Solution mining technology is widely adopted in the salt deposit mining industry. With an analysis of the solution mining technologies currently adopted, a new technology of multi-well hydraulic fracturing and Controlled solution mining is introduced in this paper, including its technical mechanism and the successful application in the mining of mirabilite in YunCheng Salt Lake, China. The engineering practice proved that the new technology for salt deposit mining is not only technically feasible, but also capable of significantly increasing the mining ratio and the production efficiency, thus minimizing the production cost. Consequently, the paper concludes that the technology of multi-well hydraulic fracturing and controlled solution mining for salt deposit is a more effective technology and deserves wider adoption.
Salt deposits such as sodium chloride, sodium sulfate and potassium chloride are important chemical materials widely mined worldwide. With the surface mineral resources gradually exhausting, the underground salt deposit is becoming the main supply for the mining industry. Meanwhile the solution cavity of salt deposits is regarded as an ideal host for oil and gas repositories due to its advantageous geological conditions and physical-mechanical characteristics [see Langer, 1993; Fuenkajorn, 1993; Staudtmeister, 1997]. In order to improve the mining ratio and take good advantage of the solution cavity of salt deposits, the study on the mining techniques of salt deposits is very meaningful.
In this paper, on the basis of an analysis of the advantages and disadvantages of the current solution mining technologies, a new technology of multi-well hydraulic fracturing and controlled solution mining for salt deposit is introduced, including its technical mechanism and the successful application on the mirabilite mining in YunCheng Salt Lake of China.
As salt minerals are easily dissolvable in water, the solution mining approach is commonly used for underground salt deposit mining. As a solvent, water is pumped into the salt deposit and dissolves the mineral on the spot, thereby the solid deposit turns into following brine which is then pumped out with the help of the residual pressure of the injected water. The solution mining method is currently regarded as an economic and effective way for salt deposit mining.
According to the number of the working wells, the presently adopted solution mining technologies can be classified into single well convection approach and double wells convection approach on the whole [see Wang, 1999; Xuan, 1997].
In the single well convection approach, the fresh water inputting and the brine outputting tubes are concentrically installed in a well. At the initial mining stage, in order to control the solution of the upside salt in the cavity, another oil or gas tube is often concentrically installed in the same well, then oil or gas is injected into the solution cavity and an isolation cushion between the water and the upside salt is thus formed. So only the parietal salt in the cavity is dissolved and a wide horizontal solution area in the cavity is gradually formed.
