In general, the movable inner sleeve can be pulled out at one time because it falls into the outer sleeve and does not contact with the hole wall. The outer casing is surrounded by rock powder, clay and gravel, which is adsorbed and clamped, so it is difficult to pull it out of the borehole at one time, and it needs to be expanded, reversed, cut and punched one by one.
(1) jacking method
Use a large 1 ~ 2 bore drilling tool cover to expand the casing in the hole. Generally, the casing expands at one time 10~20m ~ 20m, and then the casing is kicked out with the reverse cone. Then run the drilling tool to expand the casing and reverse the drill pipe, and circulate for several times to pull the casing out of the hole, as shown in Figure 3-30.
Figure 3-30 Schematic Diagram of Pipe Jacking Method
1- drilling; 2- sleeve expansion cylinder; 3- drill bit; 4 card accessories; 5-Shell
This method is mainly used in Quaternary unconsolidated strata, but it takes a long time to expand casing, and the casing head is prone to lateral deviation in large diameter interval after expanding casing, and it is difficult for the male cone to enter the casing head, resulting in casing accident.
(2) Reverse cutting method
The method of reversing casing cutting means that the left threaded coupling has been connected in the casing string at a certain interval (20 ~ 40m) before casing running. When tripping casing, the reversing drill pipe is not used, and the direction can be changed gradually. If the casing is partially stuck, a casing cutter can be used to cut the casing at the stuck position before tripping out. This method is mainly used to pull out the casing in the hole section of bedrock.
(3) One-time tripping method for loose stratum
In order to solve the problem of casing pulling in loose formation, the Exploration Engineering and Technology Research Institute of 3 13 Geological Team of Anhui Bureau of Geology and Mineral Resources developed the "loose formation well pipe tripping device" (obtained the national invention patent, patent number: ZL20081012.0).
1. Structure and working principle
The well tube releasing device in loose formation includes impact rod, ferrule, alloy blade, inclined wedge surface, upper water spray hole, central water spray hole, lower water spray hole and duckbill hole, as shown in Figure 3-3 1.
Figure 3- Structure Diagram of Loose Stratum 3 1 Well Pipe Dredging Device
1- impact rod; 2- ferrule; 3- alloy blade; 4- Inclined wedge surface; 5— Upper water spray hole; 6— Central water spray hole; 7-Lower the water spray hole; 8- duckbill hole
The release device mainly consists of a hollow cylindrical impact rod 1 and a cylindrical ferrule 2 located in the middle of the impact rod. The ferrule 2 is parallel to the central axis of the impact rod 1, and the longitudinal section of the ferrule is trapezoidal. The lower part of the cylindrical impact rod is forged into an inclined wedge surface 4, and the included angle between the inclined wedge surface and the central axis of the impact rod is 10 ~ 15, so the ferrule 2 can be made of a trapezoidal steel plate with a thickness of about 10mm, or a seamless steel tube with an inner diameter slightly larger than the outer diameter of the ferrule in the hole. The upper and lower ends of the steel tube are obliquely cut, and then cut along the longitudinal direction of the steel tube and welded in the middle of the impact rod. The inclined wedge surface 4 and the impact rod body form a duckbill hole 8 at the bottom of the impact rod, and a plurality of water spray holes are arranged at one side of the middle of the impact rod facing the ferrule.
The working principle of well pipe release device in loose formation is shown in Figure 3-32. During the stuck release operation, the upper end of the impact rod of the stuck release device is connected with the geological drill pipe (50mm or 42mm drill pipe), and the sleeve is sleeved on the casing in the hole. The impact rod impacts the sand outside the casing up and down, and at the same time, high-pressure mud is sent to the impact rod by the mud pump, and the high-pressure mud is ejected from the duckbill hole at the bottom of the impact rod, so as to drive back the stuck objects (such as mud and sand). ) on the outer wall of the casing.
Fig. 3-32 Schematic diagram of the working principle of well pipe release device in loose formation.
1-casing; 2- ferrule; 3- impact rod; 4 card accessories; 5- hole wall
2. Technical characteristics
According to the loose formation well pipe releasing device designed by the invention based on hydraulic and mechanical principles, many shortcomings of the traditional casing tripping and releasing method are overcome, and the drilling machine does not need to rotate and the long reaming pipe drilling tool is not needed for reaming, so that the reaming resistance is reduced, the accidents that the drilling tool and the casing in the borehole are broken and the casing head in the hole cannot be found are avoided, the casing in the hole is released at one time, and the tedious procedures of tripping and expanding the casing for many times are saved. The duckbill hole at the bottom of the impact rod generates high-pressure water flow, which impacts with the steel pipe ferrule up and down, so as to remove the stuck objects on the periphery of the casing and achieve the purpose of releasing the casing.
The middle part of the impact rod is provided with a plurality of water spray holes facing one side of the ferrule, and the axes of the water spray holes form different included angles with the horizontal line, so that the adhesions between the inner wall of the ferrule and the outer wall of the sleeve in the holes can be washed from different directions, so that the sleeve can be released more quickly and thoroughly.
3. Casing pulling operation
1) Mud should be prepared before casing sticking, and a loose formation well pipe sticking releaser (hereinafter referred to as the sticking releaser) matching with the outer diameter of casing in the hole should be selected.
2) First enlarge the orifice casing head by 3 ~ 5m with a short drilling tool, and then trip the tripping device.
3) After the tripping device is sleeved in the casing, connect the drill pipe, the impact rod and the active drill pipe on the machine, and start the mud pump to pump mud for drilling. Pump displacement is generally above 200L/min, which depends on casing diameter and formation conditions.
4) After the mud is sent into the borehole, the elevator is used to pull down and put down the active drill pipe on the machine, which impacts the mud in the annulus between the casing and the borehole wall and the attachments on the casing, and returns to the hole with the mud. The impact height of the main pole is generally 3 ~ 4m each time it is pulled up and down.
5) Under the action of high-pressure mud injection and impact, make the sticking releaser run all the way to the bottom of the casing, and take out the sticking releaser, so that all the casings in the borehole can be pulled out at one time.
6) The release device for the outer flat casing string has a more direct effect. If the casing is connected by an external coupling, the inner diameter of the releasing device ferrule is larger than that of the casing coupling. When encountering the coupling, lift the tripping device up and down, and the tripping device is nested in the coupling step before impact operation.
7) When using the card release device, it is forbidden for the drilling rig to actively rotate the drill pipe to prevent the card release device from being damaged.
8) If the method of tripping in and out at one time is adopted, attention should be paid when designing the drilling structure: the diameter of the drilling hole should be 2 ~ 3 grades larger than the diameter of the lower casing, centralizers should not be placed in the casing string, the gap between the casing and the hole wall should be filled with mud balls made of high-quality clay powder, the gap should be filled with high-quality polymer chemical mud, and the upper and lower casing openings should be sealed.