Prevention and control methods for shallow water flow in deepwater drilling

Shallow water flow（SWF）is a kind of common geological hazards in deepwater drilling, which has caused a large amount of financial loss. Deepwater hydrocarbon resource is being explored in China, and it is a very challenging issue to avoid and alleviate the potential harm of SWF. So it is essential to study on the prevention and control method for SWF. Four different mechanisms causing SWF were introduced: fracture inducing, storage inducing, geopressured sands in conductor intervals and transmission of geopressure through cement channels. According to the characteristics of geopressured sands and the mechanisms causing SWF, the corresponding precautions of SWF before drilling and in the process of drilling were proposed. Based on the identified SWF, five means for preventing SWF were summarized: increasing mud weight, using a seafloor diverter, using chemical grout, cementing with foamed slurry and driving the conductor through the SWF zone. The research plays an important role in preventing and controlling the deepwater SWF effectively.