Method for evaluating near-well fractured crack through Gd neutron tracing yield imaging

Abstract

The invention discloses a method for evaluating a near-well fractured crack through Gd neutron tracing yield imaging and particularly relates to the technical field of exploration and development of petroleum and natural gas. The method comprises the steps that a high heat capture cross section material Gd2O3 is added into a propping agent, by utilizing action of neutrons and Gd, Gd yields in different azimuths and the borehole macroscopic capture cross section are obtained through designed and combined array gamma imagers, and the near-well fractured crack is imaged; after a stratum is fractured, the propping agent with the Gd2O3 material with the high capture cross section is injected into the stratum; and mixed gamma energy spectrums in different azimuths are obtained through measuring of the azimuth gamma imagers, a crack imaging figure of the Gd yields on the periphery of a well is obtained after processing of the mixed gamma energy spectrums, and accordingly the azimuth, height, width and inclination of the crack are determined through the crack imaging figure. Compared with an existing evaluation technique of radioactive cracks, non-radioactive cracks and the like, the method has the characteristics that downhole crack recognition is visual, radioactive pollution is avoided, recognition of the azimuth, height, width and inclination of the crack are accurate, and sensitivity is high.

Description

technical field [0001] The invention relates to the technical field of oil and gas exploration and development, in particular to a method for evaluating near-well fracturing fractures by using Gd neutron tracer yield imaging. Background technique [0002] As a stimulation technology, hydraulic fracturing is widely used in the development of oil and gas, especially unconventional oil and gas reservoirs such as shale oil and gas. It mainly uses water pressure to fracture the rock layer, injects proppant to form artificial fractures, and at the same time changes the seepage capacity of the reservoir, so that oil or natural gas can form industrial oil and gas flow for production. Accurate evaluation of the proppant position and the height, width, azimuth, and dip angle of near-wellbore fracturing fractures is of great value for the design of fracturing models, the evaluation of unconventional oil and gas, and the optimization of production stimulation. [0003] At present, the ...

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Problems solved by technology

Due to safety, environmental protection and transportation restrictions, storage and use requirements, the promotion of radioactive tracer proppants is limited

[0004] The existing non-radioactive tracer measurement technology adds high-capture cross-section materials to the proppant, utilizes the interaction between neutrons and proppant, and uses compensated neutron instrumentation (CNL) or pulsed neutron capture before and after fracturing, respectively. The tool (PNC) performs well logging, and determines the position and height of the fractured fracture by comparing the thermal neutron count rate or capture cross-section changes of the near and far detectors before and after, or calculating the capture gamma counts produced by elements in the high thermal capture cross-section; Fractures cannot be displayed visually, and the width, azimuth, and dip of fractures cannot be accurately determined, and they are greatly affected by wellbore residues.

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