This invention provides a biodegradable modified
coating, a modified knot plugging agent for fracturing, and their preparation method, belonging to the field of
tertiary oil
recovery technology. Specifically, the dense cross-linked
network structure generated by the
Schiff base reaction between
gelatin (GL) and
glutaraldehyde (GD) serves as a
coating material for the knot plugging agent, providing it with high strength and stability without sacrificing its biodegradability. Furthermore, by changing the
reaction conditions (immersion time and
curing time) during the preparation of the coated knot plugging agent, a series of knot plugging agents adaptable to different reservoir temperatures and degradation cycles can be obtained to meet the complex conditions in perforation cluster plugging processes, thus broadening its application range.