藏北羌塘盆地托纳木地区油气成藏条件

托纳木地区位于羌北坳陷与中央隆起带毗连地带,为羌塘盆地相对稳定的构造区,主要发育上侏罗统索瓦组和雪山组。地表油气显示主要为裂隙型沥青、“油浸”灰岩和油页岩,表明研究区内存在大规模油气生成、运移和聚集过程,具备形成油气田的基本地质条件。储集层和盖层分析表明,托纳木地区储集层中等,盖层中等-有利。依据生、储、盖层的时—空配置关系,将托纳木地区生储盖划分为Ⅳ₁、Ⅳ₂、Ⅳ₃3个二级组合,其中Ⅳ2 组合最为有利,具有很高的勘探价值,Ⅳ₁组合较为有利,而Ⅳ3 组合相对较差。托纳木地区生油条件优越、成熟度适中,储集层类型多、物性较好,盖层发育,表明研究区具有良好的成藏条件。

Condition of Hydrocarbon Accumulation in Tuonamu Area in Qiangtang Basin, Northern Tibet

Tuonamu area adjacent to Qiangbei depression and the central uplift belt is a relatively stable structure area in Qiangtang basin,where develops Suowa formation and Xueshan formation of Upper Jurassic.The oil and gas shows are fractured bitumen vein,oil-immersed limestone and shale,indicating that there exists process of large-scale hydrocarbon generation,migration and accumulation as basic geologic conditions for forming oil-gas field or reservoir.The characteristics of reservoir rock and cap rock in this area indicate that they belong to medium-quality reservoir rock and medium-advantageous cap rock.The source-reservoir-cap rocks could be classified into three Class-II assemblages of IV1,IV2 and IV3,of which IV2 is the most favorable for exploration,IV1 is the better and IV3 is relatively poor.It is concluded that Tuonamu area is of good conditions for hydrocarbon accumulation such as advantageous source rock,medium maturity,multi-type reservoirs,good reservoir quality and developed cap rock.