Rock magnetic properties of drill cutting from a hydrocarbon exploratory well and their relationship to hydrocarbon presence and petrophysical properties
Libro: Remagnetization and Chemical Alteration of Sedimentary Rocks
Capítulo 14: Rock magnetic properties of drill cutting from a hydrocarbon exploratory well
and their relationship to hydrocarbon presence and petrophysical properties
Autores: Mabel Mena, Ana María Walter
Resumen: The Golfo San Jorge Basin is one of the most important hydrocarbon-producing
basins in Argentina. A study of magnetic properties performed on drill cutting from an oil
well drilled in this basin was carried out. The cutting samples, taken from an interval of
about 400 m thickness, correspond to the upper units of the Pozo D-129 Formation, the
main source rock of the basin. Magnetic susceptibility measurements were made and
rock-magnetism studies were conducted. Concentration indices of the different magnetic
species determined were calculated based on isothermal remanent magnetization
acquisition curves. A correlation analysis among magnetic properties, hydrocarbon content
and well logs (sonic, neutron, density, induction, resistivity and photoelectric factor) was
performed. Several kinds of significant correlations were found: a positive correlation
between susceptibility and relative hydrocarbon content; a positive correlation between
magnetic properties and porosities (especially good with the neutron log porosity); and
a negative correlation between the concentration indices of some magnetic species
(magnetite and pyrrhotite) and resistivity. Pyrrhotite could be directly related to the
presence or migration of hydrocarbons through the porous units.
The qualitative correlations between magnetic data and key petrophysical parameters
such as porosity, along with the association of magnetic mineralogy to hydrocarbon
presence or migration, suggest the potential usefulness of these techniques for
subsurface exploration.