Delayed Gelation Polymer Injection for Reservoir Penetration
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Solution Overview
Problem
Current polymer systems used in enhanced oil recovery gel too quickly, limiting their deep penetration into reservoirs and reducing the effectiveness of thief zone blocking, necessitating a method to delay gelation for several days to weeks and ensure stability in brine environments.
Innovation Solution
A method involving the sequential injection of carboxylated polymers, gel-delaying polymers, and crosslinkers into an in-line mixer, allowing for delayed gel formation by avoiding the creation of a separate nanogel, with specific examples using polyaspartate and polyvinyl alcohol succinate to extend gelation times to several days or more, suitable for high temperatures and brine stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If crosslinking agents such as chromic acetate are used to gel polymers, then gelation occurs quickly to block thief zones, but the polymer gels too quickly to penetrate deep into the reservoir
Solution Approach 1:
A gel-delaying polymer is introduced as an intermediary substance that temporarily prevents crosslinking. This polymer is injected first to occupy the thief zone, then a crosslinking agent is injected which is delayed from reacting by the presence of the gel-delaying polymer, allowing deep penetration before gelation occurs
Solution Approach 2:
The gel-delaying polymer is injected in advance before the crosslinking agent to prepare the thief zone for blocking. This preliminary action ensures that when the crosslinking agent arrives, the polymer is already in position but temporarily prevented from gelling, allowing deep penetration followed by controlled gelation
2Productivity
If viscosity is increased to improve sweep efficiency, then oil displacement improves, but pumping becomes difficult and gelation occurs too quickly
Solution Approach 1:
The polymer solution is injected at lower viscosity in advance to facilitate easy pumping and deep penetration. The gelation process is then triggered after penetration is achieved, increasing viscosity in situ to improve sweep efficiency without the pumping difficulties associated with high-viscosity materials
Solution Approach 2:
The system transitions from a low-viscosity state during injection to a high-viscosity gel state after placement. This dynamic change allows the material to be pumped easily initially, then transform to provide the necessary sweep efficiency once in the reservoir
3Length of moving object
If gelation time is extended to allow deep penetration, then reservoir coverage improves, but the polymer remains in flowing state too long reducing blocking effectiveness
Solution Approach 1:
The gel-delaying polymer acts as a temporary intermediary that prevents premature gelation during penetration. Once the crosslinking agent is injected and the gel-delaying polymer has served its purpose, the intermediary effect wears off and gelation proceeds, ensuring both deep penetration and effective blocking
Solution Approach 2:
The system controls the gelation parameter by introducing a delaying agent that temporarily alters the gelation kinetics. After penetration is achieved, the parameter changes back to normal gelation rate, ensuring the polymer gels at the right time and place for effective thief zone blocking
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
This approach significantly extends gelation times, allowing for deeper reservoir penetration and improved sweep efficiency by maintaining the polymers in a flowing state for longer, enhancing oil recovery and stability in harsh reservoir conditions.
Implementation Method 1
The use of ligands complexed with multivalent cations such as Al(III), Cr(III), Ti(IV) and Zr(IV) to crosslink partially hydrolyzed polyacrylamides has been a common practice to slow the rate of reactions of these cations with HPAM.
Implementation Method 2
partially hydrolyzed polyacrylamide (HPAM) crosslinked with Cr (III) gels have been widely used for water shutoff and sweep improvement in field applications
Data Source
AI summary
The disclosure is directed to methods and compositions delaying the gelation of polymers in water flooding by sequentially or co-injecting a carboxylate-containing polymer solution, a gel-delaying polymer, and gelation agent into a hydrocarbon reservoir. Delays of weeks are observed.