Oil well sand flushing operation principle and operation steps

Overview of punching sand

Sand flushing is the process of using high-speed flowing liquid to disperse the sand at the bottom of the well, and using the circulating liquid flow to bring the dispersed sand to the surface.

1.Requirements for sand washing fluid

(1) It has a certain viscosity to ensure good carrying capacity.

(2) It has a certain density to prevent blowout and leakage.

(3) Good compatibility, no damage to the reservoir.

2. Punching sand method

(1) Forward flushing: sand flushing fluid flows to the bottom of the well along the pipe string and returns to the surface from the annular space.

(2) Recoil: the opposite of positive recoil.

(3) Rotary sand flushing: The use of power source to drive the tool rotation, while the pump cycle carrying sand, overhaul sand flushing commonly used this method.

3. Sand washing scheme

Content and requirements of sand washing scheme:

(1) The geological plan of the sand-washing well must provide accurate data of the oil reservoir, the physical property of the producing reservoir, the production performance and the well depth structure.

(2) The plan should indicate the depth of the artificial well bottom, cement surface or release tool, and the location of the sand surface and the situation of falling objects in the well.

(3) The plan should provide perforated well intervals, especially high-pressure well intervals, lost well intervals and pressure values.

(4) When the plan requires the retention of part of the sand column, the depth of punching sand must be indicated.

(5) For the sand washing of the sand control well in the pipe, the structure diagram of the sand control pipe column must be marked.

(6) It must be indicated in the plan to prevent clay expansion, wax ball plugging perforation (note: at present, the use of wax ball this process has been banned in some oil fields, and it needs to be used according to the requirements of the oil field) plugging perforation, mixed gas sand flushing, etc.

Operation steps

(1) Preparation

Check the pump and liquid storage tank, connect the ground line, and prepare sufficient amount of sand washing fluid.

(2) Sand detection

When the sand washing tool is 20m away from the oil layer, the lowering speed should be slowed down. When the suspended weight drops, it indicates that the sand surface is encountered.

(3) Sand washing

Open pump circulation above 3m from sand surface, and lower pipe string to sand flushing to design depth after normal operation. The export sand content is less than 0.1%, which is regarded as qualified sand washing.

(4) Observe the sand surface

Lift the pipe string to the top of the oil layer more than 30m, stop pumping for 4h, lower the pipe string to explore the sand surface, and observe whether sand is produced.

(5) Record relevant parameters: pump parameters, sand surface parameters, return parameters.

(6) Buried sand.