| Based on the observation of outcrops, cores and thin sections, and analysis of logging data and experiment data, the sedimentary microfacies of Ordovician Majiagou Formation in Ordos Basin are studied systematically. Furthermore, the evolution models of sedimentary facies are established by synthetic analysis of paleoclimate and paleo-sedimentary patterns. It is indicated that: （1）There are two types of paleo-sedimentary framework of Majiagou Formation: sag-and-swell type and single-sag type; （2）Nine types of microfacies are developed in Ordovician Majiagou Formation. According to the combination of these sedimentary microfacies in the lateral direction at different sea level, a complete transgressive-regressive cycle can be subdivided into six stages: early, mid and late stages of transgression and early, mid and late stages of regression; （3）The distribution of sources, reservoirs and cap rocks of Majiagou Formation is controlled by paleo-climate, paleo-sedimentary pattern and sea-level fluctuation. It is concluded that the grain bank and dolomite flat developed in eastern uplifted zone and adjacent areas during transgressional period have a good reservoir-forming condition and can be expected to be a new favorable potential area of carbonate exploration. |
