Sensitivity Analysis and Prediction Method for Water Inflow of Underground Oil Storage Caverns in Fractured Porous Media

Abstract

A sensitivity analysis method is proposed for the water inflow assessment and prediction of underground water-sealed oil storage caverns in fractured porous media. First, sensitivity analysis was carried out based on the full factorial design of the seven influencing factors, i.e., the water pressure in the water curtain holes, the spacing of the water curtain holes, the rock permeability, the fracture permeability, the dip angle, the spacing, and the aperture of the fractures. Not only the main effects of the factors but also the interactions and cross effects were analyzed. Second, water flow coupling in porous media and fractures was investigated by sensitivity analysis of the water inflow. Third, two prediction models were proposed for the water inflow in porous media and fractures based on the sensitivity analysis. The results show that water inflow of the caverns was mainly concentrated in the fracture development area. Water inflow in the fractures was mainly affected by five factors in descending order of importance: fracture permeability, aperture, dip angle and spacing of fractures, and water pressure in water curtain holes. Water inflow in porous media was mainly affected by two factors in descending order of importance: rock permeability and water pressure in the water curtain holes. In addition, interactions and cross effects of the double and triple factors also significantly affected the water inflow, which cannot be neglected in the water inflow prediction model. Effectiveness evaluation of the prediction models and an engineering application were carried out. The present study can provide some reference for the site selection and preliminary design of the underground water-sealed oil storage caverns.