PREVENTION OF PDC BIT MUD PACKS

1. Adjustment of mud performance

1) Mixing oil or increasing the amount of lubricant input, so that the drill cuttings are not easy to adhere to the drill bit;

2) Increase the polymer content in the drilling fluid, control water loss, and improve the quality of mud cake;

3) Improve the inhibition of drilling fluid and reduce the hydration and dispersion of shale;

4) Reduce the viscosity and shear force of the drilling fluid, and remove the inferior solid phase in time;

5) For high-permeability sand layers, shielding temporary plugging technology can be used to reduce permeability leakage;

6) For gypsum-bearing rock formations, alkali should be added in advance to prevent it from polluting the mud.

7) Maintaining and processing the mud performance is effective to prevent the bit mud pack before and after the PDC bit enters the well; after the PDC enters the well, before starting the pump, it is also effective to clean the bit with a certain amount of detergent (surfactant).

2. Engineering technical measures for Oil drilling equipment

1) First, do a good job in the selection of the PDC bit. The design of the water hole and flow channel of the bit should be conducive to chip removal; 

2) Before running the PDC bit, the mud should be fully circulated to clean the well bore to prevent staying in the well after tripping. The drill cuttings in the eyes continue to hydrate and disperse;

3). Before entering the PDC, the drill should be drilled shortly to scrape and squeeze the mud cake of the well wall, and the thick mud cake will be thinned and compacted, so as to ensure the smooth flow of the well and eliminate the blockage; , If all the methods are adopted and the PDC bit mud bag cannot be avoided, then it is necessary to use the cone to pass the well first;

4) When drilling, apply butter to the surface of the bit runner to form a protective film to reduce the time of direct contact between the bit and the inferior solid phase in the mud, or to wrap the bit. This is useful even in deep wells.

5). When drilling, the drill bit continuously scrapes the well wall, the mud cake on the well wall or the drill cuttings remaining in the well will accumulate under the drill bit, and will be compacted on the drill bit to a certain extent, then the drilling will be carried out in the middle of the cycle. It is also necessary to rinse the drill bit;

6) During the drilling process, the speed should also be properly controlled to prevent the drill bit from suddenly rushing into the sand bridge and drilling into a pile of mud; In addition, if the speed is appropriate, the PDC bit will follow the spiral borehole track drilled by the previous bit Travel instead of drawing a lot of mud cakes on the well wall.

7) Each time you drill down to the end, you must start the pump first , try to increase the displacement as much as possible to fully flush the bottom hole and the drill bit, wait for the displacement to meet the requirements, and then lightly press and rotate to drill 0.5-1m, which is also the requirement of PDC drill bit shape.

8) Use large displacement drilling as far as possible to ensure sufficient cleaning and cooling of the PDC bit;

9) Drilling in soft mud rock should use low bit pressure, high speed and large displacement as much as possible. There is no need to blindly use high bit pressure to pursue a bit higher drilling speed.

10). The operation should be fine, and the pressure of the drill must be uniform, and it should not be large and small.

Treatment of PDC bit mud packs

1. The first principle for handling drill bit mud packs is: don't rush to drill, because the more you pack, the more powerful it is;

2. Regardless of prevention or treatment of bit mud packs, it is inevitable to adjust mud performance. If signs of mud packs are found on the drill bit, the drilling should be stopped immediately and the cleaning agent should be placed in the well to clean the bit at the first time;

3. Stop drilling, increase the displacement to strengthen the hydraulic flushing effect, lift the drill bit out of the bottom of the well, increase the speed and increase the centrifugal force to make the mud easy to throw out, and move it up and down several times, and then press down to the bottom of the well without opening the turntable. Circulate for 5-10 minutes and repeat the above process; if it is invalid within 2 cycles, you should consider tripping.