摘要:塔里木盆地塘古坳陷历经20余年勘探而成效甚微，在新的地震与钻井资料基础上，通过地层沉积对比、构造解析重新认识塘古坳陷的形成与演化，及其对勘探方向的指示研究，结果表明：1）塘古地区存在基底古隆起，寒武系自塔中向南逐渐减薄；2）本区钻揭中-下奥陶统碳酸盐岩地层连续，不存在寒武系—中奥陶统的台槽；3）上奥陶统良里塔格组沉积期在东西两侧发育巨厚的台地边缘相带，而坳陷区相变为盆地泥岩相；4）北东向冲断构造具有分层变形特点，断裂活动始于晚奥陶世早期，冲断推覆作用主要形成于奥陶纪末。结果揭示塘古坳陷经历4期构造关键演化期：1）寒武—中奥陶世与塔中连为一体的碳酸盐岩台地发育期；2）上奥陶统良里塔格组沉积期受控东南板缘俯冲与碰撞作用的台盆形成期；3）奥陶纪末强烈沉降的挤压挠曲盆地定型期；4）志留纪—泥盆纪的构造改造期。该结果为盆地构造古地理研究与深层油气评价提供了基础，并提出了勘探新方向。
关键词: 塔里木盆地/
奥陶纪/
冲断构造/
演化/
构造改造/
海相碳酸盐岩/
深层勘探
Abstract:Although undergone more than 20 years exploration by some oil and gas shows, Tanggu Depression has not been gained big discovery in the Tarim Basin. It is assumed as a new depression formed in the end of the Ordovician, or an large inherited trough from Cambrain, in which its initiation and evolution is of great significance for the tectono-paleogeography study in the Tarim Basin and hydrocarbon potential evaluation in Tanggu Depression and it periphery. Through the structural analysis based on the new seismic and drilling data, the evolution and its exploration potential of Tanggu Depression are rescreened with a new perspective. The results show：1） A large basement uplift occurred in the area and its periphery, where the thickness of Cambrian is overlapping and thinner from the north to the south. 2） There is a large area carbonate platform in Lower-Middle Ordovician covering all the area with the similar facies with its periphery, but rather than a large trough. 3） There are two carbonate platform margins along the eastern and western sides, spliting by a large depression with mudstone facies. 4） A series of thrust faults initiated in Late Ordovician, and stronger inherited thrusting in Silurian-Devonian. As a consequence, there are four stages evolution in Tanggu area：1） A carbonate inner platform development stage in Cambrian- Middle Ordovician, having a uniform platform with its periphery in large ares. 2） Depression forming stage after the deposition of Yijianfang Formation in Middle Ordovician and before the deposition of Lianglitage Formation in Late Ordovician, which is the key time for the depression initiation and forming by the subduction and collision of Altyn Ocean from the southeast. 3） The remodification stage by the faults thrusting and denudation in Silurian-Devonian by the persistent compression from the southeast uplift. 4） Stable subsidence stage after Carboniferous. It is indicated that there is a basement palaeo-uplift of inherited development in Late Ordovician-Paleogene in the southwestern area, and there is high quality evaporite caprocks that did not offset by the strong thrust faulting. Hence, rather than the thrust Ordovician blocks for a long term exploration, we proposed that there is better source-reservoir-cap assemblage, and hydrocarbon migration and accumulation in the Lower-Middle Cambrian in the southwestern of Tanggu Depression. And the paleo-highs of Lower Cambrian dolomite reservoirs could be the new breakthrough of exploration. The result indicates that the exploration should pay more attention to the palaeostructure evolution and its match with hydrocarbon accumulation process in spatiotemporal in a strong remodified basin.
Key words:Tarim Basin/
Ordovician/
Thrust structure/
Initiation and evolution/
Structural remodification/
Marine carbonate/
Super-deep exploration
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