Abstract: The experimental device of two-well dissolution cavity-building with a small spacing was set up， and the law of cavity volume expansion in different casing arrangement was studied by model test. The results indicate that cavity volume growth rate of only injecting the inlet is greater than that of the other two ways， and the cavity volume reaches to the biggest eventually. Different casing arrangements have little effect on the dissolution rate of salt wall as well as the dissolution angle in the bottom of the cavity. Injecting the two wells at the same time and injecting the inlet only form a cavity of a shape of “ship”.There will form a cavity of two “towers” in the top and a large cavity at the bottom when injecting the oil. Compared with the single well technique， two-well dissolution cavity-building expansion with a small well spacing technology has a great advantage at the early stage.

Key words: rock salt, dissolution cavity-building, model test, cavity expansion, two-well, single well