Surfactant Injection Sequence for High-Salinity Reservoirs
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Solution Overview
Problem
Current enhanced oil recovery (EOR) methods require large quantities of chemicals, particularly surfactants, which are inefficient in high-salinity subterranean formations due to retention in reservoir matrices, leading to increased costs.
Innovation Solution
A method involving the successive injection of three solutions into a subterranean formation: a first solution with a lower salinity than the formation water to pre-treat the reservoir, a second solution with a surfactant and polymer at optimal salinity for surfactant efficiency, and a third solution with a lower salinity than the first two to spread the surfactant and maintain optimal salinity across the reservoir.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If surfactants are used to mobilize residual hydrocarbons in high-salinity formations, then hydrocarbon recovery efficiency is improved, but surfactant retention in reservoir matrices increases leading to loss of efficiency and higher costs
Solution Approach 1:
A preflush solution is injected before the surfactant to modify the reservoir environment and reduce surfactant retention. The preflush prepares the formation by adjusting salinity and reducing factors that cause surfactant adsorption, allowing subsequent surfactant injection to be more efficient with less loss.
Solution Approach 2:
The salinity of injected solutions is optimized to match the optimal salinity for surfactant performance. By controlling and adjusting the salinity parameter of injection brines, the method maintains surfactant solubility and reduces partitioning into oil phases, thereby minimizing surfactant retention while maximizing hydrocarbon recovery.
2Productivity
If larger amounts of surfactants are used to overcome retention losses, then hydrocarbon recovery is improved, but process costs increase
Solution Approach 1:
The preflush treatment modifies reservoir conditions to reduce surfactant retention before the main surfactant injection, ensuring that surfactant is not wasted on adsorption but effectively used for hydrocarbon mobilization, thereby reducing the total quantity needed.
Solution Approach 2:
By optimizing injection solution salinity to match surfactant requirements, the method maximizes surfactant efficiency and minimizes loss, reducing the overall quantity of surfactant needed to achieve target recovery levels.
3Loss of substance
If alkali agents are added to decrease surfactant retention, then surfactant efficiency is improved, but water-softening systems are required increasing complexity
Solution Approach 1:
The method optimizes the salinity parameter of injection brines to reduce surfactant retention without adding alkali agents. By carefully controlling ionic composition and salinity, the method achieves reduced surfactant loss through parameter optimization rather than chemical additives, avoiding the need for water-softening systems.
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 method allows for efficient and cost-effective hydrocarbon recovery by reducing surfactant retention, minimizing chemical usage, and maintaining optimal salinity conditions throughout the reservoir, thereby enhancing sweeping efficiency and hydrocarbon extraction.
Implementation Method 1
injecting a volume of a first solution comprising polymer into the subterranean formation, the first solution having a salinity which is lower than the salinity of water in the subterranean formation
Implementation Method 2
surfactants are often used for the mobilization of residual hydrocarbons, as they tend to generate a sufficiently low hydrocarbon/water interfacial tension which makes it possible to overcome capillary forces and allow hydrocarbons to flow
Implementation Method 3
A polymer can also be added to the water to increase its viscosity and increase its sweep efficiency in recovering hydrocarbons
Implementation Method 4
injecting a volume of a third solution comprising polymer into the subterranean formation, the third solution having a salinity which is lower than the salinity of the first and the second solutions
Data Source
Figure 1~2
AI summary
The present invention relates to a method for extracting hydrocarbons from a subterranean formation, comprising: injecting a volume of a first solution comprising polymer into the subterranean formation, the first solution having a salinity which is lower than the salinity of water in the subterranean formation; injecting a volume of a second solution comprising at least one surfactant and polymer into the subterranean formation, the second solution having substantially the same salinity as the first solution; injecting a volume of a third solution comprising polymer into the subterranean formation, the third solution having a salinity which is lower than the salinity of the first and the second solutions;and collecting hydrocarbons displaced by the injected solutions.