Fiberoptic Tuned-Induction Sensors for Downhole EM Monitoring
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Solution Overview
Problem
Current electromagnetic tomography for monitoring fluid distributions in oilfield reservoirs is limited by the lack of sensitive and cost-effective transmitter and sensor designs that can withstand long-term deployment in hostile downhole conditions.
Innovation Solution
The development of fiberoptic tuned-induction sensors and systems that include coil antennas, piezoelectric elements, and optical fibers, which convert electromagnetic fields into strain changes in the optical fibers, allowing for sensitive and durable monitoring of electromagnetic fields in downhole environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic tomography is used for monitoring fluid distributions, then fluid distribution mapping capability is improved, but sensor sensitivity and durability in downhole conditions deteriorate
Solution Approach 1:
The patent replaces traditional electrical/electronic sensor systems with a fiberoptic-based sensing system. The coil antenna detects electromagnetic fields and converts them to mechanical strain in the optical fiber through a piezoelectric element, eliminating the need for electrical components in the harsh downhole environment. This substitution provides both the required measurement precision for fluid distribution mapping and the reliability needed for long-term downhole deployment.
Solution Approach 2:
The sensor employs a composite structure combining a coil antenna, piezoelectric element, and optical fiber. This composite design integrates the electromagnetic field detection capability of the coil with the strain-to-optical-signal conversion of the piezoelectric-optical fiber system, achieving both high sensitivity for fluid distribution monitoring and durability for downhole conditions.
2Measurement precision
If traditional electromagnetic sensors are deployed in downhole environments, then fluid monitoring capability is achieved, but sensitivity and cost-effectiveness deteriorate
Solution Approach 1:
The patent replaces expensive, sensitive electrical sensor components with a robust fiberoptic-based system. The optical fiber and piezoelectric element combination provides high measurement precision for fluid monitoring while being more cost-effective for downhole deployment, as it eliminates the need for complex electrical shielding, power supply, and signal conditioning electronics in the harsh environment.
3Duration of action of stationary object
If long-term deployment in hostile downhole conditions is required, then operational duration is improved, but sensor sensitivity and cost-effectiveness deteriorate
Solution Approach 1:
The patent replaces traditional electrical sensors with a fiberoptic-based system that is inherently more durable for long-term downhole deployment. The optical fiber and piezoelectric element combination maintains high sensitivity for electromagnetic field detection while withstanding the harsh downhole environment over extended operational periods, eliminating the sensitivity degradation that plagues electrical components in such conditions.
Solution Approach 2:
The composite structure of coil antenna, piezoelectric element, and optical fiber provides both the sensitivity required for accurate fluid monitoring and the durability needed for long-term deployment. The piezoelectric element acts as a robust transducer that converts electromagnetic field changes to mechanical strain on the optical fiber, maintaining measurement precision throughout the operational lifetime in hostile downhole conditions.
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
These sensors provide enhanced sensitivity and durability, enabling effective long-term monitoring of fluid distributions and reservoir conditions, optimizing production and injection strategies while withstanding harsh downhole conditions.
Implementation Method 1
a coil antenna that detects an electromagnetic field and provides a response signal
Implementation Method 2
a piezoelectric element that deforms in response to the filtered signal
Implementation Method 3
an optical fiber that is mechanically coupled to the piezoelectric element, wherein the piezoelectric element modifies a strain of the optical fiber in accordance with the filtered signal
Data Source
AI summary
A method of sensing electromagnetic (EM) fields downhole may include filtering a voltage signal induced in a coil antenna by an EM field to produce a filtered signal, said filtering being performed by a resonance tuning filter, and applying the filtered signal to a piezoelectric element to modify a strain of an optical fiber. A sensing system may include a cable deployed downhole and coupled to an interface unit. The cable has an optical fiber coupled to an array of downhole sensors, each sensor having a coil antenna coupled by a resonance tuning filter to a piezoelectric element that modifies a strain in the optical fiber in accordance with a signal induced in the coil antenna by an electromagnetic field. The interface unit measures a backscattered light to monitor the signal from each sensor in the array.