Models of gas-hydrated deposits formation in the rivers delta-fronts
Gas hydrates accumulations which were discovered in the delta-fronts of such rivers as Niger, Dnepr, Danube, etc. and associated with their detrital cones attracted attention of a lot of experts. It is found out that the gas of which the hydrates in these accumulations are formed, is delivered to a hydrates formation zone (HFZ) by ground sources (volcanoes mud gryphons, gas flares, etc.) and its temperature is higher than that of bottom water. In these conditions revealing of the most significant characteristics influencing the scale of of hydrates formation in the delta-fronts and paleo-riverbeds, is a problem of huge importance. In the course of the problem salvation the author of the paper defines the factors affecting the number of hydrates, annually accumulated in the rivers delta-fronts, and assesses the contribution of each of them in the weight, the form and the hydrate-rock parity in gas-hydrate deposits to be formed. The author concludes that the primary factors defining the hydrates-formation scale in the rivers delta-fronts are a current speed near a deposit, gas sources flow-rate and HFZ thickness over a deposit, number and the geometric shape of the sources forming a deposit as well as sedimentation accumulation rate in a river delta-front. It was also found out that some areas characterized by the raised thickness of the hydrate layer or, on the contrary, absolutely deprived of them, can be formed depending on gas sources arrangement near a deposit.