A system for monitoring a hydrocarbon-containing fluid flowing through a conduit, the system comprising: a wellbore that extends through at least a portion of an earth formation for allowing the hydrocarbon-containing fluid to flow from a producing zone of the earth formation in said wellbore; a conduit fluidly connected to the wellbore; and a measurement assembly comprising: a terahertz probe wave generator arranged to generate a terahertz probe wave with a frequency between 50 GHz and 30 THz; a terahertz probe wave detector arranged to detect at least a portion of the terahertz probe wave and generate detection signal; a terahertz probe wave path that extends between the terahertz probe wave generator and the terahertz probe wave detector, whereby at least a section of the terahertz probe wave path extends into the conduit; wherein the hydrocarbon containing fluid is a mineral hydrocarbon containing fluid and the system further comprises: a processor programmed to extract from the detection signal at least one fluid parameter selected from the group consisting of asphaltene content, asphaltene type, water content, hydrogen sulfide content, sulfur dioxide content, gas to oil ratio, and condensate gas ratio; a valve on the conduit capable of controlling the flow of the mineral hydrocarbon containing fluid through the conduit; and a controller arranged to control the valve, whereby the controller is coupled to the terahertz probe wave detector and programmed to control the valve in response to the detection signal. a wellbore that extends through at least a portion of an earth formation for allowing the hydrocarbon-containing fluid to flow from a producing zone of the earth formation in said wellbore; a conduit fluidly connected to the wellbore; and a measurement assembly comprising: a terahertz probe wave generator arranged to generate a terahertz probe wave with a frequency between 50 GHz and 30 THz; a terahertz probe wave detector arranged to detect at least a portion of the terahertz probe wave and generate detection signal; a terahertz probe wave path that extends between the terahertz probe wave generator and the terahertz probe wave detector, whereby at least a section of the terahertz probe wave path extends into the conduit; wherein the hydrocarbon containing fluid is a mineral hydrocarbon containing fluid and the system further comprises: a processor programmed to extract from the detection signal at least one fluid parameter selected from the group consisting of asphaltene content, asphaltene type, water content, hydrogen sulfide content, sulfur dioxide content, gas to oil ratio, and condensate gas ratio; a valve on the conduit capable of controlling the flow of the mineral hydrocarbon containing fluid through the conduit; and a controller arranged to control the valve, whereby the controller is coupled to the terahertz probe wave detector and programmed to control the valve in response to the detection signal. a terahertz probe wave generator arranged to generate a terahertz probe wave with a frequency between 50 GHz and 30 THz; a terahertz probe wave detector arranged to detect at least a portion of the terahertz probe wave and generate detection signal; a terahertz probe wave path that extends between the terahertz probe wave generator and the terahertz probe wave detector, whereby at least a section of the terahertz probe wave path extends into the conduit; wherein the hydrocarbon containing fluid is a mineral hydrocarbon containing fluid and the system further comprises: a processor programmed to extract from the detection signal at least one fluid parameter selected from the group consisting of asphaltene content, asphaltene type, water content, hydrogen sulfide content, sulfur dioxide content, gas to oil ratio, and condensate gas ratio; a valve on the conduit capable of controlling the flow of the mineral hydrocarbon containing fluid through the conduit; and a controller arranged to control the valve, whereby the controller is coupled to the terahertz probe wave detector and programmed to control the valve in response to the detection signal. a processor programmed to extract from the detection signal at least one fluid parameter selected from the group consisting of asphaltene content, asphaltene type, water content, hydrogen sulfide content, sulfur dioxide content, gas to oil ratio, and condensate gas ratio; a valve on the conduit capable of controlling the flow of the mineral hydrocarbon containing fluid through the conduit; and a controller arranged to control the valve, whereby the controller is coupled to the terahertz probe wave detector and programmed to control the valve in response to the detection signal.