Although the global energy demand is shifting towards a well-balanced energy mix, fossil fuels will continue to have a significant role in this transition and will maintain a big share in the energy mix portfolio. The production of oil and gas has already reached the apex in the time that most of the conventional giant reservoirs are depleting, and discoveries for new reserves have shrunk down. In conventional reservoirs, it is estimated that about two-thirds of the Original Oil in Place (OOIP) will not be produced within the field lifecycle, corresponding to an average Recovery Factor (RF) between 20% and 40%. This low recovery factors from traditional methods trigger more investments in the Enhanced Oil Recovery (EOR) techniques.
Waterflooding is one of the most commonly used technique to increase RF by raising or maintaining reservoir pressure. Lack of comprehending the driving forces in Naturally Fractured Reservoirs and reservoir heterogeneity may lead to serious conformance problems in which dealing with excessive undesirable water production becomes very challenging. Chemical EOR through an injection of a polymer solution is amongst the tested options that can be used to improve sweep efficiency. Ultimately, understanding the reservoir characteristics and having the know-how to implement the best recovery option will help to maximize the field’s lifecycle and increase the RF.
Therefore, this study investigates some key elements that have a significant influence on the overall fluid flow behavior. The work reveals insights on the impact of capillarity and wettability in heterogeneous porous media. An experimental lab-scale consisting of a 2D sandbox model, which mimics a water-wet fractured system with injection and production ports, was designed, fabricated, and tested in single-phase and two-phase flow scenarios including the injection of water and polymer solutions.
In the case of single-phase flow, a waterflood baseline scenario was studied with controlled variables, which helped to distinguish the contrast with the polymer flood case. Implementing water injection in a fractured water-wet reservoir showed that water prefers to channel through high permeable streaks, which consequently leads to poor volumetric sweep leading to significant bypassed zones.
Investigating the two-phase flow was the essence of this research. Thus, the same procedures were repeated where water and polymer were used to displace oil. During waterflooding, due to strong capillarity contrast between the matrix and fracture media, flow divergence was found to be faster towards the matrix medium where the matrix gets saturated faster than that the fracture, overriding the high permeability of the fracture. Whereas, polymer flooding exhibited better volumetric sweep in all scenarios. Numerical simulations were used to replicate the experiments. This work can give new visual insights about key recovery mechanisms in heterogeneous reservoirs using polymers.
|Date of Award||Oct 2019|
|Original language||English (US)|
- Physical Science and Engineering
|Supervisor||Hussein Hoteit (Supervisor)|
- Porous media, Water flooding, Polymer flooding, Heterogenous media, capillarity, mobility ratio