海拉尔盆地贝西南地区南屯组油气侧向运移路径综合确定及运移模式探讨

贝西南地区是目前海拉尔盆地贝尔凹陷中含油性较好的重点勘探区块,为查明油气运移对成藏的影响,采用以油气来源分析为基础、以油气分布特征为指示、以运移数值模拟为约束、以地球化学示踪为佐证的“四位一体”油气运移路径综合确定方法,对研究区南屯组的油气运移路径和运移模式进行了研究。结果表明:南屯组主要有3组油气运移路径,一是由贝西北次凹沿其短轴方向向贝西斜坡侧向运移;二是由贝西南次凹沿其短轴方向向呼和诺仁构造带运移;三是由贝西北和贝西南次凹向呼和诺仁构造带汇聚的油气,沿构造脊和断层走向向西南部运移。在明确运移路径基础上总结出3种油气侧向运移模式:沿构造脊及断层走向运移模式、同向断阶“阶梯状”运移模式和反向断阶“牙刷状”运移模式,各种运移模式控制的油气富集部位和油藏类型有较大差异。研究结果对研究区下一步的有利区优选和类似地区油气勘探具有一定的指导意义。

Comprehensive Determination of Lateral Migration Routes and Exploration of Migration Patterns of Hydrocarbons in Nantun Formation,SW Beier Sag,Hailar Basin

SW Beier Sag is currently a key exploration block with high oil reserves in Hailar Basin. In order to identify the influence of hydrocarbon migration on hydrocarbon accumulation, a "four-in-one” comprehensive determination method of hydrocarbon migration path, which was based on hydrocarbon source analysis, with hydrocarbon distribution characteristics as an indicator, migration numerical simulation as a constraint and geochemical tracing as a supporting evidence, was adopted to study the hydrocarbon migration paths and patterns of Nantun Formation in the study area. The results indicated that there were three hydrocarbon migration paths in Nantun Formation. One path was to migrate laterally from NW Beier Sub-sag to West Beier Slope along its short axis; the second path was to migrate from SW Beier Sub-sag to Huhenuoren Tectonic Belt along its short axis; and the third path was to accumulate hydrocarbon from NW and SW Beier Sub-sags to Huhenuoren Tectonic Belt and migrate to the southwest along the strike of tectonic ridge and fault. On the basis of the identification of migration paths, three types of lateral hydrocarbon migration patterns were summarized, including the migration along the strike of tectonic ridge and fault, the "stepped" migration along synclinal fault and the "toothbrush-like” migration along reverse fault. There were significant differences in the hydrocarbon accumulation sites and reservoir types controlled by the various migration patterns. The results of the study are of some significance for the next selection of favorable zones in the study area and for oil and gas exploration in similar areas.