Experimental study on storage capacity of gas storage in depleted oil reservoir
In order to study the effect of different initial water saturation on the storage capacity when the oil reservoir is reconstructed into a underground gas storage.The multi-round injection-production experiments of gas drive oil-water under different initial water saturation conditions were carried out by using the actual field core,and then analyzes the displacement efficiency and storage capacity after gas flooding oil and water under different initial water saturation conditions.The results show that under the condition of low water saturation,the relative permeability of the oil phase is significantly higher than that of the water phase and is more easily displaced,so the gas storage space is mainly improved through gas drive oil.When the water saturation is medium and high,the water phase is more easily to be displaced,and the increase of gas storage space gradually shifts from the volume contribution of displaced crude oil to the volume contribution of displaced water phase.Under the same injection-production cycles,due to the water-wet and imbibition of reservoir rock,the residual water saturation at high initial water saturation increases,the total displacement efficiency of gas-flooding oil-water decreases,so that the injection-production capacity and storage capacity of gas storage decrease relatively.The increase of initial water saturation of reservoir will reduce the total displacement efficiency of gas drive oil and water,which is not conducive to enhanced oil recovery and gas storage capacity expansion.The higher the initial water saturation is,the longer the gas storage capacity is,and the lower the injection-production capacity in the early stage of reservoir construction is.The research results can provide guidance for injection-production capacity evaluation and storage capacity analysis of reservoir-type gas storage.
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