储气库井注气压力剧变诱发微粒运移实验模拟

微粒运移是一种重要的储层损害类型，地下储气库井在注气过程中因注气压力递增或波动而诱发储层微粒运移。当前，基于储气库注气压力变化下的微粒运移机理尚不明确，且少有系统开展模拟储气库注气压力变化下的微粒运移实验研究。为此，选用相国寺储气库黄龙组碳酸盐岩储层岩心制取裂缝岩心，分别开展了应力敏感实验、气体速敏实验、模拟储气库注气压力递增和压力波动情形下的岩心流动实验，测试压力递增和压力波动的岩心渗透率和出口端微粒浊度，并借助X射线衍射和扫描电镜等手段，分析储层微粒运移的潜在微粒类型，揭示了储气库注气压力动态变化诱发储层微粒运移机理。实验表明:①驱替压力递增和压力波动实验中的压力梯度远大于速敏实验中岩心发生速敏时(微粒运移)的临界压力梯度，岩心应力敏感程度为弱~中等偏弱；②驱替压力递增和波动下岩心平均渗透率损害率分别为77%和57%；③驱替压力递增和压力波动引起储层裂缝壁面脆弱结构附着能力下降是微粒运移的重要诱发机制。分析认为，注气压力递增或频繁波动会诱发储气库储层微粒运移损害，应预防钻完井过程中外来固相微粒侵入，并对储层中固有微粒进行清除。

Experimental simulation on the fine migration induced by the violent change of the gas injection pressure of gas storage well

Fine migration is one important type of reservoir damage. Fine migration in reservoirs is induced by the progressive increase or fluctuation of gas injection pressure during the gas injection of underground gas storage well. So far, the mechanisms of fine migration induced by the change of the gas injection pressure of underground gas storage have not been clarified clearly and the experimental study on the fine migration due to the change of gas injection pressure has seldom been carried out systematically. The cores of the Huanglong Formation carbonate reservoir in Xiangguosi Underground Gas Storage were selected to prepare fractured cores. They were used to carry out stress sensitivity experiment, gas velocity sensitivity experiment, core flow experiment under the simulated progressive increase and fluctuation situations of gas injection pressure of underground gas storage and test the core permeability and outlet fine turbidity under the influence of progressive pressure increase and pressure fluctuation. And by means of X-ray diffraction and scanning electron microscope (SEM), the potential types of fine migrating in reservoirs were analyzed and the migration mechanisms of fine induced by the dynamic change of the gas injection pressure of underground gas storage were revealed. The experiment results show that the pressure gradient in the experiment with progressive displacement pressure increase and pressure fluctuation is much higher than the critical pressure gradient corresponding to the occurrence of velocity sensitivity (fine migration) in the velocity sensitivity experiment, indicating that the core’s stress sensitivity degree is weak and moderate-weak. In addition, the average damage rate of core permeability under the influence of progressive displacement pressure increase and pressure fluctuation is 77% and 57%, respectively. What’s more, the decrease of the adhesive capacity of the vulnerable structure on the wall surface of reservoir fracture caused by progressive displacement pressure increase and pressure fluctuation is the important mechanism inducing fine migration. In conclusion, progressive gas injection pressure increase or frequent pressure fluctuation can induce fine migration to damage the reservoir of underground gas storage, so it is recommended to prevent the invasion of foreign solid fine in the process of drilling and completion and remove the autochthonous fine in reservoirs.