延安周边地区页岩地球化学特征及页岩油潜力评价

doi:10.19657/j.geoscience.1000-8527.2021.001

摘要/Abstract

摘要：

延安周边地区长7泥页岩地层中获得工业油流,使得针对该地区的勘探工作开始审视页岩油目标。基于此,开展了系统化的烃源岩品质评价工作以及页岩油气潜力分析工作,以期为深入的页岩油勘探提供参考。研究表明,研究区页岩有机质丰度整体较高,平均总有机碳含量4.05%;有机质类型主体为Ⅰ型、Ⅱ₁型及Ⅱ₂型;整体进入了生油窗,处于成熟生油的热演化阶段。页岩的物质来源为陆地与湖泊的混合来源,其整体上沉积于弱还原弱氧化环境。三类有机质中,有机质含量越高,则其生烃能力也越强;Ⅰ型有机质的生烃能力最大、Ⅱ₁型有机质次之,Ⅱ₂型有机质相对最小。Ⅰ型有机质、Ⅱ₁型有机质及Ⅱ₂型有机质,页岩油含量即总游离烃量分别为10.30 mg/g、8.99 mg/g、8.14 mg/g。页岩油相态以游离态为主,吸附态相对较少。可动用性方面,页岩油的可动用资源集中于Ⅰ型有机质,Ⅱ₁型有机质可动用较差,Ⅱ₂型有机质可动用性极差。在综合勘探潜力方面,最适于进行页岩油勘探的对象是Ⅰ型有机质,其次为Ⅱ₁型有机质。Ⅱ₂型有机质基本无页岩油勘探潜力。

关键词: 鄂尔多斯盆地, 长7页岩, 地球化学特征, 页岩油

Abstract:

Industrial oil flow has been obtained in Chang 7 shale Formation in Ansai area, which turns this area into a shale oil target. Based on this, systematic quality evaluation of source rocks and shale oil potential analysis are carried out to provide reference for future shale oil exploration. The results show high organic matter abundance in the shale (average TOC=4.05%), with the main organic matter types being type I, type II₁ and type II₂. The Chang 7 shale has entered the oil-generating window and is in the oil-generating thermal stage. The shale has both terrestrial and lacustrine source inputs, and the depositional environment was weakly reducing or oxidizing. Among the three organic matter types (higher organic matter would lead to higher hydrocarbon generating capacity), type I has higher hydrocarbon generating capacity than type II₁, and type II₂ has the lowest hydrocarbon generating capacity. The shale oil content of types I, II₁,and II₂ organic matter are 10.30 mg/g, 8.99 mg/g, and 8.14 mg/g, respectively. In terms of availability, the available shale oil resources are concentrated in type I organic matter. Type II₁ organic matter is lowly available and type II₂ organic matter is poorly available. In terms of comprehensive exploration potential, the most suitable target is type I organic matter, followed by type II₁ and then by type II₂ organic matter.

Key words: Ordos Basin, Chang 7 shale, geochemical characteristics, shale oil

中图分类号:

TE135.6

师良, 赵彤彤, 查辉, 王妍妍, 霍萍萍, 范柏江. 延安周边地区页岩地球化学特征及页岩油潜力评价[J]. 现代地质, 2021, 35(04): 1043-1053.

SHI Liang, ZHAO Tongtong, ZHA Hui, WANG Yanyan, HUO Pingping, FAN Bojiang. Geochemical Characteristics and Shale Oil Potential of Shale in the Yan’an Area[J]. Geoscience, 2021, 35(04): 1043-1053.

图/表 12

图1 研究区页岩层理缝发育特征 A.S3114井,1 141.68~1 146.11 m,页岩夹泥岩(蓝线部分代表泥岩段),页岩沿层理面高度破碎,岩心照片;B.D214井,1 171.93~1 172.56 m,灰黑色页岩沿层理面破碎严重,岩心照片;C.D214井,1 170.46 m,页岩沿层理面渗油,岩心照片;D.S3114井,1 101.07 m,黑色页岩发育多个层理面,可见炭屑、鱼鳞、黄铁矿;E.D199井,1 367.97 m,具光泽的黑色页岩,层理面光滑,岩心照片;F.D214井,1 172.12 m,页岩中的微观层理缝,岩石铸体薄片(5+)(该样品取自B中红框处)

Fig.1 Development features of interlayer fractures of shale in the study area

图2 研究区典型有机质的色质谱图对比

Fig.2 Chromatogram comparison of typical organic matter in the study area

图3 研究区的有机质类型分布

Fig.3 Distribution of organic matter types in the study area

图4 研究区有机质的Tmax分布

Fig. 4 Tmax distribution of organic natter in the study area

图5 基于生标参数判别的有机质热成熟度

Fig.5 Thermal maturity of organic matter based on biomarker parametric discrimination

图6 研究区页岩的沉积环境识别图

Fig.6 Sedimentary environment discrimination diagram of shale in the study area

图7 研究区页岩有机质来源

Fig.7 Organic matter source of shale in the study area

图8 有机质含量与热解参数的关系

Fig.8 Relations between organic matter content and pyrolysis parameters

图9 热解参数随埋深的变化关系

Fig.9 Relations between pyrolysis parameters and burial depth

图10 页岩排烃特征

Fig.10 Hydrocarbon expulsion characteristics of the shale

图11 研究区页岩油资源分类图中①、②、③、④分别代表页岩油勘探潜力最大、中等、较低以及无勘探潜力4个范畴

Fig.11 Classification of shale oil resource in the study area

图12 页岩油渗流特征 A.页岩渗油,D214井,长7段,岩心照片,1 170.46 m; B.页岩渗油,D214井,长7段,岩心照片,1 152.37 m,页岩渗油; C.页岩裂缝渗油,W336井,长7段,岩心照片,1 954.47 m; D.页岩中沥青质充填,D214井,长7段,岩心照片,1 170.61 m

Fig. 12 Seepage features of shale oil

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