Chapter: 14: Rock magnetic properties of drill cutting from a hydrocarbon exploratory well and their relationship to hydrocarbon presence and petrophysical properties

MENA, MABEL; WALTER, ANA MARÍA

Remagnetization and Chemical Alteration of Sedimentary Rocks

The Geological Society of London

Lugar: London; Año: 2012; p. 217 - 228

The Golfo San Jorge Basin is one of the most important hydrocarbon-producing basinsin Argentina. A study of magnetic properties performed on drill cutting from an oil well drilled inthis 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. Magneticsusceptibility measurements were made and rock-magnetism studies were conducted. Concentrationindices of the different magnetic species determined were calculated based onisothermal remanent magnetization acquisition curves. A correlation analysis among magneticproperties, hydrocarbon content and well logs (sonic, neutron, density, induction, resistivity andphotoelectric factor) was performed. Several kinds of significant correlations were found: a positivecorrelation between susceptibility and relative hydrocarbon content; a positive correlationbetween magnetic properties and porosities (especially good with the neutron log porosity); anda negative correlation between the concentration indices of some magnetic species (magnetiteand pyrrhotite) and resistivity. Pyrrhotite could be directly related to the presence or migrationof hydrocarbons through the porous units.The qualitative correlations between magnetic data and key petrophysical parameters such asporosity, along with the association of magnetic mineralogy to hydrocarbon presence or migration,suggest the potential usefulness of these techniques for subsurface exploration.