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With the depletion of high-quality gas reservoir sites in China and the increase in demand in the natural gas market, the goal of building reservoirs has gradually shifted to complex fault block groups, low-permeability gas reservoirs, oil reservoirs, sulfur-bearing gas reservoirs, and complex salt formations, and the role of reservoir construction has become increasingly prominent. However, the construction of oil reservoir is far more complicated than that of gas reservoir, and there are few studies on the characteristics of seepage and phase change in the construction of volatile oil reservoir at home and abroad, which seriously restricts the development of oil-based gas storage. Therefore, taking PG2 volatile oil reservoir as an example, based on indoor experiments such as multiple rounds of displacement tests and phase equilibrium experiments, the formation mechanism of reservoir capacity is analyzed, and the main controlling factors of effective reservoir space are analyzed. The results show that the oil and gas miscibility pressure is37.4 MPa, higher than the designed upper pressure limit (40 MPa), indicating that miscibility will occurduring injection–production. During the cyclic interactive injection-production process, due to the extraction of injected gas, with the rounds going on, the crude oil shrinks, the dissolved gas-oil ratio and volume coefficient gradually decrease, and the crude oil density gradually increases. After five cycles of oil–gas and water–gas injection–production, oil and water remain highly permeable; however, gas–oil and gas–water two-phase permeability zones become narrower, the flow capacity weakens, and the efficiency of oil/water displacement by gas decreases to a certain extent. The gas injection displacement efficiency and gas drive sweep coefficient after water drive to gas drive are the main controlling factors for the effective building space of reservoir. The building space for increasing crude oil shrinkage mainly depends on the properties of injected gas and the original reservoir fluid, and a prediction model is established to provide technical support for the reconstruction of gas storage.

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Evaluation of Effective Storage Space for Volatile Reservoir Based on Laboratory

  • 会议论文

  • 发表日期：

    2025年

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  • Hai-yan He,
  • Jiu-li Wang,
  • Lin Shang,
  • Xiao-li Ma,
  • Yang Zhang,
  • Dan Li,
  • Cong Li,
  • Zhong-jing Tian

摘要

With the depletion of high-quality gas reservoir sites in China and the increase in demand in the natural gas market, the goal of building reservoirs has gradually shifted to complex fault block groups, low-permeability gas reservoirs, oil reservoirs, sulfur-bearing gas reservoirs, and complex salt formations, and the role of reservoir construction has become increasingly prominent. However, the construction of oil reservoir is far more complicated than that of gas reservoir, and there are few studies on the characteristics of seepage and phase change in the construction of volatile oil reservoir at home and abroad, which seriously restricts the development of oil-based gas storage. Therefore, taking PG2 volatile oil reservoir as an example, based on indoor experiments such as multiple rounds of displacement tests and phase equilibrium experiments, the formation mechanism of reservoir capacity is analyzed, and the main controlling factors of effective reservoir space are analyzed. The results show that the oil and gas miscibility pressure is37.4 MPa, higher than the designed upper pressure limit (40 MPa), indicating that miscibility will occurduring injection–production. During the cyclic interactive injection-production process, due to the extraction of injected gas, with the rounds going on, the crude oil shrinks, the dissolved gas-oil ratio and volume coefficient gradually decrease, and the crude oil density gradually increases. After five cycles of oil–gas and water–gas injection–production, oil and water remain highly permeable; however, gas–oil and gas–water two-phase permeability zones become narrower, the flow capacity weakens, and the efficiency of oil/water displacement by gas decreases to a certain extent. The gas injection displacement efficiency and gas drive sweep coefficient after water drive to gas drive are the main controlling factors for the effective building space of reservoir. The building space for increasing crude oil shrinkage mainly depends on the properties of injected gas and the original reservoir fluid, and a prediction model is established to provide technical support for the reconstruction of gas storage.