Bridge plug apparatuses containing a magnetorheological fluid and methods for use thereof

Magnetorheological fluids may regulate fluid flow downhole by forming a fluid seal using a bridge plug apparatus. Bridge plug apparatuses employing a magnetorheological fluid may be deployed in a wellbore in a retrievable configuration or in a substantially permanent configuration. Retrievable bridge plug apparatuses may comprise spaced apart magnets having a gap defined therebetween, and a reservoir of magnetorheological fluid housed within the gap. The magnets move laterally with respect to one another to expand or contract the gap and to displace the reservoir of magnetorheological fluid radially with respect to the magnets. Other bridge plug apparatuses may comprise a flow path extending between a reservoir of magnetorheological fluid and the exterior of a housing, where at least a portion of the flow path is located within a gap defined between spaced apart magnets.