A Method for Well Logging Identification and Evaluation of Low-Resistivity Gas Hydrate Layers

The Muli area has dense lithology, high hardness, poor porosity and permeability, and well-developed micro-fractures, which is different from other gas hydrate regions with unconsolidated sediment characteristics. With the gradual deepening of gas hydrate scientific research in the Muli area, some unique low-resistivity gas hydrate phenomena have been discovered. The understanding of the genesis mechanism of low-resistivity gas hydrate is not clear, which makes it difficult to identify gas hydrate layers and adversely affects the evaluation of reservoir parameters and reserves prediction. In this investigation, the well logging response law of pore-filling and fracture-filling gas hydrate reservoirs is systematically combined and the associated reservoir characteristics relationships are evaluated as a function of lithology, physical properties, reservoir space, gas hydrate and fluid distribution characteristics. Then, the correlation between cementation index and pore structure complexity index was fitted. Finally, a new gas hydrate saturation calculation model is proposed. The results show that the new saturation calculation model is in good agreement with the well logging interpretation of gas hydrate, which can identify low-resistivity gas hydrate effectively. The results of this study thus assist in terms of reliable gas hydrate exploration in the Muli area.