A fast forward algorithm of azimuthal gamma imaging logging while drilling

Chang Zong; Juntao Liu; Zhiyi Liu; Yingming Liu; Caizhi Wang; Hui Gao; Junya Duan; Jun Zhou

doi:10.1016/j.apradiso.2023.110659

A fast forward algorithm of azimuthal gamma imaging logging while drilling

Appl Radiat Isot. 2023 Apr:194:110659. doi: 10.1016/j.apradiso.2023.110659. Epub 2023 Jan 19.

Authors

Chang Zong¹, Juntao Liu², Zhiyi Liu¹, Yingming Liu³, Caizhi Wang³, Hui Gao⁴, Junya Duan⁴, Jun Zhou⁵

Affiliations

¹ School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, Gansu Province, China; Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou, 730000, Gansu Province, China.
² School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, Gansu Province, China; Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou, 730000, Gansu Province, China. Electronic address: liujuntao20082009@126.com.
³ Research Institute of Petroleum Exploration and Development, Beijing, 100083, China.
⁴ Xi'an Huineng Electronic Equipment Co.Ltd, Xi'an, 710065, Shaanxi Province, China.
⁵ China Oilfield Services Limited, Sanhe, 065201, Hebei Province, China.

PMID: 36724613
DOI: 10.1016/j.apradiso.2023.110659

Abstract

Logging while drilling (LWD) technology can evaluate the formation interface and stratigraphic properties around the borehole in real time, so as to adjust the drilling trajectory and effectively improve the reservoir encounter rate. Fast forward algorithm can be used with LWD, by comparing the fast forward results with the actual gamma LWD results, it can distinguish the formation interface more accurately. Fast forward algorithm also can provide a theoretical basis for geosteering and azimuthal gamma logging interpretation. In this paper, based on the spatial distribution law of gamma rays and The Monte Carlo N-particle code (MCNP)-driven spatial sensitivity function, a 3D fast forward method of gamma ray LWD is proposed. Compared with the traditional algorithms, the new method can realize the fast simulations of gamma ray logging in four sectors, which enables fast azimuthal imaging. The comparison shows that whether in vertical wells or high-angle wells, the results of the proposed method are in high agreement with the MCNP fine simulations. In addition, the new method improves the calculation speed by tens of thousands of times with comparable accuracy. Finally, the gamma logging-while-drilling data of a highly deviated well in a field case verifies the accuracy and applicability of the method. The algorithm can meet the requirements of LWD for fast forward modeling of azimuthal natural gamma ray logging, which is expected to be applied to geosteering and logging interpretation of high angle and horizontal wells.

Keywords: 3D; Azimuthal gamma imaging; Fast forward algorithm; LWD.