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Analysis of Accidents and Complex Situations on Drilling Site
source:admin time:2018-08-01
Drilling Site Accident:
1. Drilling Abandonment:
It refers to the wells left by the drilling crew without completing the last process of a well. It also includes some wells that are not drilled to the target layer due to drilling accidents, have not obtained the geological data required by the design, and cannot be used for oil production, gas production or auxiliary production.

2. Abandoned Zone
There are two situations:
(1) when it is decided not to continue drilling due to the drilling accident, if the geological data required by the design has been obtained for a certain well section, the well section below the well section which has not obtained the geological data required by the design is the abandoned well section;
(2) some exploratory wells have not drilled to the target layer due to the drilling accident, and have not obtained the geological data required by the design, but have passed through the oil and gas reservoir, they can If it is used as an oil production, gas production or auxiliary production well, the well section that cannot be used from below the oil and gas reservoir is the abandoned well section.

3. Abandoned Footage:
It refers to the abandoned footage due to drilling accidents that cannot be removed, or the invalid footage due to disasters and other reasons.

4. Accident Lost Time:
It refers to the time from the occurrence of the accident to the time when the accident is relieved and the normal state is restored. Accidents include downhole accidents (such as sticking and fishing), blowout accidents, surface mechanical equipment accidents, fire accidents and personal accidents, etc.

5. Repair Time:
It refers to the time when the drilling work is forced to stop and repair due to the damage or operation failure of mechanical equipment or ground buildings. Including mechanical power repair and drilling tool repair.

6. Management Down Time Lose:
It refers to the downtime caused by poor organization, untimely supply of equipment, improper allocation of labor, waiting for orders, etc.

7. Problem Handling Time:
It refers to the time to deal with excessive well deviation or wall collapse, backfilling and re drilling, lost circulation, water flooding, gas flooding, jamming in case of resistance, failure of drilling fluid circulation, deterioration of drilling fluid performance, skip drilling, poor drilling, etc.

8. Sucker Rod Failure:
The fatigue failure of the sucker rod under alternating load leads to fracture.

9. Cable Breakdown:
Due to cable quality problems, or long-term use aging, or cable corrosion and other factors, it is easy to break down. When the pump is started, the cable is broken, slipped, or even piled up, leading to underground accidents.

10. Engineering Abandoned Well:
Due to the drilling accident engineering accident, the well which can not reach the designed depth and is abandoned.


11. Downhole Accident:
Due to various factors, the string in oil and water wells meets pieces, and tools, instruments and drill strings fall into the well.

12. Down Hole Trouble:
The sudden situation that causes the normal operation interruption of drilling tools in the hole.

13. Resistance:
If the hanging weight is lower than the original one during tripping.

14. In Case of Card:
When lifting the drilling tool, if the hanging weight exceeds the original one.

15. Buried Well:
It refers to the phenomenon that the tools or drilling tools used in oil drilling cannot be lifted out of the well due to drilling accidents.

16. Hole Bending:
Borehole inclination caused by geological conditions, installation and operation of drilling equipment.

17. Borehole Collapse:
The static pressure of drilling fluid is less than the side pressure of the hole wall and the side pressure of groundwater, which leads to the failure of the stability and integrity of the hole wall.

18. Overpressure Pumping:
The circulation channel of Flushing Fluid is blocked and the pump pressure is increased.

19. Drill Rod Burying:
The drilling tool in the hole is buried by Rock Powder, Rock Debris Sedimentation or Hole Wall Collapse (or Quicksand), which can't rotate and lift, and the flushing fluid can't flow.

20. Bit Burn:
In drilling, because of poor cooling or no flushing fluid circulation, the bottom of the drilling tool and the bottom of the hole rock, rock powder and hole wall are sintered together.


21. Breaking Off:
An in hole accident in which the drilling tool breaks in the hole.

22. Run Down of Drill String:
When lifting the drilling tool, the drilling tool falls into the hole.

23. Casing Accident:
The casing in the hole moves down and is out of joint due to improper fixation or broken thread.

24. Logging Engineering Accident:
It refers to all accidents except traffic accidents in the whole process of construction. Including loss of dangerous goods, equipment damage caused by operation error, overflow during logging, blowout (whether caused by logging operation or not), etc.

25. Downhole Complexity in Drilling:
In the process of drilling, due to improper selection of drilling fluid type and performance, poor quality of well bore and other reasons, the downhole is blocked, jammed, and the drilling is seriously broken, lost circulation, blowout, etc., which can not maintain the normal drilling and other operations.

26. Drilling Accident:
It refers to the bad results such as broken drilling tools, over drilling, stuck drilling, blowout and fire caused by improper inspection, illegal operation and improper or careless measures to deal with the complex downhole situation.

27. Drill Rod Sticking:
The phenomenon that the pipe string and soil tools cannot be lifted, lowered or rotated in the well. In hole accidents in which the lifting of drilling tools in the hole is blocked due to falling block, keyway or reducing diameter of hole wall.

Sticking Accident:
The sticking accident is a drilling accident in which the drilling tool loses its freedom of movement, and it can neither rotate nor move up and down. The Drill String stops too long in the well or other reasons cause the accidents that can't be lifted, lowered or rotated, sometimes even can't be circulated. It mainly includes Sticking and Sticking Drill, Sinking and Sticking Drill, Sand Bridge and Sticking Drill, Well Collapse and Sticking Drill, Reducing and Sticking Drill, Mud Bag and Sticking Drill, Falling Object and Sticking Drill when drilling tools fall off.

1. Differential Pressure Sticking and Sticking Drill:
Due to the large pressure difference between the drilling fluid and the formation in the wellbore, the pressure difference forces the cable or the downhole instrument to cut into the Mud Cake. When the pressure difference produces a force greater than the maximum safe pulling force of the cable, the adsorption card will occur. Most of the adsorption cards are caused by the adsorption cable. This kind of situation usually occurs when the drilling fluid with high density is used in drilling or the drilling fluid is lost in the process of drilling, while the cable is stationary for a long time in the well during logging. In the process of Formation Testing or Sidewall Coring, pressure difference adhesion is easy to occur.

2. Differential Pressure Sticking Drill (Mud Cake Sticking Drill):
When the downhole drilling tool is stationary, some parts of the drill string stick to the wall of the well under the action of the downhole pressure difference and stick to the mud cake of the wall of the well. It is also called sticking and sticking or mud cake sticking. Under the action of the difference between the pressure of the drilling fluid and the formation pressure, the drill string clings to the wellbore and causes sticking.

3. Block Falling and Sticking:
As the formation and lithology are broken, when the Mud Wall protection function is not obvious, it is easy to cause block sticking with the high-speed movement and rotation of the Drill Pipe.

4. Cave in, Slough:
In the well section with extremely developed mudstone, shale, poorly cemented conglomerate or open fracture, due to the mud soaking, plus the height or pressure of the mud column in the well, or the piston swabbing of the drilling mud package, the formation on the well wall collapses.

5. Collapse Sticking:
Due to the large water loss of drilling fluid, the long time to soak the formation, the small density of drilling fluid, or the drilling fluid is not injected in time when tripping out, and the swabbing effect causes the borehole wall to collapse, which causes the drilling tool to be stuck due to the Borehole wall collapse.

6. Short Circuit Circulating Sticking:
Due to short Circuit Circulation of drilling fluid, the drill string caused by dry drilling of bit is stuck.

7. Cement Sticking:
After the completion of the cement plug, there is no timely back washing or lifting of the string, which leads to the phenomenon that the cement sealing will block the downhole string.

8. Casing Deformation and Sticking:
The phenomenon that the downhole string and tools are stuck in the casing due to the deformation of the casing, and the lifting operation cannot be carried out normally with a force equal to or larger than the hanging weight of the downhole string.

9. Scale Sticking:
The phenomenon that a large amount of scaling in the well makes the string in the well unable to be put forward normally.

10. Casing Sticking:
If the downhole situation is not well understood, the tool is run through the casing by mistake and the bit is stuck.


11. Wire Sticking:
Due to Wax Cleaning, testing and other work errors, the Steel Wire fell into the well. During fishing, due to the inaccurate judgment, the fishing tool was too deep down than the fish top, until the steel wire wrapped the drilling tool, and the steel wire was lumped when lifting up, causing sticking.

12. Wax Sticking Drill:
Sticking caused by the deposition of waxy substances in Crude Oil on the Pipe Wall.

13. Packer Stuck:
Sticking caused by packer failure after separate production and injection or casing pressure test.

14. Drilled Dry:
It refers to drilling without drilling fluid flowing through the bit.

15. Sticking of Dry Drill:
The heat generated by the bit's work on the rock can not be dissipated, resulting in the drill bit or even drill collar 16, part of the deformation on the external force Ren county and the sticking phenomenon caused by the rock debris fusion.

17. Key Hole Sticking:
The phenomenon of the drill string grinding a small groove on the wellbore to block the bit. The drilling tool is stuck due to the hole keyway. Because of the poor quality of the well bore, the sharp change of the deviation direction and the dog leg degree, the keyway is formed on the wall of the well, and the drilling tool is stuck in the keyway during the tripping out process.

18. Mud Bag Sticking:
The phenomenon that soft mud, filter cake and drilling cuttings are adhered around the bit or centralizer, or filled between the teeth or blades, or inlaid between the teeth, so that they are stuck during tripping out. Sticking of drill string caused by mud package of bit or drilling tool.

19. Sticking of Sand Bridge (Grit Setting):
Pipe string or tool sticking accident caused by sand in the well. In the production process of oil-water wells, formation sand flows into the well with oil flow, and with the change of flow rate, part of the sand precipitates gradually, thus burying part of the production string. During drilling, the circulation displacement is insufficient or insufficient, and the drilling fluid performance is not good, which results in cuttings sinking, blocking the circulation space, burying the bit and some drilling tools causing sticking.

20. Oversize (of hole):
Hole wall collapse or dissolution results in the increase of local hole diameter.

21. Hole Enlargement:
The phenomenon that the borehole diameter becomes larger due to the collapse of the sidewall rock, etc.

22. Undersize (of hole):
The phenomenon that the hole diameter of the local hole section is reduced due to the water absorption and expansion of the hole wall rock.

23. Reducing and Sticking:
Due to the sticking phenomenon caused by the reduction of the well diameter, the drill string and bit are stuck when the well is shrunk and Pooh to the small hole.

24. Slim Hole Sticking:
It is caused by the shrinkage of special formation, the mud cake thickness caused by the loss of water in the drilling fluid is less than the diameter of the bit to form a small hole plug, and the drilling tool runs disorderly or forcibly into the small hole, resulting in a sticking.

25. Pick Up Drill:
In the process of tripping out or picking up a single piece, it is blocked and stuck.

26. Falling Object Jamming:
Sticking of drill string caused by falling objects of the well. The surface tools, tools and articles fall into the well and cause sticking; the drilling tool breaks the cement ring and causes sticking.

27. Small Object Falling and Sticking:
In the workover construction, some hand tools, auxiliary tools, wellhead bolts, etc. fall into the well due to operation errors or poor inspection, causing sticking.

28. Wire Sticking:
Due to mistakes in paraffin removal, testing and other work, the steel wire fell into the well. Due to inaccurate judgment, the fishing tool was lowered too deep than the fish top, resulting in the steel wire wrapping the drilling tool and sticking caused by the steel wire agglomerating during lifting.

29. Casing Milling and Sticking:
It refers to that in the process of casing milling, the casing milling barrel or the casing milling bit is blocked and cannot be lifted, placed and rotated. It is one of the most easy problems in the soil technology of taking and changing casing.

30. Bridge Plug Card:
The expansion of shale, the collapse of formation and the extrusion of debris will form bridge plug above or around the downhole instrument, which will cause bridge plug jamming.

31. Casing Damage Stuck:
The instrument may get stuck at the damaged or broken casing.

32. Cable Sticking:
It is easy to get stuck in case of bird cage damage or armored damage caused by the tied cable.

33. Jamming at the Window of Side Drilling Window Well:
When sidetracking an old well, a window is opened on the casing to drill a deviated well.
There are two situations:
(1) the dentate crack is formed in the process of casing hole drilling, which is not a standard ellipse, and the cable or instrument is easy to be stuck in the crack;
(2) the cement ring around the window vibrates and collapses, and the drilling fluid erodes the borehole to expand, forming a step at the window.


Drilling accident:
1. Drilling Accident:
The Drilling Thread in the well is reversed, the thread is broken and tripped, the Slip Thread, the Drilling Thread is broken, the body is punctured and even twisted.

2. Bit Drop:
The common forms of bit falling are Alloy and Cone falling, which can be salvaged many times by "One Grasp" method.

3. Drill Pipe Trip:
Because the Drill Pipe thread is damaged or not tightened, the Drill Pipe is easy to trip.

4. Broken Drill Pipe:
Due to the quality problems of Drill Pipe, in addition to Sticking, Paste Drilling, Formation Shrinkage and other reasons. It makes the torque of Drill Pipe increase and break.

5. Falling Objects in the Well:
In this case, falling objects in the well refer to that there has been a drilling accident in the well, and there are drill pipes, casings and other objects left in the well. In the process of dealing with the accident, artificial iron pieces and other falling objects occur.

6. Leakage:
Because of the unconformity and permeability of the stratum, Rock Fracture, Underground Karst Cave and other reasons. Loss of mud can occur.

Bit Accident:
1. Bit Accident:
In the process of drilling, there are some accidents, such as: Roller Bit Wiping Neck, Dropping Roller, Breaking Claw, Tooth and Roller; scraper bit breaking blade and joint; PDC bit falling off or synthetic polycrystalline diamond and natural diamond falling off.

2. Bouncing:
It refers to the phenomenon that the drill bit is not easy to drill and the drilling tool will run out when it encounters limestone, dolomite or cemented dense conglomerate and other hard rock strata.

3. Choke Off Drilling, Bit Bouncing:
In the process of drilling, the bit encounters the soft hard Interface Stratum, Poor Cemented Conglomerate, Fault, Fracture and Hole, etc. because of the uneven stress and reaction on the contact surface of the bit, the rotating speed of the rotary table changes from fast to slow, and the sound changes from high to low.

4. Stop Drilling:
Stop drilling.

5. Hanging the Bit in:
The process of drilling with little bit pressure.

6. Empty Downcast, Drilling Run into Vuggy or Loopinformation:
In the process of drilling, when encountering underground cavity, karst cave or extremely loose rock stratum, the sudden decrease of WOB tends to zero, the sudden increase of ROP to a great extent, and there is a phenomenon of footage without the use of pressure device to lower itself.

7. Bit Selection:
The process of determining bit type according to formation lithology and drilling method under certain well bore structure.

8. Bit Inspection:
In order to ensure that the model, size and quality of the bit in the well meet the requirements, some inspections are carried out before entering the well.

9. Bit Life:
The normal working time of the drill before the cutting element or bearing fails.

10. Reasonable Time to Pull the Bit:
In the service life of the bit, the trip out time of the bit is determined according to the optimal drilling technical and economic indexes.

11. Overuse of Bit:
The drill bit shall continue to be used after exceeding the reasonable use time.

12. Bit Uniform Wear:
It refers to the abrasion of the cutting elements and the outer diameter of the drill bit caused by the grinding effect of the rock during the normal drilling process. Roller bit also includes bearing wear caused by friction between cavity wall and bearing.

13. Bit Unfavorable Wear:
The bit is worn out too fast or damaged in advance due to improper selection and use or falling objects in the well.

14. Bit Excessive Wear:
The bit is severely worn due to overuse.

15. Bit Bearing Failure:
The Roller bit bearing does not work properly.

16. Bit Dullness Analysis:
The wear of bit after use is analyzed. It is the basis of evaluating the selection and use of bit. Roller bit is used to evaluate the wear degree of bit through the wear classification of teeth, bearing and outer diameter.

17. Tooth Dullness Grading:
A division of the wear condition of the Teeth of a roller bit. It is divided into 8 levels. Milling Teeth are determined by the relative wear height cc of Tooth height. Level 1 for CC ≤ 1 / 8; Level 2 for 1 / 8 < CC ≤ 2 / 8; and so on until level 8. Inlay teeth are determined by the ratio of the number of teeth dropped and broken to the original total number of teeth Cx. CX ≤ 1 / 8 is level 1; 1 / 8 < CX ≤ 2 / 8 is level 2; and so on until level 8.

18. Bearing Wear Grading:
A division of the wear condition of the roller bit bearing. It is divided into 8 levels. It is determined by the ratio Z between the service time of the drill bit and the service life of the bearing (hours). Z ≤ 1 / 8 is level 1; 1 / 8 < Z ≤ 2 / 8 is level 2; and so on until level 8.

19. Bit Gage Wear:
It is directly expressed by the number of millimeters worn by the Drill Diameter. Zero indicates that the diameter has not been reduced, and the wear amount is the integer with the larger value between two adjacent integers.

20. Dull Bit Appearance:
Compared with the new bit, the used bit has obvious changes in appearance.

21. Tooth Fracture:
The Root remains on the base of the tooth.

22. Lost Tooth:
The fixed Teeth fail, and the whole inlaid Teeth fall from the Teeth holes of the wheel body.

23. Tooth Wear:
The height of Teeth is reduced or the Tooth shape is changed due to the grinding effect of strata.

24. Cone Falling:
The Cone breaks away from the bit body and falls into the well.

25. Cone Cracking:
Part of the Cone is broken, broken or cracked.

26. Cone Interaction:
There is contact between the teeth and it cannot rotate flexibly.

27. Cone Shell Erosion:
The Teeth were damaged by Hydraulic Erosion.

28. Cone Shaping:
The increase of Bearing Clearance due to wear causes the roller to rotate unevenly.

29. Cone Locked:
The Roller is stuck due to bearing failure and so on, so it can't rotate.

30. Bearing Seal Failure:
The Bearing Sealing System is damaged and drilling fluid enters the bearing chamber.


31. Bit Gauge Wear:
The diameter of the bit decreases due to the grinding effect of the sidewall or falling object on the outer edge of the bit.

32. Nozzle Falling Off:
The Nozzle Fails to be fixed and falls into the well.

33. Water Hole Thread Puncture:
The Water Hole Thread is damaged by Drilling Fluid Erosion.

34. Water Course Punture:
The sealing between the nozzle and the bit body fails, and the water hole seat is damaged due to the erosion of drilling fluid.

35. Nozzle Puncture:
The nozzle body is damaged by drilling fluid erosion.

36. Nozzle Plugging:
The nozzle is blocked by cuttings or foreign matters and the drilling fluid cannot pass through.

37. Bit Center Core Out:
The tip of the cone at the center of the bit is worn.

38. Shirt Tail Cut:
After fracture, the palm fell into the well together with the cone.

39. Shirt Tail Breaking:
Part of the palmar body is broken or cracked.

40. Severe Wear of Palm Tip:
The palmar skirt was seriously worn.

41. Bit Balling:
The bit is tightly surrounded by mud mixed with cuttings and drilling fluid.

42. Damage from Foreign Material:
Bit damage due to bottom hole drop.

Blowout Accident:
1. Blow out Accident:
Formation fluid (oil, gas and water) is ejected from the formation to the wellhead without control.

2. Overflow:
The amount of drilling fluid returned from the wellhead is larger than that of the pump, or the wellhead drilling fluid automatically overflows after the pump stops.

3. Lost Circulation, Lost of Circulation, Mud Loss, Lostreturns:
In the process of circulating mud during drilling, the mud returned from the wellhead is less than the mud pumped into the hole (after deducting the mud loss required for lengthening the hole and consolidating the well wall).

4. Kick:
The formation fluid pressure in the borehole is greater than the static pressure of the mud column, and the oil-gas water mud flows up to the wellhead in the form of boiling. Kick is sometimes a precursor to a blowout.

5. Well Blowout, Blowout:
When the formation fluid pressure in the wellbore is greater than the static pressure of the mud column, mud, natural gas, oil and water will be ejected from the wellhead without control.

6. Height of Blowout:
During blowout, the maximum perpendicularity of the ejecta from the air to the rotary table.

7. Distance of Blowout:
During blowout, the maximum horizontal distance between the falling point of ejecta and the wellhead.

8. Kill:
The operation of pumping high-density drilling fluid into a well without pressure balance to rebuild and restore pressure balance.

Stoppage accident:
1. Drill String Free Fall:
Due to equipment failure and operation error, the drill string is out of control and stuck at the bottom of the well.

2. Drill String not Well Braked:
In the process of drilling, uneven or out of control drilling will cause the drill string to slide down, resulting in the phenomenon of instantaneous excessive WOB.

3. Reverse Rotation:
When the drill is bad, the rotary table reverses.

4. Hole Straightening:
When the well deviation exceeds the specified limit, take measures to correct the well deviation to the specified limit.

5. Drill Out:
The process of drilling out the set cement left in the casing or wellbore after cementing or plugging.

6. Reverse:
When the drill is bad, the rotary table reverses.

7. Electrical Test Accident:
Accidents such as cable sticking, instrument sticking, falling of electric measuring instrument and cable breaking occurred during well completion, intermediate completion and midway electric measuring.

8. Falling Objects (FISH):
Objects (rods, pipes, tools, instruments, etc.) detained in the well due to an accident are called falling objects (FISH).

9. Accident of Falling:
Accidents caused by small tools or objects falling into the hole.

This article is excerpted from the Internet.
If you have any questions, please contact the editor.


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