关键词: 吐哈盆地, 石炭系, 二叠系, 三叠系, 盆地演化, 油气勘探

Abstract: The characteristics of hydrocarbon accumulation and potential targets of deep Carboniferous-Triassic are unclear in Turpan-Hami Basin due to the low level of exploration, poor quality of seismic data in key exploration areas such as Taibei Sag, low understanding of tectono-stratigraphic framework, and the unclear prototype basin type and evolution. In this paper, the evolution history, stages and reformation characteristics of the Carboniferous-Permian prototype Turpan-Hami Basin are analyzed and the exploration prospects of deep formations are further evaluated based on the existing geological data and previous study results and combined with tectonic environment of the basin and its adjacent areas. The study results show that the basin has experienced four stages of tectonic evolution from Carboniferous to Triassic:(1) Back arc extensional environment during the Carboniferous-Early Permian, the Turpan-Hami land block was on the ancient land, and the southern and northern margins were close to the rift, where thick sediments and marine source rocks were deposited; (2) Continuous back arc extensional environment in the Middle Permian, fault subsidence affected the interior of Turpan-Hami land block and source rocks were developed in separated continental fault depressions; (3) The back arc extension ended from the Late Permian to Early Triassic, and the Turpan-Hami block and its peripheral rifts were peneplain; (4) In the Middle Triassic, rifts surrounding the Turpan-Hami land block compressed and returned to orogeny, leading to the broad basin and foreland basin stage of Turpan-Hami land block. The subsidence types of rift, fault depression and foreland depression are obviously different, forming three stages of sedimentary framework and developing source rocks with greatly varied degree. Four positive cycles are developed in four evolution stages, forming four sets of regional reservoir-caprock assemblages. The deep multi-stage prototype basin is affected by stress inversion and strongly reformed by later foreland basin, and deep formations have geological conditions for hydrocarbon accumulation and exploration potential in the superimposed subsidence area of Taibei Sag and its periphery.

Key words: Turpan-Hami Basin, Carboniferous, Permian, Triassic, basin evolution, petroleum exploration