How to seal off the gravel layer beneath the loess formation using geological drill pipes
29 Jun,2020
After vigorously drilling with clean water for the geological drill pipe, lower the casing and cement it in place. If an ample water supply is available, continue drilling with clean water until reaching the designed well depth, then run the casing and securely cement it down.
1. Geological drill pipe After vigorous drilling with clean water, run the casing and cement it in place. If sufficient water is available, continue drilling vigorously with clean water until reaching the designed well depth, then lower the casing and securely cement it down.
2. If there’s no slurry at the bottom of the well, use an instant plugging agent.
3. Seal the leak using sawdust and a high-viscosity plugging agent. Maintain 5 m³ of slurry in the mud pit, then add 500 kg of sawdust and 5 bags of the high-viscosity plugging agent. Use the desander pump to flush the mixture for 5 minutes, simultaneously lifting the previously settled cuttings from the bottom of the pit and pushing them back into the wellbore. Afterward, inject an additional 5 m³ of water under pressure to ensure the entire 5 m³ of plugging agent fully penetrates the leakage zone. Drilling can resume after 3 hours.
4. Use quicklime (CaO) for well sealing: Introduce 0.5–1.0 tons of lump quicklime into the well. After one hour, lower a dry drill bit to the bottom of the well, then restart pumping to resume normal drilling operations.
Geological drill pipe Casing Leak-Sealing Methods
First, bridge the gap 1–3 meters below the casing shoe using kelp or an expansion plug. Second, based on the characteristics of the loss and the materials available, select an appropriate plugging method.
1. Cementing with cement
① Materials: a) 2 tons of cement; b) 0.8–1 m³ of clean water—acidic water must not be used.
② Water-cement ratio: 0.4–0.5
③ Lower the drill pipe to 0.3 meters above the bridge, then begin mixing the slurry.
④ Leak-stopping procedure:
a. First, flush the well with 2 m³ of clean water;
b. Next, inject cement slurry;
c. Once completed, add displacement fluid;
d. Apply pressure to seal the leak;
e. Finally, allow the material to cure for 48 hours.
2. Use an instant sealant
Mix 1 ton of instant sealant with 1 ton of clean water for 1–2 minutes, then quickly inject the mixture. Geological drill pipe Inside, then add the weighting fluid, complete the operation by pulling the drill string out of the hole by 100 meters, and immediately refill the wellbore with water. After waiting one hour, you can lower the drill string back down to resume normal drilling operations.
3. Seal leaks with cement slurry
Inject 10 m³ of mixed slurry into the annulus around the casing, then allow it to sit undisturbed for 3 hours to achieve sealing. Next, add 10 m³ of clean water and 20 kg of cement to the slurry tank, mix thoroughly, and then incorporate 2 bags of high-viscosity plugging agent. Finally, pump the mixture back into the well through the wellhead. Once completed, displace the slurry with an equal volume of fresh fluid, let it rest for another 3 hours, and the well should be successfully sealed.
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