热处理饱水致密砂岩的水相自吸与返排

致密砂岩气藏在开发过程中由于水相的侵入或滞留会在近井带或水力裂缝面造成水相圈闭损害,严重影响开发效益.储层高温热处理作为一种新型储层改造技术,已应用于解除近井地带水相圈闭损害.选取鄂尔多斯盆地典型致密砂岩岩样,分别采用干岩样、饱和蒸馏水、饱和3%KCl溶液以及饱和地层水的岩心开展了100～600℃的热处理实验;进行了超过阈值温度的高温热处理前后的岩心自吸、返排实验,并对热处理前后岩心的水相圈闭损害程度进行评价.研究表明,饱和蒸馏水和饱和3%KCl溶液的岩样在热处理后的增渗率明显大于干岩样和饱和地层水的岩样,且岩样热致裂的阈值温度明显降低,从干岩样时500℃降低到300℃;高温热处理增加致密砂岩孔隙度与渗透率,不仅使水相自吸量与自吸速率明显提高,而且岩心渗透率恢复率显著提升.致密岩石热致裂阈值温度可以降低,热增渗后不仅解除水相圈闭损害,而且可以预防后期作业储层水相圈闭损害.

Water imbibition and flowback in saturated tight sandstone by heat treatment

The development of tight sandstone gas reservoir is facing serious water trap damage around the wellbore because of the intrusion of water, which will seriously restrict the development benefit of tight sandstone gas reservoir. As a new type of reservoir stimulation technology, formation heat treatment has been applied in reducing the damage of water trap near wellbore. The typical tight sandstone samples with different physical properties in Ordos Basin were selected. And the samples were treated with dried, saturated distilled water, saturated 3%KCl solution and saturated formation water, respectively. Then the heat treatment experiments at 100~600 ℃ were carried out.The water imbibition and flowback experiments before and after high temperature heat treatment were carried out, and the damage degree of water phase trap in the core before and after heat treatment was evaluated. The results show that the infiltration rate of saturated distilled water and saturated 3%KCl rock sample after heat treatment is obviously higher than that of dry rock sample and saturated formation water sample, and the threshold temperature of thermal cracking is decreased obviously from 500 ℃ of dry sample to 300 ℃. The effect of high temperature heat treatment on the self-priming capacity of tight sandstone is very obvious, and the core permeability recovery rate increased significantly. The threshold temperature of thermal fracture of tight rock can be reduced, and the water trap damage of reservoir can be prevented after heat treatment.