An example of single well convection mining in Xiangyu Salt Mine

The mine is a sulphate-chloride type continental facies deposit with a depth of 230-540 m and a dip angle of 4-7. The ore body is produced in layers, with many layers and thin salt layers. The thickness of the single layer is generally 1.5-2.5 m and the maximum is 4.96 m, which is divided into six layers of industrial salt layers. The grade of sodium chloride is 76.10%-90.06%, and the impurities have a small amount of glauberite , muddy and organic matter. The main well convection method and the two-well connection method are used for halogen extraction. The annual output of brine is 1.396 million ^m3 , the brine contains NaCl260g/L, Na ₂ SO ₁ ≤36g/L, and the recovery factor is 20%. The mining sequence is from bottom to top and is mined from the edge to the center. The production wells are arranged according to the well group. There are two wells, one group of three wells or one group of four wells. The well groups are arranged in a straight line, the wells fall on the strike line, and the different well groups are staggered. Strictly distinguish between well spacing and group spacing, with small well spacing and large group spacing, the well spacing is 60-80m, the group spacing is greater than 240m, and the mining process is “multiple-layer, layered mining”. The technical measures are to seal the upper and middle industrial salt layers of the technical casings with different pipe diameters, and expose the third industrial salt layer. After the layer is finished, the second industrial salt layer is uncovered, and the small diameter technology is used. The casing is mined. Finally, the first industrial salt layer is opened by cutting or perforating. The well body structure is a 219mm diameter casing surface cementing. The technical casing has two sets of diameters of 139.7mm and 114.3mm, and the inner coupling is 50.8mm. The third industrial salt layer has a diameter of 168 to 197 mm. Convective production is divided into the construction period and the production period according to the difference in halogen production.

Slotting period: The fresh water is continuously injected into the dissolved salt layer in the well by a positive circulation operation to build a salt tank of a certain volume. At the beginning of 3 to 5 days, the water injection amount is controlled at 7-10 m ³ /h or more, and the halogen concentration is controlled to 5 to 7 ° Be', which can enhance the flow and dissolution ability of water in the cavity, and realize rapid construction of the groove. The discharged light halogen is injected back into the I mining area to collect brine. When the diameter of the cavity reaches 48m, a single well can produce more than 10m ³ /h of qualified raw brine, and the groove period is about 3.5 to 5 months.

The water injection method in the production period is mainly reverse circulation, supplemented by positive circulation, so that the output is stable at 10~12m ³ /h. As the dissolution time increases, the dissolution distance increases, the brine concentration increases, and the insoluble residue is thickened. At this time, it is prone to accidents such as blockage of the pipe, collapse of the roof, and deformation of the production string. If the "single well small flow, steady flow stability" is adopted to achieve stable production, after the two wells are connected, the single well recovery period will be ended, and one well will be injected with water, and the other well will be discharged with halogen, and large displacement and strong mining will be implemented.