Mitigation
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  Schematic of pH-­triggered polymer gelants (Carbopol) used for stopping leaks along wellbore/rock interface. Developed by the University of Texas at Austin project DE-FE0009299.
(click to enlarge)

Mitigation is a key technology area that addresses the need for both preventing and correcting any release of CO2 from its intended geologic storage reservoir. Specifically, mitigation technologies are being developed to help ensure that possible releases of CO2 through natural or man-made pathways can be sealed effectively.

Description

Mitigation strategies depend on the potential leakage source, pathways, size, and nature of the leak. Currently, several mitigation strategies are available, and more are expected as a result of ongoing research and development.

Permanent CO2 storage relies on the presence of a confining zone that will trap the CO2 for millennia. If the leak occurs through a fracture in the caprock, measures such as pumping out the CO2 to reduce the pressure in the reservoir can be used to prevent further leakage. Other options include forming a pressure barrier by increasing the pressure in the reservoir into which CO2 is leaking or by inter­cepting the CO2 in leakage paths. Another strategy involves plugging the region where leakage is occurring with barrier (low permeability) materials. Additional research is necessary to improve and test the methods for mitigating any leaks. If it is the injection well that is leaking, measures such as re-cementing can be taken to repair the well.

Research Agenda and Challenges

Wellbores and natural geologic features, including faults and fractures, could become release pathways for CO2 to migrate to the surface or into underground formations other than those intended. Research is needed to develop methods to detect and seal release pathways.

Specific mitigation research targets include:

  • By 2020: Develop improved systems for detection and remediation of CO2 leakage from wells and natural pathways. Research includes use of geomechanical simulation to assess potential caprock leakage and remediation and development of chemical additives and biomineralization technologies that may act as effective sealants without impacting injectivity and capacity efficiency in the storage formation.
  • By 2030: Develop (1) lower cost tools with higher resolution, including advanced seismic and tracer technologies for leak identification in wells and from the natural system; and (2) novel methods, such as nanocomposites and other materials, for permanent mitigation of release pathways.
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GSRA Mitigation Research Timeline (click to enlarge)

NETL-Supported Mitigation Research

NETL supports projects that are addressing research challenges within the Mitigation key technology area. Examples of projects supporting this key technology include: (1) development of an advanced novel in-situ mineralization techniques capable of sealing leaking wells over a wide range of temperatures and formation chemical environments; (2) development of a nanoparticle injection technique combined with simultaneous extraction of harmful ions (such as chlorides) from steel casing, improved injection technology for repairing leaks, and a numerical simulator that can predict the performance of this new repair technology; (3) development of a small-scale wellbore testing system and a computer model to simulate electro-migration technology; and (4) development of a method to control flow through leakage pathways, like fractures and pores, by plugging using stimuli-responsive materials.

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Schematic of engineered biofilm barrier. The biofilm serves as a means to provide long-term sealing of preferential CO2 leakage pathways in confining zone and surrounding injection wells. Montana State University project DE-FE0004478.
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The GSRA webpage offers links to detailed information on projects performing research in this area.