Genesis and Resource Potential Study of Oil Shale in Tongchuan Formation of Southern Part of Ordos Basin
|Course||Oil and Gas Field Exploration and Development|
|Keywords||the south margin of Ordos basin oil shale Tongchuan Formation resorted deoxidization freshwater lacustrine environment resources reservoir favorable profits for exploration|
As the provision of crude oil and natural gas becomes more and more intense at present, oil shale is cherished by people day by day gradually for its enormous energy and abundant availability in synthesis as an important substitute of energy, and shows both favorable economic profit and pleasant social benefit. Unfortunately, previous studies of oil shale focus more attention on industrial exploration and utilization rather than fundamental geological study.Based on the fruits of predecessors, deposit facies belt of the oil shale is divided by analysis of wild-field outcrop well logging data and petrological microfacies. And the oil shale of Tongchuan Formation distributed in the southeast margin of Ordos basin is studied systematically in the dissertation through synthetic methods and theories of multi-subjects of geochemistry, sedimentary petrology, interpretation of well logging data, identification of coal lithology, ratio method of chemical elements, abundance of organic matter and pyrogenation of organic matter, and the following cognitions are acquired.1. Oil shale of Tongchuan Formation, the organic matters of which in member of lean ore are mainly of humic-sapropel type and sapropel-humic type (Ⅱ1-Ⅱ2 type), deposited under the condition of freshwater lacustrine environment of resorted deoxidization, and can be subdivided into 3 subfacies of lakeside, shallow lake and deep lake.2. The mineral grains of sandstone in oil shale of Tongchuan Formation are predominated by feldspar and quartz, while its cementation is of organic matter. Besides, the vitrinite reflectance, Ro, of the oil shale is under 0.51%, and the pyrogenation zenith temperature of which is about 432℃. All these features show that the oil shale deposited under the conditions of immaturity-submaturity stage.3. In the oil shale of lakeside and shallow lake facies, the content of organic matter, oil content and exploration value are a little lower compared to that in deep lake face.4. Mineralization of the oil shale is conspicuously controlled by geotectonic, deposit facies belt, paleo-clamate in that geotectonic controls its distribution, thickness and oil content, while paleo-clamate and deposit facies belt influence its organic matter directly or indirectly.5. That enough provision of organic matter, stable delamination of water and deficiency inpouring of continental clast show that deep lake is advantageous condition for sediment of oil shale.6. The oil shale of Tongchuan Formation belongs to middle rank of oil shale ore in general for its wide distribution, large thickness, concentrated oil shale section and high oil content. The resources reservoir of oil shale in the area is very amazing, especially in outer county rock. On the basis of economic estimation and appropriate exploration technology, the oil shale in the study area is bound to have favorable profits for exploration.