| Popis: |
This study aims to boost the seepage capacity in the near-well area by the downhole heating so as to improve the production efficiency of low-permeability reservoir while ensuring the sidewall stability. Taking the second member of the Xujiahe Formation in Longchang as the subject, the effect of high temperature on the microstructure, mechanical property and permeability of tight sandstones were studied. The samples underwent thermogravimetric analysis, scanning electron microscopy (SEM), acoustic wave test, physical parameter measurement, uniaxial compression test and permeability test after high-temperature exposure in the range of 26 ℃ to 1000 ℃, and temperature's relevance to the composition, microstructure, mechanical parameter and permeability were analyzed. The test results showed that the internal moisture of the samples was removed continuously with the increase of temperature, and the content of clay minerals decreased by stages in the range of 26 ℃ to 1000 ℃, which led to the decrease of sample mass and apparent density. There was a threshold temperature at about 400 ℃ for the performance of tight sandstone. When the temperature was higher than 400 ℃, the compressive strength and deformation resistance of the samples decreased sharply. With the increase of temperature, more internal fractures emerged and the network size was enlarged, leading to the continuous growing increase of permeability. Therefore, it is considered that keeping the downhole heating temperature above 400 ℃ and expanding the heating range as well are conducive to improving the productivity of single well. The findings of this study are of value for evaluating the wellbore stability and stimulation effect of single well while applying the electric heating technology in tight sandstone reservoirs. |
