Abstract:

The North Ustyurt Basin,a pivotal oil and gas-bearing region in Central Asia,possesses significant exploration potential. Nevertheless,the Paleozoic strata within the basin are deeply buried,resulting in a relatively low exploration degree and insufficient research. This study aims to elucidate the tectonic evolution and sedimentary characteristics of the basin during the Late Paleozoic. Geographically,the North Ustyurt Basin is located at the junction of the northern margin of the Tethys tectonic domain and the Paleo-Asian Ocean tectonic domain. Its tectonic evolution was intricately influenced by the opening and closure of the Paleo-Tethys and Paleo-Ural Oceans,and it underwent six distinct stages: basement formation,passive continental margin,rifting,post-rifting,compression,and Neogene subsidence. During the Late Paleozoic passive continental margin stage,the basin was mainly affected by the closure of the Ural Ocean,which led to regional compressional uplift. The Carboniferous strata exhibit a characteristic west-thick,east-thin distribution,with greater thickness in the north. Drilling data from the southern region reveal the presence of the crystalline basement. The Permian Permian succession shows notable thickness variations,with thicker deposits in the northeast and thinner accumulations in the central and western parts of the basin. A significant unconformity exists between the Permian and Triassic strata. Throughout the Late Paleozoic,the basin’s water body gradually became shallower,experiencing four distinct transgressive-regressive cycles,that controlled the variations in accommodation space. The sedimentary facies types mainly include braided river,deltaic,clastic shoreline,restricted platform facies,and open platform facies. Lithofacies-paleogeographic analysis indicates that from the Late Devonian to Early Carboniferous,deep-water basins and slope deposits were developed. During the Late Carboniferous,the southern and northern basin margins were dominated by shallow-marine carbonate platforms,whereas the Permian deposits succession was primarily composed of transitional to continental sediments. This study systematically analyzes the tectonic evolution,sedimentary filling patterns,and the distribution of hydrocarbon source rocks and reservoirs in the study area. The findings provide a robust scientific foundation for subsequent oil and gas exploration strategies,block evaluation,and the optimization of exploration well placement.

Key words: Tethyan tectonic domain, tectonic evolution, sedimentary characteristics, Late Paleozoic, North Ustyurt Basin

摘要：

北乌斯丘尔特盆地是中亚重要含油气区,油气勘探潜力大,但古生界埋深较大,勘探程度低且研究不足。作者旨在明确其晚古生代构造演化过程及沉积特征。北乌斯丘尔特盆地位于特提斯构造域北缘和古亚洲洋构造域共同作用区,其构造演化受古特提斯洋和古乌拉尔洋开闭影响,经历基底形成期、被动陆缘期、裂谷期、裂谷后期、挤压期和新近纪拗陷期6个构造演化阶段。盆地晚古生代的被动陆缘期主要受乌拉尔洋闭合过程的影响,整体挤压隆升。盆地石炭系西厚东薄,北部地层厚度较大,南部地层钻遇结果显示局部古生界剥蚀至结晶基底。二叠系厚度变化较大,北东部地层相对较厚,中部及以西地区沉积厚度较小,二叠系之间存在不整合。盆地水体在晚古生代逐渐变浅,海平面经历4期海进—海退变化过程,可容空间相应增减; 沉积相类型主要包括辫状河、三角洲、碎屑滨岸、局限台地、开阔台地等; 岩相古地理显示,晚泥盆世—早石炭世发育深水盆地以及斜坡沉积,晚石炭世盆地南缘及北缘部分区域为浅海相碳酸盐岩台地沉积,二叠纪则以海陆过渡—陆相沉积为主。本次研究通过系统分析目标区域构造演化特征、沉积充填规律及烃源岩和储集层的发育范围,为后续油气勘探与区块优选和优化探井部署方案提供了科学决策依据。

关键词: 特提斯构造域, 构造演化, 沉积特征, 晚古生代, 北乌斯丘尔特盆地

CLC Number: 

• P54