Abstract: Nucleons which are chemically bound to oil and water in geological formations possess magnetic moments which align in the earth's magnetic field causing the natural nuclear paramagnetism of the formation. An A.C. magnetic field at the Larmor frequency is repetititively applied to the formation adjacent to a borehole resulting in a repetitive excitation-relaxation process of the nucleons present within an "excitation zone" which results in an amplitude modulation of the paramagnetism within this zone. This physical process results in an amplitude modulation of the earth's magnetic field in the vicinity of the excitation zone of the formation and is called the Paramagnetic Logging Effect (PLE). The PLE may be measured with logging tools in open holes and within cased well bores.

Abstract: A new method and apparatus is described which allows remote sensing and in-situ volumetric measurement of liquid petroleum reserves. A small fraction of the nuclear magnetic moments of protons in a liquid oil reserve align in the earth's magnetic field. This nuclear paramagnetism slightly alters the strength of the earth's static magnetic field above the oil reservoir. The size of the paramagnetic contribution to the earth's magnetic field is proportional to the volume of the petroleum reserve. An artificial A.C. magnetic field is applied to the bulk oil reserve at the Larmor frequency. This A.C. magnetic field causes the condition appropriate for nuclear magnetic resonance which under certain circumstances, causes the paramagnetic contribution to the earth's magnetic field to vanish. Different phenomena causing this paramagnetic contribution to vanish include saturation effects and the conditions described by rapid passage.Under these circumstances, frequency sweeping the A.C.