海拉尔盆地莫达木吉凹陷下白垩统烃源岩地球化学特征研究

The geochemical characteristics of Lower Cretaceous hydrocarbon source rocks in Modamuji depression,Hailaer basin

海拉尔盆地莫达木吉凹陷下白垩统是区域油气勘探潜在目标层系,缺乏对烃源岩地球化学特征的详细研究。通过有机地球化学方法对莫达木吉凹陷下白垩统烃源岩地球化学特征进行了研究,认为南屯组(K_1n)和大磨拐河组(K_1d)烃源岩有机质类型以Ⅱ_2-Ⅲ型为主,差异性主要体现在有机质丰度和成熟度。同时,在恢复埋藏史的基础上建立了研究区主力烃源岩在该地质时期成熟度演化模型,模拟结果显示:大二段烃源岩处于未成熟-低成熟阶,大一段烃源岩处于低成熟阶段;南二段烃源岩处于低成熟-成熟阶段;南一段烃源岩热演化程度相对较高,达到成熟生油气阶段。综合分析得出大磨拐河组(K_1d)烃源岩有机质丰度整体较高,但热演化程度低,生烃潜力小;随着埋深的增加,烃源岩热演化程度增加,到南二段(K_1n_2)开始进入成熟生烃阶段,生烃潜力较大;南一段(K_1n_1)烃源岩有机质丰度低,为差烃源岩,生烃潜力较小。

The Lower Cretaceous is the target stratum of potential regional oil-gas exploration in the Mo-damuji Depression,Hailaer Basin.Organic geochemistry methods were applied to study geochemical characteristics of Lower Cretaceous hydrocarbon source rocks from the Modamuji Depression.The results showed that the organic matter of K1 n and K1 d formation is mainly type Ⅱ2-Ⅲ with various abundance and maturity.The proposed maturity evolution model based on restoration of burial history showed that the thermal evolution extent for main source rocks is generally low.The source rocks from K1 d2 are at the im-mature to low mature stage,those from K1 d1 are at low mature stage and those from K1 n2 are at low ma-ture to mature stage.The hydrocarbon source rocks from K1 n1 showed a relatively high thermal evolution degree,which has reached the mature oil-generating stage.The comprehensive analyses indicated that K1 d hydrocarbon source rocks are generally high in organic matters with a low thermal evolution and low hydrocarbon-generating potential.The thermal evolution degree of hydrocarbon source rocks increases with the buried depth.The K1 n2 hydrocarbon source rocks have entered the mature oil-generating stage with a moderate organic matter abundance and relatively higher hydrocarbon-generating potential.The hy-drocarbon source rocks from K1 n1 are low in organic matter with relatively low hydrocarbon-generating po-tential.