Mixing Model for Produced Water Source Identification
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Solution Overview
Problem
Distinguishing between produced waters and in-situ water formation is challenging due to the injection of aquifer waters and seawater, as chemical analyses alone, such as chloride concentration measurements, are often unsuccessful in distinguishing water sources, especially in mixtures with different salinity levels.
Innovation Solution
Measuring the 18O/16O ratio (δ18O) and chloride concentration in seawater, aquifer water, and original reservoir water samples, and using these measurements to create a mixing model that determines the proportions of seawater, aquifer water, and original reservoir water in a produced water sample, accounting for the distinct geochemistry and stability of oxygen isotopes and chloride concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chemical analyses alone (e.g., chloride concentration) are used to distinguish water sources, then the method is simple and quick, but the measurement precision is insufficient to distinguish water sources in mixtures with different salinity levels
Solution Approach 1:
The patent combines multiple measurement parameters (chloride concentration and oxygen isotope ratio δ18O) into a unified mixing model approach. By merging these two independent measurements, the system achieves superior water source distinction accuracy compared to chloride alone, while maintaining operational feasibility through integrated analysis.
Solution Approach 2:
The patent introduces a new measurement parameter (oxygen isotope ratio δ18O) alongside the traditional chloride concentration measurement. This parameter change enables differentiation of water sources with similar salinity levels that cannot be distinguished by chloride alone, thereby improving measurement precision for water source identification.
2Measurement precision
If multiple measurements (δ18O and chloride concentration) are made to improve water source distinction, then the measurement precision improves, but the analysis time and cost increase
Solution Approach 1:
The patent performs preliminary measurements of δ18O and chloride concentration on source water samples (seawater, aquifer water, reservoir water) before production operations. By establishing baseline isotopic and chemical signatures in advance, the system enables rapid mixing model calculations during production, reducing real-time analysis time while maintaining high precision.
Solution Approach 2:
The mixing model uses measured δ18O and chloride values to calculate water source proportions, providing feedback that identifies breakthrough of injection water and monitors water flooding. This feedback mechanism enables timely operational decisions without requiring continuous complex analysis, effectively managing analysis time.
3Reliability
If chemical reactions caused by mixing of incompatible waters occur, then the geochemistry becomes altered, but the oxygen isotope ratios remain stable and reliable for mixing models
Solution Approach 1:
The patent uses oxygen isotope ratio (δ18O) as an intermediary tracer that remains stable despite chemical reactions. While chloride concentration and other chemical parameters may be altered by mixing and chemical reactions, the oxygen isotope ratio serves as a reliable mediator that preserves the original water source signatures, enabling accurate mixing model calculations even when water composition changes.
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
Enables accurate determination of water sources in produced water samples, facilitating operational decisions, predicting scaling problems, and identifying breakthroughs in injection water, thereby reducing time and costs in drilling and production operations.
Implementation Method 1
An 18O/16O ratio (δ18O) and a chloride concentration are measured for a seawater sample, an aquifer water sample, and an original reservoir water sample and are used to make a mixing model
Implementation Method 2
Chloride accounts for over 90% of the total anion charge in many water samples and can be accurately measured and the concentration is not readily altered
Data Source
AI summary
The disclosure relates to methods for determining an amount of seawater, an amount of aquifer water, and an amount of original reservoir water in a produced water sample using oxygen isotope ratios and chloride concentrations. An 18O/16O ratio (δ18O) and a chloride concentration are measured for a seawater sample, an aquifer water sample, and an original reservoir water sample and are used to make a mixing model. δ18O and a chloride concentration are measured in a produced water sample and the mixing model can be used to determine the amounts of each constituent in the produced water sample.