致密砂岩气藏长岩心压力损失及渗透率损害评价实验

Experiment on Long Core Pressure Loss and Permeability Damage Evaluation in Tight Sandstone Gas Reservoir

致密砂岩气藏具有低孔、低渗、孔隙结构复杂、孔隙连通性差等特点,易受到水锁效应严重损害。为此,根据致密砂岩气藏的水锁机理以及储层条件,选择对应储层的长岩心,开展了不同储层条件、不同水锁程度下的压力损失评价和渗透率损害评价实验,并提出了压力损失和渗透率损害率2个概念,表征水锁效应对压力传播过程和储层渗透率的损害程度。结果表明:在气田开发过程中,水锁效应对物性较差、气测渗透率较低的储层损害最大,应提前实施预防措施;物性较好、气测渗透率较高的储层可根据其压力损失和渗透率损害率决定是否需要采取优化措施。针对不同储层,合理地实施解除水锁工艺对于气井的生产以及经济效益具有重要意义。

Tight sandstone gas reservoirs are characterized by low porosity,low permeability,complex pore structure,and poor pore connectivity,and are susceptible to severe damage by the water blocking effect.For this reason,according to the water blocking mechanism and reservoir conditions of tight sandstone gas reservoirs,long cores corresponding to the formation were selected.Pressure loss evaluation and permeability damage evaluation experiments under different reservoir conditions and different water blocking degrees were carried out.Two concepts were proposed,namely pressure loss rate and permeability damage rate,to characterize the damage degree of water blocking effect to the pressure propagation process and reservoir permeability.The results show that:in the process of gas field development,the water blocking effect badly damages the reservoirs with poor physical properties and low gas permeability,and preventive measures should be implemented in advance;reservoirs with better physical properties and higher gas permeability can be determined whether optimization measures are needed based on the value of its pressure loss rate and permeability damage rate.For different reservoirs,the reasonable implementation of the water unblocking process is of great significance to the production and economic benefits of gas wells.