Sequence Stratigraphy Research And Palaeogeography Analysis Of Triassic In Kuqa Depression, Tarim Basin

Kuqa Depression, a foreland depression, is situated in the northern Tarim Basin, in the west tectonic strip sedimentary basin of China, an important basin with strong potential for natural Petroleum and Gas exploration, and one of the resource bases for "West to East Pipeline Project".This thesis, based on the geological survey, combine with drilling section, seismic analysis, apply the basic theories and methods of sequence stratigraphy, sedimentology and lithofacies-paleogeography to research the sequence stratigraphy, sedimentary system and lithofacies-paleogeography characteristic of Triassic of the Kuqa Depression, and offer basic data to further petroleum and gas exploration in the Triassic of the Kuqa Depression. This thesis draws primary conclusion and new fruit as follows:1 Based on the former study and the geological investigation and sample picking for the two main sections-Kuqa River section and Kapushalianghe River section, this paper clarify the stratum sequence, lithology characteristic and boundary and contact relationship between formations of the Triassic further.2 This paper conducts the outcrop sequence stratigraphic research mainly for the Triassic in study area, and divides 2 2nd-order sequences and 7(Kuqa River section) or 6(Kapushalianghe River section and Awatehe River section) 3rd-order sequences, divides 5(Xinghuo-3 well) or 4(Yinan-2 well) 3rd-order sequences, it summarizes the characteristics of sequences, system tracts and parasequences, and divides the system tracts into three kinds:alluvial system tract, lacustrine expanding system tract and lacustrine contracting system tract, divides the parasequences into two kinds:coarsening-upward parasequence and fining-upward parasequence. It also investigate the controlling factors of sequence development.3 This paper, emphasizes on the comprehensive research of facies, such as lithology, sedimentary structure, paleontology(pollen) and geochemistry(carbon and oxygen isotope), carries out detail analysis on depositional system. The depositional systems should be divided into alluvial system, delta depositional system and lake depositional system, and 6 sedimentary facies in detail.4 Based on the subfacies statistics, which use the "superiority method", the subfacies in each sequence of every section must be included. And letting the 3rd-order sequence as mapping unit, and drawing the map of lithofacies-paleogeography within developmental stages of every 3rd-order sequence, At last, it also analyzes the characteristics and evolution of sedimentary paleography of Triassic in study area, in the framework of 3rd-order sequence.5 On the basis of these research above, it analyzed the petroleum geological conditions preliminary of Triassic in Kuqa Depression, and obtained that the mudstone of semi-deep and deep lake in Huangshanjie and the mudstone of bay lake in Taliqike formation is main source rocks, and the glutenite of Ehuobulake and Kelamayi formation is main reservoir.