Gravitational differentiation characteristics of condensate gas reservoir with fault-controlled fracture-cavity structure in second block of Shunbei Oil and Gas Field: A case study of No. 4 fault zone
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    Abstract:

    The condensate gas reservoirs with fault-controlled fracture-cavity structures in Shunbei area represent a significant breakthrough in oil and gas exploration within Tarim Basin in recent years. Its efficient development holds great importance for formulating the oil and gas resource strategy in western China. The second block of Shunbei Oil and Gas Field provides the primary production of oil and gas in this area, characterized by thick and plate-like reservoir spaces. Both field production and laboratory experiments confirmed that gravitational differentiation significantly influences the vertical distribution of fluids, thereby affecting the formulation of effective development policies. However, there is less research on quantifying gravitational differentiation. The No. 4 fault zone in the second block of Shunbei Oil and Gas Field was taken as the research objective in this paper, and high-temperature and high-pressure fluid phase experiments were conducted on production wells within this study area, along with visual phase experiments to achieve quantitative characterization of gravitational differentiation. Additionally, a component gradient theoretical model was constructed based on thermodynamics and molecular dynamics principles. Exhaustion and gas injection experiments revealed that gravity sedimentation exacerbates reverse condensation phenomena while demonstrating clear evidence of gravity overlap between dry and wet gases during injection processes. By utilizing both theoretical models derived from component gradients and experimental results, the paper successfully quantified a gravitational differentiation index and determined that the theoretical model of non-isothermal component gradients was more suitable for quantitatively characterizing the gravitational differentiation index within the study area. The results show that the influence of gravitational differentiation on light components and heavy components is more significant, but its impact on intermediate components is relatively small. With the increase in depth, the proportion of heavy components increases gradually,and condensate gas reservoirs change into volatile reservoirs. The influence of gravity on the density of condensate gas reservoirs with high molar content of heavy components is more significant. The gas injection experiment results show that the gravity overlap between dry and wet gases is obvious, and the condensate gas and dry gas show an obvious gas-gas interface. The top gas injection is dominated by gravity displacement and supplemented by diffusion mixing, while the bottom gas injection is the opposite.

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MA Longjie, HU Wenge, HE Xinming, CAO Fei, LI Zongyu, BAO Dian. Gravitational differentiation characteristics of condensate gas reservoir with fault-controlled fracture-cavity structure in second block of Shunbei Oil and Gas Field: A case study of No. 4 fault zone[J]. Petroleum Geology and Recovery Efficiency,2025,32(1):1~16

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History
  • Received:October 08,2023
  • Revised:June 10,2024
  • Adopted:
  • Online: February 13,2025
  • Published: