Prevention, Repair and Mitigation of CO2 Storage Leaks Using SPI Gels
It is proposed that SPI gels be used to provide a multi-layered protective barrier for active and plugged carbon sequestration injection wells to ensure long term CO2 storage. SPI gels are patent pending, liquid silicate based gel systems that are near water viscosity until they set-up into strong, flexible gels. The gelation initiation trigger can be from an internal chemical, for a time/ temperature basis, and/ or from an external chemical, such as carbon dioxide (CO2) for a position/ contact basis. SPI gels are very versatile as concentrations and even the type of various components can be changed to fit many applications. Use of SPI gels for oilfield (waterfloods and CO2 EOR) conformance and other applications has been laboratory and field tested. However, SPI gels are now being commercialized only in CO2 EOR applications using only the external CO2 initiator. This is because available internal chemical initiators have only limited delay time capabilities before gelation occurs, at the higher SPI concentrations needed. SPI gels have been proven in the lab and in the field to last at least 1 year, but longer tests have not been made. SPI gels are solution liquids that can go into small pores that solids-laden fluids (such as cement) cannot. Therefore it can provide a better seal to the rocks. Pre-gelled SPI mixtures will also not generate a filter cake on the rock face that prevents continued mixture flow into those tight spaces. SPI gels also get stronger with CO2 contact and will not degrade or corrode over time like cement and steel. SPI gels are up to 10 times stronger than the strongest cross-linked polyacrylamide polymer gels in use today. They are also very environmentally friendly. However, longer time-delay internal chemical initiators are needed for the higher SPI strength and large volume treatments needed for this and other applications. To ensure long term carbon sequestration success it is proposed that SPI gels be studied for: 1) three paths of internal initiator research for a new longer delay (24+ hour) capable internal chemical initiator; 2) ensure durability of SPI mixtures and gels in the formation to act as a seal; 3) design formulations and volumes for pumping into the CO2 storage formation with internal / external initiator combinations to form multiple barriers to CO2 migration; and, in Phase II, 4) field test those designs in multiple CO2 EOR production wells that produce at high CO2 levels. These SPI formulations and processes can be used to form a barrier around the wellbore to PREVENT corrosion of the steel and cement of the wellbore; PREVENT, REPAIR and MITIGATE possible CO2 migration paths through existing micro-channels in the cement sheath around the well and through internal wellbore plugs; and REPAIR and MITIGATE leaks through the sealing Cap-Rock seal or through fractures. SBIR Phase II will take these formulations and commercialize them in many industrial applications.
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