@article{CAO2026, 
author = {Hongxia CAO and Haiyan WU and Hang ZHAO and Zhenguo WANG and Xingmin REN and Yanqin GUO and Baiqiang LI and Ke LUO},
title = {Sedimentary facies characteristics and distribution patterns of the sub-member Ma 51 in the Majiagou Formation, eastern Yanchang exploration block, Ordos Basin},
year = {2026},
journal = {Journal of Northwest University (Natural Science Edition)},
volume = {56},
number = {3},
pages = {627-638},
keywords = {sedimentary microfacies, carbonate rock, Fifth Member of the Majiagou Formation, eastern Yanchang exploration block, Ordos Basin},
url = {https://www.sciopen.com/article/10.16152/j.cnki.xdxbzr.2026-03-015},
doi = {10.16152/j.cnki.xdxbzr.2026-03-015},
abstract = {This study focuses on the fifth sub-member of the Majiagou Formation, specifically the first sub-member（referred to as "sub-member Ma51"）in the eastern Yanchang exploration area. Utilizing the outcomes from the meticulous delineation of smaller stratigraphic units, combined with core observations, thin-section analysis, single-well log sedimentary microfacies interpretation, and comparative inter-well section analysis, we conducted an in-depth examination of the sedimentary microfacies types and their planar distribution within the four minor layers of the sub-member Ma 514 in the study area. This analysis aims to elucidate the distributional and evolutionary patterns of sedimentary microfacies across each minor layer. The results show that the sub-member Ma 51 in the eastern Yanchang exploration area is overall a restricted platform sub-facies deposit, mainly developing mud dolomitic flat, dolomitic flat, lime flat, and muddy flat sedimentary microfacies. The sub-layer Ma 514 is characterized by the development of dolomitic flat, mud dolomitic flat, and muddy flat. Dolomitic flats are predominantly found in the northwest and central parts of the study area, while mud dolomitic flat cover the rest majority of the region. Muddy flats are notably restricted to the southwest portion of the study area. During the deposition of the sub-layer Ma 513, the expansion of dolomitic flat in the central part of the study area and muddy flat in the south has increased compared to the sub-layer Ma 514, attributed to enhanced evaporation in some local areas and an increase in terrigenous muddy input. During the sedimentation of the sub-layer Ma 512, a relative increase in water depth in the western and southwestern parts of the study area resulted in a significant reduction in the extent of dolomitic flat in the west and muddy flat in the southwest. Concurrently, lime flat emerged in some local areas of the southwest and southeast. In the sub-layer Ma 511, mud dolomitic and muddy flat predominantly occurred in the western and central parts of the study area, while dolomitic flat was mainly found in the eastern part. Additionally, lime flat developed in some northern local areas. The research results can provide scientific reference for the control mechanism of sedimentary microfacies on strongly heterogeneous carbonate reservoirs and the prediction of favorable areas for favorable reservoir distribution in the Yanchang exploration area.}
}