Special Oil & Gas Reservoirs ›› 2025, Vol. 32 ›› Issue (2): 66-72.DOI: 10.3969/j.issn.1006-6535.2025.02.008

• Reservoir Engineering • Previous Articles     Next Articles

Dynamic characteristics of water breakthrough of fishbone multilateral well in bottom water reservoirs

CUI Chunxue1, LIU Yuewu1,2, DING Jiuge1, ZHANG Guoqing3, REN Yangqi3, YANG Xiaofeng3   

  1. 1. Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;
    2. University of Chinese Academy of Sciences, Beijing 100190, China;
    3. School of Petroleum Engineering, Northeast Petroleum University, Daqing, Heilongjiang 163318, China
  • Received:2024-06-28 Revised:2025-01-05 Online:2025-04-25 Published:2025-06-16

Abstract: The efficient development of bottom-water oil reservoirs is significantly constrained by the bottom-water coning during the development process.To address this issue,the study focused on the fishbone multilateral wells in bottom-water oil reservoirs and established a dynamic prediction model for the bottom-water coning by applying theoretical methods from fluid mechanics in porous medium and reservoir engineering to investigate the distribution pattern of water breakthrough time and position along the wellbore trajectory,thus clarifying the dynamic characteristics of water breakthrough in fishbone multilateral wells and conducting a sensitivity analysis.The study results show that:the interflow interference and diversion effects between the main wellbore and multilateral wellbores result in lower flow rates in the angular region near the wellbore junction,where a larger vertical pressure gradient in the reservoir leads to earlier water breakthrough.Subsequently,the middle section of the main wellbore and the heel ends of the multilateral wellbores near the main wellbore experience water breakthrough,while the ends of the main wellbore and the toe ends of the multilateral wellbores have relatively later water breakthrough times.Increasing the water-shutoff height,oil-water density difference,main wellbore length,and branch angle can effectively mitigate the bottom-water coning/cresting.When the main wellbore length exceeds 400 m and the branch angle exceeds 30°,the increase in water breakthrough time slows down.It is more reasonable to position the wellbore height at 80% of the reservoir thickness.Heavy oil reservoirs are more prone to bottom-water cresting compared to light oil reservoirs.The research results provide significant practical guidance for oilfields to determine reasonable operating policies,delay water breakthrough time,and enhance water-free cumulative production and recovery efficiency.

Key words: bottom water reservoir, fishbone multilateral well, coning/water cresting, water breakthrough dynamic

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