What Do Fractures Look Like? A Picture Says A Lot, Even When It is Wrong

Abstract

When it comes to fracturing, experts argue about many things, but they agree that fractures do not look like lightning bolts, tree roots, or shattered glass. The sight of an image in a recent National Geographic story showing a hydraulic fracture that looked like a lightning bolt spurred Terry Engelder, a professor of geosciences at Penn State University to call the editor and complain. The geologist, whose work has long focused on natural fracturing, was spurred to action by a long-standing complaint: “Invariably illustrations of fracturing look nothing like the real thing,” he said. Real hydraulic fractures are likely to look like natural fractures. Hydraulic fracturing typically opens existing cracks, which means the fractures will generally run along the planes of natural fractures. So the picture of hydraulic fractures used to stimulate wells in the Marcellus Shale should be like the natural fractures crisscrossing the vast formation, which have been studied for more than a century. Engineers have also noticed the problem with fracturing cartoons, and even SPE has gotten complaints. “They do not look like tree roots. Things do not shatter like glass and run in all directions,” said Norm Warpinski, a Halliburton fellow for Pinnacle, Halliburton’s geophysical testing service. Fracture “complexity has to be consistent with pre-existing geologic features.” Some illustrations, like the one above are doubly bad because the design sends the message that drinking water aquifers are found near fractured zones, rather than thousands of feet away, creating a misleading impression that fracturing puts drinking water supplies at risk. But these fracturing cartoons continue to appear, likely because they are easy to find online, and offer a quick fix for designers looking for a hydraulic fracturing image other than a photo of massed pumpers on a job site. More life-like illustrations alternatives are rare. This story offers drawings that convey the blocky, angular reality of how fracturing follows natural fractures but they will not likely be the choice of an artist creating the cover for a technical conference program.