Reason, characteristics, prevention and treatment of sticking
Reason:
The main reason for sticking is that there is mud cake with large viscosity coefficient on the borehole wall, and there is a positive pressure difference between the liquid column pressure and the formation pressure in the well. Once the circulation is stopped and the drilling tool is not moved, part of the drilling tool will stick to the borehole wall and contact with the mud cake, and the drilling tool will be stuck after a period of static time.
Characteristics of the occurs under static state of drill string; Stuck in the drill collar or drill pipe; Drilling fluid circulation is normal; After sticking, if the movement is not timely, the sticking point may move up, even move to the casing shoe
Prevention
Use anti-stick drilling fluid system and well control it; As long as there is no high-pressure zone or collapse zone, near-equilibrium pressure drilling should be performed. The weighted material is mixed into the drilling fluid in the well after fully stirring; Reasonably designed drill string structure, especially the lower drill string structure, with a while drilling shock; Maintain good wellbore structure; In normal drilling, such as water faucet, hose failure, should not sitting at the wellhead for maintenance, once stuck, will lose the possibility of pressing down and turning the drill string
Solution: :
Under the premise of not exceeding the safety load of the drill pipe, it can be properly yanked and put, and the drill tool can be forcibly turned; When the upper and lower drilling tools are ineffective, immersion solution (crude oil, diesel oil, kerosene, hydrochloric acid, soil acid, clear water, salt water, alkali water, etc.) should be used.
2. The reason, characteristics, prevention and treatment of mud bag stuck
Reason:
Drilling through mudstone with strong hydration ability; Drilling fluid circulation rate is too small to carry cuttings away from the bottom of the hole; The mud cake with poor quality and is scraped and piled up by the drill bit or centralizer during drilling. Drill thorn leakage
Characteristics:
The ROP decreases gradually and the rotary torque increases gradually. Pump pressure increased; Lifting the bit has resistance; When drilling, the resistance changes with Jingxing; During tripping, the fluid level in the annular space at the wellhead drops, either very slowly, or spills as the drill pipe rises
Prevention
Adequate drilling fluid displacement; When drilling in a soft substratum, it is important to maintain low viscosity, low shear fluid properties, preferably using a scraper bit, controlling ROP or increasing the amount of time circulating the fluid. When drilling, always observe whether the pump pressure and drilling fluid outlet flow have changes; If mud bag is found, stop drilling, lift the drill bit, rotate at high speed, lower quickly, and use the centrifugal force of the drill bit and the high-speed scouring force of liquid flow to remove mud bag
Solution:
When mud bag is stuck at the bottom of the well, create a large pump volume to reduce the viscosity and shear force of drilling fluid, and at the same time, under the premise of not exceeding the safety load of drill pipe, lift with the maximum tension (with the hammer on); When conditions permit, large displacement circulation drilling fluid, greatly reduce the viscosity and shear force and add cleaning agent, strive to wash away the mud package; Injection of card release agent; Reverse or explosive reverse sleeve milling out card.
Reason:
Too little surface casing, too much soft ground exposure; Adding too much flocculant in drilling fluid; The drilling fluid displacement cannot keep up with the fast drilling speed, and the concentration of cuttings in drilling fluid is too high. Long drilling cycle, or long static time of drilling fluid in the well
Characteristics:
When drilling down, the wellhead does not return drilling fluid or reverse injection drilling fluid in the drill pipe; During tripping, the fluid level in the annulus drops and the fluid level in the drill string drops rapidly. Drilling tool into the sand bridge, before opening the pump up and down activity and rotation freely, hanging weight drop, wellhead does not return drilling fluid or return very little; When drilling, if the displacement is small or carrying sand capacity is poor, the circulation process of drilling tool up and down activity, once the pump is stopped, the drilling tool cannot be lifted, especially for solid phase free drilling fluid this situation happens especially much
Prevention
Optimized drilling fluid design; When drilling, select pump rate according to formation characteristics; Do not cut holes in poorly cemented strata; When drilling, it is found that the wellhead does not return to the drilling fluid or the backspray in the water hole of the drill pipe, should stop drilling; When tripping, it is found that the annulus fluid level does not drop, it should be stopped. Control expansion rate; When the formation is soft and the drilling rate is fast, the appropriate cycle time; In the open hole section, the drilling fluid should not be stationary for too long
Solution:
If small displacement circulation drilling fluid, maintain small displacement circulation, gradually improve the viscosity and shear force of drilling fluid, to improve the sand carrying capacity of drilling fluid, and then gradually increase the displacement of drilling fluid, and strive to open the circulation path; If the circulation of drilling fluid is lost, only the use of the inverted sleeve milling out of the card, cannot be hard pulled out of the drill
4 . Sand sinking stuck drill
Reason:
why poor cuttings suspension ability when drilling with clean water. Cuttings cannot return up in time, and the concentration of cuttings in clean water is large. Cuttings sink after single connection or pump shutdown
Characteristics:
After connecting the single root or pulling off the column, the drilling fluid will backflow and backspray. When connected with a single open pump, the pump pressure is very high or hold the pump; When the upper lift drill is blocked and cannot move or rotate, it holds back a lot
Prevention
Adjust drilling fluid performance and increase pump displacement appropriately; Shorten the time of receiving single root; When it is found that the pump pressure increases and the cuttings return is less, the drilling rate should be controlled, or the drilling tool should be stopped to increase the displacement cycle. In case of a jam, do not hard draw the drill tool, should circulate drilling fluid and activity drill tool as soon as possible; If the circulation failure, to immediately stop the pump put back water, so that the backlog of tight layer sand loose, immediately on the body of the drilling tool, pull out and then hole through the well
Solution
The treatment method is the same as the sand bridge stuck drill
5. shrinkage stuck
Reason:
Shrinkage of conglomerate, mud shale, salt rock and deep gypsum layer; Existing slim and curved Wells; Formation dislocation causes lateral borehole displacement; Run a larger stage bit into a smaller stage well; The drilling fluid properties have changed greatly.
Characteristics:
Unidirectional resistance, resistance card is fixed at a point in the well depth; Most of them occur during lifting and lowering rather than static, and only a few occur during drilling (through salt rock, hydrous mudstone, asphalt layer), when the pump pressure will gradually increase, or even lose circulation; Move up and down and rotate normally when leaving the resistance point, and loose mud cake is not often found on the drill pipe joint.
Prevention
When running a drill, centralizer, or other tool with a large diameter, carefully measure its outer diameter; Change the bottom hole structure to increase rigidity; Drilling resistance cannot be forced, should be drawn down to eliminate resistance; When drilling difficulties cannot be hard lift, should circulate the drilling fluid, take the method of backrow hole out; Control fluid loss and solid content
Solution:
In the early stage of getting stuck, the drilling tool should be vigorously active to solve the stuck; Shake the card with the shocker; If it is the compound stick of reduced diameter and adhesion, should be soaked first, If the reduction is caused by the salt formation and the drilling fluid circulation can be maintained, fresh water can be pumped to the salt formation reduction section to dissolve the salt formation while the shaker is used to shake the trap free. If the reduced diameter is caused by mud shale, can be pumped into the oil (cleaning agent, lubricant), at the same time with the shock shock solution card; If the above methods are not effective, only use the drill tool reverse or explosive reverse sleeve to mill out the card.
6. key way sticking
Reason:
The well with a large full Angle deviation rate of the well section; More trips and longer drilling cycle; Mostly occurs in hard strata (some soft strata)
Characteristics:
Only in case of tripping; If the outer diameter of the drill collar is larger than that of the drill pipe joint, the top of the drill collar will encounter obstruction when it touches the lower mouth of the keyway. In the stratum with uniform lithology, the keyway develops toward the upper and lower ends. The blocking point of each trip moves downward, and the distance is not much. When the keyway is blocked and stuck, when the pump circulates the drilling fluid, the pump pressure does not change and the inlet and outlet flow is balanced. It is difficult to start the turn table, when the tension is high in the keyway, but it can rotate freely as long as the lower drill string is free of the keyway (the suspension weight must be restored)
Prevention
Ensure the hole quality, make the full Angle change rate of the well inclination meet the requirements, avoid drilling dogleg Angle section; When drilling directional Wells, the trajectory of well depth should be simplified as far as possible under the conditions of geological conditions, and the incline should be increased more and decreased less. Use high performance bits to increase drilling speed and reduce trips; After the keyway is found, the keyway should be cut repeatedly in the keyway section to actively and timely break the keyway when drilling again
Solution:
Use the weight of the drill string to push down vigorously, adding the pressure until the jam is free; The drill string is equipped with a jaser while drilling, which can be activated to unlock the card once it is stuck. If the shock is not effective, only the use of drilling tool or explosion buckle sleeve milling out the card; If keyway stuck in limestone and dolomite strata is formed, inhibitory hydrochloric acid can be used to deal with it.
7. Falling objects stuck in the drill
The sense of responsibility is not strong, violate the operating procedures; Engineering geological factors
Characteristics:
In drilling, there is a phenomenon of outdated and holding back the drilling. The upper body drilling has resistance, and the small falling object may be lifted off, while the large falling object is more and more dead. In the process of tripping, there will be sudden resistance if there are falling objects. As long as the lifting force is not large, the lowering is relatively easy. The clamping position is generally in the drill bit or centralizer position, larger objects may also be stuck in the drill pipe joint; The circulation was normal with no change in pump pressure, displacement and drilling fluid performance
Prevention
Check wellhead tools regularly to prevent falling objects from wellhead; Minimize the pocket length below the casing shoe (1 ~ 1.5m is better), and ensure that there is high quality cement at the casing shoe to prevent cement block breakage; In the case of abnormal hanging weight or abnormal pump pressure, do not put inclinometer, steel ball and other objects into the drill pipe
Solution:
In case of falling objects stuck at the bottom of the well, the drill bit should try to solve the stuck by rotation. Under the premise of not exceeding the safe load of the drill pipe, the drill bit should be lifted with the maximum tension. In case of falling objects stuck in the drill pipe during tripping, under the premise of not exceeding the safe load of the drill pipe, the weight of all the drill pipe should be used to press down violently; With the hammer under the release card; If the cement block caused by the stuck drill, can be treated with inhibitory hydrochloric acid;
8. Dry drill stuck
Reason:
Drilling tool leakage; The gate between the pipelines is punctured or not closed; The water on the drilling pump is not good, the viscosity of drilling fluid is too high, the gas content is too much, can reduce the displacement of drilling fluid; Pump room and drilling floor work not well, resulting in interruption of drilling fluid circulation
Characteristics:
Drilling tool leakage, under normal displacement, the pump will gradually drop; The water on the drilling pump is not good, the wellhead return volume is reduced; The rate of penetration decreased significantly; The rotary table torque increases; The first stage of dry drilling is mud bag, which can move the drill tool, but has resistance when lifting. With the increase of the degree of dry drilling, the resistance becomes larger and larger until it can not be moved, resulting in stuck drilling; Dry drilling results, generally is the drill hole plugging, in addition to drilling tool leakage, is unable to open the pump cycle
Prevention
Pay attention to the pump pressure and wellhead drilling fluid return flow. If the pump pressure drops and the return flow decreases, the drilling should be stopped for inspection. If it is found that the rate of penetration decreases, the torque of the drill disc increases, or even the phenomenon of holding back the drill and knocking down the car, it should be combined with the pump pressure, wellhead drilling fluid return volume, and the characteristics of the forward drilling formation for comprehensive analysis. Pump room and drill floor work to coordinate, for reasons to stop the pump, must first inform the driller; If the stop cycle time is long, the drilling tool should be lifted from the bottom of the hole, up and down activity or rotation, never allow the drill bit pressure in the bottom of the hole with the rotary table to move the drilling tool; Degassing of gas-invading drilling fluid should be strengthened to improve water feeding efficiency of drilling pump
Solution:
When the dry drilling is not too serious and the bit has not been deformed, use the jar to hit the card; Explosive cutting; Use the original drill tool to directly reverse or explosive reverse to release the card; If the well is shallow, use reaming and casing milling to remove the card; Well filling and sidetracking;
The method of solving stuck drill accident
The movable drill string is unstuck
(1) When circulating drilling fluid is combined with movable drill tool, the sticking can be solved when it is not serious;
(2) sand stuck drill or well collapse stuck drill cannot lift the drill, can lower and rotate the drill, try to open the pump cycle, backward hole slowly lift the card;
(3) When the keyway, reduced diameter or mud bag card is drilled, the original hanging weight can be sharply released after the drill, not vigorously lifted, to prevent the more death of the card;
(4) when the drilling encounters resistance, the pressure is too large and the drilling is stuck, the larger force is used to lift the card; For differential pressure sticking, the method of lifting and releasing and turning the drill tool can be adopted to release the light sticking.
Bath solution well
When the movable drill tool cannot solve the jam, oil, salt water, bubble acid can be soaked into the well or water circulation can be adopted to loosen the sticky mud cake, reduce the viscosity coefficient, reduce the contact area with the drill tool, and reduce the pressure difference, so as to solve the jam.
The shock is unstuck
(1) In case of collapse, viscosity, expansibility and other strata that are prone to sticking during drilling, a shocker can be connected between drill pipe and drill collar. Once stuck, it can be immediately hit down or up to release the stuck.
(2) When stuck during drilling, such as reduction of diameter, keyway and other activities caused by stuck drilling cannot be solved, you can reverse open the drilling tool at the stuck point, and then connect the shock device. After the buckle, the next hit to solve the stuck. Then cycle the well, lift the drill tool, if it is stuck, you can turn the drill tool to cut the hole and gently lift it.
(3) When there is resistance in the process of drilling, the drill can not be found in time and stuck, or the light adhesion stuck, the upper hammer can be used to solve the jam.
Milling out the card of the inverted sleeve
(1) In case of serious stuck drilling, when the above methods can not be lifted or recycled, the field often uses the method of inversion and sleeve milling to remove all or part of the drilling tools in the well.
(2) Reverse is to invert the rotary table, and pour out the drill pipe in the well. The amount of drill pipe that can be poured out at a time depends on whether the thread tightness of the stuck drill pipe in the well is consistent. I want it to go backwards from the point.
(3) For the drill tool below the clamping point, the milling cylinder should be set to mill out the cuttings or falling debris outside the drill tool (the annular space between the drill tool and the borehole wall), and then pour out the drill tool. It takes a long time.
Explosion reverse buckle, sleeve milling
(1) First measure the position of the clamping point, and then use the cable to send the detonating cord from inside the drill tool to the thread of the first joint above the clamping point. When the middle part of the detonating cord is aligned with the joint, all the gravity above the clamping point of the drill tool is lifted, and a certain inverted torque is applied to the drill tool to ignite the detonating cord to make it explode.
(2) When the detonating cord explodes, intense impact and strong seismic force are generated, which causes elastic deformation of the joint part and timely inverted opening of the buckle, which is the same as the principle that when the drill pipe joint cannot be opened, the drill pipe female joint can be opened by hitting it with a sledgehammer.
(3) At the same time, due to the explosion of the detonating cord, a large amount of heat is generated, so that the drill pipe joint is heated, the thread oil is melted, and the plastic deformation is generated, which is also helpful to the thread discharge.
Explosion, sidetrack new borehole
When the above methods are ineffective, or the stuck point is deep, the method of inverted treatment is very time-consuming, and it will make the hole condition worse. The unstuck part of the drill tool can be blown up with explosives, and then the top of the drill tool left in the well is hit with cement plug, and a new hole is re-drilled.
