Solution mining with intersected wells by horizontal drilling technology has always been the most commonly used and economic and effective means for mining salt resources. However， the salt mining well set is prone to the channel blockage in the process of brine extraction due to the complex formation conditions， saturated brine crystallization， casing damage and other factors，which restricts the service life of the horizontally connected salt well set. In recent years， the commonly used methods for the repair and treatment of blocked well sets are pressurizing， scraping， and window milling. Among them， window milling from horizontal wells is widely used for workover in many salt field blocks. During workover of Well Set Y2-Y4 at Shiyantian， Ningjin， Hebei province， it was found the existing mining cavern can not be reused， and was an obstacle for the second-time intersection of the well set. It was the first time that the two wells were switched in type （changing horizontal well into vertical well and vertical well into horizontal well） to by-pass the existing cavern to realize the reuse of the old well set in this block.