A fracturing operation is done in open hole without annular space isolation. The annular space is spanned by extendable members that are located behind isolation valves. The extendable members can comprise a biodegradable plug that allows extension of the extendable members by application of pressure. With the plug remained in place, additional pressure can be delivered until at least a portion of the degradable material is pushed onto the surface of the formation. At least a portion of the pushed degradable material provides a seal between the end of the extendable members and the surface of the formation to allow pressure to build until the formation frac gradient is exceeded and the formation is fraced.