Drill String Vibration via Pressure Pulse
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Solution Overview
Problem
Directional drilling faces significant frictional resistance between the drill string and the borehole, leading to reduced penetrative efficiency and potential damage to downhole equipment, as the drill string tends to stick in the mud when operations are halted.
Innovation Solution
A pressure pulse generating apparatus is inserted into the drill string to create vibrations by using a rotor/stator assembly and nozzle system, which generates pressure pulses in the drilling fluid to agitate the drill string, reducing frictional resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the drill string is not rotating during lateral directional drilling, then frictional resistance between the drill string and borehole increases significantly, but applying force to overcome this friction results in excessive weight on the bit which can damage downhole equipment
Solution Approach 1:
The patent applies mechanical vibration to the drill string by generating pressure pulses in the drilling fluid that cause the drill string to vibrate axially. This vibration reduces the static friction between the drill string and borehole, allowing the drill string to be advanced without applying excessive weight that would damage downhole equipment. The rotor/stator assembly generates these pressure pulses by creating a pressure differential that propels the drill string upward in a vibrating motion.
Solution Approach 2:
The patent uses hydraulic principles by utilizing the drilling fluid itself as the medium to generate the vibratory force. The rotor/stator assembly creates pressure pulses in the hydraulic fluid (drilling mud) that are transmitted to the drill string, converting hydraulic energy into mechanical vibration. This allows force to be applied dynamically through fluid pressure rather than through static weight application.
2Productivity
If the drill string is stationary in the borehole, then frictional resistance increases and penetration rate decreases, but agitating the drill string requires additional energy input
Solution Approach 1:
The system uses the drilling fluid that is already being pumped through the drill string for the purpose of driving the bit and simultaneously generates the pressure pulses needed for vibration. The same hydraulic power that drives the mud motor also creates the pressure differential across the rotor/stator assembly, eliminating the need for a separate energy source for agitation. The drilling fluid serves multiple functions: cooling the bit, removing cuttings, and generating vibratory force.
3Ease of operation
If conventional drilling methods are used in lateral directional drilling, then the drill string sticks in the mud when operations are halted, but implementing vibration requires a complex apparatus in the downhole environment
Solution Approach 1:
The rotor/stator assembly is integrated into the existing drill string components and serves multiple functions: it acts as a flow restrictor to create pressure differential, a vibration generator to agitate the drill string, and a pressure pulse generator for potential telemetry. The drilling fluid serves dual purposes of driving the mud motor and generating the pressure pulses. This multi-functionality reduces the need for separate dedicated vibration generation equipment.
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
The apparatus effectively mitigates frictional resistance, allowing for increased penetration rates and preventing damage to downhole equipment by maintaining optimal drill bit weight application during directional drilling.
Implementation Method 1
The rotor/stator creates a pressure differential that generates a pressure pulse in the drilling fluid
Implementation Method 2
The pressure pulse acts on the drill string to cause vibration and agitation of the drill string, which may mitigate frictional resistance between the drill string and the well bore
Data Source
AI summary
A pressure pulse generating method and apparatus for use with a drill string includes a top and bottom subs for attaching the apparatus within the drill string; a rotor/stator; a drive assembly; and a nozzle sub which includes a nozzle assembly comprising a nozzle holder and a replaceable nozzle; and a nozzle housing having pulse openings. The nozzle holder has fluid ports which periodically align with the pulse openings as the nozzle holder rotates within the nozzle housing to achieve a desired pulse amplitude, frequency and waveform.