Abstract: A system for separation of fluids and drill cuttings received from a borehole during an under-balanced drilling procedure. The system is designed to cope with significantly varied pressures and flow rates, particularly in relation to gas content of drill fluids returned to the surface during the drilling process in a production zone, and to provide effective separation and to reduce the detrimental effect due to the presence of the drill cuttings in the returned drill fluids. In the present invention there is utilized a first stage, high pressure vessel in which a major portion of the gases ad drill cuttings are separated, and a second stage, horizontal low pressure vessel, preferably of greater volume than the high pressure vessel, in which further separating is achieved, including the separate removal of the drilling liquid to be returned to the drill tube.

Abstract: A system for separation of fluids and drill cuttings received-from a borehole during an under-balanced drilling procedure. The system is designed to cope with significantly varied pressures and flow rates, particularly in relation to gas content of drill fluids returned to the surface during the drilling process in a production zones and to provide effective separation and to reduce the detrimental effect due to the presence of the drill cuttings in the returned drill fluids. In the present invention there is utilized a first stage, high pressure vessel in which a major portion of the gases ad drill cuttings are separated, and a second stages horizontal low pressure vessel, preferably of greater volume than the high pressure vessel, in which further separating is achieved, including the separate removal of the drilling liquid to be returned to the drill tube.