Wet CO2 Injection for Aquifer Salt Precipitation
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Solution Overview
Problem
The risk of salt precipitation impairs CO2 injection in aquifers due to the dissolution of salts in formation water when dry or supercritical CO2 is injected, reducing permeability and hindering further injection.
Innovation Solution
Injecting a CO2 composition that is between 50% oversaturated and 50% under-saturated with a salt-lean fluid, which is mixed with compressed CO2 before injection, to minimize salt precipitation and maintain pore space accessibility, using a static mixer at the wellhead to control proportions and avoid corrosion in pipelines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dry or supercritical CO2 is injected into the aquifer, then CO2 storage efficiency is improved, but salt precipitation occurs which reduces permeability and hinders further injection
Solution Approach 1:
A salt-lean fluid is introduced as an intermediary substance between the CO2 and the formation water. This fluid mixes with the CO2 to create a composition that is saturated with respect to salts, preventing salt precipitation while maintaining CO2 storage efficiency. The salt-lean fluid acts as a mediator that controls the interaction between CO2 and formation water.
Solution Approach 2:
The invention changes the compositional parameters of the injected fluid by mixing CO2 with a salt-lean fluid to achieve a specific saturation state. By controlling the proportions of CO2 and salt-lean fluid, the injection composition is adjusted to be between 50% oversaturated and 50% under-saturated with salts, optimizing both storage efficiency and permeability maintenance.
2Object-affected harmful factors
If water is injected to flush brine from the injection point, then salt precipitation is reduced, but the complexity of the injection process increases
Solution Approach 1:
The invention combines the CO2 injection function with the brine flushing function into a single integrated process. By mixing salt-lean fluid with CO2 before injection, the system simultaneously achieves CO2 storage and formation water management in one step, eliminating the need for separate water injection operations.
Solution Approach 2:
The salt-lean fluid serves multiple functions: it acts as a carrier for CO2, controls salt saturation, and manages formation water interaction. This self-service approach allows the injection composition to regulate its own salt precipitation behavior without requiring additional external flushing operations.
3Productivity
If high injection rates are used to overcome capillary forces, then CO2 injection is maintained, but the fracture gradient of the cap rock is exceeded
Solution Approach 1:
The invention changes the physical parameters of the injection composition by creating a saturated CO2-salt-lean fluid mixture. This composition modification allows for optimized injection rates that maintain CO2 storage efficiency while operating below the cap rock fracture gradient, preventing geological hazards.
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 reduces salt precipitation, maintains permeability, and allows for efficient use of aquifer storage capacity by using secondary products from processing plants, with reduced water requirements and potential cost savings from recycling salt-lean fluids.
Implementation Method 1
the water in the brine dissolves in the CO2. As water is removed into the CO2 stream, salt concentration increases, eventually reaching the solubility limit and giving rise to salt precipitation
Implementation Method 2
wherein the CO2 composition is compressed to assume a liquid or supercritical state at the site of injection
Data Source
Figure 1
AI summary
A method and arrangement are proposed for injecting CO2 into a subterranean aquifer for storage therein. In order to reduce the effects of water evaporation from brine in the aquifer when dry CO2 is injected into the aquifer, the CO2 is supplied mixed with a salt- lean fluid, i.e. a fluid that contains a low concentration of ions that can precipitate out as salts. The mixing may take place at the wellhead, with the CO2 salt-lean fluids supplied via separate low-grade material pipelines. The proportion of CO2 and salt-lean fluid in the mixture is such as to obtain a CO2 composition that is saturated with salt-lean fluid at the site of injection into the aquifer. By injecting saturated or "wet" CO2, less water is evaporated from the brine and the salt precipitation is greatly reduced, so keeping the pore spaces clear and providing an increased accessible pore volume for CO2 storage.