Zhang Zhaoqian, Song Yanjie, Yin Shujun, Liu Bo, Zhao Haibo, Yan Weilin, Zheng Jiandong
School of Earth Sciences, Northeast Petroleum University, Daqing, 163318, China.
Exploration and Development Research Institute, PetroChina Daqing Oilfield Co. Ltd., Daqing, 163712, China.
Sci Rep. 2025 Jul 1;15(1):20440. doi: 10.1038/s41598-025-04771-1.
The Gulong shale in the Songliao Basin, characterized by its high clay content, poses significant challenges for the identification of sweet spots. To address this, a novel temperature-dependent retorting and 2D NMR joint experimental approach was developed to investigate the fluid characteristics of the Gulong shale under varying occurrence states. The experimental results demonstrated that the pore fluids in Gulong shale are composed of multiple components, including free water, capillary bound water, clay bound water, bound oil in small inorganic pores, adsorbed oil in organic pores, free oil in large inorganic pores, and bitumen. In addition to these fluid components, the solid components consist of clay mineral assemblages (hydroxyl groups) and kerogen, collectively making up a total of eight distinct components. Furthermore, a comprehensive T-T interpretation framework was established based on the retorting and NMR joint experiments, providing a robust tool for guiding fluid type classification using 2D NMR logging data. Analysis of advanced NMR T-T logs indicated the absence of free water in the Gulong shale. A strong correlation was observed between the normalized annual production of the horizontal section per kilometer and the free oil porosity, with the ten horizontal wells targeting high free oil content layers demonstrating the highest productivity. Additional investigations using elemental spectroscopy logging and field emission-scanning electron microscopy (FE-SEM) revealed that layers with high free oil content are associated with larger particle sizes, leading to the development of enlarged inorganic macropores. These findings provide critical insights into the key geological controls governing sweet spots in the Gulong shale, offering valuable guidance for reservoir evaluation and development.
松辽盆地古龙页岩以其高黏土含量为特征，这给甜点识别带来了重大挑战。为解决这一问题，开发了一种新型的随温度变化的干馏与二维核磁共振联合实验方法，以研究古龙页岩在不同赋存状态下的流体特征。实验结果表明，古龙页岩中的孔隙流体由多种成分组成，包括自由水、毛细管束缚水、黏土束缚水、小无机孔隙中的束缚油、有机孔隙中的吸附油、大无机孔隙中的自由油和沥青。除了这些流体成分外，固体成分由黏土矿物组合（羟基）和干酪根组成，总共构成了八个不同的成分。此外，基于干馏和核磁共振联合实验建立了一个全面的T-T解释框架，为利用二维核磁共振测井数据指导流体类型分类提供了一个强大的工具。对先进的核磁共振T-T测井的分析表明，古龙页岩中不存在自由水。每公里水平段的归一化年产量与自由油孔隙度之间存在很强的相关性，以高自由油含量层为目标的十口水平井显示出最高的产能。使用元素光谱测井和场发射扫描电子显微镜（FE-SEM）的进一步研究表明，高自由油含量的层与较大的颗粒尺寸有关，导致扩大的无机大孔隙的发育。这些发现为古龙页岩甜点的关键地质控制因素提供了重要见解，为储层评价和开发提供了有价值的指导。
