Wellbore flow control method based on double-layer continuous pipe double-gradient drilling system

Abstract

The invention relates to a wellbore flow control method based on a double-layer continuous pipe double-gradient drilling system. The control method comprises the following steps that 1) drilling fluid is enabled to enter a downhole lifting pump from an annulus of a double-layer continuous pipe through a drilling pump of a deepwater drilling platform, enter an inner pipe of the double-layer continuous pipe after passing through a flow channel conversion joint, and enter the well bottom through a drill bit water hole after passing through an inner pipe of a downhole tool combination, and pressure balance is formed in the process of entering the well bottom, wherein a motor of the downhole tool combination is hydraulically driven by the drilling fluid, and hydraulic energy is converted into mechanical energy to provide power for rotation of the downhole lifting pump and a drill bit; and 2) the drilling fluid enters an annulus of the downhole tool combination from a return hole, enters the inner pipe of the double-layer continuous pipe through the flow channel conversion joint and returns to the platform through the downhole lifting pump, and pressure balance is formed in the returning process. According to the method, the operation efficiency can be improved, downhole complex conditions are reduced, the operation safety is guaranteed, and the operation cost is reduced.

Description

technical field [0001] The invention relates to the technical field of oil and gas exploitation, in particular to a wellbore flow control method based on a double-layer continuous tubing double-gradient drilling system. Background technique [0002] my country's marine natural gas hydrate resources are rich, most of which occur in the seabed surface and shallow muddy silt deposits, without tight caprock, and have symbiosis with oil and gas, and have shallow burial depth, weak cementation, drainage and flow blockage, and environmental risks Safe and economical drilling methods are the key to deep-water and shallow-layer hydrate exploration and development. [0003] Due to the low pressure of the overlying strata caused by the seawater section, the shallow formation is loose, and the window between pore pressure and fracture pressure is narrow. Conventional deepwater drilling uses a single drilling fluid density, which is prone to serious leakage and other complicated situation...

AI Technical Summary

Problems solved by technology

Although this method solves the problem of sand production of undiagenetic hydrates in deep water and shallow layers, there is still a big gap between the trial production time and production and the economic development threshold

Images