潜江凹陷潜江组盐间细粒岩沉积特征及其对页岩含油性的控制

doi:10.13745/j.esf.sf.2020.12.8

摘要/Abstract

摘要：

江汉盆地是我国典型的内陆盐湖盆地,位于其中部的潜江凹陷发育盐间细粒沉积,近期油气勘探取得突破。为研究其沉积特征及其对页岩含油性的控制,本文基于岩心和多种测试方法将盐间细粒沉积划分出8种岩相,分别是含灰泥质云岩、云质混合细粒岩、泥质混合细粒岩、灰质混合细粒岩、灰质泥岩/泥岩、云质泥岩、硫酸盐质混合细粒岩和云质/泥质钙芒硝岩。岩相组合有A和B两种:A类岩相组合为含灰泥质云岩、云质混合细粒岩和泥质混合细粒岩,夹少量灰质混合细粒岩、云质泥岩、硫酸盐质混合细粒岩和云质/泥质钙芒硝岩;B类岩相组合为云质泥岩、硫酸盐质混合细粒岩、云质/泥质钙芒硝岩,夹少量灰质泥岩/泥岩和泥质混合细粒岩。A类岩相组合富集碳酸盐质矿物且有机质含量高,岩心上表现为灰黑色泥质岩(泥质混合细粒岩和灰质混合细粒岩)与黄褐色云质岩(含灰泥质云岩和云质混合细粒岩)频繁更替,其中夹有白色硫酸盐质岩,呈透镜体状或层状产出,说明当时环境的盐度较低,镜下纹层大部分呈较为连续的微波状或水平状。其沉积特征反映了A类岩相组合的形成环境为还原性较好、盐度较低的深水区。B类岩相组合硫酸盐矿物含量和有机质含量较低,岩心上表现为白色高硫酸盐质岩夹有黑色泥质层或黄褐色云质层,镜下观察为呈菱形片状钙芒硝,常见穿插双晶,可见明显的粒序变化,云质含量高的薄片镜下为无纹层特征。其沉积特征反映了B类岩相组合形成环境为还原性较弱、盐度较高的较浅水域。本研究将V/(V+Ni)、(S₁+S₂)/TOC、Sr/Ba和Ga/C₃₁H指数等地化参数与岩相特征相结合,进一步佐证了上述观点,并且补充说明了A类岩相组合形成于气候湿润的环境,而B类岩相组合形成环境较为干旱,且将盐间沉积划分为B、A、B三个阶段,对其进行了沉积模式的研究。结果表明:第一、三阶段气候干旱且水深较浅,湖水析出大量盐类,主要发育B类岩相组合,且硫酸盐矿物的增加使硫酸盐还原菌氧化有机质,不利于有机质富集;第二阶段降雨增加,大量淡水注入致使水体淡化且深度变深,这时水体分层性较好,还原性较强,发育A类岩相组合,有机质的保存条件好。由此可见,矿物组分上为灰泥质或云质含量高且岩心具有水平层理、镜下纹层特征明显的岩相,以及湿润气候下的还原性较强、盐度适宜且水体分层性好的深水环境等沉积特征,有助于形成含油性较好的页岩。因此,低TOC含量的B类岩相组合不是油气富集的主要岩相,富集的硫酸盐矿物会稀释有机质浓度,岩相所处的高盐度环境也会减缓微生物活动;而高TOC含量的A类岩相组合为油气富集的主要岩相,频繁的降雨稀释水体盐度,为可以产生有机质的浮游微生物创造了良好的环境,且所含云质纹层矿物间孔隙发育,有利于烃类的存储,所以成为该区内的优质烃源岩,是油气勘探开发的有利岩相。

关键词: 细粒沉积, 沉积特征, 岩相, 沉积模式, 潜江凹陷

Abstract:

The Jianghan Basin is a typical inland salt lake basin in China. The Qianjiang Sag, in the middle of the basin, developed intersalt petroliferous fine-grained sedimentary rocks, and it has seen a recent breakthrough in oil and gas exploration. In order to study its sedimentary characteristics and depositional control, eight kinds of lithofacies are identified in the sedimentary rocks using core and various tests: calcite-bearing argillaceous dolomite, dolomite, argillite or calcite mixed fine-grained sedimentary rocks, calcareous mudstone/mudstone, dolomitic mudstone, sulfate mixed fine-grained rock, and dolomitic/argillaceous glauberite. In addition, two lithofacies associations, types A and B, are identified. The type A association contains calcite-bearing argillaceous dolomite, dolomite or argillite mixed fine-grained sedimentary rocks, with small amounts of calcite mixed fine-grained sedimentary rocks, dolomitic mudstone, sulfate mixed fine-grained rock, and dolomitic/argillaceous glauberite. The type B association involves dolomitic mudstone, sulfate mixed fine-grained rock dolomitic/argillaceous glauberite, small amounts of calcareous mudstone/mudstone and argillite mixed fine-grained sedimentary rocks. The type A lithofacies association is rich in carbonate and organic matter; its cores are gray-black argillaceous rocks (argillite and calcite mixed fine-grained sedimentary rocks) and yellow-brown dolomitic rocks (calcite-bearing argillaceous dolomite and dolomite mixed fine-grained sedimentary rocks) frequently interchanging, with white sulfate rocks interspersed in the form of lenses or layers, indicating the environmental salinity at that time was relatively low. Laminates under the microscope mostly show continuous fine wave or aligned horizontally. The sedimentary characteristics show the type A association is formed in a reductive and low salinity deep water environment. The type B lithofacies association, on the other hand, is rich in sulfate and has low organic matter content; its cores are white high sulfate rocks with black argillaceous layers or yellowish-brown dolomitic layers. Microscope observation reveals rhombohedral glauberite, commonly with interspersed twin crystals, and obvious grained sequence change can be seen. The thin slices with high dolomite content are characterized by the absence of laminates under the microscope. The sedimentary characteristics show the formation environment of the type B lithofacies association is shallow water with weak reducibility and high salinity. Geochemical parameters, such as V/(V+Ni), (S₁+S₂)/TOC, Sr/Ba, and Ga/C₃₁H, combining with lithofacies characteristics, further support the above assessment and show the types A and B associations are formed in humid and dry climate, respectively. The intersalt deposition is divided into three stages, B, A, B, in a proposed sedimentary model: In the first stage, the climate is dry and the water is shallow, a lot of salts precipitate from the lake water to form mainly the type B lithofacies association. With increasing sulfate minerals, organic matter oxidation is facilitated by sulfate-reducing bacteria, which is not conducive to organic matter enrichment. In the second stage, increasing rainfall and large-scale fresh water injection cause the water salinity and depth to increase. At this time, the water has good stratification and strong reducibility to develop the type A lithofacies association, which improves the preservation conditions for organic matter. Therefore, the type B association, with low TOC content, is not the main lithofacies for oil and gas accumulation, as enriched sulfate minerals can dilute the organic matter, and the high salinity environment in the lithofacies can slow down the microbial activity. Conversely, the type A association, with high TOC content, is the main lithofacies for oil and gas enrichment. In its forming environment, frequent rainfall lowers the water salinity to create a good environment for the organic matter-producing planktonic microorganisms to grow; at the same time, pores between minerals beneficial to hydrocarbon storage develop in the dolomitic laminate, making it a high-quality source rock and favorable lithofacies for oil and gas exploration and development in the area.

Key words: fine-grained sedimentary rocks, sedimentary characteristics, lithofacies, depositional model, Qianjiang Sag

中图分类号:

P618.13

陈晨, 姜在兴, 孔祥鑫, 吴世强, 陈凤玲, 杨叶芃. 潜江凹陷潜江组盐间细粒岩沉积特征及其对页岩含油性的控制[J]. 地学前缘, 2021, 28(5): 421-435.

CHEN Chen, JIANG Zaixing, KONG Xiangxin, WU Shiqiang, CHEN Fengling, YANG Yepeng. Sedimentary characteristics of intersalt fine-grained sedimentary rocks and their control on oil-bearing ability of shales in the Qianjiang Formation, Qianjiang Sag[J]. Earth Science Frontiers, 2021, 28(5): 421-435.

图/表 12

图1 潜江凹陷构造井位图

Fig.1 Diagram showing the locations of the structural wells in the Qianjiang Sag

图2 潜江凹陷地层综合剖面图(据文献[24]修改)

Fig.2 Composite stratigraphic profile compiled for the Qianjiang Sag. Modified after [24].

图3 潜江凹陷蚌页油2井(BYY2)Eq34-10韵律层的矿物组成

Fig.3 Mineral composition of the Eq34-10 rhythm layer of Well BYY2

表1 潜江凹陷蚌页油2井(BYY2)Eq34-10韵律层各岩相的定量分类

Table 1 Quantitative classification of each lithofacies in the Eq34-10 rhythm layer of Well BYY2 in the Qianjiang Sag

大类	岩相	碳酸盐矿物含量/%		硫酸盐矿物含量/%	泥质碎屑含量/%
大类	岩相	方解石	白云石	硫酸盐矿物含量/%	泥质碎屑含量/%
碳酸盐岩	含灰泥质云岩	1020	>50	<10	>20
碳酸盐岩	泥质云岩	<10	>50	<10	>20
泥岩	灰质泥岩泥岩	>20 <10	<10 <10	<10 <10	>50 >50
钙芒硝岩	云质钙芒硝泥质钙芒硝岩	<10 <10	>20 <10	>50 >50	<10 >20
混合细粒岩	云质混合细粒岩	<50	<50(最高)	<50	<50
	泥质混合细粒岩	<50	<50	<50	<50(最高)
	灰质混合细粒岩	<50(最高)	<50	<50	<50
	硫酸盐质混合细粒岩	<50	<50	<50(最高)	<50

图4 潜江凹陷蚌页油2井(BYY2)Eq34-10韵律层岩相组合图

Fig.4 Composite diagram showing the lithofacies association in the Eq34-10 rhythm layer of Well BYY2 in the Qianjiang Sag

图5 显微镜下潜江凹陷蚌页油2井(BYY2)Eq34-10韵律层A类岩相组合的沉积特征

Fig.5 Microphotographic images revealing the sedimentary characteristics of type A lithofacies association in the Eq34-10 rhythm layer of Well BYY2 in the Qianjiang Sag

表2 潜江凹陷蚌页油2井(BYY2)Eq34-10韵律层各岩相的矿物与TOC含量

Table 2 Mineral composition and TOC content of each lithofacies in the Eq34-10 rhythm layer of Well BYY2 in the Qianjiang Sag

图6 显微镜下潜江凹陷蚌页油2井(BYY2)Eq34-10韵律灰质混合细粒岩的沉积特征

Fig.6 Microphotographic images illustrating the sedimentary characteristics of calcareous fine-grained sediment in the Eq34-10 rhythm layer of Well BYY2 in the Qianjiang Sag

图7 显微镜下潜江凹陷蚌页油2井(BYY2)Eq34-10韵律B类岩相组合的沉积特征

Fig.7 Microphotographic images showing the sedimentary characteristics of type B lithofacies association in the Eq34-10 rhythm layer of Well BYY2 in Qianjiang Sag

图8 潜江凹陷蚌页油2井(BYY2)Eq34-10韵律地化参数图

Fig.8 Composite diagram characterizing the geochemical parameters of the Eq34-10 rhythm layer of Well BYY2 in the Qianjiang Sag

图9 潜江凹陷蚌页油2井(BYY2)Eq34-10韵律矿物含量与TOC含量的相关关系图

Fig.9 Correlation between TOC and mineral contents in the Eq34-10 rhythm layer of Well BYY2 in the Qianjiang Sag

图10 江汉盆地潜江凹陷沉积模式

Fig.10 Depositional model of the Qianjiang Sag, Jianghan Basin

参考文献 39

[1]	孙焕泉, 蔡勋育, 周德华, 等. 中国石化页岩油勘探实践与展望[J]. 中国石油勘探, 2019, 24(5):569-575.
[2]	朱筱敏, 董艳蕾, 刘成林, 等. 中国含油气盆地沉积研究主要科学问题与发展分析[J]. 地学前缘, 2021, 28(1):1-11.
[3]	姜在兴, 梁超, 吴靖, 等. 含油气细粒沉积岩研究的几个问题[J]. 石油学报, 2013, 34(6):1031-1039.
[4]	APLIN A C, MACQUAKER J H S . Mudstone diversity: origin and implications for source, seal, and reservoir properties in petroleum systems[J]. AAPG Bulletin, 2011, 95(12):2031-2059. DOI URL
[5]	吴靖, 姜在兴, 梁超. 东营凹陷沙河街组四段上亚段细粒沉积岩岩相特征及与沉积环境的关系[J]. 石油学报, 2017, 38(10):1110-1122.
[6]	邹才能, 杨智, 崔景伟, 等. 页岩油形成机制、地质特征及发展对策[J]. 石油勘探与开发, 2013, 40(1):14-26.
[7]	KONG X X, JIANG Z X, HAN C, et al. Organic matter enrichment and hydrocarbon accumulation models of the marlstone in the Shulu Sag, Bohai Bay Basin, northern China[J]. International Journal of Coal Geology, 2020, 217:103350. DOI URL
[8]	张少敏, 操应长, 朱如凯, 等. 湖相细粒混合沉积岩岩石类型划分: 以准噶尔盆地吉木萨尔凹陷二叠系芦草沟组为例[J]. 地学前缘, 2018, 25(4):198-209.
[9]	田继先, 曾旭, 易士威, 等. 咸化湖盆致密油储层“甜点”预测方法研究: 以柴达木盆地扎哈泉地区上干柴沟组为例[J]. 地学前缘, 2016, 23(5):193-201.
[10]	徐田武, 张洪安, 李继东, 等. 渤海湾盆地东濮凹陷盐湖相成烃成藏特征[J]. 石油与天然气地质, 2019, 40(2):248-261.
[11]	夏刘文, 曹剑, 徐田武, 等. 盐湖生物发育特征及其烃源意义[J]. 地质论评, 2017, 63(6):1549-1562.
[12]	LI M W, CHEN Z H, CAO T T, et al. Expelled oils and their impacts on Rock-Eval data interpretation, Eocene Qianjiang Formation in Jianghan Basin, China[J]. International Journal of Coal Geology, 2018, 191:37-48. DOI URL
[13]	方志雄. 潜江盐湖盆地盐间沉积的石油地质特征[J]. 沉积学报, 2002, 20(4):608-613, 620.
[14]	罗劲, 李铭华, 郭丽彬, 等. 盐湖盆地复杂岩性区储层预测方法研究: 以江汉盆地潜江凹陷为例[J]. 石油实验地质, 2016, 38(2):273-277.
[15]	方志雄. 潜江凹陷隐蔽油藏成藏主控因素及勘探方向[J]. 石油与天然气地质, 2006, 27(6):804-812.
[16]	郑有恒. 江汉盆地潜江凹陷潜江组岩性油藏勘探方向及对策[J]. 石油实验地质, 2010, 32(4):330-333, 346.
[17]	徐崇凯, 刘池洋, 郭佩, 等. 潜江凹陷古近系潜江组盐间泥岩地球化学特征及地质意义[J]. 沉积学报, 2018, 36(3):617-629.
[18]	孙中良, 王芙蓉, 何生, 等. 潜江凹陷古近系盐间典型韵律层页岩孔隙结构[J]. 深圳大学学报(理工版), 2019, 36(3):289-297.
[19]	胡忠贵, 胡明毅, 洪国良, 等. 潜江凹陷马王庙地区新沟咀组下段重要层段沉积相特征[J]. 沉积学报, 2011, 29(4):712-723.
[20]	冉波, 刘树根, 孙玮, 等. 四川盆地及周缘下古生界五峰组-龙马溪组页岩岩相分类[J]. 地学前缘, 2016, 23(2):96-107.
[21]	KONG X X, JIANG Z X, HAN C, et al. The tight oil of lacustrine carbonate-rich rocks in the Eocene Shulu Sag: implications for lithofacies and reservoir characteristics[J]. Journal of Petroleum Science and Engineering, 2019, 175:547-559. DOI URL
[22]	HUANG C J, HINNOV L. Evolution of an Eocene-Oligocene saline lake depositional system and its controlling factors, Jianghan Basin, China[J]. Journal of Earth Science, 2014, 25(6):959-976. DOI URL
[23]	WU L L, MEI L F, LIU Y S, et al. Multiple provenance of rift sediments in the composite basin-mountain system: constraints from detrital zircon U-Pb geochronology and heavy minerals of the early Eocene Jianghan Basin, central China[J]. Sedimentary Geology, 2017, 349:46-61. DOI URL
[24]	KONG X X, JIANG Z X, ZHENG Y H, et al. Organic geochemical characteristics and organic matter enrichment of mudstones in an Eocene saline lake, Qianjiang Depression, Hubei Province, China[J]. Marine and Petroleum Geology, 2020, 114:1-15.
[25]	方志雄. 江汉盆地盐湖沉积充填模式[M]. 北京: 石油工业出版社, 2006: 1-231.
[26]	姜在兴. 沉积学[M]. 2版. 北京: 石油工业出版社, 2010: 1-424.
[27]	金忠慧. 东营凹陷古近系沙四上亚段细粒岩沉积环境研究[D]. 北京: 中国地质大学(北京), 2017.
[28]	腾格尔, 刘文汇, 徐永昌, 等. 无机地球化学参数与有效烃源岩发育环境的相关研究[J]. 地球科学进展, 2005, 20(2):193-200.
[29]	ANDREA M R. Geochemical characterization of the Woodford Shale, central and southeastern Oklahoma[D]. Norman: The University of Oklahoma, 2010.
[30]	SLATT R M, RODRIGUEZ N D. Comparative sequence stratigraphy and organic geochemistry of gas shales: commonality or coincidence?[J]. Journal of Natural Gas Science and Engineering, 2012, 8:68-84. DOI URL
[31]	ZHU Y M, WENG H X, SU A G, et al. Geochemical characteristics of Tertiary saline lacustrine oils in the Western Qaidam Basin, Northwest China[J]. Applied Geochemistry, 2005, 20(10):1875-1889. DOI URL
[32]	LI W H, LU S F, XUE H T, et al. Oil content in argillaceous dolomite from the Jianghan Basin, China: application of new grading evaluation criteria to study shale oil potential[J]. Fuel, 2015, 143:424-429. DOI URL
[33]	薛传东, 刘星, 亓春英, 等. 滇池近代沉积物的元素地球化学特征及其环境意义[J]. 岩石矿物学杂志, 2007, 26(6):582-590.
[34]	MOLDOWAN J M, PETERS K E, WALTERS C C. The biomarker guide: biomarkers and isotopes in petroleum systems and earth history[M]. Cambridge: Cambridge University Press, 2005: 1-451.
[35]	卢鸿, 孙永革, 彭平安. 轮南油田原油中三甲基苯基类异戊二烯化合物的检出及其意义[J]. 高校地质学报, 2004, 10(2):283-289.
[36]	张立平, 黄第藩, 廖志勤. 伽马蜡烷-水体分层的地球化学标志[J]. 沉积学报, 1999, 17(1):136-140.
[37]	孙中良, 王芙蓉, 侯宇光, 等. 盐湖页岩有机质富集主控因素及模式[J]. 地球科学, 2020, 45(4):1375-1387.
[38]	张跃, 陈世悦, 孙娇鹏, 等. 柴北缘石炭系克鲁克组泥页岩岩相特征与沉积环境分析[J]. 地学前缘, 2016, 23(5):86-94.
[39]	KONG X X, JIANG Z X, HAN C, et al. Genesis and implications of the composition and sedimentary structure of fine-grained carbonate rocks in the Shulu Sag[J]. Journal of Earth Science, 2017, 28(6):1047-1063. DOI URL