Polyelectrolyte Complex Delayed Gelling Agents
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Solution Overview
Problem
Current methods for reducing permeability in subterranean zones using water-soluble polymers in oil and gas fields lack effective control over gelation time, leading to premature gel formation.
Innovation Solution
A composition comprising a polyelectrolyte complex, specifically a polyanion complexed with a polycation, is used as a gelling agent, which forms nanoparticles that slowly cross-link with a water-soluble polymer like Alcoflood®, delaying gelation for several days.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cross-linking agents are used to reduce permeability in subterranean zones, then gelation occurs rapidly, but control over gelation time is lost and premature gel formation occurs
Solution Approach 1:
The patent introduces a metal ion chelator as an intermediary substance that mediates between the cross-linking agent and the polymer. The chelator temporarily binds metal ions, preventing premature cross-linking, and then releases them in a controlled manner to initiate gelation at the desired time, thus providing reliable control over gelation time while preventing premature gel formation
Solution Approach 2:
The patent applies preliminary action by pre-mixing the cross-linking agent with a metal ion chelator before injection into the subterranean zone. This preliminary complexation prevents premature gelation during injection and transport, allowing the composition to reach the target zone before gelation is initiated through controlled release of the chelator
2Duration of action of moving object
If gelation is delayed for prolonged permeability control, then permeability reduction is maintained longer, but the gelling agent must remain stable and active for an extended period
Solution Approach 1:
The metal ion chelator serves as a stability intermediary that keeps the gelling system stable during the delay period by sequestering metal ions. When the chelator degrades or releases ions, it reliably initiates cross-linking, ensuring the gelling agent remains stable throughout the extended period while maintaining readiness to gel when needed
Solution Approach 2:
The patent utilizes parameter changes in the chelator's degradation or binding affinity over time to control gelation. The chelator's properties change gradually, allowing the system to remain stable for an extended duration and then transition to gelation, providing both prolonged control and reliable activation
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 polyelectrolyte complex effectively controls and delays gelation in subterranean zones, allowing for prolonged control over permeability reduction, as demonstrated by the slow gel formation over several days, contrasting with existing rapid gelation issues.
Implementation Method 1
a polyelectrolyte complex, specifically a polyanion complexed with a polycation, is used as a gelling agent, which forms nanoparticles that slowly cross-link with a water-soluble polymer
Data Source
AI summary
A gel-forming composition for reducing the permeability of a subterranean formation or zone comprising a water soluble polymer (e.g., Alcoflood® 935) and a polyelectrolyte gelling agent comprising a polycation (e.g., polyalkylene imine) and a polyanion (e.g., dextran sulfate) is provided. The gel-forming composition is used to delay gelation in the subterranean formation.