A review of fabrication methods for biodegradable pH-Responsive nanocomposite microgels and their performance in enhanced oil recovery

Fossil fuels continue to be the predominant source of energy globally, and with many of the world's oil reserves expected to remain productive for extended periods, there is a pressing need for enhanced oil recovery (EOR) methods to satisfy the surging demand for oil. Iran plays a pivotal role in the global oil landscape, making EOR particularly vital, as more than 50 % of oil in carbonate reservoirs remains trapped. Reservoir conformance control techniques are essential for facilitating hydrocarbon flow from the reservoir to the wellbore, especially in challenging displacement scenarios. Achieving uniform sweep efficiency and maximizing hydrocarbon production requires addressing a prevalent issue in the oil industry: excessive water production from oil wells. This phenomenon not only diminishes hydrocarbon output but also curtails reservoir productivity and economic viability while posing severe environmental risks. Among various strategies to mitigate water production, chemical solutions like polymer gel injection have emerged as effective methods for water control. Recently developed techniques, such as the injection of pH-responsive microgels, offer innovative solutions for water blocking and conformance control at reservoir depths. Microgels present several notable advantages over traditional gel injection methods. These include lower operational costs due to reduced injection pressure, which minimizes mechanical damage to the reservoir. Additionally, microgels offer lower material costs and the benefit of reversible swelling, allowing for adjustments through acid washing. However, the successful application of microgels does necessitate an initial acid pre-flush step to lower the pH of the porous medium, which can escalate operational costs. Furthermore, the effective deployment of microgels is contingent upon various factors, including the site and timing of their application, the design of the injection strategy, the parameters governing the injection process, and the microgels' performance under diverse reservoir conditions. These considerations are crucial for optimizing the efficiency and effectiveness of microgel-based interventions in EOR.