High density bromide-based nanocomposite gel for temporary plugging in fractured reservoirs with multi-pressure systems

The coexistence of blowout and lost circulation in multi-pressure fractured reservoirs has always been a huge challenge to the oil industry. Although the use of high-density kill fluids can ensure the safety of well control, the problem of lost circulation in low pressure layer is still troublesome. Gel is widely used as a temporary plugging system, but the conventional gel plugging system will float when used in combination with high-density kill fluid, resulting in failure of temporary plugging. In this paper, a novel high-density bromide-based nanocomposite gel (HDGEL) was developed, the gel formation mechanism was explored, and its performance was evaluated in the laboratory. The gel is weighted by sodium bromide (NaBr), and cross-linked by covalent bonds, density 1.2–1.5 g/cm³ adjustable, and its temperature resistance can reach 160 °C. Rheological tests show that the gel solution has low initial viscosity and easy to pump. The gelation time can be adjusted from 8 to 12 h, which can be directly broken by the drill or regular jetting nozzle and then flowed back. It can be used in combination with high-density kill fluid to ensure temporary plugging effect. In the fractures with tip sizes (0.014 cm), the maximum bearing pressure of HDGEL is 17.52 MPa, and the regained-permeability recovery can reach 86.81% without the use of gel breaker. This paper introduces a new gel system for multi-pressure reservoirs that can be used in combination with high-density kill fluid and makes recommendations for its engineering application.