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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 49 (1965)

Issue: 3. (March)

First Page: 353

Last Page: 353

Title: Outlining of Shale Masses by Geophysical Methods: ABSTRACT

Author(s): A. W. Musgrave, W. G. Hicks (1)

Article Type: Meeting abstract


Shale masses are here defined as large bodies of shale at least several hundred feet in thickness. These may be formed either as diapiric masses (as described by Atwater and others) or as depositional masses. The shale masses exhibit the following properties by comparison to the normal section: (1) low velocities, in the range of 6,500^prime/sec to 8,500^prime/sec, with very little increase of velocity with depth, (2) low densities--in the range 2.1 to 2.3, (3) low resistivities--approximately 0.5 ohm-meters, and (4) high pressures--about 0.9 overburden pressure. These properties all seem to be caused by the high porosity and low permeability of these large shale masses.

Maps and cross-sections of Ship Shoal Block 113 field, offshore Louisiana, illustrate how a shale mass is outlined by geophysical means. Low velocities were measured by acoustic logs and verified by refraction shooting. Low densities were deduced from gravity maps. Low resistivities were observed on the electric logs and high pressure was deduced from drilling difficulties with heaving shales.

The shale mass, like the salt mass (commonly combined to form the domal mass), may form the updip seal for stratigraphic accumulation of oil.

End_of_Article - Last_Page 353------------


(1) Deceased. Formerly with Mid-Tex Oil & Gas Co., Midland, Texas.

Copyright 1997 American Association of Petroleum Geologists