Pressure Balanced Load Cell for Downhole Measurement
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Solution Overview
Problem
Force measurement devices, such as strain gauges, in downhole well applications are affected by differential pressure, which complicates the accurate measurement of mechanical loads like tensile, compressive, and torque loading due to hydraulic forces.
Innovation Solution
A load cell system with a chassis, sensing element, and pressure compensating piston, where the sensing element is isolated from differential pressures through a sealed chamber and strategically placed seal points, allowing for accurate measurement of mechanical loads regardless of hydraulic forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used to monitor forces in tubular components, then mechanical loads can be measured, but differential pressure generates hydraulic forces that affect measurement accuracy
Solution Approach 1:
The load cell is divided into separate pressure zones using seal points that create distinct chambers. The sensing element is isolated in a chamber separated from the tubular interior by seal points, allowing differential pressure to act on dedicated compensation areas rather than directly on the measurement mechanism.
Solution Approach 2:
A pressure compensating piston is introduced as an intermediary element between the sensing element and the differential pressure. The piston has designated pressure compensation areas that receive hydraulic forces and transfer them to the chassis, preventing these forces from reaching the sensing element while maintaining measurement accuracy.
2Ease of operation
If the sensing element is exposed to the tubular interior, then direct force measurement is possible, but hydraulic forces from differential pressure interfere with the measurement
Solution Approach 1:
The sensing element is extracted from direct exposure to the tubular interior by enclosing it in a sealed chamber. The chamber is isolated from the tubular interior through seal points, removing the harmful differential pressure environment while preserving the ability to measure mechanical loads through the chassis connection.
Solution Approach 2:
The sealed chamber acts as an intermediary barrier between the sensing element and the tubular interior. This intermediate space allows the sensing element to function in a protected environment while still responding to mechanical loads transmitted through the chassis, separating the measurement function from the harsh pressure environment.
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 system effectively separates and measures mechanical forces from hydraulic forces, providing accurate data on tensile, compressive, and torque loads, enhancing the reliability of downhole operations like drilling and milling by compensating for differential pressures.
Implementation Method 1
Pressure balanced flow through load measurement
Implementation Method 2
A plurality of seal points is created by seals between the load cell components. The seal points are located in a manner which isolates the sensing element from the effects of differential pressures
Data Source
AI summary
A technique facilitates measuring loads while compensating for the effects of differential pressure. The technique utilizes a load cell comprising a chassis and a sensing element mounted on the chassis. A housing encloses the sensing element in a chamber formed between the chassis and the housing. The housing is connected to the chassis in a manner to transfer loading, e.g. compressive, tensile, and/or torque loading. A pressure compensating piston is positioned within an interior of the chassis and the housing. A plurality of seal points is located in a manner which isolates the sensing element from the effects of differential pressures between the interior and an exterior of the load cell.