Nonionic Surfactant Blend for Tight Oil Recovery
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Solution Overview
Problem
Current enhanced oil recovery methods face challenges in accessing tight oil formations due to low permeability in rock formations like shale and tight sandstone, necessitating an effective oil displacement agent for improved recovery in Changqing reservoirs.
Innovation Solution
Development of a nonionic long chain surfactant with specific molecular formulas, combined with anionic surfactants and dissolved in formation water with optional salt and polymer solutions, to lower interfacial tension and enhance oil solubilization and wettability, facilitating improved oil recovery through surfactant-polymer and low tension gas flooding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydraulic fracturing is utilized to create adequate permeability in tight oil formations, then access to trapped oil is improved, but the complexity and cost of the recovery process increases
Solution Approach 1:
The patent changes the chemical parameters of the flooding process by using nonionic surfactants with extended chains (EO/PO ratios of 0.5-2.0) to achieve ultra-low interfacial tension (10^-3 to 10^-5 mN/m). This chemical parameter change enables effective oil displacement in tight formations without requiring hydraulic fracturing, thus improving oil recovery while avoiding the complexity of fracturing operations.
Solution Approach 2:
The patent employs composite surfactant systems combining nonionic surfactants (with specific EO/PO chain structures) and anionic surfactants in optimized ratios (90:10 to 50:50 by weight). This composite approach creates a synergistic effect that achieves superior oil displacement efficiency in tight formations, providing an alternative to the mechanically complex hydraulic fracturing method.
2Productivity
If conventional surfactants are used for oil displacement, then some oil recovery is achieved, but interfacial tension remains too high for effective recovery in tight formations
Solution Approach 1:
The patent fundamentally changes the surfactant molecular structure by incorporating extended polyethylene oxide (EO) and polypropylene oxide (PO) chains with specific EO/PO ratios (0.5-2.0). This structural parameter change enables the surfactant to reduce interfacial tension to ultra-low levels (10^-3 to 10^-5 mN/m), overcoming the limitation of conventional surfactants that leave interfacial tension too high for effective tight formation recovery.
Solution Approach 2:
The patent optimizes the local molecular structure by positioning specific hydrophilic (EO) and lipophilic (PO) segments in defined ratios along the surfactant chain. This local structural optimization allows the surfactant to effectively interact with both oil and water phases at the interface, achieving ultra-low interfacial tension that conventional surfactants cannot achieve.
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 surfactant blend effectively lowers interfacial tension, improves solubility, and enhances oil recovery, achieving up to 98% residual oil recovery in core flooding tests, demonstrating potential for enhanced oil recovery in tight oil reservoirs.
Implementation Method 1
The surfactant blend effectively lowers interfacial tension
Implementation Method 2
improves solubility
Implementation Method 3
improves oil solubilization
Implementation Method 4
enhances wettability
Data Source
AI summary
Some reservoirs have tight oil formations, such as the Changqing reservoir. The surfactant polymer flooding and low tension gas flooding are two potential chemical flooding methods for use in tight oil formations. In these methods, an oil displacement agent, or surfactant, is added. Nonionic surfactants with extended chains (by propylene oxide and ethylene oxide) from dialkyl alcohols or dialkyl amines were tested. A synergistic blend of surfactants was developed between the nonionic surfactants and anionic surfactants that lowers interfacial tension and improves surfactant solubility in water and oil.