| Author's Name: WU Dongxu1,2,3, FAN Liyong4, LI Weiling1, ZHONG Jianwei5, ZAHNG Lei4,
SHI Pingping4, ZHU Wenbo1, LU Huili1, WU Xingning1 |
| The exploration targets for marine oil and gas in the Ordos Basin have gradually shifted from the early
weathering crust reservoirs of the Majiagou Formation to the inner carbonate reservoirs below the unconformity at the top
of Ordovician. However, the research level of deep Cambrian and Ordovician in the basin is relatively low, and the overall
characteristics and configuration relationship of the source, reservoir, and cap rock are unclear. Based on the latest drilling
and seismic data, combined with basic geological work such as field outcrop investigation, laboratory analysis, core and
thin section observation, the author has compiled a series of maps of tectonics-lithofacies paleogeography, maps of
hydrocarbon source rocks and favorable sedimentary facies zones, to clarify the development characteristics and
configuration relationship of source, reservoir, and cap rocks of the Cambrian-Ordovician. The Cambrian system in the
Ordos Basin has a structural pattern of inherited uplifts developing within the platform and inherited rifts developing at the
platform edge. The southwestern and northeastern rifts of the basin control the development of Middle and Lower
Cambrian source rocks mainly in the sea troughs and bays, while the Wushenqi and Qingyang ancient uplifts control the
development of granular shoals and weathered crust reservoirs mainly in the periphery and platform edge zones of the
ancient uplifts. The Ordovician has a sedimentary pattern of multiple uplifts and depressions developing within the
platform, and the differential distribution of sedimentary facies is jointly controlled by sedimentary paleogeomorphology
and sea level changes. The three uplift zones within the platform control the distribution of favorable microfacies such as
granular shoal and gypsum dolomite tidal flat, while the two depression zones within the platform control the distribution
of marine source rocks. Tectonic-sedimentary models of the platform margin rift in Cambrian and the platform inner
depression in Ordovician control the development of source rocks and reservoirs, and form three sets of excellent sourcestorage-cap combinations, which have great potential for natural gas accumulation and are important areas for future risk
exploration in the Ordos Basin. |
