What is the cause of the drilling mud bit?
The mud performance factors: poor inhibition of mud shale hydration dispersion cannot control the solid content and high viscosity; cut, drilled cuttings are difficult to remove, easy to adsorb on the surface of drill bit, if you are using solid free drilling fluid, the bit will never happen in mud; mud is high, water loss is big, easy to the formation of a rough thick mud cake; poor lubrication, the surface can not form an effective protective film, drilling fluid in solid phase adsorbed on the bit inferior.
Bit selection factors: hydrophthalmia chip design can not meet the requirements; channel chip angle hindered the smooth out of bottom hole drilling.
Engineering Technology: small displacement drilling, can not effectively cleaning the bottom and at the same time, the return speed of drill cuttings in the well, long residence time, adhered to the wall to form a thick mud cake, especially in the upper part of drilling speed is more serious; in soft rock strata, the drilling pressure is too large, or drilling stratum with the drill bit is formed on the surface of direct contact, causing bit balling; long open hole drill is not halfway through the cycle, from the mud cake wall scraping or cuttings are bit balling.
Operation level factors: drilling speed too fast, not along the spiral drill track sliding down, but on the wall constantly scraping mud cake or cuttings, extremely easy to cause the drill bit balling is not difficult; the Kelly circular reaming bit under pressure or flush, but from the mud cake on the wall down, scraped or will drill bit balling; operation end drill is wrong, if the first start after the turntable, start the pump, will also cause bit balling; drilling in soft stratum, drilling is not uniform.
Geological factors: the drilling for upper diagenetic ooze, easy to paste on the bit surface, bit balling caused by compaction after formation of shale; although diagenesis, but easy dispersion, the borehole mud or solid content increased, adsorbed on the surface of drill bit by bit balling; or the strata containing dispersed gypsum, resulting in mud pollution, harmful solid mud in difficult to remove, the probability of bit balling is increased; the formation of high permeability, under pressure, harmful solid phase adsorption within the wellbore and cuttings did not timely carry out the formation of thick mud cake, while tripping in PDC below the drill bit caused by the accumulation of bit balling.
