Deposition of solid elemental sulfur may arouse severe damage to the formation and significantly affect the gas deliverability in sour gas reservoirs. As one main measure of stimulation, hydraulic fracturing always ceases to work due to the sulfur deposition in the fractures. To have a better understanding of the failure of fracture conductivity caused by sulfur deposition and learn the degree of fracture conductivity improved by acidification, an experimental was implemented and studied. In this paper, both the sulfur powder and an artificial fractured core were employed to simulate the process of sulfur deposition in the fractures. A further step was made to inject some hydrochloric acid into the blocked fracture caused by sulfur powder. The result showed that the fracture conductivity could be greatly reduced by the sulfur deposition. The fracture conductivity can be decreased by 17%~47% due to sulfur deposition. However, to some degree, acid-fracturing can improve the conductivity of fracture by eroding the surface of fracture. This means the failure of fracture blocked by sulfur deposition can be improved by acidification.
Experimental study on proppant embedment depth and fracture conductivity in coal seam
