石油与天然气地质 ›› 2024, Vol. 45 ›› Issue (5): 1400-1416.doi: 10.11743/ogg20240514

• 油气地质 • 上一篇    下一篇

海-陆过渡相与海相页岩气“甜点段”差异特征与形成机理

张琴1,2(), 邱振1,2(), 赵群1,2, 董大忠1,2, 刘雯1,2, 孔维亮1,2, 庞正炼1, 高万里1,2, 蔡光银1,2, 李永洲3, 李星涛3, 林文姬3   

  1. 1.中国石油 勘探开发研究院,北京 100083
    2.国家能源页岩气研发(实验)中心,河北 廊坊 065007
    3.中国石油 煤层气有限责任公司,北京 100028
  • 收稿日期:2024-04-18 修回日期:2024-06-26 出版日期:2024-10-30 发布日期:2024-11-06
  • 通讯作者: 邱振 E-mail:zhangqin2169@petrochina.com.cn;qiuzhen316@163.com
  • 第一作者简介:张琴(1985—)女,博士、高级工程师,非常规油气地质。E‑mail: zhangqin2169@petrochina.com.cn
  • 基金项目:
    中国石油天然气集团公司项目(2023ZZ0801)

Different characteristics and formation mechanisms of transitional and marine shale gas sweet spots

Qin ZHANG1,2(), Zhen QIU1,2(), Qun ZHAO1,2, Dazhong DONG1,2, Wen LIU1,2, Weiliang KONG1,2, Zhenglian PANG1, Wanli GAO1,2, Guangyin CAI1,2, Yongzhou LI3, Xingtao LI3, Wenji LIN3   

  1. 1.Research Institute of Petroleum Exploration & Development,PetroChina,Beijing 100083,China
    2.National Energy Shale Gas R&D (Experiment) Center,Langfang,Hebei 065007,China
    3.Coalbed Methane Company Limited,PetroChina,Beijing 100028,China
  • Received:2024-04-18 Revised:2024-06-26 Online:2024-10-30 Published:2024-11-06
  • Contact: Zhen QIU E-mail:zhangqin2169@petrochina.com.cn;qiuzhen316@163.com

摘要:

为了指导海-陆过渡相页岩气的勘探开发,以鄂尔多斯盆地东缘大宁—吉县地区二叠系山西组2段3亚段(山23亚段)海-陆过渡相页岩气甜点段与四川盆地南部地区志留系龙马溪组一段1亚段(龙一1亚段)1小层海相页岩气甜点段作为研究对象,开展系统的岩心观察、薄片鉴定、全岩-黏土X射线衍射、有机地球化学分析、扫描电镜观察、N2低温吸附、CH4等温吸附以及主、微量元素分析实验,系统对比研究了海-陆过渡相与海相页岩气甜点段的特征与形成机理。研究结果表明:① 海相页岩气甜点段稳定分布与发育;海-陆过渡相页岩气甜点段横向不连续,纵向多层段发育。② 海-陆过渡相页岩气甜点段总有机碳含量(TOC)高,处于中-高成熟阶段,有机质以Ⅱ2-Ⅲ型为主;海相页岩气甜点段TOC较高,处于高-过成熟阶段,有机质以Ⅰ-Ⅱ1型为主。③ 海-陆过渡相页岩气甜点段矿物组成以黏土矿物为主,黏土矿物孔隙以介孔和宏孔为主,它们控制游离气的赋存;有机质以发育微孔为主,它是比表面积的主要贡献者,控制吸附气的赋存。海相页岩气甜点段以石英矿物为主;页岩有机质同时发育微孔和介孔,它们是页岩气赋存的主要储存空间。④ 海-陆过渡相页岩气甜点段以吸附气为主,平均占66.06 %;海相页岩气以游离气为主,吸附气占11.15 % ~ 43.75 %。⑤ 海-陆过渡相和海相页岩气甜点段有机质富集均受到古气候、古环境以及地质事件控制,但陆源碎屑输入对海-陆过渡相页岩气甜点段有机质富集具有重要控制作用。⑥ 鄂尔多斯盆地海-陆过渡相页岩气单井最高产量达到7.9×104 m3/d,研究和勘探表明海-陆过渡相页岩气具有良好的勘探前景。

关键词: 差异性, 海-陆过渡相, 海相, 甜点段, 页岩气, 四川盆地, 鄂尔多斯盆地

Abstract:

To provide guidance on the exploration and production of transitional shale gas, we investigate the sweet spots of transitional shale gas in the 3rd submember of the 2nd member of the Shanxi Formation (the Shan 23 submember) in the Daning-Jixian block along the eastern margin of the Ordos Basin and those of marine shale gas in the 1st sublayer of the 1st submember of the 1st member of the Longmaxi Formation (the Long 11 submember) in the southern Sichuan Basin. A combination of core and thin section observations, whole-rock and clay mineralogy by X-ray diffraction (XRD), organic geochemical analysis, scanning electron microscopy (SEM), N2 adsorption, CH4 isothermal adsorption, and major and trace element analyses, is applied to conduct a systematic comparative study on the characteristics and formation mechanisms of these sweet spots. The results indicate that the sweet spots of marine shale gas exhibit stable distributions and consistent development, while those of transitional shale gas show lateral discontinuities and occur across multiple layers vertically. The sweet spots of transitional shale gas feature high total organic carbon (TOC) content, medium to high maturity, and gas-prone organic matter of kerogen type Ⅱ2-Ⅲ. In contrast, the sweet spots of marine shale gas are characterized by relatively high TOC content, high to over maturity, and oil-prone organic matter f kerogen type Ⅰ-Ⅱ1. In the sweet spots of transitional shale gas, clay minerals are prevalent, where mesopores and macropores take a larger portion governing the occurrence of free gas. Organic matter in these sweet spots principally exhibits micropores, which contribute significantly to the specific surface area and determine the occurrence of adsorbed gas. In contrast, the sweet spots of marine shale gas display a dominance of quartz minerals. Their organic matter contains both micropores and mesopores, which serve as primary storage spaces for shale gas. The sweet spots of transitional shale gas predominantly exhibit adsorbed gas (average proportion: 66.06 %), while those of marine shale gas show predominant free gas, with adsorbed gas accounting for merely 11.15 % ~ 43.75 %. The organic matter enrichment in both types of sweet spots is governed by paleoclimate, paleoenvironment, and geologic events. Moreover, terrigenous debris input also plays a significant role in the formation of transitional shale gas sweet spots. The maximum single-well production of transitional shale gas in the Ordos Basin has been determined at up to 79,000 m3/d, demonstrating promising prospects for exploring transitional shale gas in the basin.

Key words: differentiation, transitional facies, marine facies, sweet spot, shale gas, Sichuan Basin, Ordos Basin

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