Abstract: A safety drilling system for preventing collapse of water-sensitive formation in the upper part of a high-pressure saltwater layer, which includes a wellhead equipment, a downhole drilling tool, a first injection pipeline, a second injection pipeline, a first return pipeline and a second return pipeline. Upon encountering a high-pressure saltwater layer while drilling, the system injects heavy mud into the annulus of a wellhead through the first injection pipeline to form a heavy mud cap, such that a fluid column pressure in the annulus balances the pressure of the high-pressure saltwater layer. In this case, a fluid column pressure in a drill string is lower than the pressure of the high-pressure saltwater layer.

Abstract: A safety drilling system for preventing collapse of water-sensitive formation in the upper part of a high-pressure saltwater layer includes a wellhead equipment, a downhole drilling tool, a first injection pipeline, a second injection pipeline, a first return pipeline and a second return pipeline, and further includes a drilling method, wherein after encountering a high-pressure saltwater layer while drilling, heavy mud is injected into the annulus of a wellhead through the first injection pipeline to form a heavy mud cap, such that a fluid column pressure in the annulus balances the pressure of the high-pressure saltwater layer; in this case, a fluid column pressure in a drill string is lower than the pressure of the high-pressure saltwater layer.