关键词: 塔里木盆地, 煤型气, 油型气, 腐泥型烃源岩, 腐殖型烃源岩, 热演化程度

Abstract:

There are two sets of effective source rocks in Tarim Basin, including Cambrian-Ordovician sapropelic matters and Triassic-Jurassic humics. The spatial distribution and the thermal maturity of two sets of effective source rocks controlled the genetic type and regional distribution of natural gas. Two genetic types of natural gas in the basin can be clearly identified according to the carbon isotope composition of methane and its homologue, namely oil-type gas and coal-type gas. Generally, the coal-type gas is derived from the humic matters, whereas the oil-type gas stems from the sapropelics. The coal-type gas is preserved in the traps along the margin of the basin, including Kuqa Depression, Southwest Depression and Southeast Depression, while the oil-type gas is mainly distributed in Tabei Uplift, North Depression, Central Uplift and the northern part of Southwest Depression. Based on the theoretical and empirical carbon isotope fractionation patterns, the oil-type gas can be further divided into the primary gas and oil-cracking gas. The primary gas geographically limits in Tabei Uplift, while oil accumulated in Lunnan, Mandong, Hetianhe and Tazhong attributes to the secondary cracking. The distribution of different oil-type gas greatly depends on the thermal maturity of the sapropelic matter.

Key words: Tarim Basin, coal-type gas, oil-type gas, sapropelics, humics, thermal maturity