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<p>Conventional biomarker-based oil–source correlation is often ineffective for high-maturity light oils and condensates due to extremely low concentrations and pervasive contamination. To address this limitation, we developed and validated a methodology that uses macrophysical properties and phase behavior parameters as practical discriminators for hydrocarbon origin tracing. This integrated approach was applied to resolve the complex petroleum system of the Bozi and Dabei segments in the western Kuqa Depression (Tarim Basin), a region characterized by multiple source rocks and multi-stage charging. Specifically, we employed confined (gold-tube) pyrolysis of representative Middle Jurassic source rocks from the Kuqa Depression: lacustrine mudstones (Qiakemake Formation, J<sub>2</sub><i>q</i>) and coaly rocks (Kezilenuer Formation, J<sub>2</sub><i>kz</i>). Experiments were conducted across a wide maturity range (Easy%Ro of 0.49–4.45%), and then the molecular composition of the generated pyrolysis products (C<sub>1</sub>–C<sub>5</sub>, C<sub>6</sub>–C<sub>14</sub>, C<sub>15+</sub>) was quantified. Subsequently, we adopted the Soave–Redlich–Kwong equation of state to conduct pressure–volume–temperature fluid phase behavior modeling of these synthetic fluids, yielding key quantitative parameters under standard surface conditions including gas-to-oil ratio (GOR), density, viscosity, and dryness coefficient. These data were systematically compared with a comprehensive dataset of measured production data from 73 wells penetrating volatile oil, condensate, wet gas, and dry gas reservoirs. The results revealed distinct, maturity-dependent evolutionary trends for fluids generated from the lacustrine versus coaly source rocks, which supported a definitive oil–source correlation: oils were predominantly sourced from the J<sub>2</sub><i>q</i> mudstones, while gases originated from the J<sub>2</sub><i>kz</i> coal measures. The pronounced heterogeneity in reservoir phase state is attributed to multi-source charging and late-stage gas washing, processes controlled by the differential tectonic evolution of the Bozi and Dabei segments. This study resolved the hydrocarbon origins in the Kuqa Depression and provides a critical methodological framework for petroleum systems where traditional biomarker applications are ineffective. Meanwhile, this paper bridges the gap between experimental geochemistry and reservoir fluid dynamics, offering a macroscopic perspective for oil–source correlation in high-maturity, multi-source petroleum systems globally.</p>

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Oil–Source Correlation Using Macrophysical and Phase Parameters of Hydrocarbon Fluids: Application to Condensates and Light Oils, Western Kuqa Depression, Tarim Basin

  • 期刊论文

  • 发表日期：

    2026年7月5日

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  • Zhihua He,
  • Chengsheng Chen,
  • Shuyong Shi,
  • Chao Wu,
  • Tao Mo,
  • Naidong Chen,
  • Yunpeng Wang

摘要

Conventional biomarker-based oil–source correlation is often ineffective for high-maturity light oils and condensates due to extremely low concentrations and pervasive contamination. To address this limitation, we developed and validated a methodology that uses macrophysical properties and phase behavior parameters as practical discriminators for hydrocarbon origin tracing. This integrated approach was applied to resolve the complex petroleum system of the Bozi and Dabei segments in the western Kuqa Depression (Tarim Basin), a region characterized by multiple source rocks and multi-stage charging. Specifically, we employed confined (gold-tube) pyrolysis of representative Middle Jurassic source rocks from the Kuqa Depression: lacustrine mudstones (Qiakemake Formation, J2q) and coaly rocks (Kezilenuer Formation, J2kz). Experiments were conducted across a wide maturity range (Easy%Ro of 0.49–4.45%), and then the molecular composition of the generated pyrolysis products (C1–C5, C6–C14, C15+) was quantified. Subsequently, we adopted the Soave–Redlich–Kwong equation of state to conduct pressure–volume–temperature fluid phase behavior modeling of these synthetic fluids, yielding key quantitative parameters under standard surface conditions including gas-to-oil ratio (GOR), density, viscosity, and dryness coefficient. These data were systematically compared with a comprehensive dataset of measured production data from 73 wells penetrating volatile oil, condensate, wet gas, and dry gas reservoirs. The results revealed distinct, maturity-dependent evolutionary trends for fluids generated from the lacustrine versus coaly source rocks, which supported a definitive oil–source correlation: oils were predominantly sourced from the J2q mudstones, while gases originated from the J2kz coal measures. The pronounced heterogeneity in reservoir phase state is attributed to multi-source charging and late-stage gas washing, processes controlled by the differential tectonic evolution of the Bozi and Dabei segments. This study resolved the hydrocarbon origins in the Kuqa Depression and provides a critical methodological framework for petroleum systems where traditional biomarker applications are ineffective. Meanwhile, this paper bridges the gap between experimental geochemistry and reservoir fluid dynamics, offering a macroscopic perspective for oil–source correlation in high-maturity, multi-source petroleum systems globally.