Two-Stage Solvent Injection for Heavy Oil Recovery
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Solution Overview
Problem
Current methods for heavy oil recovery, such as Steam Assisted Gravity Drainage (SAGD), face challenges with high energy consumption, solvent retention, and limited recovery rates, necessitating the development of more efficient techniques to reduce solvent and steam usage while enhancing oil production.
Innovation Solution
The Expanding Solvent Steam-Assisted Gravity Drainage (ES-SAGD) process involves a two-stage solvent injection strategy, where a lighter solvent is injected initially for a shorter period, followed by a heavier solvent for a longer period, to optimize oil recovery and reduce solvent retention, thereby improving the steam-to-oil ratio and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional SAGD process is used to recover heavy oil, then oil production rate is improved, but energy consumption and solvent retention increase
Solution Approach 1:
The patent divides the solvent injection process into two distinct stages: a first stage using a first solvent and a second stage using a second solvent. This segmentation allows optimization of each stage independently, reducing overall energy consumption while maintaining high oil production rates. The first solvent stage prepares the reservoir by initial mobilization, while the second solvent stage completes the recovery with reduced energy input.
Solution Approach 2:
The patent changes the parameter of solvent type between two stages, using different solvents with different properties optimized for different phases of the recovery process. This parameter change enables more efficient mass transfer and reduces the total energy required for heavy oil mobilization and production.
2Device complexity
If single solvent injection is used, then process simplicity is maintained, but solvent retention and recovery efficiency worsen
Solution Approach 1:
The patent segments the solvent injection into two stages with different solvents, where the first solvent performs initial mobilization and the second solvent completes the extraction. This segmentation reduces overall solvent retention in the reservoir by optimizing the function of each solvent stage, thereby reducing substance loss while maintaining operational simplicity.
Solution Approach 2:
The patent implements a two-stage process where the first solvent is effectively discarded after initial mobilization, and the second solvent is used for efficient recovery. This approach minimizes solvent retention by ensuring that the final recovery stage uses a solvent that is optimized for extraction efficiency, thereby reducing the amount of solvent left in the reservoir.
3Productivity
If longer solvent injection period is used, then recovery rate is improved, but steam-to-oil ratio and energy efficiency worsen
Solution Approach 1:
The patent divides the injection period into two segments with different solvents and durations. The first stage uses a first solvent for a shorter period to achieve initial mobilization, and the second stage uses a second solvent to complete recovery. This segmentation achieves high recovery rates without requiring prolonged injection periods, thereby maintaining favorable steam-to-oil ratios and energy efficiency.
Solution Approach 2:
The patent implements periodic action by alternating between two solvent injection stages with different characteristics. This periodic approach allows the system to achieve complete recovery through two distinct phases rather than continuous single-solvent injection, optimizing the steam-to-oil ratio and energy efficiency while maintaining high productivity.
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 results in increased heavy oil mobility, reduced solvent retention, and enhanced recovery rates, improving the economic viability of the process by minimizing solvent and steam usage, and achieving better exploitation of heavy oil and oil sands reservoirs.
Implementation Method 1
a lighter solvent is injected initially for a shorter period, followed by a heavier solvent for a longer period, to optimize oil recovery
Implementation Method 2
two-stage solvent injection strategy... to optimize oil recovery and reduce solvent retention
Implementation Method 3
Steam Assisted Gravity Drainage (SAGD)... injecting steam and a first solvent into said injection well... injecting steam and a second solvent
Implementation Method 4
Steam Assisted Gravity Drainage uses at least two horizontal wells--one at the bottom of the formation and another about 5 meters above it. Steam is injected into the upper well, the heat melts the heavy oil, which allows it to drain by gravity into the lower well
Data Source
AI summary
A steam-assisted gravity drainage method is described that includes a two stage solvent injection scheme, wherein steam plus solvent injection is followed by steam plus heavier-solvent injection. The two solvent injections improve recoveries of both the heavy oil and the injected solvent while limiting steam requirements, thus improving the economics of the method.