Experimental study on the influence of water injection displacement on the shape of the cavity built by horizontal well

The salt-cavern gas storages in China are generally characterized by thin salt rock layers and thick interlayers. To deal with this situation, this paper proposed a horizontal-well multistep cavity construction technology which has low cavity construction cost and high cavity formation rate. A physical similarity experimental platform was established to experimentally study the influences of different displacements on the horizontal cavity shape. And the relationship between the shape expansion of the cavity built by horizontal well and the displacement was studied. It is indicated that when the displacement is 5-10 mL/min, the development of the cavity is not uniform, and it is eventually in the shape of shoe. When the displacement is 20-30 mL/min, the cavity is in the regular shape of cylinder with smaller top height difference. There is a critical displacement of cavity construction, which is 20 mL/min. When the displacement is higher than the critical value, the cumulative salt production of cavity A per unit time decreases with the increase of the displacement; and when it is lower than the critical value, the cumulative salt production of cavity A per unit time increases with the increase of the displacement. By adjusting the cavity construction parameters rationally, the horizontal cavity is ultimately in the shape of tunnel. The research results provide certain theoretical base for the application of horizontal-well multistep cavity construction technology and the technical support and reference for the large-scale application of horizontal-well cavity construction in salt-cavern gas storages.