellbore fracture density and width are of great significance for fracturing model optimization and productivity prediction. [0003] At present, the radioactive tracer evaluation technology is gradually eliminated due to restrictions on safety, ...

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Problems solved by technology

[0004]However, the existing non-radioactive tracer evaluation methods all have the problem of low fracture response sensitivity. At the same time, under the condition of high fracture density, neutron self-shielding effect The count saturation of the existing non-radioactive tracer evaluation method cannot accurately and quantitatively calculate the fracture parameters and other deficiencies.

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