Chapter 5.2 Flow and Transport Properties of Salt Rocks 5 J.L. Urai · Z. Schléder · C.J.Spiers · P.A. Kukla 5.2.1 Introduction Ductile evaporites play a key role in controlling the dy- namical evolution of many sedimentary basins. We re- view the mechanical and transport properties of these rocks focusing on halite, bischofite and carnallite. Reli- able modelling of salt flow during basin evolution, or of salt flow related to long-term engineering challenges, requires extrapolation of experimentally-derived flow laws to strain rates much lower than those attainable in the laboratory. This extrapolation must be based on an understanding of the microscale deformation mecha- nisms operating under these conditions, obtained by combining studies of natural laboratories with experi- mental work. The engineering creep laws generally used in the salt mining industry are based on dislocation creep processes quantified in laboratory experiments of necessarily limited duration. However, a large body of evidence clearly demonstrates that under conditions of long-term deformation, grain boundary dissolution-pre- cipitation processes, such as solution-precipitation creep (or “pressure solution”) and dynamic recrystallisation, play a significant role. The operation of these processes can cause major changes in rheology. Moreover, the high fluid pressures associated with deforming evapo- rite systems can lead to dramatic increases in permeabil- ity, strongly reducing sealing capacity. These properties must be incorporated in quantitative models of evaporite basins to obtain realistic descriptions of salt behavior at the necessary range of length and time scales. Table 5.2.1 List of the main evaporite minerals and the wireline log properties of evaporite rocks formed by these. Name Formula Density GR Neutron “Porosity” Sonic transit time kgm -3 API % msft -1 Bischofite MgCl 2 . 6 H 2 O 1560 0 > 60 100 Carnallite KMgCl 3 . 6 H 2 O 1570 220 65 78 Epsomite MgSO 4 . 7 H 2 O 1710 0 > 60 Sylvite KCl 1860 500 -3 74 Halite NaCl 2040 0 -3 67 Kainite MgSO 4 KCl . 3 H 2 O 2120 245 45 Gypsum CaSO 4 . 2 H 2 O 2350 0 >60 52 Kieserite MgSO 4 · (H 2 O) 2590 0 38 Calcite CaCO 3 2710 0 -1 49 Polyhalite K 2 Ca 2 Mg(SO 4 ) 4 ·2 (H 2 O) 2790 180 15 57 Langbeinite K 2 Mg 2 (SO 4 ) 3 2820 275 0 52 Dolomite CaCO 3 MgCO 3 2870 0 1 44 Anhydrite CaSO 4 2980 0 -2 50