Experimental Study of Sand Production and Mud Erosion Phenomena for Sand Mud Alternate Layer

Methane hydrates are crystalline, ice-like compounds under specific thermodynamic conditions. The existence of methane hydrates is confirmed in the Nankai Trough, an offshore area of Japan. Japan's Methane Hydrate Research and Development Program (MH21) has been under way at this area. In the early 2013, the world's first intentional gas production attempt from marine gas hydrate deposits was tried and accomplished in the Daini Atumi Knoll area of the Eastern Nankai Trough. For gas production, depressurization method has been considered as a promising gas production technique from methane hydrate reservoirs. However, considering of continuous gas production over a long period, there is still something to clarify. The methane hydrate crystals are very small and existed in the intergranular pores of sandy layer of turbidite sediments. When the intergranular methane hydrates will be dissociated, it is considered that dissociated gas and water flow will cause sand production and mud erosion phenomena of turbidite sediments. The production of framework sands into a well is one of the problems plaguing the gas because of its adverse effects on well productivity and equipment. If the eroded mud is accumulated in the pore space of sand, skin is generated and permeability becomes lower. In addition, mud erosion has a negative effect for the well stability. This research presents an experimental study to understand sand production and mud erosion phenomena for sand mud alternate layer. The aims of this study are to understand these phenomena and clarify driving forces. In our experiments, we used an artificial sedimentary core and performed experiments under various conditions. As the results, the driving forces of these phenomena are not dissociation gas flow but water flow through pore.