地下储气库应力敏感性实验研究

在储气库运行过程中，由于气体的采出和注入，使得多次注采期间岩石净上覆压力发生周期性变化，随之导致储层岩石物性参数发生周期性变化，从而影响储气库的注采能力，因而研究储气库储层应力敏感特征具有重要意义。为此，以实验手段研究了地下储气库在气体注入和采出过程中地下储层的应力敏感性。实验选用2块渗透率不同的人造砂岩岩心，测试了在4次净上覆压力升降过程中的储层渗透率变化。实验结果表明：随着净上覆岩层压力的增加，岩心渗透率呈下降趋势，初期渗透率下降较快，后期渗透率下降程度减小，应力敏感性变弱；净上覆压力周期性变化过程中，岩石渗透率不可能完全恢复到原始值，存在着一定程度的滞后效应；岩石渗透率越高，应力敏感特性越明显。

LABORATORY RESEARCHES ON STRESS SENSIBILITY OF UNDERGROUND GAS STORAGE

The operation of gas storage, such as gas withdrawal and injection, tends to change the net overburden stress of rocks periodically in several gas injection-withdrawal cycles, which will bring about periodical changes on physical property of reservoir rocks. Accordingly, it will affect the injection-withdrawal capacity of gas storage. Thus, it's important to study the sensibility characteristics of reservoir stress. Laboratory tools are adopted. Two artificial sandstone cores with different permeability are selected to test the permeability change situation during the four ascending-descending periods of the net overburden stress. The test result shows that the permeability of sandstone core tends to decline while increasing the net overburden stress of the rock. The permeability drops sharply at the early stage. However, at the final stage, it tends to slow down and the stress sensibility becomes weakening. During the periodical changes of net overburden stress, the core permeability is impossible to restore to its initial value and certain lag-effect occurs. The higher permeability the rock has, the more obvious the stress sensibility characteristic will be.