Wellbore fluid compositions containing a base fluid; at least one synthetic fiber; and a particulate solid; where one or more of the at least one synthetic fiber and the particulate solid are completely or substantially acid soluble are provided. In another aspect, methods of reducing loss of wellbore fluid in a wellbore to a formation are provided, including: introducing into the wellbore a fluid composition comprising one or more synthetic fibers and one or more particulate solids.