Shock Tool Mandrel Assembly Axial Oscillation
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Solution Overview
Problem
Existing downhole oscillation systems face challenges in efficiently converting cyclical pressure pulses in drilling fluid into axial oscillations, leading to reduced rate of penetration and increased friction between the drillstring and the borehole formation, which can result in stick slip and increased weight-on-bit requirements.
Innovation Solution
The shock tool design includes a mandrel assembly with fixably coupled annular pistons that directly actuate the mandrel, utilizing pressure pulses to induce axial reciprocation, and additional static pistons to enhance the axial force applied to the mandrel, allowing for increased amplitude of reciprocal extensions and contractions without increasing drilling fluid pressure or tool diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cyclical pressure pulses are applied to the drillstring, then axial oscillations are induced to reduce friction, but the conversion efficiency from pressure pulses to axial oscillations is insufficient
Solution Approach 1:
The shock tool utilizes hydraulic pressure pulses transmitted through the drilling fluid to actuate pistons that convert the pressure energy into mechanical axial oscillations. The pistons are directly coupled to the mandrel, creating an efficient hydraulic-mechanical conversion system that transforms cyclical pressure variations into effective axial reciprocation motions.
Solution Approach 2:
The invention replaces traditional mechanical vibration generation systems with a pressure pulse-based actuation system. Instead of using complex mechanical vibrators or motors downhole, the system uses fluid pressure pulses transmitted through the drillstring to directly actuate the oscillation mechanism, simplifying the mechanical system while improving energy conversion efficiency.
2Force
If additional static pistons are added to enhance axial force, then the net axial force on the mandrel increases, but the device complexity increases
Solution Approach 1:
The shock tool merges multiple piston elements into a integrated assembly where first and second pistons work together on the same mandrel. The pistons are coupled to the same mandrel assembly, allowing their forces to combine additively on the mandrel while sharing common structural support and sealing arrangements, thereby achieving force multiplication without proportional increases in overall system complexity.
Solution Approach 2:
The mandrel assembly serves multiple functions: it supports both pistons, provides common sealing surfaces, transmits the combined axial forces from both pistons, and couples the oscillation force to the drillstring. This multi-functional design allows the system to achieve enhanced axial force with minimal additional components beyond the dual piston arrangement.
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 solution improves the efficiency of axial oscillations, reducing friction and enhancing drilling performance by directly actuating the mandrel with pressure pulses and increasing the net axial force, thereby improving rate of penetration and reducing stick slip occurrences.
Implementation Method 1
The first annular piston is disposed at the second end of the mandrel assembly and sealingly engages the outer housing... transferring the pressure pulses through the drilling mud to the first annular piston... moving the mandrel axially relative to a housing of the shock tool
Implementation Method 2
The second annular piston is axially positioned between the first annular piston and the upper end of the outer housing... configured to move axially relative to the mandrel assembly and the outer housing... increasing the amplitude of reciprocal extensions and contractions
Data Source
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AI summary
A shock tool for reciprocating a drillstring includes an outer housing. The outer housing has a central axis, a first end, a second end opposite the first end, and a passage extending axially from the first end to the second end. In addition, the shock tool includes a mandrel assembly coaxially disposed in the passage of the outer housing and configured to move axially relative to the outer housing. The mandrel assembly has a first end axially spaced from the outer housing, a second end disposed in the outer housing, and a passage extending axially from the first end of the mandrel assembly to the second end of the mandrel assembly. The mandrel assembly includes a mandrel and a first annular piston fixably coupled to the mandrel. The first annular piston is disposed at the second end of the mandrel assembly and sealingly engages the outer housing.