Drill pipe failure can be caused by many factors. These include corrosion, chemical composition, and vibration. If you are in the business of drilling for oil and gas, you should be aware of these factors. Identifying and preventing these causes is vital. Failure can be prevented by identifying the causes as early as possible.
Friction and wear
Drill pipe is the component that makes up most of a drill string that extends back up to the surface. It is a long, tubular section with a predetermined outside diameter. The section has a male (“pin”) and female (“box”) connection, which are threaded to ensure mating of drill pipe segments.
Drill pipe fatigue failures can be caused by a variety of reasons, including excessive cyclic stresses, internal and external pressure, and high mud rates. Drill pipe fatigue can also result in fractures and microcracks. These problems are most often caused by corrosion and cyclic stress.
One of the most common causes of drill pipe failure is drilling with a worn drill bit. This can cause drill pipe to twist and fall to the bottom of the hole. It can also be caused by a foreign object, such as a fish, in which case operators can use specialist tools to remove it. You might want to purchase a heavy weight drill pipe next in case your current drill pipe no longer functions.
A dynamic drag and torque model is another useful tool for predicting drill string failure. It allows engineers to model the interactions between drill string and borehole walls and predict the force on both surfaces. This information can help them develop more effective drilling technologies. If you want to make your drilling operation safer, you must study the six most common causes of drill pipe failure.
Drilling jars use a principle that allows the drill pipe to store energy while being pushed down into the hole. This principle makes it difficult to maintain constant pressure in the bottom hole annulus. A jet sub helps alleviate the pressure generated by the drill string and is typically placed several joints above the drill pipe-to-drill collar transition. It is usually equipped with two or three jet nozzles.
The failure of drill pipes was caused by wash-out and pitting corrosion. The pitting was initiated at the outer surface and propagated along the pipe by multiaxial fatigue. The chemical composition and pH of drilling mud were studied to determine the mechanism of pitting corrosion. The basic drilling muds included Bentonite plus lime and caustic soda. A reverse scan polarization test revealed that drill pipe pitting potential was increased in passivating mud. A similar electrochemical behavior was also observed in tube casing.
The chemical composition of drill pipe failure was determined from the samples by using non-destructive testing, chemical composition analysis, optical microscope, and material property testing machines. A special technique called SEM with EDS was used to investigate the fractured pipe. The chemical composition of the drill pipe revealed that the fracture occurred due to hydrogen sulfide stress corrosion cracking. High hardness, high strength, and stress corrosion sensitivity of the drill pipe are important factors affecting its failure.
The presence of a high concentration of hydrogen sulphide (H2S) in the drilling fluids can lead to rapid brittleness of drill string. The presence of lime in drilling fluids can reduce the amount of hydrogen sulphide and control the amount of acid gases present. Hydrogen sulphide also degrades protective films in steel and reacts with steel.
Moreover, the formation of a crack source in drill pipes is influenced by the presence of metallurgical defects in the pipe. These defects lead to a decrease in the ultimate strength of the pipe and to premature failure. Therefore, it is necessary to control the chemical composition of drill pipes.
Vibration is one of the most common factors behind drill pipe failure. It can affect drill collars, drill pipes, and other equipment in the downhole environment. In fact, downhole vibration can cause premature and frequent failures of drill collars. To reduce the risk of premature failure of drill collars, vibration analysis is necessary.
Drill pipe bends are most likely to happen near the drill collar. This is because the collar has higher rigidity than the body of the drill pipe. This results in bending of the drill pipe, which occurs around 50 cm from the joint. If the drill pipe is bended by vibration, it will most likely break near its joint. If the drill pipe is thin near the drill collar, bending will occur only near the end of the thickened section of the drill pipe. The joint is unlikely to bend the pipe, so the bending force will be applied to the thin wall of the drill pipe.
Vibrations can cause a variety of problems, but the most common one is fatigue. This fatigues drill pipe components, causing excessive bends and rapid damage. It also accelerates the wear and tear on drill collars and causes the drill string to unwind. Fortunately, the driller can manage the problem by increasing the RPM of the bit.
In the study, a simplified analytical vibration model is used to analyze drill string vibrations. By using this model, the downhole dynamic torque of drill strings can be calculated. This information can help oil and gas operators better understand vibration problems in their drill string and correct them. Changing rotary speeds and top drive torque limits can also help to correct these problems.
Sour gas field
Drill pipe failure is a very common occurrence in sour gas fields. In a sour gas field, the drillpipes must be able to withstand high H2S levels for prolonged periods of time. Fortunately, there are new grades of drill pipe that address this issue. These new grades can be used to extend the drilling envelope and safely advance sour gas development.
Several factors can lead to SSC in drill pipe, including a high tensile stress, high concentrations of H2S, low pH, high pressure, high chloride content, and lower temperatures. Due to the high risk of SSC, material selection for drill pipe in sour fields is more complicated than for other applications. For example, while production tubing is exposed to a more known environment, drill strings are exposed to a much more unpredictable environment.
One of the best ways to prevent the problems associated with sour gas fields is to ensure that the proper permits are in place. A license from the Texas Railroad Commission is required to permit a sour gas field. However, the Commission is failing to adequately regulate oil and gas wells. As a result, hydrogen sulfide poisoning caused by a sour gas field is a very serious issue. Recently, two workers at an Aghorn oilfield near Odessa died after being exposed to H2S.
A well with sour gas is known to be incompatible with high-strength steel. This gas is very hazardous to human health, living organisms, and the environment. That is why historically, wells with sour gas were carefully plugged and abandoned. During drilling operations, however, steel tubulars are exposed to H2S and are susceptible to catastrophic failure.
Drill bit jamming
One of the main reasons for drill pipe failure is that the drill bit jams. When this happens, the drill pipe breaks, and the driller is left with an expensive repair bill. One of the best ways to prevent drill bit jamming is to keep the bit lubricated. Keeping the bit lubricated can reduce tool wear and tear, and prolong drill pipe life.
Another common cause of drill pipe failure is mechanical sticking, which can occur in a number of ways. For example, drilling too fast or through formations of varying hardness may cause the drill pipe to get stuck. Another common cause is using too much pulldown or inclination. In this case, the drill bit will drill a hole that is full gauge, but will jam in the formation and stop drilling. If this happens, the drill string will break and the tophead rig will stop rotating.
If you are using a drilling pipe and the drill bit jams, try using drilling fluid to clear the drill pipe of cuttings. Another method is to use a winch to winch the drill pipe out of the borehole. If that fails, you can use a pipe wrench to reverse the rotation of the pipe. However, you should use the pipe wrench only for one turn.
Drill pipe failure is a costly problem. If you do not properly clean your drill cuttings, the drilling fluid can backflow up the pipe. This backflow is a sign that your borehole is caving in. In some cases, you can prevent caving by using a thicker drill mud.