Abstract: Tight sand gas reservoirs generally have relatively high levels of water saturation in their original state, and tests have shown that the permeability of dry cores is more than 10 times higher than that of the original water-containing cores. In addition, various water-based working fluids will seep into a formation upon contact with the reservoir, which leads to liquid phase retention. This increases the water saturation of matrices near the well or fracture plane, thereby further decreasing the gas phase permeability of the reservoir and greatly reducing its productivity. To solve this problem, we developed a reservoir drying agent called "ACHM". We first experimentally evaluated drying agents by measuring the depletion of formation waters after injecting the drying agents. Chromatography and X-ray diffraction (XRD) methods were also used to analyze the gases produced by the reactions between the drying agent and water, and the composition of their residues. The experimental results indicate that ACHM has a delay in its reaction time that is inversely proportional to the temperature. The water consumption of the drying agent is not affected by the type and salinity of the formation waters, and the optimal molar mixing ratio of the two drying agents was 0.25.

Key words: tight sand reservoirs, water block, drying agent, formation waters, evaluation experiments