THE THERMODYNAMICS OF MUD DIAPIR/VOLCANO FLUID AND ITS INFLUENCE ON GAS HYDRATE OCCURRENCE

The effect of mud diapir/mud volcano fluid on gas hydrate occurrence is a key problem to exploration of hydrate distribution in a mud diapir/mud volcano development zone. In this paper, we studied the thermodynamics of mud diapir/mud volcano fluid and its influence on gas hydrate occurrence, and the reason for giving up drilling of hydrate at the station SH5 of the Shenhu area of the Pearl River Mouth Basin in the northern South China Sea is discussed. The station of SH5 is located above a mud diapir.It seemed very hopeful in the beginning, but failed to collect hydrate samples successfully by drilling later on, since mud diapir piercing through the hydrate stability zone had made the deep thermal fluids migrating along the mud diapir and fracture channels.This process changed the temperature field of the hydrate stability zone and resulted in the decomposition of gas hydrates. Therefore, the mud diapir or mud volcano fluid thermal effect may directly influence the occurrence of hydrates. Exploring the movement of mud diapirs/mud volcanoes fluids and their thermal effects on hydrate accumulation will not only provide a theoretical basis for the research of gas hydrates accumulation dynamics under a fluid leakage tectonic environment, but also be important to gas hydrate exploration and development as well as resource assessment.