Salt Rock: a Strategic Geomaterial in Brazil

Abstract

This paper presents a new challenge under study in Brazil: the offshore storage of natural gas and CO 2 in salt (halite) caverns opened by solution mining in shallow and ultradeep water. The salt rock mechanics in Brazil started with the underground mining of sylvinite (NaCl.KCL) overlying tachyhydrite (CaCl2.MgCl2.12H2O) and research initiated in the 1970s (Costa 1984), to enable the mining of this ore. Applying a numerical simulation of drilling and excavation, the exploration and operation of mines were possible for more than 35 years. The same technology has also been used in the stability analysis of several salt caverns opened by solution mining of halite (NaCl). With the discovery of the giant pre-salt reservoirs in Brazil, underlying about 2000 m of stratified salt rocks, with the presence of tachyhydrite, all the knowledge acquired in the conventional and solution mining designs was ready to be used. More than 200 pre-salt wells have been designed and drilled successfully using the same methodology and computer codes. These approaches are proposed here as a solution to the presented challenge.