A FEM study of the fluid injection-induced earthquakes caused by the seepage-induced propagation and interaction of fissures

Pumping polluted water into the ground using injection wells is an effective way of disposing waste water resulting from oil and gas production. However, this disposal causes earthquakes. According to the currently accepted theory, the disposed fluids increase the pore fluid pressures and reduce the effective stresses in existing faults causing their mobilization. In this study, a seepage force is believed to be the cause of the earthquakes. When the seepage force resulting from the fluid injection is effective, it causes the rock skeleton to be compressed. Under seepage-induced compression, the tips of isolated small fissures present in the rock, developed zones of tensile stresses. These tensile stresses cause the formation of secondary tensile cracks that grow and interact with the pre-existing fissures creating a discontinuity (fault) that is mobilized by fluid pressures. The feasibility of this hypothesis for earthquake development is analyzed using a FEM analysis.