Re-Energization Shale Oil Reservoirs with Nanofluid Prefracturing: Mechanism Simulation and Case Study

Unconventional oil is a significant alternative energy source. However, its low porosity and permeability present technical challenges, making it difficult to inject water and extract oil effectively. Replenishing formation energy and hydraulic fracturing for oil recovery are effective development methods. This paper combines both methods and proposes the use of nanofluid for prefracturing re-energization. We first analyze the characteristics of nanofluid and the process of prefracturing re-energization. Laboratory experiments were conducted to evaluate the benefits of nanofluid. Numerical simulation was then employed to characterize the prefracturing re-energization process, focusing on flow laws and flow space. A mechanistic model was developed to analyze the injection pressure and sweep efficiency during the prefracturing re-energization process. A predictive mechanistic simulation framework was developed that establishes a direct mapping between the nanofluid's functionalities and dynamic reservoir parameters. Simulation results quantitatively demonstrated that the nanofluid-based prefracturing re-energization yields significantly higher long-term recovery and more effective pressure maintenance compared to conventional water preinjection or no re-energization, primarily due to enhanced imbibition and improved fluid mobility. Finally, we share the positive outcomes of a pilot test conducted in the Jimusar shale oil reservoir. This paper offers a new approach to addressing the challenges of energy replenishment and fracturing for oil displacement in shale oil development.