Wutongqiao Salt Mine Oil Pad Method Mining Example

The mining area is located on the west side of the Weiyuan anticline structure. The ore body is a single salt layer with a thickness of 20~26m, containing more than 95% NaCl and a depth of 1050~1100m. Seam top plate 1 ~ 2m thick anhydrite-containing layer and the black halogen, H 2 S, limestone gas, the vertical tension crack fissures; hard floor gypsum, limestone sand, broken along the bedding. The mine created a water-soluble mining process for the tail pipe packer oil pad. Its drilling structure is shown in Figure 1. The surface casing diameter is 325mm × 291.77m (bit diameter 400mm), the technical casing diameter is 219mm × 1075.08m (bit 280mm), the ore section is naked, and the diameter is 188mm. The process comprises two stages of three-pipe oil pad construction and tail pipe packer section on the process of dissolution and recovery.
Fig.1 Schematic diagram of the structure of Luo 22 #三管油垫
1-half water; 2-water; 3-oil; 4-overburden; 5-underburden; 6-underburden;
7-63.5mm center tube; 8-136.5mm ring tube; 9-173.5mm technology sleeve
    One or three tube oil pad construction stage
The main operation technology at this stage is to solve the method of water injection and oil injection, to stabilize the thickness of the oil cushion layer and the height of the step, to prevent the upper solution and develop the side dissolution.
Water injection operation: In the initial stage of the tank construction, the positive circulation is used to inject the fresh water horizontally through the sieve hole at the end of the central pipe, and the reverse circulation can also be used to horizontally inject the water through the "guide device" installed at the lower end of the water pipe. In the initial stage, the water is injected with a small displacement (8~12m 3 /h). With the expansion of the salt tank, the water injection amount (up to 20m 3 /h) is appropriately increased. In order to meet the needs of building a low tank, the water injection volume remains relatively constant for a certain period of time. Stable, avoid large fluctuations in the fluctuation of the oil layer under the well.
Oil filling operation: oil is injected from the outer annulus to form an oil cushion on the outside of the water outlet. Calculate the oil demand in the well with the salt tank side dissolution rate and the required oil cushion thickness. According to the development of the salt tank, replenish the oil at any time to keep enough oil in the well to ensure a certain thickness of the oil cushion. In order to prevent the upper tank from being raised when the water pipe is drained during the construction stage, the oil is replaced with saturated brine before the pipe is lifted, and the water is injected after the lower pipe is injected first, and then the water injection is started. Luo 22 # is built in 372 days. The diameter of the salt trough is 78.6m, the trough height is 4m, the volume is 5740.4m 3 , and the brine is 79597m 3 .
    Second, the tail pipe packer step on the soluble recovery stage
After the tank is built, the water pipe is pulled out, and the tail pipe and the center pipe with the packer are placed to form a three-pipe structure. The packer is used to fill the annulus between the technical casing and the tail pipe at a predetermined well depth, and the two-tube structure is above the packer. The oil filling method of the two-pipe oil pad method is adopted, that is, the oil and water are paralleled, and the oil is injected by means of water flooding. After the oil water is separated, an oil cushion layer is formed below the sealer seal ring to the open hole section of the tail pipe outlet. Control the effect of dissolution.
The upper dissolved production method is similar to the traditional oil pad method. The height of the tail pipe can be adjusted up and down to control the height of the oil cushion layer, and the ladder segments and oil discharge can be divided. When each step starts to produce, it must be produced in the same way as the oil pad is built, and the amount of oil is increased. At the same time, there is a large cavity on the outlet side of the tail pipe to gradually increase the water injection amount. The solution on the ladder starts to use reverse circulation operation. The initial control water injection amount is 20~30m 3 /h. It is necessary to refuel frequently, then gradually increase the displacement to 40~45m 3 /h. In the initial stage, take “over-fueling” and take the “pre-fueling” in the medium term. "Measures, etc., in order to strictly control the height of the ladder.
When the water-filled mining process of the oil pad is used to raise the water injection pipe during the tank construction process, the height of each lifting should not be too large, and the upper height of the first step should be appropriately reduced so as to expand the diameter of the cavity to 100m when the first step is dissolved. . In the upper production process, the average daily salt intake is 277.63 tons, and the average brine content of brine is 316.43 g/L. The diameter of the cavity is 101.4m, the height of the step is 1.4m, the average thickness of the oil cushion is 1.91cm, and the average fuel consumption per ton of salt is 0.196kg.

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