Abstract
The quality of hydrocarbon source rocks is affected by the sedimentary paleoenvironment. A paleoenvironment with anoxia and a high paleoproductivity is beneficial to source rocks. The paleoenvironment of the Lower Ordovician Meitan Formation of the Sichuan Basin and its adjacent areas is lacking, restricting the oil and gas exploration of the Ordovician in the Sichuan Basin and its adjacent areas. In this paper, the content of major and trace elements of 50 samples was tested to clarify the paleoenvironment of the Meitan Formation. The paleoclimate, paleosalinity, paleoredox, and paleoproductivity during the deposition of the Meitan Formation were analyzed. The control effect of the paleoenvironment on the development of source rocks was clarified, and the favorable paleoenvironment for source rock development was pointed out. The results show that the paleoenvironment of the Meitan Formation has the following characteristics: humidity, brackish water, oxygen depletion, anoxia environment, and high paleoproductivity. These characteristics are conducive to the development of poor and moderate source rocks. The source rocks of the Meitan Formation were developed in the north, west, and south of the Sichuan Basin and its adjacent areas. The organic matter of the source rocks is mainly typed II1 kerogen, and the quality is evaluated as poor-medium source rocks having the potential of generating oil and gas. This study can provide fundamental parameters for the further exploration of Ordovician petroleum.
Highlights
The hydrocarbon generation and the expulsion intensity and amount are affected by tectonic thermal evolutions, and by the quality of source rocks, including organic matter abundance, type, and maturity
The oil and gas discoveries of the Ordovician in the Sichuan Basin and its adjacent areas are mainly concentrated in the Lower Ordovician
Typical wells and geological sections of the Sichuan Basin and its adjacent areas were selected for geochemical experiments
Summary
The hydrocarbon generation and the expulsion intensity and amount are affected by tectonic thermal evolutions, and by the quality of source rocks, including organic matter abundance, type, and maturity These parameters are affected by the paleoclimate and sedimentary environment, such as paleosalinity, paleoredox, and paleoproductivity [1,2,3]. The Ordovian of the Sichuan Basin and its adjacent areas, in southwestern China (Figure 1), have been regarded as a concurrent layer for oil and gas exploration of the Silurian and the Cambrian, and no large oil and gas fields have been found. The oil and gas discoveries of the Ordovician in the Sichuan Basin and its adjacent areas are mainly concentrated in the Lower Ordovician. Tongzi Formation and the Upper Ordovician Baota Formation, and the karst-fractured reservoirs are mainly found [5]. 4.0/).
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