昭通太阳背斜山地浅层页岩气“三维封存体系”富集成藏模式
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本文为国家科技重大专项(编号 2017ZX05063)和中国石油集团公司专项(编号2019F- 31)联合资助的成果。


“Three- dimensional closed system” accumulation model of Taiyang anticline mountain shallow shale gas in the Zhaotong demonstration area
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    摘要:

    本文系统分析了太阳地区构造断裂系统、顶底板条件、沉积岩相、优质页岩展布、源储条件及富集高产规律,提出了“多场协同多元耦合”共同作用下太阳背斜区山地浅层页岩气“三维封存体系”富集成藏赋存模式,具有5个特征:① 页岩储层上覆龙马溪组一段二亚段—石牛栏组厚层致密页岩和泥灰岩,下伏临湘组—宝塔组厚层致密瘤状灰岩,具有良好的封隔层条件,形成了封存体系的顶板和底板;② 压扭应力背景下形成的断裂系统属于挤压性逆冲断层、压扭性走滑断层,断层的纵向封闭性好,有效地保护了优质页岩气藏;③ 断层两盘页岩气层对接岩性均为致密泥灰岩和灰岩,侧向封堵性防止了页岩气泄漏点出现,使得山地浅层页岩气仍具有连续型气藏特征;④ 前陆盆地“水体滞留+火山灰沉降”造就了“海洋漂浮生物繁盛+缺氧强还原”深水陆棚沉积环境,形成了“富碳、高硅、低黏、高脆”的优质烃源岩储集体,构建了“规模生烃、高效吸附富集”的页岩微纳米级储集孔隙空间;⑤ 页岩储层具有相对小的地应力和两向水平应力差,既利于在中低泵压下的储层压裂施工作业,又具备体积压裂打碎页岩形成复杂缝网和气井获得高产的关键要素。提出了复杂构造区山地浅层页岩气“多元富集高产”的规律性认识,即:前陆盆地深水缺氧强还原环境促使了“富碳、高硅、低黏”页岩储层发育(沉积成岩控制源储特征)、持续良好的三维封闭保存体系有效保护了富有机质页岩生烃留烃富烃和超压保孔(保存条件控制天然气藏)、页岩脆性与地应力以及水平应力差决定了体积压裂改造的难易程度并影响了人造页岩气藏的构建效果(应力可压性控制人造气藏)、Ⅰ类优质页岩气储层连续厚度和地层压力系数决定了页岩气禀赋的资源储量丰度与气井高产(烃储禀赋控制单井产量)。研究成果对中国南方复杂构造区海相浅层页岩气的高效勘探开发具有重要的借鉴引领和指导意义。

    Abstract:

    This study aims to realize the large- scale and efficient development of the Taiyang shallow shale gas and provide a reference for the shallow shale gas exploration in other areas. To achieve this objective, the tectonic fault system, roof and floor conditions, sedimentary facies, high quality shale distribution, hydrocarbon storage conditions and the law of enrichment and high yield in the Taiyang region are systematically analyzed. Five characteristics of the proposed “three- dimensional closed system” compartment accumulation model of mountain shallow shale gas in the Taiyang anticline are: ① The overlying thick layer of dense shale and marlstone of the second sub- segment of the first member of the Longmaxi Formation to the Shiniulan Formation, and the underlying thick layer dense nodular limestone of Linxiang and Baota Formations, form a good barrier conditions of roof and floor of the compartment. ② The fault system, formed against a background of compressive and torsional stress, belongs to compressional thrust fault and compression- torsional strike- slip fault with good longitudinal sealing, which effectively protects high quality shale gas reservoir. ③ The lithology of the connection between the two sides of shale gas layers on the fault is dense marl and limestone. There is no leakage point for shale gas because of the good lateral sealing of the fault, so the mountain shallow shale gas still has the characteristics of continuous gas reservoir. ④ The “water retention+volcanic ash deposition” in foreland basin created the deep- water shelf sedimentary environment of “flourishing marine floating organisms+anoxic strong reduction”, formed the high- quality hydrocarbon source rock reservoir with “rich carbon, high silicon, low viscosity and high fragility”, and constructed the shale micro- nanometer reservoir pore space with “large- scale hydrocarbon generation and efficient adsorption and enrichment”. ⑤ The shale reservoir has relatively low in- situ stress and two- direction horizontal stress difference, which is not only conducive to the fracturing operation of the reservoir under medium and low pump pressure, but also has the key factors for fracturing the shale to form complex fracture network and gas well to obtain high yield. Based on these results, the law of “Four enrichment and high yield” of the shallow mountain shale gas in the complex structure area is achieved: the deep water anoxic and strong reduction environment in foreland basin promotes the development of carbon- rich, high- silicon and low- viscosity shale reservoirs (sediment controls reservoir); the continuous good three- dimensional closed storage box system effectively protects the hydrocarbon generation, hydrocarbon retention, hydrocarbon enrichment and overpressure pore protection of organic rich shale (preservation controls gas); shale brittleness, in- situ stress and horizontal stress difference determine the difficulty of SRV fracturing and affect the construction effect of artificial shale gas reservoir (stress controls occurrence); the continuous thickness and formation pressure coefficient of class I high- quality shale gas reservoirs determine the resource and reserve abundance of shale gas and the high production of gas wells (hydrocarbon reservoir control production). The research results are of great significance for the efficient exploration and development of shallow marine shale gas in the complex tectonic area in South China.

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梁兴,单长安,张朝,徐政语,徐进宾,王维旭,张介辉,徐云俊.2021.昭通太阳背斜山地浅层页岩气“三维封存体系”富集成藏模式[J].地质学报,95(11):3380-3399.
Liang Xing, Shan Changan, Zhang Zhao, Xu Zhengyu, Xu Jinbin, Wang Weixu, Zhang Jiehui, Xu Yunjun.2021.“Three- dimensional closed system” accumulation model of Taiyang anticline mountain shallow shale gas in the Zhaotong demonstration area[J]. Acta Geologica Sinica,95(11):3380-3399.

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  • 收稿日期:2020-05-04
  • 最后修改日期:2020-09-08
  • 录用日期:2020-09-21
  • 在线发布日期: 2021-11-24
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