Page 260 - Geochemical Remote Sensing of The Sub-Surface

Geochemical Remote Sensing of the Subsurface
Edited by M. Hale
Handbook of Exploration Geochemistry, Vol. 7 (G.J.S. Govett, Editor)
9 Elsevier Science B.V. All rights reserved 233
Chapter 7

AEROSPACE DETECTION OF HYDROCARBON-INDUCED ALTERATION

H. YANG, F.D. Van der MEER and J. ZHANG

INTRODUCTION

The continuing development of remote sensing has been of considerable significance
to earth scientists in general and exploration geologists in particular. Beginning in the
1930s, aerial photography was used to map structure and stratigraphy. Since the 1970s,
imagery from satellite platforms equipped with the multispectral scanning system
(MSS), the thematic mapper (TM), SPOT and radar systems has been used to obtain
synoptic views of the geology of an area and conduct basin-wide assessments (Halbotay,
1980; Moore and Anderson, 1985). Airborne platforms carrying multispectral scanning
systems and imaging spectrometers, have been used routinely to provide imagery for
geological mapping and identification of prospect-scale structures. The use of side-
looking radar images and synthetic aperture radar (Goetz and Rowan, 1981; Froidevaux,
1980) provided the possibility to enhance subtle expression of subsurface geologic
structures. In general the key to the successful application of remote sensing imagery in
hydrocarbon exploration is its integration with other exploration data such as seismic,
well, gravity and magnetic data. Researchers have also attempted to use remote-sensing
imagery to detect the distinct spectral characteristics of surface manifestations of
hydrocarbon microseepages, originating from oil and gas reservoirs at depth. This
chapter provides an overview of the background to the direct detection of onshore
hydrocarbon microseepage by remote sensing techniques and the results achieved to
date.

Hydrocarbon microseepage

The occurrence at surface of hydrocarbon seeps suggests that an oil or gas reservoir
leaks even though it acts as a trap for hydrocarbons. Macroseepage is the visible
presence of oil and gas seeping to the surface. Macroseeps have been documented in
various parts of the world (Davidson, 1963; Sittig, 1980; Hunt, 1981; Davis, 1967;
Tedosco, 1995). Microseeps are invisible trace quantities of hydrocarbons seeping to the