STRATIGRAPHY OF THE TRIASSIC UPPER TONGCHUAN FORMATION SHALE AND ITS RESOURCES POTENTIAL FOR OIL AND GAS DEVELOPMENT IN HEJIAFANG AREA, SHAANXI, CENTRAL CHINA

The stratigraphy of the Mid to Late Triassic deposits in Hejiafang area of the Ordos Basin, Central China, is characterized by a relatively conformable, genetically related sedimentary succession of fluvial, interfluvial, wetland and lacustrine deposits, as well as evaporates and paleosols. Ten (10) oil-bearing beds or bedsets were identified from this section's thick (over 1,300 meters in thickness) sedimentary sequences, among which the Zhangjiatan Bed of the early Late Triassic age was considered one of the most oil-bearing or oil-contributing beds in this area. Detailed analyses of the lithologic and cyclic stratigraphic sequences, geophysical well logs and formation evaluations, as well as organic geochemistry features, point out the Geochemical Characteristics and sedimentary environment,then show the efficacy of focusing future exploration and development on the Zhangjiatan Bed in this area and associated oil-generating and/or oil-trapping beds, due to its favoring not only oil exploration, but also potential extraction of natural gas.