Study on the Influence of Gas Hydrate Reservoir Creep on Borehole Wall Deformation

Abstract

Abstract Hydrate decomposition caused by long-time drilling operations will reduce the strength of the reservoir and increase the risk of borehole wall damage. At the same time, the creep characteristics of the hydrate reservoir may also lead to engineering problems such as borehole shrinkage and sticking in the later stage of drilling, which seriously affects the drilling safety. The creep parameters are introduced to explore the influence mechanism of hydrate decomposition, and hydrate-bearing sediment creeps characteristics on wellbore mechanical behavior. The influence law of sediment shale content and hydrate saturation on wellbore stability during hydrate reservoir drilling is analyzed. The result shows the hydrate-bearing sediments creep characteristics will lead to the homogenization of stress distribution in different directions of the hydrate reservoir around the well, make theplastic yield zone shape around the well to circular, and may lead to the overall collapse of the well wall. Drilling for a long time will lead to a greater hydrate decomposition range and plastic yield zone around the well. Lower initial hydrate saturation, smaller sediment strength, and larger initial plastic strain and yield range of the formation. Increase of shale content will enhance the creep characteristics of sediments and aggravate yield degree of formation.