Despite the relative simplicity of the equipment of the wells operated by the open flow oil production method, it performs important functions and should be very reliable, since accidents with this equipment can lead to blowouts and fires. The most important element in the Xmas tree is locking devices. The main requirement for them is the complete tightness of their valves. After analyzing the working conditions of Christmas-tree gate valve, their failure can be divided into four groups. Reasons for failure due to corrosion; deformation and fractures; wearing out; deposition of different substances on the working surfaces of equipment. However, while in operation, the valve elements are intensely worn out as they contact with oil which contains abrasive particles. As a result, they must be repaired or replaced with new ones. For the prediction of the locations and magnitude of the Xmas tree elements wear (on the example of a gate), the article offers a method based on the use of simulation modeling in the Flow Simulation software environment. As a result of the research, it is established that the maximum wear (according to the given boundary conditions) occurs in the gate valve and its value is 26 mm / year. The distribution of wear on the surface of the gate is uneven. It concentrates on two mutually mirrored surfaces. The simulated wear is similar to the gate wear which occurs in real industrial conditions. The suggested method of studying the wear of the valve elements is correct and can be applied when designing oil and gas equipment that operates under similar conditions