A drilling system (400, 500, or 600) for controlled delivery of unknown fluids comprising: a blowout preventer comprising a wellbore fluid return line that directs unknown wellbore fluids to a choke manifold (135 or 135a); an instrumented mud-gas separator (300 or 300a) that receives unknown wellbore fluids from the choke manifold (135 or 135a), the instrumented mud-gas separator (300 or 300a) comprising a fluid level sensor or a pressure sensor that outputs a sensor signal comprising a sensed fluid level or a sensed pressure level of the instrumented mud-gas separator (300 or 300a); and characterized in further comprising: a control system that controls the choke manifold (135 or 135a) that directs unknown wellbore fluids to the instrumented mud-gas separator (300 or 300a) based on the sensor signal to maximize a flow rate of the unknown wellbore fluids to the instrumented mud-gas separator (300 or 300a) while maintaining the instrumented mud-gas separator (300 or 300a) in an operational state by: opening the choke manifold (135 or 135a) fully or in a stepwise incremental manner until fully opened while the sensed fluid level or sensed pressure level of the instrumented mud-gas separator (300 or 300a) is within an operational range, closing the choke manifold (135 or 135a) in a stepwise incremental manner if the sensed fluid level of the instrumented mud-gas separator (300 or 300a) meets or exceeds an operational liquid level maximum or if the sensed pressure level of the instrumented mud-gas separator (300 or 300a) meets or exceeds an operational pressure maximum, and closing the choke manifold (135 or 135a) fully if the sensed fluid level of the instrumented mud-gas separator (300 or 300a) meets or exceeds a critical liquid level maximum or meets or falls below a critical liquid level minimum or if the sensed pressure level of the instrumented mud-gas separator (300 or 300a) meets or exceeds a critical pressure maximum or meets or falls below a critical pressure minimum. a blowout preventer comprising a wellbore fluid return line that directs unknown wellbore fluids to a choke manifold (135 or 135a); an instrumented mud-gas separator (300 or 300a) that receives unknown wellbore fluids from the choke manifold (135 or 135a), the instrumented mud-gas separator (300 or 300a) comprising a fluid level sensor or a pressure sensor that outputs a sensor signal comprising a sensed fluid level or a sensed pressure level of the instrumented mud-gas separator (300 or 300a); and characterized in further comprising: a control system that controls the choke manifold (135 or 135a) that directs unknown wellbore fluids to the instrumented mud-gas separator (300 or 300a) based on the sensor signal to maximize a flow rate of the unknown wellbore fluids to the instrumented mud-gas separator (300 or 300a) while maintaining the instrumented mud-gas separator (300 or 300a) in an operational state by: opening the choke manifold (135 or 135a) fully or in a stepwise incremental manner until fully opened while the sensed fluid level or sensed pressure level of the instrumented mud-gas separator (300 or 300a) is within an operational range, closing the choke manifold (135 or 135a) in a stepwise incremental manner if the sensed fluid level of the instrumented mud-gas separator (300 or 300a) meets or exceeds an operational liquid level maximum or if the sensed pressure level of the instrumented mud-gas separator (300 or 300a) meets or exceeds an operational pressure maximum, and closing the choke manifold (135 or 135a) fully if the sensed fluid level of the instrumented mud-gas separator (300 or 300a) meets or exceeds a critical liquid level maximum or meets or falls below a critical liquid level minimum or if the sensed pressure level of the instrumented mud-gas separator (300 or 300a) meets or exceeds a critical pressure maximum or meets or falls below a critical pressure minimum. opening the choke manifold (135 or 135a) fully or in a stepwise incremental manner until fully opened while the sensed fluid level or sensed pressure level of the instrumented mud-gas separator (300 or 300a) is within an operational range, closing the choke manifold (135 or 135a) in a stepwise incremental manner if the sensed fluid level of the instrumented mud-gas separator (300 or 300a) meets or exceeds an operational liquid level maximum or if the sensed pressure level of the instrumented mud-gas separator (300 or 300a) meets or exceeds an operational pressure maximum, and closing the choke manifold (135 or 135a) fully if the sensed fluid level of the instrumented mud-gas separator (300 or 300a) meets or exceeds a critical liquid level maximum or meets or falls below a critical liquid level minimum or if the sensed pressure level of the instrumented mud-gas separator (300 or 300a) meets or exceeds a critical pressure maximum or meets or falls below a critical pressure minimum.