| Author's Name: FAN Liyong1, WU Dongxu2, REN Junfeng1, WANG Yongxiao2, WEI Liubin1,
ZHANG Hao2, LI Weiling2, LU Huili2, ZHU Wenbo2,3,4 |
| The Lower Paleozoic marine carbonate rocks in the Ordos Basin represent a critical natural gas exploration
target in China. However, problems such as strong reservoir heterogeneity and complex hydrocarbon accumulation
controlling factors have severely restricted large-scale and efficient exploration and development. This study integrates
the latest exploration results with regional seismic profiles, focusing on key scientific issues such as lithofacies
paleogeographic evolution, genetic types and controlling factors of reservoirs, and source-reservoir configurations, to
systematically investigate the distribution patterns of high-quality carbonate reservoirs and evaluate their exploration
potential. The main findings are as follows: (1) The Early Paleozoic sedimentary environment underwent a complete
evolutionary sequence from mixed sedimentary shelf (Mantou to Xuzhuang Formation) to carbonate ramps (Zhangxia to
Majiagou Formation) and finally to rimmed platforms (Upper Majiagou Formation). Among these, the inner ramp grain
shoal facies belts around paleo-uplifts and marine basins exhibit the most favorable reservoir properties. (2) Reservoir
development is jointly controlled by depositional microfacies, penecontemporaneous dissolution, supergene karstification,
and dolomitization. Five types of reservoirs are identified in the Cambrian-Ordovician succession: grain shoal, algal
mound, bioturbated, moldic pore, and dissolution vug types. These reservoirs are predominantly distributed along paleouplifts, basin margins and slope breaks. (3) Based on comprehensive analysis of tectonic-sedimentary framework, sourcereservoir relationships, and sealing conditions, three highly prospective exploration zones are delineated: the eastern
Wuyin marine basin, both flanks of the Yitong marine basin, and the western Shenmu-Mizhi platform depression, with a
total area of 10.5×104 km2. This study provides critical theoretical support and practical guidance for gas exploration in
marine carbonate rocks of the Ordos Basin. |
