Preparation and investigation of self-healing gel for mitigating circulation loss

Lost circulation is a common and complex downhole accident in the process of oil and gas drilling. Traditional bridge plugging material has the limitation of poor adaptability to lost formations. Therefore, this study synthesized a new self-healing plugging material to improve the plugging success rate; specifically, the hydrophobic association polymer lauryl methlacrylate-acrylamide-acrylic acid containing Fe3+ was modified via curdlan to form a composite gel with high strength and self-healing properties. The self-healing time, mechanicalness and rheological properties of the self-healing gel were systematically evaluated. The results showed that the modification of curdlan could significantly improve the mechanical properties and rheological strength of self-healing gel, and the chelating structure formed by Fe (3+) and carboxyl groups could further enhance the mechanical properties of the self-healing gel. Toughness and storage modulus of the LF0.15C2 self-healing gel with the introduction of curdlan and Fe3+ could reach 30.2 kJ/m(3) and 3,458 Pa, respectively. Compared with conventional gel materials, composite gels with self-healing properties exhibited better pressure-bearing capacity of 2.5 MPa, and could effectively avoid causing plugging at the entrance of the fractures by high-concentration inert material and improve the pressure-bearing capacity. In addition, the plugging mechanism of the self-healing gel modified via curdlan in formation fractures was analysed in detail. The self-healing gel modified via curdlan prepared in this work has application potential as a lost circulation material in the field of oil and gas drilling.

Automated summary

This study synthesized a new self-healing plugging material by modifying hydrophobic association polymer with curdlan and Fe3+. The results showed that the modified gel had improved mechanical and rheological properties, with a strength of 30.2 kJ/m(3) and a storage modulus of 3,458 Pa. Compared to conventional gel materials, the self-healing gel exhibited better pressure-bearing capacity and could effectively avoid plugging at fractures.