What does the reverse circulation seal do?

Does the subject want to ask, "What role does reverse circulation play?" Suction. Reverse circulation produces negative pressure on the suction of mud, which adversely affects the stability of the hole wall, while positive circulation produces positive pressure on the hole wall. Reverse circulation means that the drill pipe sucks out the circulating mud with cuttings, replenishes the mud at the top of the hole, and keeps the liquid level in the hole, thus ensuring the stability of the hole wall. Reverse circulation can greatly reduce the ineffective labor of repeatedly grinding cuttings and greatly improve drilling efficiency. Suitable for rock stratum, gravel and dense soil layer.