This about-fishing-operations video technically covers the techniques and common tools used in wireline pipe recovery operations with animated simulated explanation. covered points:
Fishing definition,
String sticking causes,
String sticking solutions,
Free point determination, and
Pipe cutting tools.
Fishing services are frequently used to retrieve unwanted objects from the well bore such as tools or equipments and twisted or broken sections of pipes or tubing. Fishing also includes the recovery of stuck drilling or production strings. Stuck drill pipe or tubing results in costly downtime and occurs into often both in openhole and cased hole situations. The causes of string sticking are numerous. Sand or heavy mud in the well bore can build up in the annulus to create sticking.
During drilling and tripping, the string can make a groove into the high side of an openhole. This groove called a key seat can lead to sticking on all types of wells. Differential sticking can occur when a hydrostatic pressure of the mud column exceeds the pressure exerted by the porous underground formation. As the mud filter cake increases in thickness, the likelihood of differential or well-stuck drill cutters also increases. There are other reasons for string sticking but, whatever the cause, the object in all cases is to determine at what point the string is stuck and at what point it's free. The free point can be determined with a special electronic free-point tool run on wire line. The free point tool is security attached to the wire line and both are small enough to be run inside the stuck well pipe or tubing.
As the driller applies torque or stress to the string, this free point tool measures the difference in pipe stress in the section between the two fixed points. The stress in the section of the pipe is sensed by the downhole detector and electronically transmitted to the surface panel where this is displayed on readout meter. The downhole free point reading is directly proportional to the amount of torque or stretch being applied to re-string from the surface. After making calculations to estimate the stuck point, experienced wire line operators begin taking readings slightly above the calculated stuck point. As the stuck pint is approached, readings will wait until the detector is in the stuck section of the string indicating no pipe movement. Through this method of data interpretation, a skilled wire line operator determines the free point precisely. Only by combining all available well bore information with specialized experience, expert operator can compensate for various downhole conditions to determine the actual free point.
The Stresstectors is extremely sensitive to torque and stretch. It can detect even sudden movement including intention, compression, and right or left hand torque. Reading left hand torque is essential in certain fishing situations. Another advantage of the Stresstector design is its durability. It can be run in combination with string shot explosives which reduces the time involved in freeing the stuck string. A new version of the Stresstector, the Stresstector II, is introduced for slim hole, coil tubing and high temperature situations. The smallest sized Stresstector II of 5/8 inch diameter has been developed to handle pressures up to 20000 psi and over 400 degrees Fahrenheit.
Regardless of which detectors is used once the actual free point is determined, the free pipe can be removed from the well bore after backing-off from the stuck section of pipe. A backoff is made by applying left hand torque and holding that torque by the controlled explosive charge placed across a connection is detonated. The explosion allows the connection to be unscrewed without damaging the threads. The freed pipe is then removed from the well bore. It is often necessary to cut a section of pipe or tubing to remove it. Among the cutting tools available is the Chemical Cutter which uses hydrofluoric acid to cut pipes. The chemical cutter cutes the tubing without leaving a flare or debris. This makes it easier to recover with an overshot fishing tool. Another cutting device is Jet Cutter severs pipe with the shaped explosive charge. Like the Chemical Cutter, the Jet is matched to the size of tubing being cut. The Jet Cutter is also used to cut drill pipe casing, and crusted pipes. The Jet Cutter leaves a flared fish top which must be prepared before the fish can be caught. Still another tool used in fishing is the Severn Tool. The Severn Tool utilizes the powerful explosive charge run on wire line which serves drill pipe, heavy weight drill pipe, and drill colors when conventional back-off techniques are not possible. Watch the video for more information about it
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As the driller applies torque or stress to the string, this free point tool measures the difference in pipe stress in the section between the two fixed points. The stress in the section of the pipe is sensed by the downhole detector and electronically transmitted to the surface panel where this is displayed on readout meter. The downhole free point reading is directly proportional to the amount of torque or stretch being applied to re-string from the surface. After making calculations to estimate the stuck point, experienced wire line operators begin taking readings slightly above the calculated stuck point. As the stuck pint is approached, readings will wait until the detector is in the stuck section of the string indicating no pipe movement. Through this method of data interpretation, a skilled wire line operator determines the free point precisely. Only by combining all available well bore information with specialized experience, expert operator can compensate for various downhole conditions to determine the actual free point.
The Stresstectors is extremely sensitive to torque and stretch. It can detect even sudden movement including intention, compression, and right or left hand torque. Reading left hand torque is essential in certain fishing situations. Another advantage of the Stresstector design is its durability. It can be run in combination with string shot explosives which reduces the time involved in freeing the stuck string. A new version of the Stresstector, the Stresstector II, is introduced for slim hole, coil tubing and high temperature situations. The smallest sized Stresstector II of 5/8 inch diameter has been developed to handle pressures up to 20000 psi and over 400 degrees Fahrenheit.
Regardless of which detectors is used once the actual free point is determined, the free pipe can be removed from the well bore after backing-off from the stuck section of pipe. A backoff is made by applying left hand torque and holding that torque by the controlled explosive charge placed across a connection is detonated. The explosion allows the connection to be unscrewed without damaging the threads. The freed pipe is then removed from the well bore. It is often necessary to cut a section of pipe or tubing to remove it. Among the cutting tools available is the Chemical Cutter which uses hydrofluoric acid to cut pipes. The chemical cutter cutes the tubing without leaving a flare or debris. This makes it easier to recover with an overshot fishing tool. Another cutting device is Jet Cutter severs pipe with the shaped explosive charge. Like the Chemical Cutter, the Jet is matched to the size of tubing being cut. The Jet Cutter is also used to cut drill pipe casing, and crusted pipes. The Jet Cutter leaves a flared fish top which must be prepared before the fish can be caught. Still another tool used in fishing is the Severn Tool. The Severn Tool utilizes the powerful explosive charge run on wire line which serves drill pipe, heavy weight drill pipe, and drill colors when conventional back-off techniques are not possible. Watch the video for more information about it
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