Journal of Oil and Gas Technology
Vol.41 No.01(2019), Article ID:29543,7 pages
10.12677/JOGT.2019.411004

The Geochemical Characteristics of Source Rock of the Gaoyuzhuang Formation of Well LLD1 in Niuyingzi Area of Lingyuan-Ningcheng Basin

Lei Zheng1, Youjun Tang1*, Yongfei Li2, Xiaoyong Gao2, Wenming Zong2, Qiushi Sun2, Daxiang He1

1School of Resources and Environment, Yangtze University, Wuhan Hubei

2Shenyang Institute of Geology and Mineral Resources, CGS, Shenyang Liaoning

Received: May 21st, 2018; accepted: Nov. 24th, 2018; published: Feb. 15th, 2019

ABSTRACT

Well LLD1 was drilled in Niuyingzi Area of Lingyuan-Ningcheng Basin in the west of Liaoning Province. Oil and gas indications were found in the Gaoyuzhuang Formation in the Mesoproterozoic. The geochemical characteristics of the source rocks were systematically analyzed in the study. The results indicate that the distribution of n-alkanes series in saturated hydrocarbons is substantially complete in all source rocks with an evident unimodal pattern. The distribution of C27~C29 regular steranes presents a dominance of C27 steranes, indicates a predominantly aquatic organisms input in the organic matter of relative source rocks. There exist high relative contents of pregnane and C19~C29 tricyclic terpane/C29~C35 hopane ratio, as well as maturity parameters related to steranes and hopanes; it also indicates that all source rocks are matured. Moreover, a lower (Pr/Ph) ratio and relatively high gammacerane concentration indicate an anoxic deposition environment of partial reduction.

Keywords:Source Rock, Biomarker, Mesoproterozoic, Niuyingzi Area, Lingyuan-Ningcheng Basin

凌源–宁城盆地牛营子地区辽凌D1井高于庄组烃源岩地球化学特征

郑磊1,唐友军1*,李永飞2,郜晓勇2,宗文明2,孙求实2,何大祥1

1长江大学资源与环境学院,湖北 武汉

2中国地质调查局沈阳地质调查中心,辽宁 沈阳

作者简介:郑磊(1993-),男,硕士生,现主要从事油气地球化学方向的学习与研究工作。

收稿日期:2018年5月21日;录用日期:2018年11月24日;发布日期:2019年2月15日

摘 要

辽西凌源–宁城盆地牛营子地区钻探的辽凌D1井,在中元古界高于庄组发现了油气显示。系统地分析了高于庄组烃源岩的地球化学特征,研究结果表明:烃源岩饱和烃中正构烷烃分布基本完整,呈明显的单峰态前峰型,具有C27规则甾烷优势,指示了有机质来源以低等水生生物贡献为主;较高的孕甾烷相对含量和C19~C29三环萜烷/C29~C35藿烷比值,以及较高的甾烷和升藿烷成熟度参数值,均表明烃源岩出于成熟阶段;而低的Pr/Ph和较高伽马蜡烷含量指示了偏还原的沉积环境。

关键词 :烃源岩,生物标志物,中元古界,牛营子地区,凌源–宁城盆地

Copyright © 2019 by author(s), Yangtze University and Hans Publishers Inc.

This work is licensed under the Creative Commons Attribution International License (CC BY).

http://creativecommons.org/licenses/by/4.0/

1. 区域地质概况

凌源–宁城盆地位于辽西坳陷西南部,横跨辽宁西部、河北北部和内蒙古东南部,盆地整体呈南东向展布,总面积约为6600 km2,其中牛营子地区位于该盆地东南部,属于辽宁省凌源市 [1] 。凌源–宁城盆地经历了复杂的构造活动,发育大量的深大断裂和次级断裂,可划分为6个次级构造单元,分别为宁城断陷区、黄土梁子断陷区、三十家子断陷区、牛营子凹陷区、老虎洞凹陷区及刀尔登凸起区(图1) [2] 。另外,研究区出露有中–新元古代、古生代寒武纪–奥陶纪、中生代三叠纪–侏罗纪–白垩纪及第四纪的地层,且广泛发育不同年代的侵入岩。其中,中元古界高于庄组在牛营子地区及邻区广泛分布,整体上发育一套海相碳酸盐岩沉积,其岩性主要为灰白色泥质白云岩、深黑色白云岩、灰黑色灰岩等。

2. 样品与试验方法

研究共选取了4件高于庄组泥质白云岩样品,先进行总有机碳质量分数(w (TOC))、岩石热解、氯仿沥青“A”质量分数及族组分分析,再进行饱和烃气相色谱–质谱分析。其中,w (TOC)分析采用CS-400

Figure 1. The division of location and tectonic unit and outcropped strata of Lingyuan-Ningcheng Basin

图1. 凌源–宁城盆地地理位置、构造单元划分及出露地层

碳硫分析仪;岩石热解分析采用OGE-VI油气评价工作站;色谱–质谱分析在安捷伦6890色谱仪及安捷伦5975i质谱仪上进行,色谱–质谱试验分析条件及程序参见文献 [3] 。

3. 结果与讨论

3.1. 高于庄组烃源岩地球化学特征

研究的烃源岩样品主要为辽凌D1井(LLD1井)的高于庄组黑色泥质白云岩,分别对其进行了岩石热解分析、w (TOC)分析结果(表1)表明:研究区高于庄组黑色泥质白云岩的w (TOC)相对较低,为0.29%~0.99%,平均0.65%,生烃潜量(w (S1 + S2))为0.26~0.81 mg/g,平均0.52 mg/g,属于较差烃源岩。另外,高于庄组烃源岩最高热解峰温(tmax)为475˚C~487˚C,均大于465˚C,处于成熟–高成熟阶段,已大量生烃。

3.2. 正构烷烃和无环类异戊二烯烷烃

正构烷烃是石油中重要的、也是结构最简单的组分,其组成和含量受热演化程度、生物降解、水洗作用及有机质类型等影响 [4] 。一般来说,高丰度的长链正构烷烃 ( C 22 + ) 主要来源于高等植物的蜡 [5] ,且高碳数的碳优势指数 [6] 和奇偶优势 [7] 与成熟度和有机质组成密切相关。通常认为,姥鲛烷(Pr)形成于偏氧化环境,植烷(Ph)形成于偏还原环境,且Pr/Ph小于1.0为偏还原环境,Pr/Ph大于2.0则为偏氧化环境。

原油饱和烃中正构烷烃的分布型态往往能指示有机质输入特征或反映成熟度的差异,前峰型主要指示藻类等低等水生生物贡献为主或高热演化成熟度;单峰态后峰型主要指示高等植物输入为主;双峰型反映了低等水生生物与高等植物的双重贡献 [8] 。

图2可知,高于庄组烃源岩饱和烃正构烷烃碳数分布比较完整,分布范围为nC14~nC35,呈单峰态前峰型,主峰碳为nC17或nC18,高碳数正构烷烃含量逐渐降低,无明显奇偶优势和碳优势,Pr/Ph范围为0.70~0.94,均小于1.0,指示弱氧化–弱还原的沉积环境(图2)。

Figure 2. The total ion chromatograms of the saturated hydrocarbon from the source rock extracts in Gaoyuzhuang Formation of Well LLD1

图2. LLD1井高于庄组烃源岩抽提物饱和烃总离子流图

3.3. 萜类化合物

萜类化合物广泛分布于石油和沉积有机质中,其主要来源于细菌(原核生物)膜的类脂物 [9] 。藿烷系列化合物作为主要的五环三萜类化合物,由4个六元环和1个五元环组成,通常含有27~35个碳原子,其来源与细菌中特定的细菌藿烷聚醇有关,如细菌藿烷四醇 [10] 。而三环萜烷主要来源于规则的C30类异戊二烯 [11] ,也可能与原始的藻类相关 [12] 。大量研究表明 [13] [14] [15] [16] [17] ,三环萜烷的分布差异与沉积环境和有机质来源密切相关,其中C19和C20三环萜烷来源于浅水陆源高等植物,而在海相或咸水湖相烃源岩及其相关原油中往往以C23三环萜烷为主。

三环萜烷具有比藿烷系列化合物更高的热稳定性,因此,随成熟度增大,三环萜烷相对含量会逐渐增大。由图3可知,LLD1井不同深度的高于庄组烃源岩均具有相似的三环萜烷和藿烷系列化合物分布特征,其C19~C29三环萜烷的相对含量高,C19~C29三环萜烷与C29~C35藿烷的比值为0.88~2.75,仅个别样品中该比值小于1.0,且Ts/(Ts + Tm)为0.41~0.52。结果表明,高于庄组烃源岩的成熟度较高。

样品中除了检测出较丰富的、完整的藿烷系列化合物外,部分样品中还含有丰富的莫烷系列化合物。藿烷系列化合物容易受到热成熟度和生物降解的影响。根据分子结构的差异,莫烷系列化合物的热稳定性明显低于藿烷系列化合物,从而使得莫烷系列化合物在热演化成熟度达到生油窗时,其相对含量较低 [18] 。另外,也有学者指出莫烷与藿烷比值在一定程度上也受母质输入和沉积环境的控制 [19] ,可能与陆生高等植物输入相关 [20] 。LLD1井高于庄组烃源岩中莫烷系列化合物含量均较低,C30莫烷/C30藿烷为0.14~0.18,表明其成熟度较高。另外,根据C31升藿烷R和S构型的异构体的相对含量可以分析原油的成熟度,R构型为生物构型,热稳定性较低,随埋深加大会转化为较为稳定的S型,当镜质体反射率(Ro)为0.6%左右时,C31升藿烷与22S/(22S + 22R)比值达到平衡,约为0.57~0.62 [21] 。LLD1井高于庄组烃源岩中C31升藿烷与22S/(22S + 22R)比值分布范围为0.58~0.62,已达到平衡点,表明原油为成熟原油,且烃源岩已进入生烃高峰期。

Figure 3. The distribution characteristics of tricyclic and hopanes of the source rock extracts in Gaoyuzhuang Formation of Well LLD1 (m/z = 191, 1290.8 m)

图3. LLD1井高于庄组烃源岩抽提物中三环萜烷和藿烷系列的分布特征(m/z = 191,1290.8 m)

伽马蜡烷被认为源自于四膜虫醇,可以表征海相或非海相烃源岩的沉积环境,高含量的伽马蜡烷往往与高盐度导致的水体分层有关,指示偏还原沉积环境 [22] ,其与C30藿烷比值可用于油油对比和油源对比分析 [23] 。LLD1井高于庄组烃源岩中伽马蜡烷的含量较高(图3),表明其水体盐度存在一定的差异。

3.4. 甾类化合物

C27、C28、C29规则甾烷广泛应用于分析有机质来源及有效的油油和油源对比等。通常,C27和C28甾烷主要来源于细菌、低等水生生物,而相对高丰度的C29甾烷往往与高等植物贡献相关,且其相对含量可以用来判识不同的沉积环境 [24] ,并被广泛应用于油源对比分析 [25] 。

图4可知,LLD1井高于庄组烃源岩中规则甾烷、重排甾烷及孕甾烷均分布明显。规则甾烷的相对含量主要呈不对称的“V”字型分布,略显C27甾烷优势,反映其母质输入中以低等水生生物贡献为主; C27重排甾烷/C27~C29规则甾烷的平均值为0.20 (图4)。此外,孕甾烷和升孕甾烷一般认为是来自生物激素孕甾醇和孕甾酮,与高盐度的沉积环境相关,或由热演化中规则甾烷的侧链断裂形成。LLD1井高于庄组烃源岩中孕甾烷和升孕甾烷含量较高。

Figure 4. The distribution characteristics of steranes of the source rock extracts in Gaoyuzhuang Formation of Well LLD1 (m/z = 217)

图4. LLD1井高于庄组烃源岩抽提物中甾烷系列的分布特征(m/z = 217)

随着成熟度的增加,R构型的生物标志物会逐渐向S构型转化,直到达到平衡。据此,规则甾烷中常用的成熟度参数主要为C29甾烷20S/(20S + 20R)和C29甾烷ββ/(ββ + αα)。高于庄组烃源岩中C29甾烷20S/(20S + 20R)和C29甾烷ββ/(ββ + αα)参数值分布范围分别为0.35~0.45和0.37~0.45,表明高于庄组烃源岩成熟度相对较高。

4. 结语

LLD1井高于庄组烃源岩中w (TOC)较低,属于较差的烃源岩,岩石热解参数显示烃源岩处于成熟–高成熟阶段,烃源岩饱和烃中正构烷烃分布基本完整,呈明显的单峰态前峰型,C27、C28、C29规则甾烷呈C27甾烷优势,指示了有机质来源以低等水生生物贡献为主;较高的孕甾烷相对含量和C19~C29三环萜烷与C29~C35藿烷比值,以及较高的甾烷和升藿烷成熟度参数值,均表明烃源岩达到成熟阶段,而低的Pr/Ph和较高伽马蜡烷含量指示了偏还原沉积环境。

基金项目

中国地质调查局项目(DD20160167);中国石油科技创新基金项目(2017DG5007G0105);国家自然科学基金项目(41730424)。

参考文献

[1] 肖飞, 李永飞, 郜晓勇, 等. 凌源-宁城盆地牛营子地区侏罗系海房沟组烃源岩地球化学特征: 以牛D1井为例[J]. 矿物岩石地球化学通报, 2018, 37(1): 94-102.

[2] Gregory, A.D., Meng, J., Cao, W., et al. (2009) Triassic and Jurassic Tectonics in the Eastern Yanshan Belt, North China: Insights from the Controversial Dengzhangzi Formation and Its Neighboring Units. Earth Science Frontiers, 16, 69-86. https://doi.org/10.1016/S1872-5791(08)60090-1

[3] 李美俊, 王铁冠, 张卫彪. 塔河油田奥陶系原油C(26)降胆甾烷分布特征及地质意义[J]. 石油实验地质, 2015, 37(1): 64-70.

[4] Peters, K.E. and Walters, C.C. (2005) The Biomarker Guide: Biomarkers and Isotopes in Petroleum Exploration and Earth History Seconded. Cambridge University Press, Cambridge, 612-613.

[5] Brooks, J.D. and Smith, J.W. (1969) The Diagenesis of Plant Lipids during the Formation of Coal, Petroleum and Natural Gas-II. Coalification and the Formation of Oil and Gas in the Gippsland Basin. Geochimica et Cosmochimica Acta, 33, 1183-1194. https://doi.org/10.1016/0016-7037(69)90040-4

[6] Bray, E.E. and Evans, E.D. (1961) Distribution of n-Paraffins as a Clue to Recognition of Source Beds. Geochimica et Cosmochimica Acta, 22, 2-15. https://doi.org/10.1016/0016-7037(61)90069-2

[7] Scalan, E.S. and Smith, J.E. (1970) An Improved Measure of the Odd-Even Predominance in the Normal Alkanes of Sediment Extracts and Petroleum. Geochimica et Cosmochimica Acta, 34, 611-620. https://doi.org/10.1016/0016-7037(70)90019-0

[8] Bourbonniere, R.A. and Meyers, P.A. (1996) Sedimentary Geolipid Records of Historical Changes in the Watersheds and Productivities of Lakes Ontario and Erie. Limnology and Oceanography, 41, 352-359. https://doi.org/10.4319/lo.1996.41.2.0352

[9] Ourisson, G. and Albrecht, P. (1982) Predictive Microbial Biochemistry from Molecular Fossils to Procaryotic Membranes. Trends in Biochemical Sciences, 7, 236-239. https://doi.org/10.1016/0968-0004(82)90028-7

[10] Ourisson, G. and Rohmer, M. (1987) Prokaryotic Hopanoids and Other Polyterpenoid Sterol Surrogates. Annual Review of Microbiology, 41, 301-33. https://doi.org/10.1146/annurev.mi.41.100187.001505

[11] Aquino Neto, F.R. (1983) Occurrence and Formation of Tricyclic Terpanes in Sediments and Petroleums. Advances in Organic Geochemistry, John Wiley & Sons Ltd., Chichester, 659-667.

[12] Azevedo, D.A. (1992) Novel Series of Tricyclic Aromatic Terpanes Characterized in Tasmanian Tasmanite. Organic Geochemistry, 18, 9-16. https://doi.org/10.1016/0146-6380(92)90138-N

[13] Xiao, H. (2018) Occurrence and Distribution of Unusual Tri- and Tetracyclic Terpanes and Their Geochemical Significance in Some Paleogene Oils from China. Energy & Fuels, 32, 7393-7403. https://doi.org/10.1021/acs.energyfuels.8b01025

[14] Volk, H. (2005) Geochemical Comparison of Fluid Inclusion and Present-Day Oil Accumulations in the Papuan Foreland-Evidence for Previously Unrecognised Petroleum Source Rocks. Organic Geochemistry, 36, 29-51. https://doi.org/10.1016/j.orggeochem.2004.07.018

[15] Zumberge, J.E. (1987) Prediction of Source Rock Characteristics Based on Terpane Biomarkers in Crude Oils: A Multivariate Statistical Approach. Geochimica et Cosmochimica Acta, 51, 1625-1637. https://doi.org/10.1016/0016-7037(87)90343-7

[16] Huang, H. (2017) Impacts of Source Input and Secondary Alteration on the Extended Tricyclic Terpane Ratio: A Case Study from Palaeozoic Sourced Oils and Condensates in the Tarim Basin, NW China. Organic Geochemistry, 112, 158-169. https://doi.org/10.1016/j.orggeochem.2017.07.012

[17] Tao, S. (2015) Geochemical Application of Tricyclic and Tetracyclic Terpanes Biomarkers in Crude Oils of NW China. Marine & Petroleum Geology, 67, 460-467. https://doi.org/10.1016/j.marpetgeo.2015.05.030

[18] Seifert, W.K. and Moldowan, J.M. (1980) The Effect of Thermal Stress on Source-Rock Quality as Measured by Hopane Stereochemistry. Physics & Chemistry of the Earth, 12, 229-237. https://doi.org/10.1016/0079-1946(79)90107-1

[19] Rullkotter, J. and Marzi, R. (1988) Natural and Artificial Maturation of Biological Markers in a Toarcian Shale from Northern Germany. Organic Geochemistry, 13, 639-645. https://doi.org/10.1016/0146-6380(88)90084-8

[20] Saksen, G.H. and Bohacs, K.M. (1995) Geological Controls of Source Rock Geochemistry through Relative Sea Level; Triassic, Barents Sea. Springer, Berlin, 25-50.

[21] Zumberge, J.E. (1987) Terpenoid Biomarker Distributions in Low Maturity Crude Oils. Organic Geochemistry, 11, 479-496. https://doi.org/10.1016/0146-6380(87)90004-0

[22] Damsté, J.S.S. (1995) Evidence for Gammacerane as an Indicator of Water Column Stratification. Geochimica et Cosmochimica Acta, 59, 1895-1900. https://doi.org/10.1016/0016-7037(95)00073-9

[23] Xiao, H. (2019) Geochemical Characteristics of Cretaceous Yogou Formation Source Rocks and Oil-Source Correlation within a Sequence Stratigraphic Framework in the Termit Basin, Niger. Journal of Petroleum Science and Engineering, 172, 360-372. https://doi.org/10.1016/j.petrol.2018.09.082

[24] Moldowan, J.M. and Seifert, W.K. (1985) Relationship between Petroleum Composition and Depositional Environment of Petroleum Source Rock. American Association of Petroleum Geologists, 69, 1255-1268.

[25] Enric (2000) A New Geochemical-Sequence Stratigraphic Model for the Mahakam Delta and Makassar Slope, Kalimantan, Indonesia. AAPG Bulletin, 84, 12-44.

[编辑] 孙巍

NOTES

*通信作者。

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