A technique facilitates greasing of valves on a well tree, e.g. a frac tree, according to a simple process which enables selected, individual valves to be greased when desired. In some applications, the greasing process may be automated and controlled via a greasing control system. According to an embodiment, a greasing system is connected with grease ports at a plurality of actuatable valves located in a well tree. The greasing system has a plurality of grease valves which may be associated with each of the actuatable valves, e.g. with each of the grease ports. A pump is used to pump grease to the grease valves and the grease valves are selectively actuated to open positions to provide controlled greasing of desired actuatable valves so as to remove debris from and to lubricate selected actuatable valves.