Study on Fluid Behaviors of Foam-Assisted Nitrogen Flooding on a Three-Dimensional Visualized Fracture–Vuggy Model

Abstract

Tahe Oilfield, located in northwest China, is an unconventional fracture–vuggy carbonate reservoir. The foam-assisted nitrogen gas flooding technology has been proven to be a potential EOR technology. However, the flow behaviors of foam-assisted nitrogen gas in fracture–vuggy structures are not clear due to the complex fracture–vuggy structures and their strong heterogeneity. In this work, a three-dimensional visualized fracture–vuggy model is designed and fabricated to investigate the fluids behaviors of foam-assisted N2 flooding and classify the residual oil types after foam-assisted N2 flooding. Experimental results reveal that foam slug can enlarge the sweep efficiency, suppress the formation of nitrogen gas channeling, and detach the oil film. Additionally, the evolution processes of the gas–oil and oil–water interfaces are investigated and analyzed. Moreover, the residual oil types after foam-assisted N2 flooding and nitrogen gas flooding, respectively, are classified and summarized. Compared to nitrogen gas flooding after water flooding, 12.36% more oil can be recovered through foam-assisted N2 flooding. This work further studies the fluid flow behaviors of foam-assisted N2 in the three-dimensional visualized fracture–vuggy carbonate model and also confirms the previous achievements.

Factors Influencing the Rheology of Methane Foam for Gas Mobility Control in High-Temperature, Proppant-Fractured Reservoirs

“…Gas HnP in tight oil reservoirs and foam flow in fractures are still limited and in their early stages of development, so a better understanding of how foam rheology evolves in fractures is vital to continued optimization and improvement of this EOR method [1,44,45]. A lot of work has been conducted to observe foam behavior in non-propped hydraulic fractures and naturally fractured reservoirs using parallel plate setups [44,46,47], fractured shale and carbonate cores [12,39,[48][49][50][51], acrylic fracture network models [52,53], and fracture networks in marble slabs to represent the fracture environment in tight oil reservoirs [45]. Because of the complexity of fracture networks and the difficulty of foam generation in extreme conditions, many studies have used simulation models to look at foam rheology in propped and non-propped fractures [14,29,50,54,55].…”

“…This literature review showed that there is still a substantial gap in understanding the rheology of foam flow in proppant-filled fractures under realistic conditions. Most work performed on foam propagation in fractures is focused on the success of using foam to improve conformance control and boost ultimate oil recovery rather than understanding the physics of foam propagation in such a system [24,39,43,48,49,53]. While some have briefly looked at the effect of foam quality and flow rate on foam rheology in fractures, the lack of a systematic experimental design to truly characterize these effects is evident [46,52,55,58].…”

The Enhanced Oil Recovery Effect of Nitrogen-Assisted Gravity Drainage in Karst Reservoirs with Different Genesis: A Case Study of the Tahe Oilfield

“…When the injection volume of foam-assisted N 2 reaches a reasonable level, the foam accumulates in the flow passage, reduces the fluid fluidity, and, therefore, effectively inhibits gas channeling, and obviously improves the sweep efficiency of the injection medium. Foam-assisted N 2 has an excellent effect on oil film stripping, oil emulsion, and oil droplet carrying, which improves microdisplacement efficiency [18,19].…”

Experimental Investigation on Cracking Characteristics of Dry and Saturated Shales in Nitrogen Fracturing after Liquid Nitrogen (LN2) Injection

“…There have been many studies on waterless fracturing fluids, such as liquefied petroleum gases [12][13][14], supercritical carbon dioxide or liquid carbon dioxide [15][16][17], high energy gas [18,19], nitrogen foam [20,21], and LN 2 [6,11]. These waterless fracturing technologies have been applied.…”