Liu Haiwen, Xu Yaohui, He Taohua, Cai Yiling, Hao Wanxin, Zhao Ya, Zhang Ke, Wen Zhigang, He Jiayi, Zeng Qianghao
Hubei Key Laboratory of Petroleum Geochemistry and Environment, Yangtze University, Wuhan 430100, China.
College of Resources and Environment, Yangtze University, Wuhan 430100, China.
ACS Omega. 2025 Mar 12;10(11):11607-11617. doi: 10.1021/acsomega.5c00806. eCollection 2025 Mar 25.
Obtaining core samples from ultradeep hydrocarbon source rocks poses significant challenges, and the more readily available hydrocarbon source rock cuttings are often contaminated to varying degrees by oil-based drilling fluids (OBDF). This makes it difficult to obtain the real geochemical characteristics of ultradeep hydrocarbon source rocks, which is one of the key problems faced by ultradeep oil and gas exploration at present. To address the issue of OBDF contamination in rock cuttings, this study examines rock cuttings from well T in the Kuqa Depression (∼6980 m) and cores from other wells within the same stratigraphic position as examples. By comparing molecular geochemical parameters from both cores and rock cuttings, this study evaluates the decontamination effects of three different treatment methods: twice-extraction method (TEM), extraction method of hydrocarbons from kerogen adsorption (EMHK), and microablation. Results reveal significant differences in biomarker compounds extracted from source rock cuttings processed by TEM. Biomarkers from the first extraction are largely consistent with those of oil-based drilling fluids, which indicates that the rock cuttings have suffered from different degrees of contamination. Big particle rock cuttings exhibit relatively lower contamination levels, and their biomarker compounds from the second extraction are similar to those from the core. On the other hand, biomarker compounds extracted by EMHK differ notably from those in oil-based drilling fluids and exhibit partial similarity with uncontaminated core samples, but certain parameters remain inconsistent, likely due to incomplete pretreatment (e.g., insufficient solvent washing before kerogen making). In contrast, biomarker parameters and GC-MS spectra of surface-stripping powders obtained via microablation initially show contamination similar to OBDF. However, biomarker parameters and GC-MS spectra from the inner portions of big particles processed via microablation closely align with those of uncontaminated cores, reflecting the authentic geochemical characteristics of source rocks. Comparatively, TEM demonstrates incomplete decontamination, and the effectiveness of EMHK is heavily influenced by the thoroughness of pretreatment. Microablation effectively reveals the true biogenic signature of ultradeep hydrocarbon source rocks. Thus, the broader adoption and application of microablation techniques hold great promise for advancing global ultradeep hydrocarbon exploration.
从超深层烃源岩获取岩芯样本面临重大挑战，而更容易获取的烃源岩岩屑往往受到油基钻井液（OBDF）不同程度的污染。这使得难以获取超深层烃源岩的真实地球化学特征，这是目前超深层油气勘探面临的关键问题之一。为解决岩屑中油基钻井液污染问题，本研究以库车坳陷井T（约6980米）的岩屑以及同一地层位置其他井的岩芯为例进行研究。通过比较岩芯和岩屑的分子地球化学参数，本研究评估了三种不同处理方法的去污效果：二次萃取法（TEM）、从干酪根吸附中提取烃类的方法（EMHK）和微蚀。结果显示，经二次萃取法处理的源岩岩屑中提取的生物标志物化合物存在显著差异。第一次萃取的生物标志物与油基钻井液的生物标志物基本一致，这表明岩屑受到了不同程度的污染。大颗粒岩屑的污染程度相对较低，其第二次萃取的生物标志物化合物与岩芯的相似。另一方面，通过从干酪根吸附中提取烃类的方法提取的生物标志物化合物与油基钻井液中的显著不同，并且与未受污染的岩芯样本部分相似，但某些参数仍然不一致，可能是由于预处理不完全（例如，在制备干酪根之前溶剂洗涤不足）。相比之下，通过微蚀获得的表面剥离粉末的生物标志物参数和气相色谱 - 质谱光谱最初显示出与油基钻井液相似的污染。然而，通过微蚀处理的大颗粒内部的生物标志物参数和气相色谱 - 质谱光谱与未受污染的岩芯密切吻合，反映了源岩的真实地球化学特征。相比之下，二次萃取法显示去污不完全，从干酪根吸附中提取烃类的方法的有效性受预处理彻底程度的严重影响。微蚀有效地揭示了超深层烃源岩的真实生物成因特征。因此，更广泛地采用和应用微蚀技术有望推动全球超深层油气勘探。
