In Situ CO2 Foam Generation for Reservoir Sequestration
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Solution Overview
Problem
Traditional CO2 sequestration processes in depleted oil and gas reservoirs have low efficiency due to the low specific gravity of CO2, causing it to migrate upwards and collect at the top of the reservoir, reducing its dissolution into formation fluids and resulting in low trapping efficiency.
Innovation Solution
Introducing a surfactant solution into the upper portion of the reservoir and CO2 into the lower portion, allowing them to intermingle in situ and form a CO2-based foam, which increases the apparent viscosity of CO2, reducing its mobility and enhancing sequestration efficiency by maintaining a pressure below the fracture pressure and using separate or adjacent injection wells to avoid pressure gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CO2 is injected into the reservoir, then CO2 sequestration is achieved, but CO2 migrates upwards due to low specific gravity and collects at the top of the reservoir, reducing dissolution into formation fluids and resulting in low trapping efficiency
Solution Approach 1:
A surfactant solution is introduced as an intermediary substance that interacts with CO2 to form a foam. This foam acts as a mediator that modifies CO2's physical properties, increasing its apparent viscosity and reducing its mobility. The surfactant solution enables CO2 to be retained in the reservoir by transforming it from a free-gas phase that migrates upward into a foam structure that remains distributed throughout the reservoir pore space.
Solution Approach 2:
The physical parameters of CO2 are changed by transforming it from a free gas phase into a foam phase. This phase transformation alters CO2's apparent viscosity, density, and mobility characteristics. The foam structure increases CO2's effective viscosity and reduces its buoyancy-driven upward migration, thereby improving distribution stability and trapping efficiency throughout the reservoir.
2Ease of operation
If surfactant solution and CO2 are co-injected through the same well, then injection operation is simplified, but pressure gradients cause blockage at injection points and reduce injectivity
Solution Approach 1:
The injection process is segmented into two separate operations: first, the surfactant solution is injected through one well to establish foam-generating zones in the reservoir; second, CO2 is injected through a separate well to form foam in situ. This segmentation prevents the pressure gradient blockage problem by avoiding simultaneous injection of both components through the same well, while still achieving the desired foam formation for CO2 sequestration.
3Reliability
If reservoir pressure is increased to maintain CO2 in supercritical state, then CO2 density increases improving sequestration, but pressure approaches fracture pressure reducing reservoir safety
Solution Approach 1:
The patent utilizes phase transitions of CO2 by allowing it to transition between supercritical and gaseous states. CO2 is injected in a supercritical state for efficient sequestration, then transitions to a gaseous state when forming foam with the surfactant solution. This phase transition mechanism enables effective CO2 retention without requiring the reservoir pressure to be maintained at unsafe levels接近 fracture pressure.
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 increases CO2 sequestration efficiency by prolonging its interaction with formation water, reducing upward mobility, and preventing blockage at injection points, allowing for greater CO2 storage and retention in the reservoir.
Implementation Method 1
the CO2 and surfactant solution migrate away from the wells and intimately intermingle to form CO2-based foam in situ
Implementation Method 2
A surfactant solution (foaming agent) may also be injected with the CO2 to generate a foam using the CO2
Implementation Method 3
due to the low specific gravity of CO2, causing it to migrate upwards and collect at the top of the reservoir
Implementation Method 4
maintaining a reservoir pressure at a value less than the fracture pressure of the reservoir utilizing a pressure relief well
Data Source
AI summary
A method for increasing CO2 sequestration efficiency in depleted reservoirs by increasing injectivity is provided. This method includes the steps of introducing a surfactant solution into an upper portion of the reservoir through an injection well and introducing CO2 to a lower portion through another injection well such that the CO2 and surfactant solution migrate away from the wells and intimately intermingle to form CO2-based foam in situ. The surfactant solution and CO2 may also be introduced through the same injection well, where the surfactant solution is introduced to an upper portion of the reservoir and the CO2 is introduced into a lower portion. The pressure may be maintained at a value less than the fracture pressure of the reservoir utilizing a pressure relief well.