苏北盆地溱潼凹陷阜二段不同岩性烃源岩的地球化学特征及生烃潜力对比

doi:10.19657/j.geoscience.1000-8527.2023.049

摘要/Abstract

摘要：

古近系阜宁组二段是溱潼凹陷页岩油勘探的主要目标层系,具有良好的油气勘探前景。前人已经对研究区阜二段烃源岩生烃潜力及地球化学特征开展了比较系统的研究,但对阜二段不同亚段、不同岩性烃源岩地球化学特征及形成环境的差异性研究还相对薄弱,给研究区阜二段页岩油甜点预测、资源潜力评价以及油气源分析带来困难。本文选取阜二段具代表性的泥页岩样品,利用地球化学分析手段,对不同亚段、不同岩性烃源岩的地球化学特征、生烃潜力和形成环境进行对比研究。结果表明,研究区阜二段E₁ $f 2 4$ 、E₁ $f 2 5$ 烃源岩有机质丰度最高,以Ⅱ₁型有机质为主;E₁ $f 2 2$ 、E₁ $f 2 3$ 烃源岩有机质丰度较高,以Ⅱ₁型和Ⅱ₂型有机质为主;E₁ $f 2 1$ 烃源岩有机质丰度相对较低,有机质类型主要为Ⅱ₂型。研究区阜二段烃源岩岩性比较复杂,主要包括泥岩、钙质泥岩和钙质页岩等。泥岩主要分布于E₁ $f 2 4$ 、E₁ $f 2 5$ ,有机质丰度最高,以Ⅱ₁型与Ⅰ型有机质为主,沉积于弱氧化-弱还原的淡水环境,主要为低等水生生物为主的混源型有机质。钙质页岩与钙质泥岩主要分布于E₁ $f 2 1$ 、E₁ $f 2 2$ 以及E₁ $f 2 3$ ,其中钙质页岩有机质丰度较高,有机质类型主要为Ⅱ₁型,部分为Ⅱ₂型,沉积于强还原的咸水环境,混源型有机质来源;钙质泥岩有机质丰度为低-中等,有机质类型以Ⅱ₂型为主,含少量Ⅱ₁型与Ⅲ型,沉积于半咸水的还原环境,为混源型有机质来源。阜二段烃源岩处于低成熟-成熟阶段。可以根据Pr/Ph、Ga/C₃₀H、C₂₄TeT/C₂₆TT以及ααα20RC₂₇甾烷/ααα20RC₂₉甾烷等参数的分布特征把阜二段三类不同岩性的烃源岩区分开。这些认识可为研究区阜二段不同层段和不同岩性烃源岩的油气资源潜力评价、油源对比和页岩油勘探提供地球化学依据。

关键词: 苏北盆地, 溱潼凹陷, 泥页岩, 生烃潜力, 地球化学特征, 沉积环境

Abstract:

The second member of Paleogene Funing Formation (E₁f₂) is the main target interval of shale oil exploration and has good prospects of oil and gas exploration in Qintong Sag.Predecessors have studied the hydrocarbon generation potential and geochemical characteristics of source rocks in the E₁f₂ in the study area systematically, but the study on the geochemical characteristics and forming environment of source rocks in different sub-members and lithology of the E₁f₂ is still relatively weak, which brings difficulties to the prediction of shale oil sweet spots and resource potential evaluation, as well as the correlation of oil-sources in the E₁f₂ in the study area.In this paper, some representative shale samples of the E₁f₂ in typical wells are selected, and the geochemical characteristics, hydrocarbon generation potential and formation environment of different sub-sections and lithologic source rocks of E₁f₂ in the study area are compared by using geochemical experimental techniques.The results show that the source rocks of E₁ $f 2 4$ and E₁ $f 2 5$ in the study area have the highest abundance of organic matter, mainly type Ⅱ₁ organic matter.The abundance of organic matter in E₁ $f 2 2$ and E₁ $f 2 3$ source rocks is high, mainly type Ⅱ₁ and Ⅱ₂ organic matter.The abundance of organic matter in E₁ $f 2 1$ is relatively low, and the type of organic matter is Ⅱ₂.The lithology of source rocks in the E₁f₂ in the study area is relatively complex, mainly including mudstone, calcareous mudstone and calcareous shale.Mudstone is mainly distributed in E₁ $f 2 4$ and E₁ $f 2 5$ , with the highest abundance of organic matter, mainly type Ⅱ₁ and type Ⅰ organic matter, deposited in weak oxidation-weak reduction freshwater environment, mixed source organic matter dominated by lower aquatic organisms.The calcareous shale and calcareous mudstone are mainly distributed in E₁ $f 2 1$ , E₁ $f 2 2$ and E₁ $f 2 3$ .The organic matter abundance of calcareous shale is higher, and the organic matter type is mainly type Ⅱ₁, a few Ⅱ₂, which is deposited in a strongly reducing saline water environment and mixed source organic matter source.The organic matter abundance of the calcareous mudstone is low-medium, and the type of organic matter type is mainly Ⅱ₂, with a small amount of Ⅱ₁ and Ⅲ, which is deposited in the reducing environment of brackish water and is the source of mixed source organic matter.The source rocks of E₁f₂ are in low mature-mature stage.According to the distribution characteristics of Pr / Ph, Ga / C₃₀H, C₂₄TeT / C₂₆TT and ααα20RC₂₇ sterane / ααα20RC₂₉ sterane, the source rocks of three different lithologies in the E₁f₂ can be distinguished.These understandings can provide geochemical basis for the evaluation of oil and gas resource potential, oil-source correlation and shale oil exploration in different intervals and lithologic source rocks of the E₁f₂ in the study area.

Key words: Subei Basin, Qintong Sag, argillaceous shale, hydrocarbon generating potential, geochemical characteristic, depositional environment

中图分类号:

P618.13

李志鹏, 余麒麟, 昝灵, 余文端, 张枝焕. 苏北盆地溱潼凹陷阜二段不同岩性烃源岩的地球化学特征及生烃潜力对比[J]. 现代地质, 2023, 37(05): 1345-1357.

LI Zhipeng, YU Qiling, ZAN Lin, YU Wenduan, ZHANG Zhihuan. Geochemical Characteristics and Hydrocarbon Generation Potential of Different Lithologic Source Rocks in the Second Member of Funing Formation in Qintong Sag, Subei Basin[J]. Geoscience, 2023, 37(05): 1345-1357.

图/表 13

图1 苏北盆地溱潼凹陷区域地质构造图及阜二段地层柱状图(图(c)修改自文献[1]) (a)苏北盆地构造位置图;(b)溱潼凹陷地质构造图;(c)阜二段地层沉积柱状图

Fig.1 Regional geological structure map of Qintong Sag, Subei Basin and stratigraphic map of the second member of Funing Formation ((c) modified from reference[1])

图2 溱潼凹陷阜二段测井响应特征岩性识别图

Fig.2 Logging response characteristic of lithology identification in the second member of Funing Formation, Qintong Sag

图3 溱潼凹陷典型井阜二段烃源岩层系岩性组合剖面

Fig.3 Lithologic combination profile of source rocks of typical wells in the second member of Funing Formation, Qintong Sag

图4 溱潼凹陷阜二段烃源岩TOC和S1+S2有机质丰度划分 (a)不同亚段烃源岩有机质丰度相关图;(b)不同岩性烃源岩有机质丰度相关图

Fig.4 Plot of TOC versus S1+S2 of source rock samples from the second member of Funing Formation, Qintong Sag

图5 溱潼凹陷阜二段烃源岩HI和Tmax有机质类型划分图 (a)不同亚段烃源岩HI和Tmax有机质类型划分图;(b)不同岩性烃源岩HI和Tmax有机质类型划分图

Fig.5 Plot of Tmax versus HI of source rock samples from the second member of Funing Formation, Qintong Sag

图6 溱潼凹陷阜二段烃源岩TOC与HI关系图 (a)不同亚段烃源岩TOC与HI关系图;(b)不同岩性烃源岩TOC与HI关系图

Fig.6 Plot of TOC versus HI of source rock samples from the second member of Funing Formation, Qintong Sag

图7 溱潼凹陷阜二段烃源岩显微组分三角图 (a)不同亚段烃源岩显微组分三角图;(b)不同岩性烃源岩显微组分三角图

Fig.7 Triangular diagram of macerals of source rocks in the second member of Funing Formation, Qintong Sag

图8 溱潼凹陷阜二段烃源岩埋藏深度-Ro相关图(a)及Ro等值线图(b)

Fig.8 Plot of Ro versus burial depth (a) and the contour map of Ro (b) in the second member of Funing Formation, Qintong Sag

图9 溱潼凹陷阜二段不同类型烃源岩部分生物标志物谱组成特征

Fig.9 Characteristics of partial biomarker spectra of different types of source rocks in the second member of Funing Formation, Qintong Sag

图10 溱潼凹陷阜二段不同类烃源岩Ph/nC18与Pr/nC17关系图[23?-25] (a)、C29ααα(20R)/C27ααα(20R)与Pr/Ph关系图(b) [25?-27]

Fig.10 Plots of Ph/nC18 versus Pr/n C 17 [ 23 - 25 ] (a) and C29ααα(20R)/C27ααα(20R) versus Pr/Ph [25?-27] (b) of different source rock samples from the second member of Funing Formation, Qintong Sag

图11 溱潼凹陷阜二段不同类型烃源岩C27-C29规则甾烷三角图[25,28-29]

Fig.11 C27-C29 regular sterane triangulation of different types of source rocks in the second member of Funing Formation, Qintong Sag[25,28-29]

图12 溱潼凹陷阜二段不同岩性烃源岩Pr/Ph与Ga/C30藿烷关系图[36](a)及Pr/Ph与DBT/PHE关系图[37-38](b)

Fig.12 Plots of Pr/Ph verses Ga/C30 hopene[36] (a)and Pr/Ph verses DBT/PHE[37-38] (b) of different types of source rocks in the second member of Funing Formation, Qintong Sag

图13 溱潼凹陷阜二段不同岩性类型烃源岩生物标志物参数对比箱状图

Fig.13 Box diagrams of biomarker parameters comparison of different types of source rocks in the second member of Funing Formation, Qintong Sag

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