乌尔逊凹陷泥页岩演化特征及潜力区预测

乌尔逊凹陷为海拉尔盆地南部重要的含油区,具有较大勘探潜力。笔者通过油源对比确定乌尔逊凹陷主力烃源岩层,分析不同区域源岩发育特征及有机质丰度、类型等地球化学指标,评价乌尔逊凹陷主力烃源岩生油成熟期和成藏阶段,通过流体包裹体均一化温度的测量,来判断油气充注史,预测优先勘探潜力部位。研究发现,乌尔逊凹陷不同区域油源不完全相同,乌尔逊北部油藏源于南屯组泥页岩母质,乌尔逊南部区域除了南屯组泥页岩,还有铜钵庙组暗色泥岩生成的油流混入。乌尔逊凹陷具有两期成藏:第一期为伊敏组后期—青元岗组早期,原油由烃岩层排出、运移注入圈闭成藏;第二期为青元岗组后期构造活动使早期油藏原油重新调整分配注入新的圈闭成藏。综合分析认为乌北洼陷西侧、乌南洼陷东侧构造带为两个重要的勘探潜力带。

Evolution characteristics and potential area prediction of shale in Wuerxun Sag

Wuerxun Sag is an important oil-bearing area in the south of Hailaer basin, which has great exploration potential. This paper determines the main source rocks in Wuerxun Sag by oil source correlation, analyzes the development characteristics of source rocks in different regions and geochemical indicators such as organic matter abundance and type, evaluates the oil generation maturity and accumulation stage of main source rocks in Wuerxun Sag, and judges the oil and gas filling history and predicts the preferred exploration potential position by measuring the homogenization temperature of fluid inclusions. It is found that the oil source in different areas of Wuerxun Sag is not identical. The oil reservoir in the north of Wuerxun Sag is derived from the parent material of mud shale rock of Nantun formation. In the south of Wuerxun Sag, besides the mud shale of Nantun formation, there is oil flow from dark mudstone of Tongbomiao formation. Wuerxun Sag has two stages of hydrocarbon accumulation: The first stage is from the later Yimin formation to the early Qingyuangang formation; The second stage is the late structural activity of Qingyuangang formation, which makes the early oil reservoir redistribute and inject new traps. It is considered that the west side of Wubei sag and the east side of Wunan sag are two important exploration potential zones.