Guide: PF 105 – Density


  Gravity exploration must account for the horizontal and vertical differences in density which occur in subsurface geologic features. Gravity anomalies require lateral density discontinuities such as stratigraphic or structural changes in the subsurface. Vertical density differences in the subsurface will change the bias or overall amplitude level of a gravity map or profile but will not produce gravity anomalies. Learning Objectives After [...]

Guide: PF 106 – Magnetic Susceptibility


  Magnetic susceptibility is known as the ratio of the magnetization of a material to the magnetic field strength; it is a tensor when these two quantities are not parallel, otherwise it is a number. The magnetic susceptibility of a rock is proportional to the volume percent of magnetic minerals. Magnetic susceptibility (k) is a trace property of the rocks because the percentage [...]

Guide: PF 107 – Velocity


  Velocity, in this context, is the speed (distance / time) of sound (a compression wave) through rock (which may contain fluid and gas). Velocity may be used to determine rock densities and convert seismic information from time to depth. The rock velocity which correlates to its density is measured as interval velocity. That is the velocity between two depths; i.e., a thickness [...]

Guide: PF 108 – Salt Magnetic Susceptibility


Airborne magnetic surveying for petroleum exploration continues to routinely and indisputably reveal interesting and measurable magnetic anomalies (as small as 0.1 nT under the best survey conditions) which arise from geological variations within the sedimentary section. These so-called intra-sedimentary magnetic anomalies are detectable from aeromagnetic data acquired with stringent aeromagnetic survey design and acquisition specifications/techniques. Usually often only new or recent vintage data (typically since [...]


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