Abstract: The installation combines with at least one production well-head an oil/gas separator of substantial vertical elongation and of which the major part may be housed in a pit sunk and lined closed to the working well, which permits of wide fluctuations in the oil/gas level between the high and low control points while ensuring sufficient submersion of the pump with which the separator is equipped. This apparatus makes it possible separately to draw off the gas on the one hand and the sufficiently degasified oil on the other, from a peripheral site to a central production station.