Application of rock magnetic parameters for oil exploration: a case study of oriented cores obtained from the Akebono SK-4D borehole in Yufutsu area, Hokkaido, Japan

Abstract

Rock magnetic property is utilized for oil exploration on the basis of three parameters bulk magnetic susceptibility, remanent magnetization and anisotropy of magnetic susceptibility AMS. Initial magnetic susceptibility obtained from non-oriented borehole samples is a crucial parameter for reliable modeling of geomagnetic anomaly. Information of remanent magnetization and AMS derived from oriented core samples provides us with insights into tectonic movement and microscopic fabric of reservoir, respectively. As a case study, rock magnetic experiments are presented, using oriented granite cores obtained from the Akebono SK-4D borehole in the Yufutsu area, Hokkaido, Japan. The analyzed samples at the top of the Cretaceous basement are characterized by relatively low magnetic susceptibility and stable, easterly-deflected thermoremanent magnetization that implies tectonic rotation. Maximum axis K 1 of AMS coincides with the intersection of two fracture systems within the granitic basement rocks, which implies the direction of maximum permeability. AMS parameters, reflecting microscopic alignment of minerals precipitated on fracture surface, may be useful to assess properties of fractured reservoir.

Magnetic properties of siliceous marine sediments in Northern Hokkaido, Japan: a quantitative tectono‐sedimentological study of basins along an active margin

“…The above consideration denies structural control on the AMS fabric as attained by precipitation of authigenic minerals on the surface of fractures, which results in the elongate axis being parallel to the average fracture plane (Itoh & Amano, ; Itoh et al ., ). Instead, sedimentological control on the AMS fabric is plausible in the case of the studied sedimentary rocks.…”