渤海海域深层潜山油气地球化学特征及油气来源
李慧勇1, 徐云龙2,3, 王飞龙1, 罗小平2,3, 于海波1
1.中海石油(中国)有限公司天津分公司;
2. “油气藏地质及开发工程”国家重点实验室•成都理工大学;
3.成都理工大学能源学院
通讯作者:徐云龙,1988年生,博士研究生;主要从事石油与天然气有机地球化学、油气成藏方面的研究工作。地址:(610059)四川省成都市成华区二仙桥东三路1号。ORCID:0000-0003-2792-1363。E-mail: xuylcdut@163.com

作者简介:李慧勇,1978年生,高级工程师,博士;主要从事海上油气勘探方面的研究工作。地址:(300450)天津市滨海新区海川路2121号。ORCID:0000-0002-7041-0430。E-mail: lihy@cnooc.com.cn

摘要

渤海湾盆地渤海海域渤中19-6深层潜山构造带周缘发育多个富烃深次洼,油气聚集条件复杂,对其油气的有机地球化学特征及主要来源认识尚不明确。为此,利用饱和烃及轻烃色谱、色谱—质谱、天然气组分及碳同位素组分检测等地球化学测试技术对该潜山构造带的原油、天然气与其周缘富烃深次洼烃源岩的地球化学特征进行对比分析,运用油—源生物标志化合物分析技术,系统研究了渤中19-6潜山构造带油气的来源与特征。结果表明:①渤中19-6深层潜山构造带周缘凹陷主要发育古近系东营组二段下亚段、东营组三段、沙河街组一段及沙河街组三段上亚段等4套烃源岩,其中东三段和沙三上亚段烃源岩为其主力烃源灶,有机质丰度较高,为偏腐泥混合型有机质类型,已进入生烃高峰期;②深层太古界潜山及上覆古近系孔店组天然气为典型的油型气,具有不同成熟度天然气混合特征,成藏过程具有多阶段性;③浅层与深层油气来源都具有3套烃源岩混源输入的特征,但仍存在着差异性,其中浅层油气来源以东三段烃源岩的输入为主,并且可能存在着东二下亚段烃源岩的输入,而深层油气来源则以沙三上亚段烃源岩的输入为主。结论认为,该区油气源条件复杂,油气源主要以周缘富烃深次洼内沙三上亚段烃源岩为主,其深层凝析气藏表现出多期次油型气输入的特征。

关键词: 渤海湾盆地; 渤海海域; 渤中凹陷南部; 深层潜山; 有机地球化学; 烃源灶; 生物标志化合物; 油源对比
Geochemical characteristics and sources of oil and gas in deep buried hills,Bohai Sea area
Li Huiyong1, Xu Yunlong2,3, Wang Feilong1, Luo Xiaoping2,3, Yu Haibo1
1. Tianjin Branch Company of CNOOC, Tianjin 300452, China;
2. State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation//Chengdu University of Technology, Chengdu, Sichuan 610059, China;
3. College of Energy, Chengdu University of Technology, Chengdu, Sichuan 610059, China
Abstract

Many hydrocarbon-rich deep subsags are developed in the periphery of the BZ19-6 deep buried-hill structural belt in the Bohai Sea area, Bohai Bay Basin, and their hydrocarbon accumulation conditions are complicated. So far, the organic geochemical characteristics and main sources of their oil and gas have not been figured out. In this paper, the geochemical characteristics of crude oil and natural gas in this belt and those of the source rocks of hydrocarbon-rich deep subsags around the buried-hill structure belt were analyzed by means of geochemical testing technologies, such as saturated hydrocarbon and light hydrocarbon chromatography, chromatography-mass spectrometry, detection of natural gas components and carbon isotope components. Then, the sources and characteristics of oil and gas in the BZ19-6 deep buried-hill structural belt were studied systematically by using the oil-source biomarker analysis technology. And the following research results were obtained. First, in the peripheral sags of this belt are mainly developed four sets of source rocks, i.e., the lower submember of the second Member of Paleogene Dongying Fm (E2 d21), the third Member of Dongying Fm (E2 d3), the first Member of Shahejie Fm (E2 s1) and the upper submember of the third Member of Shahejie Fm (E2 s32). Among them, E2 d3 and E2 s32 are the principal hydrocarbon source kitchens. Their organic abundance is relatively high and their organic matter is of sapropel-prone mixed type. And now they are in the peak stage of hydrocarbon generation. Second, natural gas in the Archean deep buried hill and its overlying Paleogene Kongdian Fm (E1 k) is typical oil-type gas. It presents the mixed characteristics of natural gas with different maturities and multiple stages of hydrocarbon accumulation process. Third, the source of oil and gas in shallow layers is different from that in deep layers, though they both present the mixed source input characteristics of three sets of source rocks. The oil and gas in shallow layers is mainly derived from E2 d3 source rocks and possibly from E2 d21 source rocks, while the oil and gas in deep layers is mainly derived from E2 s32 source rocks. In conclusion, the hydrocarbon source conditions in this area are complex, the hydrocarbon source is mainly contributed by the E2 s32 source rocks in the hydrocarbon-rich deep subsags in the periphery of this belt, and the deep condensate gas reservoirs are characterized by multi-stage oil-type gas input.

Keyword: Bohai Bay Basin; Bohai Sea area; Southern Bozhong Sag; Deep buried hill; Organic geochemistry; Hydrocarbon source kitchen; Biomarker; Oil source correlation
0 引言

潜山油气藏是指位于区域不整合面之下的较老地层中凸起的含油气体, 其烃源主要来自上覆或侧向较新烃源岩, 不整合面或断层面是油气运移的通道[1, 2]。近年来, 渤海湾盆地渤中凹陷周缘凸起带及斜坡带陆续发现大中型潜山油气田, 如PL9-1、渤中28-1油气田等[3, 4, 5]。渤中19-6潜山构造带为近期发现的较大型含油气构造带, 发育太古界深层花岗岩潜山储层和其上覆的古近系古新统孔店组沙砾岩储层, 均为优质储层, 新近系中新统馆陶组储层发育也较好[6]。构造带周缘发育多个富烃深次洼, 且构造带多层次立体含油气, 其油气来源及聚集条件极其复杂, 深、浅层天然气与原油有机地球化学特征及油气主要来源不明确。因此, 需要对其油气来源及聚集机理开展研究。

笔者通过对渤中19-6潜山构造带天然气及原油有机地球化学特征开展分析, 结合其周缘富烃深次洼烃源岩有机地球化学特征, 运用油— 源生物标志化合物分析技术, 在前人沉积— 构造演化特征研究的基础上, 系统研究渤中19-6潜山构造带油气来源特征, 以期为该区下一步油气勘探提供理论支撑。

1 地质概况

渤海湾盆地是典型的裂谷盆地[7], 渤中19-6潜山构造带及周缘发育古近系古新统— 始新>, Wang Feilong1, Luo Xiaoping2,3, Yu Haibo1

1. Tianjin Branch Company of CNOOC, Tianjin 300452, China;
2. State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation//Chengdu University of Technology, Chengdu, Sichuan 610059, China;
3. College of Energy, Chengdu University of Technology, Chengdu, Sichuan 610059, China
Abstract

Many hydrocarbon-rich deep subsags are developed in the periphery of the BZ19-6 deep buried-hill structural belt in the Bohai Sea area, Bohai Bay Basin, and their hydrocarbon accumulation conditions are complicated. So far, the organic geochemical characteristics and main sources of their oil and gas have not been figured out. In this paper, the geochemical characteristics of crude oil and natural gas in this belt and those of the source rocks of hydrocarbon-rich deep subsags around the buried-hill structure belt were analyzed by means of geochemical testing technologies, such as saturated hydrocarbon and light hydrocarbon chromatography, chromatography-mass spectrometry, detection of natural gas components and carbon isotope components. Then, the sources and characteristics of oil and gas in the BZ19-6 deep buried-hill structural belt were studied systematically by using the oil-source biomarker analysis technology. And the following research results were obtained. First, in the peripheral sags of this belt are mainly developed four sets of source rocks, i.e., the lower submember of the second Member of Paleogene Dongying Fm (E2 d21), the third Member of Dongying Fm (E2 d3), the first Member of Shahejie Fm (E2 s1) and the upper submember of the third Member of Shahejie Fm (E2 s32). Among them, E2 d3 and E2 s32 are the principal hydrocarbon source kitchens. Their organic abundance is relatively high and their organic matter is of sapropel-prone mixed type. And now they are in the peak stage of hydrocarbon generation. Second, natural gas in the Archean deep buried hill and its overlying Paleogene Kongdian Fm (E1 k) is typical oil-type gas. It presents the mixed characteristics of natural gas with different maturities and multiple stages of hydrocarbon accumulation process. Third, the source of oil and gas in shallow layers is different from that in deep layers, though they both present the mixed source input characteristics of three sets of source rocks. The oil and gas in shallow layers is mainly derived from E2 d3 source rocks and possibly from E2 d21 source rocks, while the oil and gas in deep layers is mainly derived from E2 s32 source rocks. In conclusion, the hydrocarbon source conditions in this area are complex, the hydrocarbon source is mainly contributed by the E2 s32 source rocks in the hydrocarbon-rich deep subsags in the periphery of this belt, and the deep condensate gas reservoirs are characterized by multi-stage oil-type gas input.

Keyword: Bohai Bay Basin; Bohai Sea area; Southern Bozhong Sag; Deep buried hill; Organic geochemistry; Hydrocarbon source kitchen; Biomarker; Oil source correlation
0 引言

潜山油气藏是指位于区域不整合面之下的较老地层中凸起的含油气体, 其烃源主要来自上覆或侧向较新烃源岩, 不整合面或断层面是油气运移的通道[1, 2]。近年来, 渤海湾盆地渤中凹陷周缘凸起带及斜坡带陆续发现大中型潜山油气田, 如PL9-1、渤中28-1油气田等[3, 4, 5]。渤中19-6潜山构造带为近期发现的较大型含油气构造带, 发育太古界深层花岗岩潜山储层和其上覆的古近系古新统孔店组沙砾岩储层, 均为优质储层, 新近系中新统馆陶组储层发育也较好[6]。构造带周缘发育多个富烃深次洼, 且构造带多层次立体含油气, 其油气来源及聚集条件极其复杂, 深、浅层天然气与原油有机地球化学特征及油气主要来源不明确。因此, 需要对其油气来源及聚集机理开展研究。

笔者通过对渤中19-6潜山构造带天然气及原油有机地球化学特征开展分析, 结合其周缘富烃深次洼烃源岩有机地球化学特征, 运用油— 源生物标志化合物分析技术, 在前人沉积— 构造演化特征研究的基础上, 系统研究渤中19-6潜山构造带油气来源特征, 以期为该区下一步油气勘探提供理论支撑。

1 地质概况

渤海湾盆地是典型的裂谷盆地[7], 渤中19-6潜山构造带及周缘发育古近系古新统— 始新