Changes

==Detection of heavier hydrocarbons==

==Detection of heavier hydrocarbons==

Volatile and semivolatile heavier hydrocarbons such as aromatic compounds, gasoline-range hydrocarbons, and even normal or biodegraded oils can also be found, particularly where migration occurs along fault and fracture pathways. These different manifestations have led to the development of different techniques for sampling and analyzing hydrocarbons. It is beyond the scope of this chapter to discuss the advantages and limitations of specific methods or sampling procedures; however, such information is available in publications by Abrams<ref name=ch18r2>Abrams, M., A., 1996, [http://archives.datapages.com/data/specpubs/memoir66/01/0001.htm Distribution of subsurface hydrocarbon seepage in near-surface marine sediments], in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 1–14.</ref> Barwise and Hay<ref name=ch18r6>Barwise, T., Hay, S., 1996, [http://archives.datapages.com/data/specpubs/memoir66/28/0363.htm Predicting oil properties from core fluorescence], in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 363–371.</ref> Brooks et al.<ref name=ch18r9>Brooks, J., M., Kennicutt, M., C., Carey, B., D., 1986, Offshore surface geochemical exploration: Oil & Gas Journal, October 20, p. 66–72.</ref> Horvitz<ref name=ch18r16>Horvitz, L., 1985, Geochemical exploration for petroleum: Science, vol. 229, p. 821–827., 10., 1126/science., 229., 4716., 821</ref> Jones and Drozd<ref name=ch18r17>Jones, V., T., Drozd, R., J., 1983, Predictions of oil or gas potential by near-surface geochemistry: AAPG Bulletin, vol. 67, p. 932–952.</ref> Klusman<ref name=ch18r18>Klusman, R., W., 1993, Soil gas and related methods for natural resource exploration: New York, John Wiley & Sons, 483 pp.</ref> Price<ref name=ch18r30>Price, L. C., 1986, A critical overview and proposed working model of surface geochemical exploration, in Davidson, M. J., ed., Unconventional Methods in Exploration for Petroleum and Natural Gas IV: Dallas, Texas, Southern Methodist Univ. Press, p. 81–129.</ref> Richers and Maxwell<ref name=ch18r34>Richers, D., M., Maxwell, L., E., 1991, Application and theory of soil gas geochemistry in petroleum exploration, in Merrill, R., K., ed., Source and Migration Processes and Techniques: AAPG Treatise of Petroleum Geology, Handbook of Petroleum Geology, p. 141–158.</ref> Schiemer et al.<ref name=ch18r38>Schiemer, E., J., Stober, G., Faber, E., 1985, Surface geochemical exploration for hydrocarbons in offshore areas—principles, methods and results, in Petroleum Geochemistry in Exploration of the Norwegian Shelf: London, Graham and Trotman, p. 223–238.</ref> and Schumacher and Abrams.<ref name=ch18r39>Schumacher, D., 1996, Hydrocarbon-induced alteration of soils and sediments, in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: AAPG Memoir 66, p. 71–89.</ref>

Volatile and semivolatile heavier hydrocarbons such as aromatic compounds, gasoline-range hydrocarbons, and even normal or biodegraded oils can also be found, particularly where migration occurs along fault and fracture pathways. These different manifestations have led to the development of different techniques for sampling and analyzing hydrocarbons. It is beyond the scope of this chapter to discuss the advantages and limitations of specific methods or sampling procedures; however, such information is available in publications by Abrams<ref name=ch18r2>Abrams, M., A., 1996, [http://archives.datapages.com/data/specpubs/memoir66/01/0001.htm Distribution of subsurface hydrocarbon seepage in near-surface marine sediments], in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 1–14.</ref> Barwise and Hay<ref name=ch18r6>Barwise, T., Hay, S., 1996, [http://archives.datapages.com/data/specpubs/memoir66/28/0363.htm Predicting oil properties from core fluorescence], in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 363–371.</ref> Brooks et al.<ref name=ch18r9>Brooks, J., M., Kennicutt, M., C., Carey, B., D., 1986, Offshore surface geochemical exploration: Oil & Gas Journal, October 20, p. 66–72.</ref> Horvitz<ref name=ch18r16>Horvitz, L., 1985, Geochemical exploration for petroleum: Science, vol. 229, p. 821–827., 10., 1126/science., 229., 4716., 821</ref> Jones and Drozd<ref name=ch18r17>Jones, V., T., Drozd, R., J., 1983, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0067/0006/0900/0932.htm Predictions of oil or gas potential by near-surface geochemistry]: AAPG Bulletin, vol. 67, p. 932–952.</ref> Klusman<ref name=ch18r18>Klusman, R., W., 1993, Soil gas and related methods for natural resource exploration: New York, John Wiley & Sons, 483 pp.</ref> Price<ref name=ch18r30>Price, L. C., 1986, A critical overview and proposed working model of surface geochemical exploration, in Davidson, M. J., ed., Unconventional Methods in Exploration for Petroleum and Natural Gas IV: Dallas, Texas, Southern Methodist Univ. Press, p. 81–129.</ref> Richers and Maxwell<ref name=ch18r34>Richers, D., M., Maxwell, L., E., 1991, Application and theory of soil gas geochemistry in petroleum exploration, in Merrill, R., K., ed., Source and Migration Processes and Techniques: AAPG Treatise of Petroleum Geology, Handbook of Petroleum Geology, p. 141–158.</ref> Schiemer et al.<ref name=ch18r38>Schiemer, E., J., Stober, G., Faber, E., 1985, Surface geochemical exploration for hydrocarbons in offshore areas—principles, methods and results, in Petroleum Geochemistry in Exploration of the Norwegian Shelf: London, Graham and Trotman, p. 223–238.</ref> and Schumacher and Abrams.<ref name=ch18r39>Schumacher, D., 1996, Hydrocarbon-induced alteration of soils and sediments, in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: AAPG Memoir 66, p. 71–89.</ref>

==Indirect methods==

==Indirect methods==