The subject matter of the present disclosure is directed to developing a method of measuring the amount of producible oil and the producible oil saturation in shale-oil reservoirs using sample source rock. Further, the physical and chemical properties and amounts of producible oil in shale-oil reservoir samples may be determined. First and second solvents are applied to a sample source rock to extract petroleum from the sample source rock. The extracted source rock, the twice-extracted source rock, and the first and second extracted petroleum may be analyzed to determine the characteristics and properties of the reservoir rock.