Craquelure, the fine pattern of cracks found in old paintings, presents a rare opportunity to reach beyond the physical sciences for help in understanding a geological process as inscrutable as the development of joints in a fractured reservoir.
Craquelure, the fine pattern of cracks found in old paintings, presents a rare opportunity to reach beyond the physical sciences for help in understanding a geological process as inscrutable as the development of joints in a fractured reservoir. Masterpieces in the Louvre (Paris, France) and other national galleries, like bedded sedimentary rocks, are jointed (i.e., cracked) composite materials with welded contacts between substrate and joint-bearing medium. The analogy goes even further because differences in properties between the substrate and the joint-bearing medium greatly influence a number of characteristics of joint growth patterns including fractal properties (Duccio, 1300), propagation direction (Duccio, 1311), spacing vs. bed thickness (Francesca, 1455), orientation (Master of St. Giles, 1500), abutting relationships (Clouet, 1530), degree of systematic development (Rembrandt, 1660) and lack of systematic development (Chardin, 1736). In particular, the degree to which the joint-bearing medium is subject to ‘tectonic’ stress predetermines the extent to which a number of these joint patterns develop (Hals, 1647). Regardless of the particulars, it is clear that the masterpieces and sedimentary rocks even share two common loading configurations: the joint-normal load (canvas support) and the thermoelastic load (wood support). When ‘tectonic’ stresses are not present mudcracks (Fouquet, 1455), columnar joints, and spiral joints (David, 1791) propagate under thermoelastic loading. In the masterpieces, ‘tectonic’ stresses arise from the way the substrate was stretched, dried, or woven and these stresses are responsible for controlling the orientation of systematic joints again under joint-normal loading (David, 1813). Systematic joints may fan or curve if the substrate provides local stress concentrations (da Vinci, 1503). Preparation may also cause the substrate to deform in oroclinal-like bends as indicated by concomitant jointing in the host medium (Cassatt, 1893). Finally, cross joints are less systematic and, hence, the role of tectonic stress is less clear (Goya, 1798).