Washing the well means that due to the engineering needs, during the workover operation, the well washing medium is injected from the pumping equipment through the wellbore or the drill pipe, and the material in the wellbore (liquid phase, solid phase, gas phase) is carried to the ground, thereby changing The nature of the media in the wellbore meets the requirements of the job.
The method of washing the well is: pumping the clean water with the original drilling pump, that is, after the water is changed, the circulation is further washed, and the well is washed, and the water is washed; the water circulation is stopped, and the piston is continuously lifted up and down in the well pipe to cause pressure surge. Destroy the mud wall of the well wall and at the same time dredge the pores of the aquifer, which is called the piston washing; the piston washing needs to be alternately repeated; before the pumping test, the centrifugal pump or the compressed air machine is used to pump the groundwater to reach the water and stabilize the water, and then proceed. Pumping tests, called pumping and compressed air washing; in addition to washing wells with carbon dioxide, pickling wells.
The well washing is divided into positive circulation washing, reverse circulation washing and mixed washing. Generally, different washing methods are selected according to the needs. The advantages of positive circulation washing are high flow rate of washing liquid, high pressure and strong flushing ability. The tool and the bottom of the well can have a better flushing effect, which can reduce the chance of the drill cuttings being repeatedly broken, and can also double as a power source to rotate the drilling tool.
Reverse circulation drilling is divided into gas lift reverse circulation, air reverse circulation, pump suction reverse circulation, etc. It has the advantages of achieving geological sand recovery, improving drilling efficiency of leakage layer, reducing or eliminating leakage of drilling fluid, protecting reservoirs, It can reduce pump loss, extend the life of mud pump pump, and have flexible well control.
The mixed circulation well washing makes up for the shortcomings of the flushing of the larger drilling diameter by the positive circulation washing well, but it cannot continuously carry out the drilling construction and increases the auxiliary time. Only by comprehensively selecting the correct well washing method in all aspects can a better well washing effect be achieved.