Chapter 26 - Gas Migration in Seismically Active Areas

Abstract

This chapter focuses on the upward gas migration from petroleum reservoirs to the earth's surface, which depends on the distribution and types of vertically and subvertically oriented faults, fracture zones, and the permeability along them. There are two groups of factors facilitating gas migration to the surface in seismically active areas: seismic activity can form vertical and subvertical faults and fractures above petroleum reservoirs, and seismic vibrations can considerably increase the permeability due to desorption of gas from the rock matrix. Due to increasing rates of upward gas migration over petroleum reservoirs after earthquakes in seismically active areas, gas leakage may present more serious environmental problems compared to those in the relatively quiet (seismically) areas. To enhance oil and gas production, artificial sources of seismic waves can be applied to the petroleum reservoirs. Substantial subsidence may cause movement of the tectonic blocks and produce a technologically induced earthquake.