不同泥岩相有机质赋存特征及对比表面积的影响——以渤海湾盆地沾化凹陷古近系为例

Occurrence of organic matter in different mudstone lithofacies and its influence on specific surface area:A case study of the Paleogene in the Zhanhua Sag, Bohai Bay Basin

刘伟新 朱晓军 马安林 蔡进功 卢龙飞

Liu Weixin Zhu Xiaojun Ma Anlin Cai Jingong Lu Longfei

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. 同济大学海洋地质国家重点实验室, 上海 200092 3. 南京大学地球科学与工程学院, 南京 210093

Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China 2. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China 3. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China

对沾化凹陷古近系L井沙三下亚段不同埋藏深度的泥页岩岩心和薄片进行分析,及X-射线衍射、热解、比表面积检测,结果显示,L井沙三下亚段泥页岩可分为贫有机质纹层的岩相A和富有机质纹层的岩相B,前者有机碳含量(TOC)低,比表面积较大,后者有机碳含量高,比表面积较小。从比表面积与TOC相关性来看,岩相A呈正相关收敛状,而在岩相B则呈发散状,表明岩相A中的有机质主要吸附于矿物表面,而岩相B的有机质主要呈纹层状富集。有机质赋存状态的差异对泥页岩比表面积的影响较为明显,富有机质纹层岩相B的岩石比表面积低于贫有机质纹层岩相A,而不同岩相中矿物对比表面积的贡献度相近,表明不同岩相(A和B)比表面积的差异与有机质纹层的多寡有关。

Some core and cast thin section samples of shales were collected from different depths of the lower section of the third member of the Paleogene Shahejie Formation in well L in the Zhanhua Sag. X-ray diffraction (XRD), pyrolysis and specific surface area (SSA) measurements were applied to examinethe characteristics of organic matter (OM) occurrence and analyze the effect of OM on the SSA of different mudstone lithofacies. Results showed that the shales can be categorized into lithofacies A (lack of organic laminae) and lithofacies B (rich in organic laminae). The former has a low TOC content with high SSA, and the latter has a high TOC content with low SSA. The relationship between TOC and mineral SSA is convergent in the lithofacies A and divergent in the lithofacies B, which indicates that OM in the lithofacies A is mainly adsorbed on mineral surfaces while OM in lithofacies B is chiefly accumulated as organic laminae. The variation of OM occurrence clearly affected shale SSA. The SSA of lithofacies A is lower than that of lithofacies B, and the contribution of minerals to SSA is similar in both lithofacies, which indicates that the variation of SSA in different lithofacies (A and B) is correlated with the abundance of organic laminae.

国家自然科学基金(41372130)和国家油气重大专项(2016ZX05006-001)资助。

https://doi.org/10.11781/sysydz201602204