11-20 of 37 Common Complex Drilling Problems Judgment and Solutions

11.    What is the reason for bit bouncing during tripping in? How to handle it?
1)    Encountering hard interlayers or soft hard interface formations.
2)    Excessive bit pressure or drilling string not well braked.
3)    Encountering gravel layers or limestone caves.
4)    Upper strata collapse block.
5)    Junks fell underground.
6)    The tricone bit is stuck.
7)    Bit balling.
Solution: If it is due to geological reasons, the bit pressure and speed can be adjusted to eliminate it. If it is caused by drill bits or junks, pull out immediately to check.

12.    What's the reason for the rotary doesn't turn when drilling? How to handle it?
1)    The rotary chain is broken, or the drilling rig transmission chain is broken.
2)    There is a malfunction in the air circuit.
3)    The rotary is broken.
4)    The universal shaft of the rotary is broken.
5)    The diesel engine stopped (due to lack of fuel)
6)    Severe bit bouncing underground can cause clutch slippage or sprain the diesel engine to shut down.
When handling, first inspect from the ground, eliminate each item one by one, and then analyze the underground situation. If it is due to underground reasons, the drilling tool should be immediately lifted to prevent bit jumping.

13.    What are the phenomena when drilling into oil and gas layer? What should be noted?

14.    What are the phenomena of gypsum contamination? How to handle it?
Gypsum contamination is caused by the contamination of calcium salts, resulting in a deterioration of performance. The phenomenon is that viscosity and shear force increase, water loss increases, cake becomes thicker, calcium content increases, and the flowability of drilling fluid is poor.
Handling measures:
1)    Minor pollution can be treated with soda ash, sodium bicarbonate, barium carbonate phosphate, etc.
2)    If there is severe pollution, calcium treated drilling fluid can be used instead.

15.    What is the reason for the sudden drop of pump pressure during tripping in? How to check? How to handle it?
The reasons for the sudden drop of pump pressure during tripping in are pump failure or poor water supply, pipeline leakage causing reverse circulation, drilling tool damage, nozzle of drill bit damage, drilling tool breakage, formation leakage, drilling fluid gas invasion, etc.
The inspection method is to first check the ground, the working condition of the pump, whether the water supply is good, whether there is any leakage or reverse circulation in the pipeline gate, and whether the pump pressure gauge is accurate. Then consider whether the downhole drilling tools have been punctured, broken, or leaked.
Solution: Emergency repairs should be organized for ground related issues, and the drilling fluid should be degassed. The reason for the downhole drilling tools should be immediately pulled out and thoroughly inspected, breakout with power tongs with low speed. Do not pull or brake abruptly to prevent the drilling tool from breaking. Leak prevention work should be carried out for well leaks.

16.    What is the phenomenon of drilling tools breaking during drilling? How to judge?
The phenomenon is:
1)    The hanging load of the weight indicator decreases, and the pump pressure decreases.
2)    Reduce the load on the table.
3)    There have been changes of Kelly in after round trip.
Method of judgment:
1)    Pull out the drilling tool to check the hanging load of the weight indicator.
2)    Check if the pump is working properly and if the pump pressure gauge is damaged;
3)    Verify Kelly in.

17.    What are the phenomena of breakage of drill collar or drill bits while tripping in? How to judge and handle it?
The phenomenon is a decrease in pump pressure, a reduction in table load, a sudden slowdown when tripping in, and an insignificant decrease in hanging load.
Judgment method: pull out the drilling tool to calibrate the Kelly in and hanging load, check if the table load is reduced, and check if the drilling speed changes significantly.
Solution: First check the depth and Kelly in, and if there are any changes, immediately pulling out for inspection.

18.    Why is there bit balling? What is the phenomenon? How to handle it?
When drilling into soft clay formations, the drilling speed is fast, the displacement is small, and the drilling fluid performance is poor, especially with high viscosity and shear force, which can easily cause bit balling. In addition, reverse circulation of drilling fluid during tripping in and continuing drilling after stopping the pump can cause dry drilling and result in bit balling.
Phenomenon: The drill bit does not work properly after bit balling, causing sticking and jumping. The drilling speed significantly decreases, the table load increases, the pump pressure slightly increases, and bit jumping while moving the drilling tool.
Solution: If bit balling is found, the first step is to frequently or quickly ream down, trip in with lightly pressure, and increase the displacement. Secondly, process the drilling fluid asap based on the downhole and formation conditions. If the processing is ineffective, pull out immediately. When starting the pulling out, the speed should be slow to prevent stuck. If necessary, a square Kelly can be connected to circulate the drilling fluid and pull out through backreaming. When pulling out, it is necessary to frequently inject drilling fluid. If drilling fluid cannot be injected, segmented square Kelly should be connected for circulation.

19.    What is the phenomenon of saltwater contamination? How to judge and handle it?
The phenomenon of saltwater contamination is:
1)    Viscosity increase.
2)    Increased water loss. Thickening of filter cake.
3)    Increased salt content.
4)    When saltwater contamination is severe, the density decreases.
Judgment method: First, conduct a comprehensive performance analysis of the drilling fluid, and then analyze the salt content to compare whether the formation prediction has reached the saline or salt rock layer.
Solution: First, kill the well and stop contaminating the drilling fluid. If encountering a high-pressure saltwater layer, inject enough drilling fluid into the well at once. Drilling jamming is most likely to occur during well killing, and all measures should be taken to prevent it. Immediately handle the drilling fluid after kill well. If the salt content is less than 2000ppm, use a general treatment agent. If it is greater than 5000ppm, high salt resistance and high-efficiency water loss agents can be added, or saltwater can be used for tripping in. If there are no weighting materials or treatment agents on site, the pulling out should be immediately started to prevent drill jumping.

20.    Why did the well collapse occur? How to judge and handle it?
The reason for the collapse of the well is:
1) Failure to inject drilling fluid in a timely manner during pulling out resulted in a decrease in fluid pressur, leading to well collapse.
2) Long drilling cycle, poor drilling fluid property, especially low density, excessive water loss, unstable wellbore, and easy formation of periodic wellbore collapse.
3) Improper handling of drilling fluid, excessive water addition, and formation collapse.
4) Long drilling stoppage time, sedimentation of drilling fluid, deterioration of property, and induction of well collapse.
5) Loose and fractured formations with poor cementation are susceptible to drilling fluid immersion, which weakens their cementation force and causes well collapse.
6) The interlayer between the quicksand layer, gravel layer and its clay lose stability, resulting in the collapse of a large section of the well.
7) The drilling speed is too fast, resulting in suction.
Judgment of well collapse:
1) During tripping in, there is a sudden bit bouncing, pump pressure increases or pump failure, and the table cannot rotate.
2) Backflow of drilling fluid during pulling out, severe reversal during breakout, getting stuck while round trip, and pump failure during circulation are all phenomena of well collapse.
Solutions:
1) Try to maintain and restore the circulation of drilling fluid and move the drilling tools as much as possible (rotating or round trip over large distances). Adjust the property of drilling fluid, consolidate the wellbore, and bring out collapsed rock blocks.
2) When the loose formation well collapses and the pump cannot circulate. Currently, it is necessary to start pulling out and inject drilling fluid while starting and lift it within the safe load according to the operating procedures.
3) After the drilling tools are pulled out, prepare enough drilling fluid with good property, and then trip in for reaming down. Pay attention to the pump pressure to prevent pump jamming and pipe stuck when tripping in until the wellbore is unobstructed.