Negative pressure analysis for the penetration installation of conductor suction anchor in marine hydrate reservoirs

Marine gas hydrate reservoirs are shallow with weak soil cementation and low load bearing capacity, so the production test wells faces the problem of wellhead subsidence and instability obviously, which can be solved effectively by using the conductor anchor node. In order to ensure the conductor anchor node to penetrate to the designated position safely, a negative pressure window prediction method for the penetration installation of conductor anchor node in marine hydrate reservoirs was developed based on its structural characteristics, according to the design specification of suction anchor. Then, the soil parameters of the hydrate production test wells in the South China Sea were selected for case analysis, and their calculation results were verified by means of the finite element model of conductor anchor node-soil nonlinear contact. It is indicated that the negative pressure window prediction method for conductor anchor node has good applicability and can provide reasonable prediction of penetration resistance, self-weight penetration depth and negative pressure window. The penetration resistance of conductor anchor node presents the trend of nonlinear increasing with the increase of penetration depth, and the self-weight penetration depth is shallower where the soil has higher shearing strength. What’s more, with the increase of the penetration depth, the allowable negative pressure increases linearly while the required negative pressure increases nonlinearly, and the negative pressure window gets narrow gradually. The research results provide technical reference for the field installation and application of the conductor anchor node for hydrate test production in the South China Sea.