Petroleum Exploration in Geologically Complex Areas: Opportunities for Geochemical and Non-Seismic Hydrocarbon Detection Methods

Abstract

The petroleum potential of geologically complex areas — such as highly faulted and folded terranes — is often poorly known due to technical challenges affecting seismic acquisition and imaging. When these areas occur in jungles and highlands, the logistical challenges only add to the difficulty of evaluating the petroleum potential of such terranes. For such areas, surface geochemical and non-seismic hydrocarbon detection methods provide an opportunity to reliably detect and map the elevated hydrocarbon concentrations and hydrocarbon-induced changes commonly associated with undiscovered oil and gas accumulations. It has long been known that (1) all petroleum basins exhibit some type of near-surface hydrocarbon leakage, (2) that petroleum accumulations are dynamic and their seals imperfect, (3) that hydrocarbon seepage can be active or passive, and that it can be visible (macroseepage) or only detectable analytically (microseepage). The surface and near-surface expressions of hydrocarbon migration and seepage can take many forms ranging from elevated hydrocarbon concentrations in soils to complex mineralogic, microbial, and geophysical changes. While such hydrocarbon leakage does not require significant faulting and fracturing, the common presence of faults and fractures in structurally complex and tectonically active terranes provides additional migration pathways for hydrocarbon seepage and microseepage. Hydrocarbon detection surveys in geologically complex areas require careful planning, close sample spacing, and are most effective when results are integrated with satellite remote sensing data and available geophysical data. Such surveys are ideally suited for an early stage evaluation since they can quickly identify those parts of the area possessing the highest petroleum potential, as well as determine the characteristics of petroleum in the areas of interest. The inclusion of hydrocarbon detection surveys early in an exploration strategy focuses attention and resources on a relatively small number of high potential areas, thereby minimizing both risks and expenses. The presentation will be illustrated with examples from Asia and South America.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015