储气库注采过程中有效应力变化模拟试验

Simulation Tests of Effective Stress Changes in Gas Storage during Injection and Production

储气库周期注采过程中有效应力变化会使储层发生应力敏感,为了了解应力敏感对储气库储层渗透率的影响程度,为优化储气库注采制度提供依据,开展了考虑与不考虑有效应力作用时间的碳酸盐岩应力敏感试验,测试了试验过程中岩样的渗透率,并运用扫描电镜等手段,观测了考虑有效应力作用时间试验前后岩样裂缝的壁面。试验结果表明:不考虑有效应力作用时间时,碳酸盐岩裂缝岩样和基块岩样的应力敏感程度分别为弱—中等偏弱和无;考虑有效应力作用时间时,碳酸盐岩裂缝岩样和基块岩样的应力敏感程度分别为中等偏强和弱;随着有效应力作用时间增长,岩石裂缝壁面微凸体的破碎与微裂纹的萌生和扩展会强化岩样的应力敏感性。研究表明,为了弱化储气库储层的应力敏感程度,应合理控制储气库的注采压力。

The change of effective stress in the periodic injection-production process of underground gas storage will cause stress sensitivity of the reservoir.In order to understand the influence of stress sensitivity on permeability of gas storage reservoir and to provide the basis for optimizing the injection and production system of gas storage,stress sensitivity tests with consideration of effective stress action duration and without were carried out on carbonate rock samples,and the permeability of the rock samples in the test process were tested.By means of scanning electron microscope(SEM),the fracture wall of rock samples before and after the test considering the effective stress action duration was observed.The test results show that the stress sensitivity of carbonate fractures and matrix rock samples is weak-moderately weak and none without consideration of action duration,while the stress sensitivity of fracture and matrix rock samples considering the effective stress action duration is moderately strong-strong and weak.With the increase of effective stress action duration,the breaking of micro-protrusions on rock fracture walls and the initiation and propagation of micro-fractures will strengthen the stress sensitivity of rock samples.The results show that for the purpose to weaken the stress sensitivity of underground gas storage,the injectionproduction pressure of underground gas storage should be controlled reasonably.