Potential Implications on Gas Production from Shales and Coals

Publication Overview

The main aims of the study are to assess the global potential for geological storage of CO₂ in shale and coal formations and the impact of gas production from shales on CO₂ storage capacity in underlying deep saline aquifers by compromising caprock integrity. The study would comprise a comprehensive literature review to provide guidance on the following issues:

• Global status of hydrocarbon production from shales and CBM and potential effects on CO₂ storage both in the producing shales/ coals themselves and underlying hydrocarbon reservoirs and/or deep saline formations. The focus should be on gas production, but with reference to oil production from shales;
• Current status of research into geological storage of CO₂ in shales and coals;
• Potential nature and rate of trapping processes; mechanisms of storing CO₂.
• CO₂ injectivity into shales and coals, with reference to fracturing practices employed by industry;
• Containment issues arising from shale fracturing, both for shales as a storage medium per se, and in terms of caprock integrity for underlying storage units, particularly deep saline aquifers;
• Methods for assessing storage capacities for CO₂ storage in shales and coals;
• High level mapping and assessment of theoretical/effective capacities;
• Potential economic implications of CO₂ storage in shales and coals.

Publication Summary

• Exploitation of gas from both shale and coal will leave the formations with increased permeability and injectivity and therefore with increased potential to store CO₂.
• Large scale demonstration has yet to take place to confirm CO₂ storage capability and capacity for both shale and coal. Though demonstration projects are more advanced for coal with several small scale projects injecting CO₂ into wet coal seams (where there have been some injectivity problems related to coal swelling) and one project into an already dewatered coal seam.
• Overlap between potential shale gas exploration and potential storage reservoirs in deep saline formations may be considerable geographically, but much less so in 3D. Therefore use of both resources should be possible if well managed, though this will need considered on a case by case basis.
• There are still some uncertainties regarding CO₂ storage in shale and coal, and knowledge gaps where further research is needed have been identified as part of this study.