Downhole Ion-Selective Sensor Array for Water Source Identification
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Solution Overview
Problem
In oil production wells, identifying the source of increasing water production is challenging, as it often originates from specific perforations, leading to inefficiencies and increased costs due to unnecessary water disposal.
Innovation Solution
Deploying an ion-specific sensor downhole to measure ion concentrations at multiple positions, using ion-selective field effect devices to differentiate between fluids and locate the source of undesirable fluids, allowing for targeted corrective action such as sealing off problematic perforations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional flow meters and production logging tools are used, then fluid production can be measured, but the source of increasing water production cannot be identified
Solution Approach 1:
The patent divides the wellbore into multiple depth segments using an array of ion-selective sensors positioned at different depths. Each sensor measures ion concentration in its local zone, allowing the system to segment the water production source identification into discrete depth intervals. This segmentation enables pinpointing the exact perforation interval contributing to water production.
Solution Approach 2:
The patent introduces ion concentration as an intermediary parameter to indirectly identify fluid sources. Instead of directly detecting water origin, the system measures ion concentrations (particularly chloride and bromide ions) that serve as fingerprints for different fluid sources. This intermediary measurement allows differentiation between formation water, injected water, and oil phase fluids.
2Measurement precision
If ion-selective sensors are deployed to identify fluid sources, then source location precision is improved, but device complexity increases
Solution Approach 1:
The patent employs ion-selective field-effect transistor (ISFET) sensors that serve multiple functions: they measure ion concentration, detect fluid type, and provide depth-positioned information. Each sensor in the array is a multi-functional element that simultaneously performs chemical sensing and spatial localization, reducing the need for separate measurement systems.
Solution Approach 2:
The patent replaces complex mechanical sampling systems and laboratory analysis with solid-state ion-selective field-effect transistor sensors. These electronic sensors directly measure ion concentrations in situ downhole, eliminating the need for mechanical fluid sampling, transport, and external analysis equipment.
3Measurement precision
If multiple ion concentration measurements are taken at different depths, then water source identification is improved, but measurement time and cost increase
Solution Approach 1:
The patent performs preliminary characterization of ion concentrations in different fluid types during the survey operation itself. By measuring ion concentrations at multiple depths simultaneously with the sensor array, the system preliminarily identifies which depth intervals contribute water production, enabling rapid source localization without requiring multiple separate survey passes.
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
Effectively identifies the source of water production issues, enabling precise intervention to reduce water flow and minimize costs associated with unwanted water disposal by pinpointing and sealing off specific perforations.
Implementation Method 1
ion specific field effect device
Data Source
AI summary
In a particular embodiment, a method is disclosed for determining a source of a fluid downhole. The method includes deploying an ion selective sensor downhole, exposing the fluid to the ion selective sensor downhole, measuring an ion concentration at different places within the fluid and using that information to identify a source of the fluid from the ion concentration profile. In another particular embodiment, an apparatus is disclosed for estimating a source of a fluid. The apparatus contains a tool deployed in a well bore, an ion selective sensor in the tool, a processor in communication with the ion selective sensor and a memory for storing an output from the ion selective sensor.