西西伯利亚盆地北部大气田的形成条件和分布规律

Formation and Distribution of Giant Gas Fields in Northern West Siberian Basin

西西伯利亚含油气盆地是俄罗斯联邦面积最大、油气储量最大和产气量最高的一个含油气盆地,也是20世纪70年代以来世界上新开发的特大型含油气盆地之一。截至2007年年底,西西伯利亚盆地天然气的已发现可采储量为16.1×1012m3,其中未开发油气田中的储量占9.96×1012m3,未发现资源量为31.6×1012m3。以盆地中57个大气田的资料为基础,结合盆地的构造—沉积演化过程,应用含油气系统的研究思路与方法,通过综合分析盆地北部生、储、盖等油气成藏要素,认为上侏罗统巴热诺夫组及其相当的层系是西西伯利亚盆地北部最重要的生气层,其有机碳含量超过7%;白垩系顶部的赛诺曼阶砂岩是大多数大气田(80%的天然气)的储层,平均厚度达800m。盆地内发育了大量复杂的构造—地层圈闭,已发现的大气田主要分布在努尔明长垣、梅德韦日长垣等盆地北缘的隆起区。未来天然气勘探的主要目标与储量增长区仍是南喀拉—亚马尔、纳德姆—塔兹含油气省。

West Siberian Basin is the largest petroliferous basin of Russian Federation, which is one of the largest petroleum basins in the world newly developed since 1970s, with largest area, most hydrocarbon reserves and highest production. By the end of 2007, the ultimate recoverable reserves of natural gas of West Siberian petroleum basin is 16.1×1012m3, in which the reserves of undeveloped oil & gas fields occupy 9.96×1012m3 and the undiscovered resources account for 31.6×1012m3. Based on the data of 57 large gas fields, combined with the tectono-depositional evolution process of the basin, applying the research idea and method of petroleum system, and through analyzing the reservoir-formation elements of generation, reservoir and cap rock, it is considered that Bazhenov Formation of Upper Jurassic and the equivalent ones are the most significant gas-generation rock of northern West Siberian Basin, in which the organic carbon content occupies more than 7%. Cenomanian rock located at the top of Cretaceous Formation is the reservoir of most large gas fields (80% natural gas), with 800m in average thickness. A vast number of complex structural-stratigraphic traps are generated in the basin and large gas fields that have been found concentrate in the uplift area of the northern margin of the basin including Nurmin and Medvezh, etc. In the future, the exploration target of increasing natural gas reserves will still be the oil-bearing provinces of Kara-Yamal and Nadym-Taz.