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Phenomenon And Process Of Pdc Bit Balling

(1), the cause of cone bit balling 1, geological factors: the upper part of the formation being drilled is not a rock ooze, easily paste to drill the surface, causing the bit balling after compaction; shale formations although diagenetic, but easy hydration dispersed wellbore within muddy or solid content increase, resulting adsorption bit balling on the bit surface; or strata containing dispersed like gypsum, after pollution caused by mud, mud are difficult to remove harmful solid, the drill was balling chances increase ; high formation permeability, under pressure effect, within the wellbore adsorption harmful solid and not in a timely manner to carry out cuttings to form thick mud cake in the bottom of accumulation caused PDC drill bit balling when tripping. 2, mud performance factors: poor inhibition mud, unable to control the dispersion of shale hydration; cut solid content and viscosity is too high, drilled cuttings are difficult to remove, easily adsorbed on the surface of the drill, if you are using non-solid phase drilling fluids, drill bits will never happen balling; high mud weight loss, easy to form a thick cake is too rough; poor lubrication, surface drill can not form an effective protective film, the poor quality of the drilling fluid solid Phase easily adsorbed on the drill bit. 3, engineering and technical factors: Drilling small displacement, can not effectively clean the bottom and drill, while return on insufficient speed, long residence time in the well cuttings, adhere to the wall to form a thick cake, especially in the upper part of the drill more serious high speed; soft shale formations, drilling pressure is too large, formation or drill cuttings and direct contact surface, causing bit balling; long open now not been drilled midway cycle, scraped from the wall of mud cake or drill cuttings will be balling. 4, bit selection factors: water hole chip design can not meet the requirements; runner chip angle hampered the smooth drill cuttings from the bottom. 5, the operating level factors: excessive speed drill, drill not track down the spiral downward slide, but the constant scraping mud cake on the borehole wall or cuttings, can easily cause bit balling; when drill Difficult Kelly is not connected to draw the eye wash cycle drill, but under the pressure or undershoot, scraped from the wall cake or drill cuttings will be balling; drilling in the end when the operating method is wrong, if the first start turntable After starting the pump, the same will cause bit balling; when drilling in soft formations, sending drill uneven. (2), PDC bit balling a common phenomenon, the drilling footage was slow significantly elevated or drilling; 2, increase or decrease the WOB WOB no significant effect on the drilling speed; 3, formation changes It has little influence on the drilling rate; 4, under normal circumstances the pump pressure increased slightly or no significant change; but sometimes with high pump pressure, and even blocked the drill water hole, blocking circulation channel; 5, the tooth can not be effectively drill eat into the formation, showing smaller torque or torque fluctuation range is reduced; 6, tripping a "pull piston" phenomenon; 7, after a short drilled from under the drilling speed significantly slower, continue drilling may gradually restore the original ROP The mud pack to lift or continue to slow down caused serious unable drilling mud pack; 8, drilling hole washout occurs, a short-circuit loop, after processing drilling speed significantly slower. (3), PDC bit balling prevention 1, adjust the mud performance 1), contaminated lubricant or increase in volume, so that the cuttings difficult to stick to the drill bit; 2) increase the polymer content of the drilling fluid, control water loss and improve the quality of mud cake; 3) improve the drilling fluid inhibition, reducing dispersion shale hydration; 4), reduce drilling fluid viscosity, shear force, the timely removal of low-quality solid phase; 5) of hypertonic sand, you can use temporary blocking technology to reduce the permeability loss; 6) containing cream rock, should be added to the base in advance, to prevent its pollution mud. 7), maintenance deal with mud performance, before and after the PDC drill bit into the well to prevent bit balling are valid; PDC back into the well, before opening the pump, configured a certain amount of cleaning agent (surfactant) drill bit to clean also have some effect . 2, oil drilling equipment engineering and technical measures 1), first do the work of PDC bit selection, drill water hole, flow channel design should be conducive to the chip; 2), the PDC drill bit before the next should be fully circulating mud, cleaning the wellbore to prevent tripping after staying in the borehole cuttings continue hydration dispersion; 3) under the PDC before the first short tripping, scraping mud cake on the wall, squeezing, pull the thick mud cake thin, compacted, try to ensure the smooth flow of the borehole, to eliminate the resistance card; the high incidence of bit balling , if all the methods can not avoid the PDC bit balling, then the first trip to the well through the use of cone became necessary means 4), when the drill bit channel surface painted in butter, a protective film is formed to reduce the time the drill bit and mud in direct contact with the poor quality of the solid phase, or wrap the drill, in so doing we will be in deep wells also have a role; 5), the next drill constantly scraping the wall, mud cake on the borehole wall or stuck in the well cuttings will accumulate at the bit, to a certain extent will be compacted in the drill, then drill midway cycle, Rinse the drill is its necessity; 6), under drilling process should be properly controlled speed to prevent sudden drill into the sand bridge, into a pile of mud; and in addition, if the speed properly, PDC drill bits will drill down on a spiral drilled borehole trajectory travel, rather than on the wall under a lot of cake Huala. 6), each drill must be open when the pump in the end, to maximize the full flush displacement downhole and drill, and other emissions to meet the requirements and then gently press rotary drilling 0.5-1m, which is the PDC bit modeling requirements. 7), try using a large displacement drilling, to ensure adequate cleaning and cooling PDC drill bit; 8), into the soft mud, we should try to use low WOB, high speed, large displacement, there is no need to blindly use high WOB to pursue that only high-speed drilling a small point, it is just the use of roller bits the way; 9), the operation should be fine, send the drill pressure must be uniform, not suddenly large and small. (4)、 PDC bit balling processing 1, bit balling process first rule is: do not rush Chisel, because the more packed the more powerful; 2, stop drilling, increase the displacement strengthen water flushing effect, put on the drill bit from the bottom, increase speed to increase the centrifugal force is easy to throw mud, and up and down dramatically activities several times, then under the pressure to the bottom is not open turntable 5-10 minute cycle, the above process is repeated; if the two cycles weeks invalid, you should consider starting drilling. 3, regardless of bit balling prevention or treatment, are necessary to adjust the mud performance, found signs of drill mud pack, should immediately stop drilling and configure cleaner for the first time into the wells to drill for cleaning. (End)

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