Untethered near-wellbore stimulation

A method for stimulating a near-wellbore area, comprising:

• dropping an untethered stimulation tool from a wellhead into a tubular disposed in a wellbore at least partially filled with a wellbore fluid, the untethered stimulation tool comprising:
• a main body, wherein the main body is formed at least in part from a material that is buoyant in the wellbore fluid;
• a ballast;
• a magnet;
• and
• a pressure pulse generator, wherein the untethered stimulation tool is configured to, when the ballast is attached to the untethered stimulation tool, descend downhole within the tubular by a force of gravity;
• coupling the untethered stimulation tool by the magnet to an interior surface of the tubular upon arrival of the untethered stimulation tool at a downhole location proximate the perforation;
• when the untethered stimulation tool is coupled by the magnet to the interior of the tubular, activate a pressure pulse generator to transmit pressure pulses into the perforation, thereby dislodging material from the perforation;
• de-coupling the untethered stimulation tool from the interior surface;
• after de-coupling the untethered stimulation tool, releasing the ballast, thereby permitting the untethered stimulation tool to ascend uphole, driven at least partially by a buoyant force exerted by the wellbore fluids;
• and
• after releasing the ballast, retrieving the untethered stimulation tool at the wellhead.