Interpretation model and field application of dynamic oil-water flow⁃ back and production of shale reservoirs after fracturing
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    Abstract:

    Flowback and early production of shale reservoirs usually show obvious characteristics of oil-water co-production after large-scale volume fracturing. Quantitative analysis of dynamic oil-water flowback and production has become a new method to explain fracture and reservoir parameters. However, the interpretation model and application of dynamic oil-water phase flowback and production are still insufficient at present. Based on the hypothesis of fracturing fluid occurrence after fracturing in shale reservoirs,this paper first established the flow equations of the water phase and oil phase considering fractures and then deduced the analytical solution and characteristic solution of the dynamic oil phase and water phase interpretation models by introducing pseudo-time and pseudo-pressure to linearize the equations. Finally, the paper developed a dynamic flowback and production interpretation method combining oil phase chart fitting and water phase linear analysis. The results show that in the log-log diagnostic curve, the oil phase flow exhibits linear flow in the stimulated zone with a slope of 1/2 and controlled flow at the stimulated zone boundary with a slope of 1, while the water phase flow exhibits linear flow in the fracture with a slope of 1/2 and controlled flow at the fracture boundary with a slope of 1. The established interpretation model of dynamic oil-water flowback and production can well explain the fracture and reservoir parameters. The half-length of fracture of the fracturing well, fracture conductivity, width and permeability of stimulated zones are well inversed based on the reservoir,fracturing, and dynamic data of a shale block in western China. Among them,the half-length of the fracture is in the range of 50-130 m; the fracture conductivity is in the range of 20-80 mD·m; the permeability of the stimulated zones is in the range of 0.01-0.05 mD; the width of the stimulated zones is in the range of 24-27 m. According to the inversion of fracture and stimulated zone parameters, the numerical simulation model of fractured horizontal well flowback and production is established. Moreover, the simulated output based on the interpretation results is in good agreement with the actual value, and the later predicted value is reasonable. The interpretation model of dynamic flowback and production established in this paper improves the dynamic analysis method of shale reservoirs and provides a basis for quantitative analysis of flowback and production characteristics of shale reservoirs, evaluation of fracturing effect, and formulation of efficient development countermeasures.

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JIA Pin, PAN Quanyu, YU Shuxin, LI Binhui, CHENG Xiaogang, CHENG Linsong, NIU Langyu. Interpretation model and field application of dynamic oil-water flow⁃ back and production of shale reservoirs after fracturing[J]. Petroleum Geology and Recovery Efficiency,2024,31(6):127~139

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History
  • Received:February 11,2023
  • Revised:August 10,2024
  • Adopted:
  • Online: December 05,2024
  • Published: