The development of effective source rocks is the key to Mesoproterozoic hydrocarbon accumulation in Ordos area. In this paper, the geological characteristics of the Agulugou Formation source rocks in Shujigou area were studied by means of field geological investigation, microscopic section identification and geochemical analysis. Researches show that the source rocks of Agulugou Formation are carbonaceous slate and phyllite, and the original rocks are black sand-bearing shale. The contents of organic carbon in the source rocks are high, and the value ranges from 0.34% to 9.56%, with an average of 3.3%. The types of organic matter are Ⅰ and Ⅱ1 kerogen. The value of R_o ranges from 3.57% to 4.68%, and the T_max value is from 404 ℃ to 562 ℃. These results show that the thermal evolution of source rocks is high, and is in the over-mature stage. The distribution pattern of rare earth elements is a slightly right-leaning pattern with slight enrichment of LREE and no obvious differentiation of LREE and HREE. The δCe values range from 0.74 to 0.92, showing a negative Ce anomaly, and the δEu range is relatively large, ranging from 0.95 to 4.83, that indicates that the deposit of the source rocks formed in a transitional environment from reduction to oxidation. The content of trace elements indicates that the Agulugou Formation deposited in a back-plateform basin with a water depth of less than 250 m, and the sedimentary facies were fluvial-shore sands, shallow water carbonaceous-argillaceous deposits of the barrier island. Combined with the above research, it shows that the Mesoproterozoic source rocks in the study area are mainly good-excellent source rocks formed in the reduction-oxidation environment, and the hydrocarbon generation geological conditions are favorable.

The Lower Paleozoic Ordovician system in the western Ordos Basin has attracted much attention because of its great potential for oil and gas exploration, and the carbonate rock developed in the Middle Ordovician Keliomori Formation is expected to be the next exploration target layer, so study on its sedimentary characteristics can provide geological basis for the exploration of Ordovician gas in the west margin. By means of outcrops investigation, core observation and thin section identification, the characteristics of petrology, sedimentary facies types and spatial distribution of the Keliomori Formation are studied. It is shown that the Keliomori Formation is mainly composed of thin layer micrite, calcirudyte, calcarenite, calcisiltite, bioclastic limestone and black shale. They have micrite structure, granular structure, and thin layer, lamellar, nodular, brecciform structure, slump and Bauma sequence can be seen. The sedimentary facies platform front slope and deep water slop-trough, which are distributed in a narrow strip along the north-south direction. From east to west, the platform front slope facies develops in the open sea platform close to the Ordos base, and rapidly changes into deep water slop-trough facies westward, and the sea water has a gradual deepening trend.