Drilling fluid backflow system for offshore drilling without marine riser

Abstract

The invention provides a drilling fluid backflow system for offshore drilling without a marine riser. The drilling fluid backflow system comprises a drilling fluid volume control unit, an open water area drilling rod, a drilling fluid backflow pipeline, a drilling fluid backflow pump installed on the drilling fluid backflow pipeline and a drilling fluid processing device; the drilling fluid volume control unit is directly installed on a well head or above a blowout preventer without the marine riser, and the top of the drilling fluid volume control unit is open towards seawater; the drilling rod extends from a drilling platform through the volume control unit and performs a drilling operation passing through the interior of the volume control unit; the drilling fluid backflow pipeline is connected with the volume control unit through a hose, the drilling fluid backflow pump is sequentially installed on a pipe section in the backflow pipeline in the axial direction and used for pumping drilling fluid flowing into the backflow pipeline from the volume control unit to back to the drilling platform, and the drilling fluid is recycled after being treated by the drilling fluid processing device. The drilling fluid backflow system is not limited by the size and the water depth of a drilling ship, capable of effectively recovering the drilling fluid, and suitable for full-water-depth drilling operation.

Description

technical field [0001] The disclosure belongs to the technical field of offshore energy exploitation, and relates to a drilling fluid return system for offshore riser-free drilling. Background technique [0002] Drilling operations in the sea can realize the development and utilization of seabed energy, and can carry out the exploitation of energy such as oil, natural gas and combustible ice. In order to realize deepwater drilling and ultra-deep drilling, riserless drilling technology can be used in deepwater drilling operations. However, for ultra-deep water drilling operations, the existing large-scale drilling equipment uses large-diameter risers, which need to be installed with high-pressure well control pipelines, and the installation is done underwater, which cannot guarantee the safety of the installation, and at the same time, the cost is high. [0003] Specifically, the main function of the large-diameter riser is to realize the return flow of drilling fluid and th...

AI Technical Summary

Problems solved by technology

However, the application water depth of riserless drilling technology is limited. As the water depth increases, no matter when the test increases the operating water depth to more than 2000 meters, or by installing a rotary control head (rotary control head, RCD) on the top of the BOP, the drilling fluid The return flow of the drilling fluid is limited to a certain extent. Since the hydrostatic pressure generated by the long drilling fluid return line on the wellbore will greatly affect the stability of the wellbore, there are obvious limitations in using this method in deep sea areas.

In the process of riserless drilling, the drilling fluid is pumped into the wellbore, and then the drill cuttings are returned to the drilling ship from the nearby drilling fluid return pipeline. It is not feasible to use the underwater rotary control head method. In 2,000-meter deep-sea drilling or deeper drilling scenarios, the pumping capacity of the pump is limited, and it is impossible to pump sufficient volume and specific gravity of drilling fluid back to the drilling ship

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