Differential Geochemical Characteristics and Control Mechanism of Source Rocks in the Shuixigou Group, Turpan–Hami Basin

ABSTRACT The Turpan – Hami Basin is a momentous petroliferous basin in western China. The Jurassic Shuixigou Group is the key stratum for oil and gas exploration in coal–measure source rocks, characterized by multi–layer and multi–type hydrocarbon accumulation. Tectonic activity is a critical factor that controls the development and distribution of source rocks. Based on geochemical results, this study clarifies the differences in the geochemical characteristics of the Shuixigou Group source rocks and control mechanisms. The control of tectonic–palaeogeography on the formation and development of source rocks is discussed herein. The geochemical characteristics of source rocks controlled by tectonic activities are significantly different. The Early Jurassic tectonic uplift caused frequent advances and retreats of the water body. Under conditions of differential subsidence and humid climates, organic matter in the Badaowan Formation was dominated by terrigenous input, and deposited in a reducing to weakly oxidizing environment. During the sedimentary period of the Sangonghe Formation, the maximum lake transgression of the Shuixigou Group was reached owing to crustal subsidence, and the organic matter was primarily derived from aquatic organisms; type II kerogen was deposited in a reducing environment. Owing to the continuous compression of the Bogda Mountains in Tthe Middle Jurassic, the water body was shallow in a weak reduction–oxidation environment. Coupled with multiple terrestrial inputs, the Xishanyao Formation was deposited as a thick coal seam in the whole area under the swamp facies. Therefore, tectonic activity is one of the vital reasons for the differences in the geochemical characteristics of the Shuixigou Group source rocks. Clarifying hydrocarbon generation differences and geochemical characterization of different types of source rocks in the Shuixigou Group is highly significant (i) to understand the distribution of source rocks and (ii) for oil and gas exploration.