Workover rigs are used in onshore basins but they are often in limited number and they may not attend all the maintenance requests. We consider here the problem of scheduling the rigs over a time horizon in order to minimize the total oil loss due to the idle production states. Three mixed integer linear models are proposed. The first one improves an existing scheduling-based formulation. The second one uses an open vehicle routing approach and the third one is an extended model for which a column generation strategy is developed. Several improvements are presented as well as two heuristics coupled with column generation. To our knowledge, the first optimal values for medium-size instances of the problem are presented in this paper. The results show the potential of the column generation and its interest in a practical context.