Hydrocarbon occurrence and exploration in and around igneous rocks

Abstract

Abstract Hydrocarbons can occur within and around igneous rocks, sometimes in commercially significant quantities. Igneous or closely associated rocks can be hydrocarbon sources in the conventional sense (biotic) as well as possibly through abiotic processes. Maturation is extremely variable, depending on the extrusive/intrusive nature of the activity and the relative importance of a deep heat source. Igneous volatiles and hydrothermal fluids may also be important in mobilizing and moving hydrocarbons. Igneous rocks can have good reservoir qualities, and they can produce their own trapping structures as well as being part of a larger feature. Many exploration methods are individually unreliable in and around igneous rocks, and an integrated approach is most effective. Seismic, magnetotelluric, gravity and magnetic surveys may all provide helpful information. Geological mapping, geochemistry and remote imagery may also be helpful. Evaluation of potentially commercial hydrocarbon accumulations requires interpretation of well logs, which may have unusual characteristics. Drill stem and production tests may also be needed for evaluation before exploration ends and development begins.