Basement rocks are important oil and gas reservoirs in various areas of the world. Such reservoirs include fractured or weathered granites, quartzites, or metamorphics. In South America, basement reservoirs occur in Venezuela and Brazil. In North Africa, basement oil and gas production occurs in Morocco, Libya, Algeria and Egypt. Significant basement reservoirs occur in the West Siberia basin as well as in China. In the USA, basement-derived oil production occurs in a number of areas, including California (Wilmington and Edison fields), Kansas (El Dorado and Orth fields) and Texas (Apco field). In Southeast Asia, basement reservoirs are the main contributor of oil production in Vietnam. In Indonesia, to date oil and gas production from basement rocks has been minimal. However, the recent large gas discovery in pre-Tertiary fractured granites in southern Sumatra has led to a focusing of exploration in Indonesia for basement reservoirs.
Figures & Tables
Hydrocarbons in Crystalline Rocks
‘Commercial oil deposits in basement rocks are not geological “accidents” but are oil accumulations which obey all the rules of oil sourcing, migration and entrapment; therefore in areas of not too deep basement, oil deposits within basement rocks should be explored with the same professional skill and zeal as ccumulations in the overlying sediments’, Landes et al. (1960), AAPG Bulletin.
Given that most OPEC countries are currently at or within 5% Production capacity, there is a growing need to look for ‘new oil’ and other hydrocarbons in non-traditional sources.
While oil and gas fields in crystalline basement are still discovered mostly by accident, as shown in this book, such reservoirs can be very prolific, especially if the basement rock is highly faulted or fractured. The chapters in this volume cover a diverse range of topics related broadly to the theme of hydrocarbons in crystalline rocks, and challenge explorationists’ definition of basement rock, which needs to be less narrow and more responsive to new geological ideas.