Simulation of fluid migration in a mud volcano offshore SW Taiwan

Abstract:

Mud volcanoes are usually associated with high methane flux rate, frequent gas flares, chimney structures and other biologic and chemical evidences from seepage analysis. Our study area is situated on the upper slope of the accretionary wedge offshore SW Taiwan where a large mud volcano is present. In this area, field observations indicate an unusual heat flow pattern, with high values on the top of the mud volcano and low in the trough. In this study, we simulate the heat transfer process with a 10 km deep 2D model in the vicinity of the mud volcano. We take the lowest heat flow measurement along the profile as the reference that is associated with conduction as the only heat transfer mechanism. Conduits with geometry determined from reflection seismic image are then introduced such that the studied geothermal system, equipped with both advection and conduction might fit the unique pattern of the observed heat flow measurements. Our results show that a simple heat conduction hypothesis cannot fit the measured heat flow data, and the fluid advection may play an important role in this case. We simulate both conduction and advection models using the COMSOL finite element package. The depth of advection initiation is determined based on the conduits identified from reflection seismic image. Simulation results reveal a preliminary estimate of the upward fluid flow speed which is quite consistent with previous studies in the lower slop west of our study area. We conclude that the advection of upward fluid flow is an important component for the studied geothermal system. In the future, we will focus on fine tuning the seismic data processing to get better constraints on the geometry of mud volcanoes and the fluid conduits.Mud volcanoes are usually associated with high methane flux rate, frequent gas flares, chimney structures and other biologic and chemical evidences from seepage analysis. Our study area is situated on the upper slope of the accretionary wedge offshore SW Taiwan where a large mud volcano is present. In this area, field observations indicate an unusual heat flow pattern, with high values on the top of the mud volcano and low in the trough. In this study, we simulate the heat transfer process with a 10 km deep 2D model in the vicinity of the mud volcano. We take the lowest heat flow measurement along the profile as the reference that is associated with conduction as the only heat transfer mechanism. Conduits with geometry determined from reflection seismic image are then introduced such that the studied geothermal system, equipped with both advection and conduction might fit the unique pattern of the observed heat flow measurements. Our results show that a simple heat conduction hypothesis cannot fit the measured heat flow data, and the fluid advection may play an important role in this case. We simulate both conduction and advection models using the COMSOL finite element package. The depth of advection initiation is determined based on the conduits identified from reflection seismic image. Simulation results reveal a preliminary estimate of the upward fluid flow speed which is quite consistent with previous studies in the lower slop west of our study area. We conclude that the advection of upward fluid flow is an important component for the studied geothermal system. In the future, we will focus on fine tuning the seismic data processing to get better constraints on the geometry of mud volcanoes and the fluid conduits.