2-D electrical resistivity tomography assessment of hydrate formation in sandy sediments

Abstract

Laboratory hydrate formation process simulation provides a theoretical support for determining the dynamic revolution behaviors of actual hydrate reservoirs. In view of this, based on the ITS electrical resistance tomography (ERT) module, a dedicated apparatus was developed to simulate the in-situ core-scale distribution of natural gas hydrate directly during the process of hydrate formation and dissociation in artificial sediments. Beach sand was used as porous media to simulate the formation of methane hydrate and assess the 2-D ERT evolution characteristics simultaneously. The findings were obtained. (1) The apparent average resistance values of hydrate-bearing sediment system are determined by the combination of hydrate forming rate and salt-removing effect, showing fluctuation rise behaviors during the process of hydrate formation. (2) When the hydrate forming rate is high enough, hysteresis influence of salt-removing effect on apparent average resistance value is observed. After the hydrate formation, there still exists a mass transfer process controlled by the difference of salt ion concentration. (3) Difference between original and real-time ERT distribution indicates a heterogeneous formation process of hydrate within the sediments. In conclusion, initial gas–water contact relationship and distribution is the virtual factors for hydrate heterogeneous distribution behaviors, while that of spatial difference of ion concentration caused by the salt-removing effect plays a key role in promoting local hydrate formation position change.

Keywords

• Natural gas hydrate
• Electrical resistivity
• Electrical conductivity
• Electrical resistance tomography
• Salt-removing effect
• Process monitoring