Subsea Wellbore Kick Return Line Diversion Method
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Solution Overview
Problem
Existing methods for removing fluid influx from wellbores during drilling, such as 'shutting in the well' and increasing mud density, can lead to excessive pressure and risk of wellbore fracture, and require the influx to pass through the mud return pump, which may exceed its operational limits.
Innovation Solution
A method that detects fluid influx by monitoring the return pump's increased rate, diverts flow through a choke line to equalize fluid flow in and out of the wellbore, and uses a less dense fluid in the riser to maintain wellbore pressure and displace the influx without passing it through the pump, ensuring safe circulation and preventing wellbore fluid entry from higher-pressure formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional kick control methods are used to remove fluid influx from the wellbore, then the influx can be removed, but the pressures necessary to be applied to the mud return pump and its connecting lines may be exceeded
Solution Approach 1:
The patent introduces a kick return line as an intermediary pathway to divert fluid influx away from the mud return pump. The kick return line connects the wellbore annulus directly to the surface, providing an alternative route that bypasses the pump and its connecting lines, thereby preventing pressure overload on these components while still enabling safe removal of the influx
Solution Approach 2:
The patent segments the fluid return pathway into two separate channels: the original mud return line for normal drilling fluid circulation, and a new kick return line specifically for influx removal. This segmentation allows independent control of each pathway, enabling influx to be diverted through the kick return line without affecting the mud return pump operation
2Stress or pressure
If the well is shut in to control fluid influx, then pressure control is achieved, but drilling operations are halted and productivity is reduced
Solution Approach 1:
The patent enables continuous drilling operations by providing a dedicated kick return line that handles influx removal separately from the main drilling fluid circulation system. This allows the drilling process to continue uninterrupted while the influx is simultaneously circulated out through the kick return line, eliminating the need to shut in the well and maintain continuous productivity
3Stress or pressure
If mud density is increased to control fluid influx, then hydrostatic pressure is increased to prevent further entry, but excessive pressure may cause wellbore fracture
Solution Approach 1:
The patent extracts the influx removal function from the main drilling fluid system by creating a separate kick return line. This allows the influx to be circulated out without requiring increased mud density, as the kick return line provides a dedicated pathway that can handle the influx separately from the weight-bearing drilling fluid column, thereby eliminating the risk of excessive hydrostatic pressure causing wellbore fracture
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for safe and controlled removal of fluid influx without exposing the wellbore to excessive pressure, maintaining wellbore integrity and preventing further fluid entry, while avoiding the need to shut in the well or increase mud density.
Implementation Method 1
The density is selected to provide sufficient hydrostatic pressure in the wellbore to prevent fluid in the pore spaces of the rock formations from entering the wellbore
Implementation Method 2
A fluid outlet of the wellbore is coupled to an inlet of a mud return pump. An outlet of the return pump is coupled to a return line to the water surface
Implementation Method 3
The interface level in the riser between the less dense fluid and the fluid pumped through the drill string is then increased to increase fluid pressure at the bottom of the well
Data Source
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AI summary
A method for removing a fluid influx from a subsea wellbore drilled using a pump to return fluid from the wellbore to the surface. The method includes detecting the influx when a rate of the return pump increases. Flow from the wellbore is diverted from the return pump to a choke line when the influx reaches the wellhead. A choke in the choke line is operated so that a rate of fluid pumped into the wellbore is substantially equal to a flow rate through the choke line. Fluid flow from the wellbore is redirected to the return pump inlet when the influx has substantially left the well.