The main types of drilling rigs include core drilling rigs, exploration drilling rigs, geological drilling rigs, and coal mine tunnel drilling rigs. Downhole accidents are unavoidable during the construction process of each type of rig. Once a downhole accident occurs during construction, different methods should be selected for handling according to the type of accident and the material conditions. Generally, the following methods and steps can be adopted:

Step 1: Lift, strike, vibrate, fish, wash, grab, magnetically attract, adhere, work loose, and jack;

(1) Lift: When equipment capacity permits, a hoist in combination with a pulley block can be used to forcefully pull up the obstructed drilling tools in the hole. When drilling tools are stuck or buried, this method is generally used, but attention must be paid to the condition of the wire rope, crown block, derrick, drilling rig, and foundation. It is best to be equipped with a "tension gauge" to prevent personal injury accidents.

(2) Strike: Use the vibration force of a drop hammer to strike the accident drilling tools upward or downward. This method is suitable for shallow holes or accidents involving falling blocks and steel shot jamming. This method is simple and therefore often used. When using a drop hammer to strike and handle downhole accidents, a pulley drop hammer and other safe drop hammer devices can be used. When using a drop hammer to handle downhole accidents, note: it is best not to directly tie and strike the drop hammer with the hoist; when the hole wall is unstable and prone to collapse, this method should not be used, otherwise the accident will worsen.(3) Vibrate: Connect a mechanical vibrator to the upper end of the accident drilling tools and tighten it with the hoist, so that the accident drilling tools receive strong vibration and are freed. However, attention must be paid to preventing the downhole drilling tools from being unscrewed due to vibration.

(4) Fish: Use a male/female tap, pipe catcher, etc. to retrieve dropped or broken accident drilling tools. This is a commonly used method for handling accidents.

(5) Wash: Lower small-diameter drilling tools (or drill pipes) or casing into the hole, and use the high-pressure fluid flow of a mud pump to wash out the buried or stuck material around the accident drilling tools. However, this method must be used under the condition that the hole wall is stable.

(6) Grab: Use a grab bucket with teeth at the lower part to handle small objects or inclinometers that have fallen into the hole.

(7) Magnetically attract: Use a magnet fisher to attract and retrieve small objects that have fallen into the hole, or to align the broken end of accident drill pipes leaning against the hole wall, in combination with a tap for fishing.

(8) Adhere: Use sticky mud, yellow wax, asphalt, etc. to adhere and retrieve small objects that have fallen into the hole, or the matrix or diamonds of diamond bits.

(9) Work loose: Use the hoist to pull, the drop hammer to strike up and down, or run the machine to sweep up and down, to handle obstructed accident drilling tools that still have some room for movement.

(10) Jack: Use a jack (screw type and hydraulic type) or adjust the hydraulic pressure of a hydraulic drilling rig to jack up the accident drilling tools. This is also a commonly used method. However, note: when using a jack to pull, the bearing capacity of the drill pipe should be considered to prevent breaking it; special attention should also be paid to preventing the slips from flying out and injuring people.

Step 2: Back off, sleeve, cut, and hook;

(1) Back off: Use left-hand thread drill pipes and a tap, find the neutral point, and back off as many accident drill pipes as possible, then combine with other methods for handling. This is because "backing off" is not a separate method for handling downhole accidents. When backing off drill pipes, safe methods such as backing off drilling tools with a wire rope or using a ratchet pipe back-off device should be adopted. In addition, prevent personal injury accidents caused by elastic reverse rotation when backing off drilling tools.

(2) Sleeve: Use drilling tools one size larger than the drilling tools to ream the hole and sleeve out, so it is only suitable for softer rock formations and rock formations in shallow holes. When accident drill pipes remain in the hole, they must first be "backed off" and then "sleeved." During reaming, a guide should be used to prevent the hole from bending.

(3) Cut: Use a pipe cutter to cut and retrieve the accident drilling tools in sections. This method is used when the drilling tools are stuck or buried too tightly and are relatively long. "Cutting" is often used to handle core barrel or casing accidents.

(4) Hook: Use specially made hooks, fishing spears, etc. to guide and align the end of accident drill pipes leaning to the side, or hook the enlarged joint, to lift out the accident drilling tools, or to retrieve wire ropes and cables that have fallen into the hole.

Step 3: Peel, pass through, sweep, and soak;

(1) Pass through: Use drilling tools 1-2 sizes smaller (preferably 2 sizes smaller) than the accident drilling tools originally used for drilling, first pass through the center of the accident drilling tools, and use their vibration, rotation, and impact to reduce or eliminate the jamming resistance on the outside of the accident drilling tools, then handle them with the "fishing" method. When the core barrel coupling, core barrel, and sediment tube remain at the bottom of the hole, before using the "pass through" method, first handle them with methods such as "peeling."

(2) Peel: Use a grinding bit with the same diameter as the original accident drilling tools to peel off a layer from the outer periphery of the core barrel or sediment tube coupling and sediment tube down to the threads, and then remove the coupling.

(3) Sweep: Use a specially made flat bit to split or sweep away the thick-diameter drilling tools or bits remaining in the hole, and then remove them. When "sweeping" or "splitting," pay attention to bit jamming and multiple splitting.

(4) Soak: Inject diesel oil, alkaline water, or hydrochloric acid into the hole to soak the stuck drilling tools that are buried or adhered by mud cake, so that the accident drilling tools and the hole wall become loose, facilitating handling.

Step 4: Bypass and blast.

(1) Bypass: Use an eccentric wedge for deflecting drilling to bypass the accident drilling tools. When using this method, it must be carried out according to the geological design.

(2) Blast: Load explosives into a specially made blasting cartridge, send it from inside the drilling tools to the predetermined hole depth for explosion, blast off the drill pipe and then retrieve it, or use it to handle stuck casing by loosening it with vibration or blasting out the casing.