塔里木盆地塔北隆起碳酸盐岩油气成藏特点

Hydrocarbon Accumulation Characteristics of the Carbonate Rock in the Northern Uplift of the Tarim Basin

塔北隆起自早古生代以来经历了长期的挤压隆升剥蚀过程,结合寒武系膏盐的塑性上拱,形成了两种基本的碳酸盐岩圈闭类型,即风化壳潜山和内幕背斜圈闭。塔北隆起南临古生代满加尔凹陷、北临中新生代库车坳陷,具有捕获南北两侧海陆两相油气来源的条件,经历了海西期、燕山期和喜马拉雅山期3期成藏。储集空间主要靠溶蚀孔洞和裂缝。石炭系中—上泥岩段和白垩系卡普沙良群泥岩两套区域性盖层对碳酸盐岩风化壳潜山油气聚集起着至关重要的作用。不整合面和断裂是控制塔北隆起油气成藏的两个最关键的因素,不整合面既控制着岩溶储层的发育分布又是油气侧向运移的优势通道;断裂活动形成破碎带、裂缝带进而改善储层性能,同时断裂也是油气垂向运移的优势通道。

The Northern Uplift of the Tarim Basin had undergone a long-term compressional uplifting and erosion since the Early Paleozoic, and also integrated with the upwarp of the Cambrian gypsum formation, thus forming two basic types of carbonate rock traps, namely, weathered-crust buried hills and insider anticline traps. The northern uplift, bounded by the Paleozoic Manjiaer marine sag in the south and Mesozoic and Cenozoic Kuqa depression in the north, possesses the conditions that arrest hydrocarbon from both marine and terrestrial sources, and experienced three hydrocarbon accumulation phases in the Hercynian Yanshan and Himalayan. The main reserve spaces are cavities and cracks. Two regional caprocks, Upper- and Middle-Carboniferous mudstone and Cretaceous Kapushaliang Group mudstone play the most important roles in the formation of hydrocarbon reservoir. Unconformity surface and fracture are the two key factors controlling oil/gas reservoir in the north uplift： the former not only controls development and distribution of hydrocarbon accumulation but provides the preponderant pathway on lateral migration; and the latter resulted in the formation of broken zone, further improved reservoir performance. Meanwhile, fracture is the preponderant pathway on vertical migration of hydrocarbon.