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泸州中区深层—超深层龙马溪组页岩微纳米孔隙结构及气体赋存机制

Micro‑nano Pore Structure and Gas Occurrence Mechanism of Deep to Ultra‑deep Longmaxi Formation Shale in the Central Luzhou Area

龚鑫¹, 黎菁¹, 何嘉¹, 罗谋兵¹, 曾云凤², 邱峋晰³, 高智¹, 杨成¹, 唐田¹

Environment and Resource / 2026,8(8): 363-369 / 2026-08-19 16 14

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• Information:

  1. 中国石油川庆钻探工程有限公司地质勘探开发研究院，成都；
  2. 中国石油集团东方地球物理勘探有限责任公司西南物探研究院，成都；
  3. 四川页岩气勘探开发有限责任公司，成都

• Keywords:
  Deep shale; Longmaxi Formation; Micro‑nano pores; Full‑range pore characterization; Pore connectivity; Gas occurrence
  深层页岩; 龙马溪组; 微纳米孔隙; 全孔径表征; 孔隙连通性; 气体赋存
• Abstract: Strong compaction and high to over-mature thermal evolution have substantially modified the pore system of the deep to ultra-deep Longmaxi shale in the central Luzhou area. Eight core samples from seven wells in the Long- 1¹ submember, buried at 4059–4620 m, were investigated by argon-ion-polished field-emission scanning electron microscopy, CO₂ adsorption, N₂ adsorption-desorption, high-pressure mercury intrusion, low-field nuclear magnetic resonance, and spontaneous imbibition-centrifugation tests. The observed pore types comprise kerogen pores, pyrobitumen pores, intragranular clay-mineral pores, intergranular siliceous-mineral pores, and dissolution pores in siliceous and carbonate minerals. Cellular and spongy pores are widely developed within pyrobitumen and constitute the principal organic-matter pore space. Calculations integrating component abundance and areal porosity indicate pore contributions of approximately 49.98% from organic matter, 24.66% from clay minerals, 19.43% from siliceous minerals, and 5.93% from carbonate minerals. Total pore volume ranges from 14.48 to 32.53 μL/g (average 19.83 μL/g), whereas total specific surface area ranges from 22.27 to 46.42 m²/g (average 34.15 m²/g). Mesopores account for most of the pore volume, while micropores dominate the specific surface area. NMR-derived saturated porosity is 3.62%–8.38%, centrifuged porosity is 3.18%~7.30%, and the minimum cut-off pore diameter is 6.08–18.88 nm, showing that movablefluid responses mainly occur in mesopores and part of the macropore system. Among the three structural settings, slope samples display relatively high organic-pore contributions and connected pore volumes, together with generally higher predicted total gas contents. These observations suggest that storage performance is controlled by the joint arrangement of micropore adsorption interfaces, effective mesopore volume, and macropore-microfracture transport capacity. Under deep high-temperature and high-pressure conditions, the relative role of adsorbed gas decreases, whereas high-density free gas becomes increasingly important to total gas content and recoverability. 泸州中区龙马溪组深层—超深层页岩经历了强压实和高—过成熟演化，其孔隙是否保存、不同尺度孔隙能否相互连通，直接关系到页岩气的赋存与产出。选取龙一1亚段7口井的8件岩心样品，埋深为4059～4620m，采用氩离子抛光场发射扫描电镜、CO2吸附、N2吸附—脱附、高压压汞、低场核磁共振以及自发渗吸—离心联测，对孔隙形态、全孔径结构和流体可进入性进行对比分析。观察到的孔隙主要包括干酪根孔、焦沥青孔、黏土矿物粒内孔、硅质矿物粒间孔，以及硅质矿物和碳酸盐矿物溶蚀孔。焦沥青内部普遍出现蜂窝状或海绵状孔隙，是有机质孔的主要组成部分。按组分含量与面孔率综合估算，有机质、黏土矿物、硅质矿物和碳酸盐矿物的孔隙贡献依次约为49.98%、24.66%、19.43%和5.93%。样品总孔体积介于14.48～32.53μL/g，平均为19.83μL/g；总比表面积为22.27～46.42m2/g，平均为34.15m2/g。中孔提供了较多孔体积，而微孔控制了大部分比表面积。核磁测试获得的饱和孔隙度为3.62%～8.38%，离心孔隙度为3.18%～7.30%，最低截止孔径为6.08～18.88nm，表明可动流体响应主要涉及中孔和部分宏孔。三类构造位置中，斜坡样品的有机质孔贡献及连通孔体积相对较高，对应的预测总含气量也整体较高。由此认为，深层—超深层页岩储集性能取决于微孔吸附界面、中孔有效体积以及宏孔—微裂缝输导能力的共同配置；在高温高压条件下，吸附气所占比例趋于下降，高密度游离气对总含气量和可采性的影响更为突出。
• DOI: 10.35534/er.0803052 (registering DOI)
• Cite: 龚鑫，黎菁，何嘉，等．泸州中区深层—超深层龙马溪组页岩微纳米孔隙结构及气体赋存机制［J］．环境与资源，2026，8（3）：363-369.