Sequestration of CO_2 in Salt Caverns

摘要

Permanent storage of CO_2 in dissolved salt caverns is one of the geological options for reducing anthropogenic greenhouse gas emissions into the atmosphere. Alberta is singularly well endowed with suitable salt deposits. Of these, the Lotsberg Salt of east central Alberta is the best of the three major salt-bearing zones, and is geographically close to present and future sources of CO_2 associated with fossil fuel development projects in Alberta. The characteristics of the Lotsberg Salt and overlying strata are presented in the context of the long-term future of stored CO_2. There are a number of features that indicate a high level of security against leakage and migration of gas back to the biosphere. A procedure for the creation, testing, and filling of a salt cavern is presented. A critical requirement was to achieve a reasonable long-term prediction of the behaviour of the cavern during slow closure, while taking into account the pressure and volume behaviour of the gas within the cavern. This was achieved with a semi-analytical model that predicts long-term pressures and volume changes. There appear to be no technical obstacles or undue risks identified that would militate against the use of salt caverns for permanent CO_2 sequestration. It is an option that can be seriously considered in Alberta, or in other geographical locations where the geological conditions are suitable.