During the drilling process, the phenomenon that the drilling tool is stuck in the well and cannot move freely due to various reasons is called sticking. It mainly includes keyway sticking, sand sinking sticking, well collapse sticking, differential pressure sticking, reduced diameter sticking, falling object sticking, sand bridge sticking, mud bag sticking and drilling tool falling off. Formation structure, poor drilling fluid performance, improper operation, etc. may cause sticking, which must be analyzed according to the specific situation in order to effectively solve the sticking.
 1) Keyway sticking
Keyway sticking mostly occurs in hard strata, where well deviation or azimuth change is large, forming a dog leg. During drilling, the drill string rotates close to the dogleg section. During tripping, the drill string pulls and scrapes up and down on the dogleg section, grinding a keyway on the well wall, and lifting
The drill bit is stuck when pulled into the bottom of the keyway. The keyway sticking is characterized by no resistance in tripping, normal drilling and normal pump pressure, but sticking is often encountered when tripping out to the dog leg. It becomes more serious with the increase of the well depth; it can be lowered but not raised, and in severe cases
Probably stuck.
To prevent the occurrence of keyway sticking, first of all, the borehole quality must be ensured to avoid the occurrence of dog-leg sections with large inclination; when tripping out or tripping out again, the keyway should be repeatedly redrawn in the keyway section to damage the keyway in time, and the keyway should be started slowly when tripping out to the keyway section.
, Smooth operation, high-speed trip-out is strictly prohibited.
 2) Sanding and sticking
When drilling with drilling fluid with low viscosity and low shear force, due to its poor ability to carry rock cuttings in suspension, the rock cuttings will sink once the pump is stopped. The longer the pump is stopped, the more sand will sink. In severe cases, the sinking rock sand may block the annulus.
, bury the drill bit and part of the drill string to form a stuck drill. At this time, if the pump is turned on too hard, the formation will be leaked or the jam will become tighter. The performance of sand sticking is: restart the pump circulation, the pump pressure is very high or the pump is blocked;
It is more and more difficult to lift and lower, and the resistance is very large when rotating, and it cannot even rotate. The performance is that the drilling fluid spray potential is very large after receiving a single column or tripping out to unload the column.
 3) Well collapse and sticking
In the water-absorbing and swelling mud, shale, poorly cemented conglomerate sandstone and other formations, it occurs more often during drilling or ream. The main reason is that due to the large water loss of the drilling fluid, the time to soak the formation is longer; the density of the drilling fluid is small, or
Drilling fluid is not filled in time when tripping out and the borehole wall collapses due to suction, causing sticking. Generally, before serious well collapse, large mud cakes and small strata fall off first, which cannot be drilled to the bottom after changing the bit. Sometimes large mud cakes and small strata are carried in the drilling fluid.
The uncut upper rock of the block; the sudden occurrence of drilling stoppage during drilling, the rise of pump pressure due to resistance in lifting, the stoppage of pump and the failure of drilling tools to rotate, etc., all indicate that the well may be caved and stuck.

 4) Differential pressure sticking drill (adhesion sticking drill)
In horizontal well drilling, the downhole drilling tool is close to the lower borehole wall by gravity. Under the action of downhole pressure difference, some parts of the drilling string will stick to the borehole wall, and the drilling string and the mud cake of the borehole wall will be bonded together. The longer the static time is, the contact area between the drilling tool and the mud cake will be.
The greater the resulting stuck drill, known as the differential pressure stuck drill.
 5) Diameter-reducing sticking drill
Shrinkage sticking often occurs in expansive formations and well sections with good permeability and porosity. Due to the poor performance of drilling fluid and large water loss, it is easy to form gelatinous loose mud cake on the borehole wall. When the pump displacement is small and the return speed of drilling fluid is low, it is easy
More clay particles, cuttings and weighting agents precipitate on the mud cake, resulting in the reduction of the well diameter.
The main manifestations of the reduced diameter sticking drill are: the position where it encounters resistance is fixed, the pump pressure increases during circulation, the lifting is difficult, the lowering is easy, and the upper part of the drill pipe joint is often soft mud cake. High quality drilling fluid with low density, low solid phase and low water loss
, or mixed with oil, and ream the hole in the blocked well section of the next drill to expand the diameter of the reduced diameter, often active drilling tools can effectively prevent the reduced diameter stuck drill. In the plastic creep formation, including salt layer, paste layer or paste-containing rock layer, plastic mudstone formation in a certain
Under the action of stress and temperature, it has obvious plastic creep ability. In drilling, if the pressure of the fluid column formed by drilling fluid is not enough to resist its plastic deformation, it is easy to cause serious diameter reduction sticking rapidly.
 6) Falling object sticking
Due to careless operation, oil rags, slips, tongs or other small tools are dropped into the well, and they are stuck between the well wall and the drilling tool or between the casing and the drilling tool, resulting in sticking of the falling objects. This kind of sticking is obvious, as long as the operation is strictly carried out
Regulations, strengthen the sense of responsibility can be avoided.
 7) Sand bridge sticking
The phenomenon of sand arching or sand plug jamming the drill string due to the accumulation of sand particles in the formation or wellbore is called sand bridge sticking. The preventive measure is to clear the "big belly" well section in time and strengthen the circulation of the "big belly" well section. In addition, there are
It can be seen that there are many causes of sticking, such as mud bag sticking and drilling tools falling off. Therefore, in addition to actively preventing sticking, correct judgment and analysis should be carried out in the event of sticking to find out the real cause of sticking.
Therefore, correct and effective measures should be taken to solve the card in time to avoid further deterioration of the accident.