Interrelationships among seismic and short-term tectonic activity, oil and gas production, and gas migration to the surface

Abstract

Environmental impacts of (1) oil and gas production from hydrocarbon fields, (2) seismic and short-term tectonic activity, and (3) increase in upward gas migration along faults and fractures due to seismic activity are discussed. Natural seismic activity, generally underestimated for platform conditions, may cause disruption of oil and gas production. There is a vast amount of experimental data showing the influence of the processes of petroleum production on local seismic activity and demonstrating that petroleum production may be the cause not only of ground subsidence but may also trigger small- and medium-size earthquakes. In turn, experiments with artificial sources of vibro-seismic energy show that seismic vibrations (artificial or natural) may cause an increase in gas migration to the surface. This means that in seismically active areas, gas leakage at the surface over petroleum reservoirs can present more serious environmental problems, compared to the areas with relatively low seismic activity. Increased hydrocarbon gas migration from the oil and gas fields to the surface can be caused by artificial seismic sources. The authors observed that upon release of artificial energy to the reservoirs, the migration of gases to the surface increases. Additional information for identification of faults that may serve as structural traps for hydrocarbons may be obtained via monitoring short-term tectonic activity in the vicinity of hydrocarbon fields and monitoring of gas concentration anomalies near the earth surface over petroleum fields. The multi-parametermonitoring of tectonic, seismic and geochemical factors in the Tengiz (a very large oilfield in Kazakhstan) gives an important example of the system aimed at monitoring of the potential environmental hazards related to interaction of tectonic and seismic factors with petroleum production.