pH-Responsive Polymeric Microparticles for Reservoir Thief Zone Blocking
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Solution Overview
Problem
In hydrocarbon recovery processes, particularly in CO2 or CO2 Water Alternating Gas flooding, high permeability zones (thief zones) divert injected fluids away from lower permeability zones, leading to inefficient hydrocarbon recovery due to the heterogeneity of reservoir rock strata and limitations in existing methods for modifying permeability at low pH.
Innovation Solution
Development of expandable crosslinked polymeric microparticles with labile internal crosslinks that expand under low pH conditions, allowing efficient propagation through the reservoir matrix and impeding fluid flow to divert injected fluids into less swept zones, without requiring special carrier fluids or being sensitive to salinity changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional permeability modification methods are used in high permeability thief zones, then fluid flow control is achieved, but the methods fail at low pH conditions and cannot effectively divert fluids into less swept zones
Solution Approach 1:
The patent applies parameter changes by using pH-responsive crosslinking chemistry. The crosslinking reaction is designed to occur specifically at low pH conditions (acidic environment), transforming the polymer from a linear chain to a crosslinked gel structure. This parameter change (pH-triggered crosslinking) enables the system to adapt to acidic reservoir conditions while maintaining reliable permeability modification effectiveness.
Solution Approach 2:
The patent introduces an intermediary substance - a pH-sensitive crosslinking agent or functional group within the polymer structure. This intermediary mediates between the low pH environment and the desired gel formation, enabling the crosslinking reaction to proceed selectively under acidic conditions without requiring additional chemicals or altering the natural reservoir chemistry.
2Productivity
If injected fluids are diverted away from thief zones, then hydrocarbon recovery efficiency is improved, but existing methods cannot ensure uniform sweep of lower permeability zones
Solution Approach 1:
The patent applies dynamics by creating a time-dependent gel formation process. The polymer is injected in a soluble, linear form that can flow freely through the reservoir. Over time, the pH-triggered crosslinking occurs in-situ, transforming the polymer into a crosslinked gel structure that blocks flow paths. This dynamic transformation ensures uniform distribution of the blocking agent throughout the reservoir, achieving reliable and uniform fluid sweep across both high and low permeability zones.
3Ease of operation
If special carrier fluids or high salinity solutions are used, then polymer propagation through reservoir is enhanced, but the system becomes more complex and requires additional chemical additives
Solution Approach 1:
The patent applies self-service by designing the polymer system to utilize the natural low pH conditions of the reservoir environment for its own propagation and crosslinking. The polymer contains pH-sensitive functional groups that automatically trigger crosslinking when exposed to acidic conditions, eliminating the need for external pH adjustment chemicals, special carrier fluids, or high salinity solutions. The system serves itself by using the reservoir's inherent chemistry to achieve both propagation and gel formation.
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 microparticles effectively modify permeability and enhance hydrocarbon recovery by allowing deep penetration and expansion within the reservoir, improving the mobilization and recovery rate of hydrocarbons, even in challenging pH conditions, and reducing the need for costly well intervention methods.
Implementation Method 1
expandable crosslinked polymeric microparticles with labile internal crosslinks that can propagate through the reservoir pore structure, expanding under low pH conditions
Data Source
AI summary
A composition comprising crosslinked expandable polymeric microparticles capable of hydrolysis at or below neutral pH and a method of modifying the permeability to water of a subterranean formation by introducing such compositions into the subterranean formation is disclosed and claimed. This invention further relates to compositions and methods for the recovery of hydrocarbon fluids from a subterranean reservoir or formation subjected to CO2 or CO2 Water Alternating Gas flooding at low pH and increases the mobilization and/or recovery rate of hydrocarbon fluids present in the subterranean formations.