Journal of
Petroleum and Gas Engineering

  • Abbreviation: J. Petroleum Gas Eng.
  • Language: English
  • ISSN: 2141-2677
  • DOI: 10.5897/JPGE
  • Start Year: 2010
  • Published Articles: 114

Review

Study on cyclic water injection of offshore weak volatile reservoir considering hysteresis effect

Jianting Huang
  • Jianting Huang
  • Tianjin Branch of China National Offshore Oil Corporation (CNOOC) Ltd., Tianjin, China.
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Jintao Wu
  • Jintao Wu
  • Tianjin Branch of China National Offshore Oil Corporation (CNOOC) Ltd., Tianjin, China.
  • Google Scholar
Guangming Pan
  • Guangming Pan
  • Tianjin Branch of China National Offshore Oil Corporation (CNOOC) Ltd., Tianjin, China.
  • Google Scholar
Hao Li
  • Hao Li
  • Tianjin Branch of China National Offshore Oil Corporation (CNOOC) Ltd., Tianjin, China.
  • Google Scholar
Peng Shi
  • Peng Shi
  • Tianjin Branch of China National Offshore Oil Corporation (CNOOC) Ltd., Tianjin, China.
  • Google Scholar


  •  Received: 30 July 2020
  •  Accepted: 16 February 2021
  •  Published: 31 March 2021

Abstract

Based on the theoretical analysis of capillary hysteresis and relative permeability hysteresis and reservoir numerical simulation, a water injection strategy study was conducted for an offshore weak volatile oil fields after long-term depletion development. The results show that if the capillary hysteresis and relative permeability hysteresis are not considered, the recovery prediction results of the subsequent water injection development will be too small and large, respectively, which is inconsistent with the actual situation. Compared with conventional water injection, cyclic water injection can increase the recovery rate by 1.1%. Its oil displacement presents the characteristics of “three zones and two bands” along the direction from injection to production with water enrichment zone, water stagnation and oil drainage band, oil enrichment zone, oil stagnation and gas drainage band and secondary gas generation zone, respectively. To reduce the influence of the secondary gas cap, the water injection strategy after long-term depletion development includes two slugs of enhanced water injection and cyclic water injection. The timing to turn from enhanced water injection to cyclic water injection is when the formation pressure recovers to bubble point pressure. The optimal half-period of the cyclic water injection phase is 2 months. After the oilfield changed from depletion development to water injection development, the decline rate was improved from 20.8 to -12.7%. The double-slug water injection strategy considering the hysteresis effect can improve the recovery factor by 18.3%, and provide a practical basis for the efficient development of weak volatile reservoirs.

Key words: Capillary force hysteresis, relative permeability hysteresis, weak volatile reservoir, cyclic water injection, water injection strategy.