Abstract: A technique facilitates forming cavities, e.g. perforations, into a geological formation. A jetting tool is moved downhole into a borehole, and an abrasive fluid is pumped down through the jetting tool. The abrasive fluid is discharged under pressure through a plurality of jetting nozzles to form jets of the abrasive fluid which act against a surrounding wall, e.g. a casing or other borehole wall. The jetting nozzles, and thus the jets, are oriented such that a rebound effect of the jets does not detrimentally impact the jetting tool. Consequently, the jets can be used to cut perforations through the surrounding wall and into the formation without eroding or otherwise detrimentally affecting components of the jetting tool.