川东北地区二叠系大隆组深层页岩气储层孔隙结构及其分形特征

Pore structure and fractal characteristics of deep shale gas reservoirs in the Permian Dalong Formation, northeastern Sichuan Basin

何陈诚 赵永强 俞凌杰 卢龙飞 刘伟新 潘安阳 李楚雄

HE Chencheng ZHAO Yongqiang YU Lingjie LU Longfei LIU Weixin PAN Anyang LI Chuxiong

1. 中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214126; 2. 中国石化 油气成藏重点实验室, 江苏 无锡 214126; 3. 页岩油气富集机理与高效开发全国重点实验室, 江苏 无锡 214126; 4. 国家能源页岩油研发中心, 江苏 无锡 214126

1. Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China; 2. SINOPEC Key Laboratory of Petroleum Accumulation Mechanisms, Wuxi, Jiangsu 214126, China; 3. State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Efficient Development, Wuxi, Jiangsu 214126, China; 4. State Energy Center for Shale Oil Research and Development, Wuxi, Jiangsu 214126, China

页岩储层特性是影响页岩气富集和开采的关键因素之一。四川盆地北部发育的上二叠统大隆组是重要的海相优质烃源岩，而针对川东北地区大隆组页岩储层的研究还有待深入。以川东北地区大隆组深层页岩为研究对象，利用高分辨率场发射扫描电镜、二氧化碳吸附、氮吸附及高压压汞等技术，开展大隆组深层页岩储层不同孔径孔隙结构的定性—定量研究，并运用基于二氧化碳吸附的V-S模型、氮吸附的FHH模型和高压压汞的分形几何模型对不同孔径的孔隙进行分形拟合，表征页岩孔隙结构的复杂程度和非均质性特征。结果表明，川东北地区大隆组深层页岩储层发育丰富的纳米级有机孔和少量的无机孔，有机孔发育特征随有机质显微组分不同和分布形式差异而显示强的非均质性。大隆组深层页岩孔隙结构与龙马溪组深层页岩相似，以介孔和微孔为主，占总孔体积的90%以上；页岩孔隙结构主要受有机质丰度的影响。分形特征研究结果显示，深层页岩宏孔非均质性强于介孔和微孔。其原因可能为深层页岩微孔孔径较小，分布集中，成因单一，受成岩作用影响较小，孔隙结构较为简单，具有较小分形维数；而宏孔孔径较大，分布范围较广，成因多样，易受成岩作用影响，表现出强非均质性。深层页岩微孔—介孔因其丰富的储集空间和较强的自相似性，有利于页岩气的赋存、渗流和开采。

The characteristics of shale reservoirs play a crucial role in the enrichment and exploitation of shale gas. The Upper Permian Dalong Formation in the northern Sichuan Basin is a significant marine-derived high-quality hydrocarbon source rock that requires further detailed investigation. This study conducted qualitative and quantitative analyses on the pore structure of deep shale reservoirs within the Permian Dalong Formation in northeastern Sichuan. Various methods such as high-resolution field emission scanning electron microscopy, CO2 adsorption, N2 adsorption, and high-pressure Hg injection measurements were employed. Fractal fitting using the V-S model based on CO2 adsorption, the FHH model based on N2 adsorption, and the fractal geometry model based on high-pressure Hg injection was utilized to characterize the pore structure of deep shale. The findings revealed that deep shale reservoirs in the Dalong Formation in northeastern Sichuan Basin contain abundant nano-scale organic pores and limited inorganic pores. The development of organic pores exhibits strong heterogeneity influenced by maceral differences and organic matter distribution. Similar to Longmaxi Formation shale, the pores in the Dalong Formation are predominantly micropores and mesopores, comprising over 90% of the total pore volume and primarily influenced by organic matter abundance. The research on fractal dimension characteristics suggests that macropores in deep shale exhibit stronger heterogeneity compared to mesopores and micropores. Due to their smaller size and minimal diagenetic impact, micropores and mesopores have simpler structures with lower fractal dimensions. On the other hand, macropores display significant heterogeneity due to their larger size, wide distribution range, diverse genesis, and susceptibility to diagenesis. Due to their abundant reservoir space and strong self-similarity, micropores and mesopores in deep shale are conducive to the occurrence, seepage and exploitation of shale gas.

国家自然科学基金(U19B6003-03、41972164)和中国石化科技部项目(P23132)联合资助。

https://doi.org/10.11781/sysydz202402263