西藏羌塘盆地——中国油气资源战略选区的首选目标

研究表明羌塘盆地在油气资源的许多方面可与中东特提斯油气集聚区相类比，因而成为中国油气资源战略选区的首选目标之一。羌塘盆地的构造部位相当于中东特提斯构造域的北亚带和中亚带，羌塘盆地晚古生代是一个被动大陆边缘盆地，中生代是一个复合式前陆盆地，新生代叠置成为第三纪走滑断陷盆地；羌塘盆地内发育有良好的生储盖组合，生油岩主要为三叠 系－株罗系的尼岩、灰岩和油页岩，烃源层处于成熟、过成熟阶段，生油高峰期为晚侏罗世－古近纪，局部发现厚达70余米的油 页岩，初步估计油气资源总量为50亿吨左右；盆地内发育有孔渗极佳的碎屑岩、白云岩以及生物礁（滩）岩等储集层，其次生孔隙的形成期与烃岩的生油高峰期一致；盆地内发育泥岩、泥灰岩和石膏等多套盖层，累计厚度可达3000多米，尤其是发育中东油田最好的石膏储层，累计厚度达177m，其中，仅中株罗统布曲组最大单层厚度达93m；盆地内发育数十个形态好、保存完整的大中型背斜和穹隆圈闭构造，它们均定型于株罗纪末期，为油气运移和圈套闭创造了良好的条件；盆地内共发现油气 显示190余处，其中包括5处液态油苗，数处见厚达数厘米的板状沥青，并发现面积约10km^2的古油气藏一个；藏北高原 抬升属整体的均一抬升，剥蚀强度不大，岩浆活动广泛，但除盆地东部外，规模小，对油气的破坏性不大。因此，盆地内具有一定的保存条件。

The Qiangtang Basin in Xizang as the target area for the oil and gas resources in China

Comparable with the Middle East petroleum provinces in the Tethyan domain, the Qiangtang Basin is selected as the target area for the oil and gas resources in China. The basin lies in northern Xizang, with an average elevation of 4900 m, and a total area of 18×10⁴km². Tectonically, it is assigned to the eastern part of the Tethyan tectonic domain, corresponding to the northern and middle subzones of the Middle East Tethyan tectonic domain. The basin behaved as a passive continental marginal basin during the Late Palaeozoic and a complex foreland basin during the Mesozoic, upon which the Tertiary strike-slip fault basin overlapped during the Mesozoic. The excellent reservoir-, seal-, and source-prone facies are well developed in the basin:the source rocks consist mostly of Triassic-Jurassic mudstones, limestones and oil shales, and the hydrocarbon-bearing formations are getting mature or supermature. The oil-gener tion peak period may be traced back to the Late Jurassic-Paleogene. The oil shales locally reach 70 m or more in thickness, with an estimated total reserve of ca. fifty milion tons. The highly porous and permeable clastic rocks, dolostones and organic reefs (banks) are also observed in the basin as the reservoir rocks. The secondary porosities were developed during the periods corresponding to oil-generation peak periods. There occur in the basin several suites of cap rocks consisting of mudstones, marls and gypsum, with a total thickness of more than 3000 m. The best gypsum reservoirs in the Middle East oil fields are also identified in the basin, with a total thickness of 177 m. The single bed of the Middle Jurassic Tongbuqu Formation may be 93 m in maximum thickness. Decades of well-preserved large-or medium-sized anticlines and domal trap structures formed during the latest Jurassic have provided the excellent conditions for the trap and migration of oil and gas. Other discoveries include 190 oil shows and several slab asphalt beds and one ancient oil pool with an area of about 10 km². The completely homogeneous tectonic uplift, less intense denunation, and widespread but small-scale magmatism on northern Xizang Plateau may facilitate the formation of oil and gas resources.