Hydrocarbon Occurrences in Igneous and Metamorphic Rocks: Plays of the 1990s

Danny W. Harrelson

A review of available geologic literature has indicated numerous references detailing the occurrences of hydrocarbon in igneous and metamorphic rocks. Notable among these references is a paper by Chung-Hsiang P'an and a group of papers edited by Sidney Powers. Collectively, these papers conclude a biogenic source for hydrocarbons, most of which occur in (1) weathered igneous and metamorphic reservoir rocks that are higher than the source rocks (e.g., Amarillo field) or (2) igneous and metamorphic rocks that exert structural or stratigraphic control on the reservoir or source rocks (e.g., Jackson dome and the Wiggins anticline-Hancock ridge). It should be noted that a new twist on the abiogenic origin of some inert hydrocarbon gases (i.e., helium and nitrogen) proposes a d gassing of igneous and metamorphic rocks from sources in the underlying mantle. Recent European "super-deep" tests (e.g., the Siljan Ring and the Kola SG-3 testholes) have attempted, with mixed results, to verify this theory.

Drilling for these deep igneous and metamorphic prospects today is considered at or below economic basement or worse--a rank wildcat. However, these plays should become increasingly commercial in the 1990s as deeper drilling technology progresses, the current oil glut is eliminated, and more exotic deep gas prospects become accepted.

AAPG Search and Discovery Article #91029©1989 AAPG GCAGS and GC Section of SEPM Meeting, October 25-27, 1989, Corpus Christi, Texas.