A New Neutron Gamma Density Algorithm Based on Drill-Collar Inelastic Gamma Information
Source abstract
Abstract
Neutron gamma density (NGD) logging, as a safer and more environmentally friendly density logging method, has been applied in logging while drilling (LWD) for many years. However, most NGD algorithms have low density sensitivity and exhibit significant errors in the presence of gas and high-salinity water. To address the above issues, the inelastic gamma information of the drill collar is simulated by the Monte Carlo method, and its impact on NGD sensitivity and the results are studied. Using the drill-collar inelastic gamma information, a new neutron gamma density algorithm is proposed. The study shows that the drill-collar inelastic gamma information occupies a large proportion of the total inelastic gamma count recorded by the detector, which reduces the sensitivity of the NGD algorithms using the total inelastic gamma information. By eliminating the contribution of the drill collar from the total inelastic gamma count, the density sensitivity of the NGD algorithms can be significantly improved. In addition, the drill-collar inelastic gamma information is closely related to high-energy fast neutrons and can be used to correct the fast neutron distribution in NGD logging. The new NGD algorithm, utilizing the drill-collar inelastic gamma information, has excellent performance in the presence of gas and high-salinity water. However, similar to the other algorithms, the new algorithm is still affected by other environmental factors such as borehole, lithology, and shale. Furthermore, this new algorithm does not require any additional modifications to existing NGD tools and can work with other NGD algorithms.
Source: crossref · Quality: baseline
Research context
OpenAlex topics: Drilling and Well Engineering · Hydrocarbon exploration and reservoir analysis · Geothermal Energy Systems and Applications
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
Affiliations
Key Laboratory of Exploration Technologies for Oil and Gas Resources (Yangtze University), Ministry of Education, Wuhan 430100, China
College of Geophysics and Petroleum Resources, Yangtze University, Wuhan 430100, China
PetroChina Oil, Gas & New Energies Company, Beijing 100007, China
Funding
National Oil & Gas Major Project
References (36)
Show source-provided references
1. Aitken, J.D., Adolph, R., Evans, M., Wijeyesekera, N., McGowan, R., and Mackay, D. (2002, January 20–22). Radiation sources in drilling tools: Comprehensive risk analysis in the design, development and operation of LWD tools. Proceedings of the SPE International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production, Kuala Lumpur, Malaysia.10.2118/73896-MS ↗
2. Badruzzaman, A., Badruzzaman, T., Zalan, T.A., and Mai, K. (2004, January 7–9). Multi-sensor through-casing density and saturation measurement concepts with a pulsed neutron source: A modeling assessment. Proceedings of the SPE International Petroleum Conference in Mexico, Puebla, Mexico.10.2118/89884-MS ↗
3. Badruzzaman, A., Barnes, S., Bair, F., and Grice, K. (2009, January 4–6). Radioactive sources in petroleum industry: Applications, concerns and alternatives. Proceedings of the Asia Pacific Health, Safety, Security and Environment Conference, Jakarta, Indonesia.10.2118/123593-MS ↗
4. A novel framework for neutron-gamma density logging: Semi-empirical modeling, directional neutron sources, and experimental benchmarking10.1038/s41598-025-04222-x ↗
5. Improving the pulsed neutron-gamma density method with machine learning regression algorithms10.1016/j.petrol.2022.110962 ↗
6. Source-less density measurement using an adaptive neutron-induced gamma correction method10.1007/s41365-023-01274-4 ↗
7. Enhancing accuracy and range of sourceless density
8. Data-processing methods for D–T source neutron-gamma density logging while drilling10.1007/s41365-025-01671-x ↗
9. Wilson, R.D. (1995, January 21–28). Bulk density logging with high-energy gammas produced by fast neutron reactions with formation oxygen atoms. Proceedings of the IEEE Nuclear Science Symposium and Medical Imaging Conference Record, San Francisco, CA, USA.
10. Archer, M.P., Odom, R.C., Wilson, R.D., and Bailey, S.M. (June, January 30). Pulsed neutron density measurements: Modeling the depth of investigation and cased-hole borehole uncertainties. Proceedings of the SPWLA 40th Annual Logging Symposium, Oslo, Norway.
11. Odom, R.C., Wilson, R.D., and Ladtkow, R.K. (2001, January 21–23). Log examples with a prototype three-detector pulsed-neutron system for measurement of cased-hole neutron and density porosities. Proceedings of the SPE Rocky Mountain Petroleum Technology Conference, Keystone, PA, USA.10.2118/71042-MS ↗
12. Reichel, N., Evans, M., Allioli, F., Mauborgne, M.-L., Nicoletti, L., Haranger, F., Laporte, N., Stoller, C., Cretoiu, V., and El Hehiawy, E. (2012, January 16–20). Neutron-gamma density (NGD): Principles, field test results and log quality control of a radioisotope-free bulk density measurement. Proceedings of the SPWLA 53rd Annual Logging Symposium, Cartagena, Colombia.
13. Formation density from a cloud, while drilling
14. Neutron-gamma density measurement method using the mass attenuation coefficient function10.1007/s41365-025-01815-z ↗
15. Wang, H., Yue, A.Z., Zhang, X.L., Tang, J., He, X., Luo, X., and Han, B. (2022). Bulk density response and experimental study of pulsed neutron-gamma density logging. Front. Earth Sci., 10.10.3389/feart.2022.803775 ↗
16. Al-Mudhaf, M., Al-Fayez, F., Alasaker, H., Al-Saeedi, A.M., Al-Samhan, S., Saleem, A., Azmi, S.M., Aldhafeeri, O.F., Ali Haji, D., and Dasgupta, S. (2025, January 3–6). Sourceless logging while drilling platform enables reservoir evaluation in complex and high-risk drilling environment: A case study from Abdali and Ahmadi Field, Kuwait. Proceedings of the ADIPEC, Abu Dhabi, United Arab Emirates.10.2118/228962-MS ↗
17. Luycx, M., and Torres-Verdín, C. (2017, January 9–11). Resolution and accuracy of neutron-gamma density measurements compared to conventional gamma-gamma density measurements. Proceedings of the SPE Annual Technical Conference and Exhibition, San Antonio, TX, USA.10.2118/187114-MS ↗
18. Physics, applications, and limitations of borehole neutron-gamma density measurements10.1190/geo2018-0088.1 ↗
19. Zhang, Q.Y. (2019). Research on Pulsed Neutron Dual-Spectrum Density Logging Method Based on D-T Neutron Source. [Master’s Thesis, China University of Petroleum (East China)].
20. Improved formation density measurement using controllable D-D neutron source and its lithological correction for porosity prediction10.1007/s41365-022-00988-1 ↗
21. Jacobson, L., Durbin, D., and Reed, S. (2004, January 26–29). An improved formation density measurement using PNC tools. Proceedings of the SPE Annual Technical Conference and Exhibition, Houston, TX, USA.10.2118/90708-MS ↗
22. Quirein, J., Smith, H., Chen, D., Perkins, T., and Reed, S. (2005, January 26–29). Formation density prediction using pulsed neutron capture tools. Proceedings of the SPWLA 46th Annual Logging Symposium, New Orleans, LA, USA.
23. Mirto, E., Weller, G., el-Halawani, T., Grau, J., Berheide, M., Allioli, F., Evans, M., Berto, R., Borghi, M., and Firinu, M. (2006, January 12–15). New developments in sourceless logging-while-drilling formation evaluation: A case study from Southern Italy. Proceedings of the SPE Europec/EAGE Annual Conference and Exhibition, Vienna, Austria.10.2523/100351-MS ↗
24. Accuracy and borehole influences in pulsed neutron gamma density logging while drilling10.1016/j.apradiso.2011.04.023 ↗
25. Evans, M., Allioli, F., Cretoiu, V., Haranger, F., Laporte, N., Mauborgne, M.-L., Nicoletti, L., Reichel, N., Stoller, C., and Tarrius, M. (2012, January 8–10). Sourceless neutron-gamma density (SNGD): A radioisotope-free bulk density measurement: Physics principles, environmental effects, and applications. Proceedings of the SPE Annual Technical Conference and Exhibition, San Antonio, TX, USA.10.2118/159334-MS ↗
26. Al-Rubaiyea, J., Al-Bader, A., Al-Houli, M., Al-Najim, A., Al-Duwaish, M., and Elsherif, A. (2015, January 15–16). An innovative approach to formation evaluation with a sourceless LWD technology: A case study from partitioned zone between Kuwait and Saudi Arabia. Proceedings of the SPE Middle East Intelligent Oil and Gas Conference and Exhibition, Abu Dhabi, United Arab Emirates.10.2118/176806-MS ↗
27. A new method for calculating bulk density in pulsed neutron-gamma density logging10.1190/geo2018-0821.1 ↗
28. Modeling and simulation of neutron-gamma density logging: Impact of mudcake thickness and barite content on measurement accuracy10.1016/j.net.2025.103883 ↗
29. A LWD gas-reservoir recognition method based on the inelastic gamma information of the drill collar10.1016/j.geoen.2023.211684 ↗
30. A method to describe inelastic gamma field distribution in neutron gamma density logging10.1016/j.apradiso.2017.08.024 ↗
31. A method of determining formation density based on fast-neutron gamma coupled field theory
32. Application analysis on the different neutron gamma density (NGD) logging methods10.1016/j.apradiso.2021.109672 ↗
33. Galford, J., Truax, J., Hrametz, A., and Haramboure, C. (2009, January 21–24). A new neutron-induced gamma-ray spectroscopy tool for geochemical logging. Proceedings of the SPWLA 50th Annual Logging Symposium, The Woodlands, TX, USA.10.2118/123992-MS ↗
34. Application and quality control of core data for the development and validation of elemental spectroscopy log interpretation
35. Haranger, F., Allioli, F., Berheide, M., Craddock, P., Øpsen, D.F., Grau, J., Horstmann, M., Maggs, D., Mauborgne, M.-L., and Pallain, A. (2023, January 10–14). A step change in neutron-induced gamma ray spectroscopy: Using a high-resolution LABR3:Ce detector in an integrated LWD tool. Proceedings of the SPWLA 64th Annual Logging Symposium, Lake Conroe, TX, USA.
36. Segesman, F., and Liu, O. (1971). The Excavation Effect. Transactions of the SPWLA 12th Annual Logging Symposium, SPWLA.