Casing drilling refers to the use of casing instead of drill pipe to apply torque and drill pressure to the drill bit, to achieve the drill bit rotation and drilling. The whole drilling process no longer use drill pipe, drill collar, etc. , drill bit is the use of wire rope fishing, in the casing to achieve drill bit lift, that is, to achieve no drill replacement drill bit drill. Reduce the start and drill and blowout, card drilling and other accidents, improve drilling safety, reduce drilling costs.
Casing drilling has obvious advantages compared with conventional drilling pipe drilling, it is a technical revolution of drilling engineering, it can bring great economic benefits to oil field operators. Casing drilling has the following characteristics:
Casing drilling uses standard well casing, and enables drilling and casing operation to be carried out simultaneously;
2. The bottom hole assembly is installed at the lower end of the casing string and can be quickly taken out through the inside of the casing with steel wire rope. The continuous circulation of mud can be maintained during the extraction process;
3. During the whole drilling process, the casing is kept straight to the bottom of the well to improve the well control condition;
4. The casing is only drilled into the formation in one direction and is no longer pulled out. Unless it is confirmed that the well is dry after drilling, the last casing string may be pulled out;
5. Many existing drilling techniques can be used in casing drilling, such as directional drilling, cement injection, logging, coring and well testing;
6. The main difference between the application of these technologies and the original one is that they no longer rely on drill pipe, but on wire rope to replace drill bit;
7. Casing drilling is carried out with standard oilfield casing. The only difference is that casing coupling or thread needs to be improved to provide the required torque for drilling;
Reduce trip time. It is about 5-10 times faster to use wire rope to trip and replace drill bit than traditional drill pipe;
2. Save the purchase, transportation, inspection, maintenance and replacement costs related to drill pipe and drill collar;
3. Because there is always a casing in the wellbore, and there is no longer the swabbing effect on the wellbore when the drill pipe is running, the well control situation is improved;
4. It eliminates the swabbing and pressure pulsation caused by running the drill pipe;
5. The continuous circulation of mud can be maintained when the bit is lifted and lowered by steel wire rope, which can prevent the accumulation of cuttings and reduce the occurrence of well kick;
6. It improves the return velocity of annulus and the condition of cleaning wellbore. When the mud is pumped into the casing, the internal diameter of the mud pump is larger than that of the drill pipe, which reduces the hydraulic loss and thus reduces the power of the drilling mud pump. When the mud returns from the annular space between the casing and the wellbore, the up return speed is increased and the cuttings carrying out condition is improved due to the reduction of the annular area;
7. It can reduce the size of the drilling machine, simplify the structure of the drilling machine and reduce the cost of the drilling machine.
8. The rig is lighter and easier to move and operate. Labor volume and cost will be reduced;
The basic point of casing drilling technology, tools and equipment is to cancel the conventional drill pipe and replace it with casing.