Nuclear Techniques ›› 2020, Vol. 43 ›› Issue (5): 50502-050502.doi: 10.11889/j.0253-3219.2020.hjs.43.050502

• NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH • Previous Articles     Next Articles

Study on density logging method based on γ-ray broad beam attenuation model

Ningning YANG1,Yuxin ZHANG2,Huawei YU2()   

  1. 1.Measurement and Control while Drilling Technology Center of Sinopec Oilfield Service Corporation, Dongying 257078, China
    2.School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China
  • Received:2020-01-19 Revised:2020-03-14 Online:2020-05-15 Published:2020-05-07
  • Contact: Huawei YU E-mail:yhwlog@163.com
  • About author:YANG Ningning, female, born in 1980, graduated from China University of Petroleum (Hua Dong) with a master's degree in 2009, focusing on measurement and control while drilling technology
  • Supported by:
    National Natural Science Foundation of China(41674129);National Science and Technology Major Project(2016ZX05021-001);National Key Research and Development Program of China(2016YFC0302802)

Abstract: Background

With more and more attention paid to low-density gas hydrate formation, higher requirements are raised for density measurement range and accuracy of density logging.

Purpose

This study aims to improve the accuracy of density logging in low-density formation by using board beam attenuation model.

Methods

Firstly, the attenuation law of γ-ray narrow beam used for density logging was analyzed. Secondly, a response model based on broad-beam γ-ray density logging was derived by combining with the broad-beam γ-ray attenuation law, hence the calculation formula of formation density was obtained by scaling. Finally, the Monte Carlo N Particle Transport Code (MCNP) was used to simulate the density logging response in low-density formation, meanwhile, the application scope and accuracy of two attenuation laws in density logging were compared and analyzed.

Results

The response relationship of gamma rays in the formation can be better described by the broad beam attenuation model in density logging, while the narrow beam response relationship is only a special case of broad beam. By using the formation density formula based on the broad beam γ attenuation model, the density measurement range is expanded to 1.00~3.00 g?cm-3. Furthermore, for gas hydrate formation with density ranging from 1.00 g?cm-3 to 1.60 g?cm-3, its average measurement error of the far detector is reduced from 0.092 g?cm-3 to 0.009 g?cm-3, and that of the near detector is reduced from 0.251 g?cm-3 to 0.029 g?cm-3.

Conclusions

The board beam γ-ray attenuation model can be used to greatly improve the accuracy and measuring range of density logging, and this provides theoretical and methodological basis for accurate measurement of gamma ray density logging in low-density formation in the future.

Key words: Density logging, Broad beam γ attenuation, Monte Carlo simulation, Low-density formation

CLC Number: 

  • TL99,P631.8+17