The geological sequestration of carbon dioxide (CO_2) into deep saline formations has been proposed as a viable means of reducing atmospheric greenhouse-gas emissions. Examples of suitable target formations for geo-sequestration have been presented in the literature, with studies usually considering high-quality reservoirs. Most subsurface formations are heterogeneous, with varying permeability and porosity distributions. If CO_2 is injected into a heterogeneous formation, the increased baffling in the formation and reduced permeability in parts of reservoir may inhibit the flow of CO_2 towards potential leak points in the reservoir. Injectivity into low-quality rock is a concern for heterogeneous formations. Injection programs involving multiple wells and appropriate well-completion strategies may be able to overcome injectivity problems for these candidate formations. By considering low-quality heterogeneous saline formations as possible target formations, the opportunity for geo-sequestration is expanded.
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