Operations for improving the gas flow in the wellbore adjacent zone.
Florinel Şuţoiu, Ion Foidaş, Mihail Avramescu
Vol. 33, no. 2 (2016), s. 531-546, 
During the whole period of a natural gas reservoir exploitation, from the start of production until the total reservoir energy depletion, may apear some phenomena which by their nature can affect the natural gas flow from the layer into the well. The flow resistance greeted by gas in the adjacent borehole may have multiple causes. In the majority of cases, geological elements are those which definitive influence the behaviour in exploitation of those reservoirs, so the existence of some traps due to the continuity and discontinuity character of the porous-permeable medium or to some reservoir parameters with low values, drasticaly reduces the posibility of extraction of a bigger volume of geological gas resource. Also the exploitation performances of gas reservoirs, through different wells, are major affected because of the skin factor. This produces an increased flow resistance in the adjacent zone of the borehole which is a plus to the resistance caused by the hydrodynamic imperfection to the mode and open degree of the productive layer. During the maturity stage of natural gas reservoirs, a special attention is granted to prevention and control of this unwanted effects which may affect natural gas flow from the reservoir into the well, through different operations. The stimulation of these productive layers through different operations aiming the reduction of geological nature constraints, thereby become a complex approach having the finality the increasing of exploitation performances itself. In Romgaz were tested and are used a series of stimulation technologies of the productive layers. From there historic we conclude that perforations or re-perforations using deep penetration tools, acidizing and nitrogen injection are applied with success to the productive wells. Regarding the increasing of the recovery factor for wells with high water income or for wells with mixed flow regime or with water drive regime, were successfully tested the polymer injection technology that helps to maintaining or optimising the productive wells.