The need of cutting the costs of new oil wells in the San Jorge Basin led YPF S.A. to study the option of reducing well diameters. For an effective cost reduction, it was necessary to be able to case the hole with diameters smaller than 4.5 inches. The problem of a completion in 3.5 inches or less was the inability to efficiently lift the production with traditional methods. Initially a monobore type completion was tested, in detriment of pump setting depth and pump efficiency due to the presence of gas. The introduction of a mechanical pumping system lifting fluids through coiled tubing made possible the solution of the problems of the pump depth and efficiency. The paper describes the type of installation and procedure followed to run the system. The success of this type of installation will allow the operator to produce in wells cased with 3.5 inches or less, matching the efficiency of conventional wells cased with 5.5 inches, in a range of production volumes compatible with most of the wells in the basin. At the same time, the system offers the advantage of using conventional technology such as beam pump on the surface and mechanical pump at the bottom of the well.