Polyacrylamide Gel Plugs for Water Control
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Solution Overview
Problem
Excessive water production in subterranean formations reduces hydrocarbon recovery and increases operational costs due to the need for environmentally hazardous chromium-based gel systems, which are not suitable for all temperature ranges and regulatory environments.
Innovation Solution
A method involving the use of a low molecular weight polyacrylamide and a multi-aldehyde crosslinking agent to form a fluid impermeable plug in porous formations, reducing permeability and minimizing fluid loss, with glyoxal and glutaraldehyde being preferred crosslinking agents for their environmental friendliness and low thermal activation requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If chromium-based crosslinkers are used to form gel systems for controlling water production, then rapid gelation occurs in low temperature reservoirs (less than 12 hours), but environmental regulations prohibit their use in many areas
Solution Approach 1:
The patent extracts and removes the harmful chromium-based crosslinking agents from the gel system while retaining the essential gelation function. This is achieved by substituting chromium crosslinkers with alternative crosslinking mechanisms that do not involve toxic metals, thereby eliminating environmental harm while maintaining water production control capabilities
Solution Approach 2:
The patent employs biodegradable polymer gels that can naturally degrade over time, replacing permanent chromium-based systems. These short-lived gel structures perform their water control function temporarily and then break down into harmless components, avoiding long-term environmental contamination while still providing effective gelation at low temperatures
2Object-generated harmful factors
If gel systems are used to plug high permeability channels and reduce water flow, then water production is controlled, but hydrocarbon production is decreased due to water taking the place of other fluids
Solution Approach 1:
The patent applies gelation selectively to specific high-permeability channels and thief zones where water flow is excessive, rather than uniformly treating the entire formation. This localized approach allows hydrocarbons to continue flowing through untreated zones while water is controlled in problematic areas, maintaining overall productivity while achieving water reduction
Solution Approach 2:
The patent employs dynamic gel systems that can adjust their properties in response to changing flow conditions and temperature gradients within the formation. These gels can reversibly change their permeability control characteristics, allowing them to adapt to varying production rates and maintain optimal balance between water control and hydrocarbon flow over time
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 system effectively reduces fluid permeability in subterranean formations, enhancing hydrocarbon recovery by forming a stable, environmentally friendly gel barrier that prevents water inflow, even at temperatures up to 150°F, without the need for additional chemicals or additives.
Implementation Method 1
pumping into the reservoir or a void a crosslinkable fluid comprising a low molecular weight polyacrylamide and a multi-aldehyde crosslinking agent and forming a fluid impermeable reaction product from the polyacrylamide and crosslinking agent
Implementation Method 2
gel systems have been used to control water production and reduce the flow of produced water through high permeability channels within the formation. Such gellants plug pore spaces of the formation and prevent fluid movement, often by means of a controlled, delayed chemical reaction
Data Source
AI summary
Water and gas flow into a subterranean reservoir may be reduced by pumping into the reservoir a multi-aldehyde crosslinking agent and a low molecular weight polyacrylamide capable of crosslinking with the crosslinking agent. The reaction product forms a gel plug impermeable to water and gas.