PCCT measurements of the consolidation characteristics, constrained modulus and compressional wave velocity for fine-grained sediment collected from Area C, Krishna-Godavari Basin during India's National Gas Hydrate Program, NGHP-02

Abstract

Understanding how effectively methane can be extracted from a gas hydrate reservoir requires knowing how compressible, permeable, and strong the overlying seal sediment is. This data release provides results for flow-through permeability, consolidation, and direct shear measurements made on fine-grained seal sediment from Site NGHP-02-08 offshore eastern India. The sediment was collected in a pressure core from the Krishna-Godavari Basin during the 2015 Indian National Gas Hydrate Program Expedition 2 (NGHP-02). Gas hydrate is a crystalline solid that forms naturally in the sediment of certain marine and permafrost environments where pressure is relatively high (equivalent to the pressure measured at ~300 meters water depth or more) and temperature is relatively low (but generally above freezing). The concentration of methane can be high enough to make certain gas hydrate occurrences potentially relevant as energy resources. To extract methane from gas hydrate, the in situ formation (generally a coarse-grained, gas-hydrate-bearing sediment interval) can be depressurized by drawing pore water out through a production well. As the pore pressure falls below the gas hydrate stability limit, the solid gas hydrate breaks down, releasing gas and water that migrate toward the production well for collection. How effectively the production well can depressurize the gas-hydrate-bearing interval depends on how permeable the overlying seal sediment is. If the seal is permeable, depressurizing the reservoir to extract methane causes water to flow out of the seal and into the reservoir. This can limit the ability of the production well to maintain the low reservoir pressure required to break down gas.