Drill String Fluid Displacement During Trip-Out
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Solution Overview
Problem
During the process of removing a drill string from a wellbore, fluid tends to cling to the inner and outer surfaces of the pipe, leading to waste, hazards, and pollution, and there is a challenge in maintaining controlled fluid pressure to prevent fluid flow between the casing and the drill string, known as U-tubing.
Innovation Solution
A method involving determining a desired dry pipe length, calculating the hydrostatic pressure, injecting pressurized gas to displace fluid from the drill string, and using a float valve to prevent fluid flow, allowing for the removal of a dry pipe portion from the wellbore.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If drill string is removed from wellbore without fluid displacement, then tripping operation is simpler and faster, but fluid clings to pipe surfaces causing waste, hazards and pollution
Solution Approach 1:
The method performs preliminary fluid displacement by injecting pressurized gas into the drill string before removal to create a dry pipe portion, preventing fluid from clinging to the pipe surfaces during tripping operations
Solution Approach 2:
The method extracts fluid from the upper portion of the drill string by injecting pressurized gas to displace the fluid downward, separating the fluid that would otherwise cling to the pipe surfaces during removal
2Object-generated harmful factors
If pressurized gas is injected to displace fluid and create dry pipe, then fluid waste and pollution are reduced, but additional equipment and process complexity are required
Solution Approach 1:
The drill string itself serves multiple functions: it acts as both the drilling tool and the conduit for injecting pressurized gas to displace fluid, eliminating the need for separate injection equipment
Solution Approach 2:
The system uses the drill string's own interior space and pressure differential to displace fluid, with the gas injection process utilizing the existing drill string infrastructure rather than requiring external specialized equipment
3Reliability
If float valve is used to prevent U-tubing, then fluid pressure control is improved, but device complexity increases
Solution Approach 1:
The float valve acts as an intermediary device at the bottom of the drill string that selectively allows gas to pass through while preventing fluid from flowing upward, controlling pressure without requiring complex external systems
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 effectively removes the drill string with minimal fluid loss, maintaining controlled pressure and preventing U-tubing, thus reducing waste and pollution while ensuring efficient tripping operations.
Implementation Method 1
calculating a hydrostatic pressure for a column of fluid having a height corresponding to the dry pipe length determined in step a); injecting into the drill string a pressurized gas having a pressure at least as great as the pressure calculated in step b) so as to displace the fluid
Implementation Method 2
preventing fluid from flowing from the annulus into the drill string
Data Source
AI summary
A method for removing a drill string from a wellbore, the drill string comprising a plurality of pipe segments, the wellbore and the drill string defining an annulus, the annulus and the drill string containing a fluid, comprises: a) determining a desired dry pipe length; b) calculating a hydrostatic pressure for a column of fluid having a height corresponding to the desired dry pipe length; c) injecting into the drill string a gas having a pressure at least as great as the pressure calculated in step b) so as to displace fluid from an upper portion of drill string, thereby creating a dry pipe portion, wherein the length of the dry pipe portion corresponds to the desired dry pipe length; d) preventing fluid from flowing from the annulus into the drill string; and e) removing at least a part of the dry pipe portion from the wellbore.