Dual Effect of Hydrothermal Fluid on Shale Oil Reservoir in Gulong Sag, Songliao Basin: Constrained by C-O Isotope and Geochemistry

Junhui Li, Xiuli Fu, Yue Bai, Haixin Zhang, Zongbao Liu () and Rongsheng Zhao ()
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Junhui Li: Exploration and Development Research Institute of Daqing Oilfield Company Ltd., Daqing 163712, China
Xiuli Fu: Exploration and Development Research Institute of Daqing Oilfield Company Ltd., Daqing 163712, China
Yue Bai: Exploration and Development Research Institute of Daqing Oilfield Company Ltd., Daqing 163712, China
Haixin Zhang: National Key Laboratory of Green Exploitation of Continental Shale Oil with Multi-Resource Collaboration, Daqing 163002, China
Zongbao Liu: National Key Laboratory of Green Exploitation of Continental Shale Oil with Multi-Resource Collaboration, Daqing 163002, China
Rongsheng Zhao: College of Earth Sciences, Jilin University, Changchun 130061, China

Energies, 2024, vol. 17, issue 16, 1-17

Abstract: Hydrothermal activity is widespread in sedimentary basins, but its dual effects (chemistry and temperature) on shale reservoirs are rarely discussed. In this research, we systematically collected 33 well core samples from Q 1 to Q 9 units in Gulong Sag, Songliao Basin, and analyzed them using a variety of analytical techniques, including a field emission scanning electron microscopy (FE-SEM), an energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), and stable C-O isotopes. Combined with the collected vitrinite reflectance (Ro), total organic carbon (TOC), and soluble hydrocarbon content data, which is the sum of free oil (pyrolysis S 1 ) and sorb oil content (pyrolysis S 2 ), the results show that (1) Q 4 and Q 8 units have large amounts of hydrothermal minerals, and its C-O isotope obviously shifts to negative, which implied those units are the main hydrothermal fluid influence area; (2) the hydrothermal activity occurred in the late depositional period of Q 1 –Q 9 units such that its geochemistry has little effect on the proliferation of algae blooms, but its high temperature calculated by δ 18 O temperature formulas (around 208 °C) promoted the organic matter maturation process around Q 4 and Q 8 ; and (3) the overpressure caused by hydrothermal activity protected the shale reservoir and minimized the decrease in mineral reservoir brittleness index caused by hydrothermal fluid influence. We suggest that the shale reservoir affected by hydrothermal fluid will become a good geology “dessert”, and its upper and/or lower bounds can form an engineering “dessert” due to the precipitation of large amounts of brittle carbonate minerals.

Keywords: hydrothermal fluid; C-O isotope; geochemistry; organic matter; brittleness; shale reservoir (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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