Flow Splitting Device for Gas Reverse Circulation Drilling

A flow splitting device for gas reverse circulation drilling, comprising:

• an upper joint for connecting with a double-wall drill pipe;
• an inner tube, which is arranged in the upper joint and defines a first passageway in communication with an inner chamber of the double-wall drill pipe, a second passageway in communication with an annular space of the double-wall drill pipe formed between the inner tube and the upper joint;
• a lower joint, having an upper end fixedly connected with the upper joint and a lower end for connecting with a drill tool;
• and
• a flow guiding member provided between the upper joint and the lower joint, for allowing gas from the annular space of the double-wall drill pipe to enter into the drill tool after passing through the second passageway, and gas from the drill tool to return to a wellhead after passing through the first passageway and the inner chamber of the double-wall drill pipe,
• wherein a flexible sealing mechanism is provided on the upper joint, so that the upper joint is rotatable relative to the flexible sealing mechanism, the flexible sealing mechanism extending radially outward relative to the upper joint and the lower joint to form a sealing contact with a wellbore wall.