Investigation on Fracture Intervention in Rock Hydraulic Fracturing Test through CT Scanning

摘要

Up to now, the issue of detection of the sub-millimeter hydraulic fracturing cracks in large scale rock samples subjected to hydraulic fracturing tests remains to be tackled. Three different kinds of nano-meter CT imaging interventional enhancer using gold, mercury, and bismuth were proposed based on the principle of X-ray absorption and attenuation. The hydraulic fracturing samples were scanned before and after treated by the aforementioned three interventional materials respectively using industrial X-ray CT scanner. The comparisons were made from the following two aspects: before and after the interventional treatment for each interventional material and three different interventional techniques. The following conclusions can be obtained: 1) the interventional enhancers are capable of improving the imaging effect of hydraulic fracture in rock samples, which is mainly reflected in the gray contrast and resolution of the enhanced X-ray CT imaging; 2) nano-gold and nano-bismuth provide better outcome on the fracture imaging; 3) nano-bismuth based interventional technique can capture the cracks width as low as 0.2 mm. The nano-gold interventional enhancer can increase the crack detection ability by 18.75% with respect to the crack width. However, the nano-mercury base interventional technique seems to be less effective; 4) nano-scale heavy materials can be used as enhancers to improve the detecting capability of the micro-cracks in the hydraulic fracturing samples using CT scanning technique.