Laboratory evaluation of nitrogen injection for enhanced oil recovery: Effects of pressure and induced fractures

Fahandezhsaadi, M ; Sharif University of Technology | 2019

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  1. Type of Document: Article
  2. DOI: 10.1016/j.fuel.2019.05.039
  3. Publisher: Elsevier Ltd , 2019
  4. Abstract:
  5. Nitrogen has emerged as a suitable alternative to carbon dioxide for injection into hydrocarbon reservoirs worldwide to enhance the recovery of subsurface energy. Nitrogen typically costs less than CO2 and natural gas, and has the added benefit of being widely available and non-corrosive. However, the underlying mechanisms of recovery following N2 injection into fractured reservoirs that make up a large portion of the world's oil and gas reserves are not well understood. Here we present the laboratory results of N2 injection into carbonate rocks acquired from a newly developed oil reservoir in Iran with a huge N2-containing natural gas reservoir nearby. We investigate the effectiveness of N2 injection for enhanced oil recovery in immiscible conditions before and after gas breakthrough under a low and high differential pressures across the core. In addition to the effects of pressure, we further illuminate the impacts of fractures—induced on the cores—to assess the displacement behavior and oil recovery factor. Our findings show that an ultimate oil recovery factor of more than 40% can be achieved by N2 injection in non-fractured cores even at immiscible conditions. The ultimate recovery and the onset times for oil production and gas breakthrough are found to be lowered by increasing differential pressures as well as inducing fractures (e.g., 17% reduction in ultimate recovery due to fracturing). However, at a given time when gas-oil interface has not yet reached the production zone (outlet), both increasing differential pressures and fractures transiently enhance the recovery efficiency. As a result, the impact of fractures is more pronounced in lower differential pressures, while the impact of differential pressures is stronger in the absence of fractures. Interestingly, our results attest to the role of molecular diffusion across fracture-matrix interface as the main recovery mechanism in fractured media, which controls the system dynamics before and after breakthroughs. The results not only provide a new perspective into how differential pressures and fractures fundamentally control the effectiveness of N2 flooding but also further show the promising prospects of N2 injection for EOR even at immiscible conditions. © 2019 Elsevier Ltd
  6. Keywords:
  7. Diffusion ; Fracture ; Gas breakthrough ; Immiscible injection ; Nitrogen ; Carbon dioxide ; Gases ; Injection (oil wells) ; Natural gas ; Oil well flooding ; Petroleum reservoir engineering ; Petroleum reservoirs ; Phase interfaces ; Proven reserves ; Recovery ; Differential pressures ; Enhanced oil recovery ; Fracture-matrix interface ; Hydrocarbon reservoir ; Laboratory evaluation ; Natural gas reservoir ; Oil and gas reserves ; Recovery mechanisms ; Enhanced recovery
  8. Source: Fuel ; Volume 253 , 2019 , Pages 607-614 ; 00162361 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/pii/S0016236119307811