Quantitative characterization and influencing factors of free oil content in lacustrine shale: A case study of Funing Formation in the Gaoyou Sag, Subei Basin

Tian LIU; Xiaoping LIU; Qidong LIU; Hongliang DUAN; Shili LI; Biao SUN; Zuxian HUA

doi:10.11743/ogg20230409

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Publishing Language: Chinese

Quantitative characterization and influencing factors of free oil content in lacustrine shale: A case study of Funing Formation in the Gaoyou Sag, Subei Basin

Tian LIU^{¹^,²}, Xiaoping LIU^{¹^,²}(), Qidong LIU^³, Hongliang DUAN^³, Shili LI^³, Biao SUN^{¹^,²}, Zuxian HUA^{¹^,²}

National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China

College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China

Research Institute of Exploration and Development, SINOPEC Jiangsu Oilfield Company, Yangzhou, Jiangsu 225009, China

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Abstract

The lacustrine shale samples were selected from the second member of the Funing Formation in Gaoyou Sag, Subei Basin, to precisely and quantitatively evaluate the free oil content and its controlling factors of lacustrine shale. The mineral composition, hydrocarbon generation capacity, pore structure, oil-bearing properties, and other characteristics of the samples were analyzed using X-ray diffraction tests, TOC content measurement, multistep rockeval pyrolysis, high pressure mercury injection, organic matter extraction and 2D NMR. The results show that the shale is rich in quartz, feldspar, calcite, dolomite, clay, and other minerals. The TOC is between 0.61% and 3.70%. The R_o is between 0.70% and 0.72%, indicating the source rocks being in the mature stage. The reservoir space is mainly composed of intergranular and organic pores. Two-dimensional NMR, which can efficiently detect and characterize the occurrence of free oil, was employed to help extracting free light and heavy hydrocarbons as well as soluble organic matter from the samples, and performing spectra analysis before and after the extraction, on which light oil zone, solid organic matter zone, hydroxyl compound zone, and water zone were identified. Post-extraction solid organic matter content was found to have a good correlation with TOC. Pre-extraction NMR-based light hydrocarbon content and NMR-based differential light hydrocarbon content between pre-extraction and post-extraction show a relatively strong linear connection with pyrolysis free oil content. The free oil content rises initially and then fall as the felsic mineral content rises, and it is positively correlated with TOC as a whole. The free oil contents in type Ⅰ and Ⅱ₁ kerogen source rocks are higher than those of other kinds. The right degree of thermal evolution of source rocks increases the ratio of light hydrocarbons and mobility of kerogen-generated hydrocarbons, as well as free oil content. Shale reservoirs with high porosity, specific pore volume, and median value of pore throat radius are conducive to free oil enrichment.

Keywords

free oil content nuclear magnetic resonance Funing Formation lacustrine shale Gaoyou Sag Subei Basin

CLC number: TE122.1 Document code: A Article ID: 0253-9985(2023)04-0910-13

References

[1]

HOU Lianhua, ZOU Caineng, YU Zhichao, et al. Quantitative assessment of the sweet spot in marine shale oil and gas based on geology, engineering, and economics: A case study from the Eagle Ford Shale, USA[J]. Energy Strategy Reviews, 2021, 38: 100713.