Sedimentary Microfacies and Depositional Model of Fine-Grained Rocks in the Middle Ordos Basin

Detailed sedimentary microfacies research is important to determine favorable target areas for oil and gas exploration. In order to clarify the sedimentary microfacies characteristics of Chang 7 in the Ordos Basin, the types and distribution of Chang 7 sedimentary microfacies were studied using logging, core, analysis and testing data. The results show that delta facies is developed in the Chang 7, mainly in the delta front subfacies, including distributary channel, natural levee, interdistributary bay and mouth bar. The underwater distributary channel sand body, as the skeleton sand body, is relatively well developed and is the main place for oil and gas accumulation. The thick fine sediments in Chang 7 sedimentary period are mainly mudstone and silty mudstone. Multi channel sand bodies and extremely thick fine-grained rocks form a high-quality source reservoir cap rock association.