Comprehensive plugging method for karst leakage

Abstract

The invention relates to a comprehensive plugging method for karst-cavity leakage, which sequentially includes the following steps: (1) When drilling into a karst leakage, stop drilling first, and immediately start drilling after determining the position and size of the karst cave; (2) Prepare three types of large, medium and small positive Tetrahedral framework materials and mix them evenly; (3) Calculate the single delivery volume and total delivery volume of the building materials; (4) Put the building materials in the middle of the wellbore until the total delivery volume is completed; (5) Lower the drilling tool assembly, and before the end, advance a drill pipe Turn on the pump, start the turntable, and move the tool to move the frame material into the cave to form a bridge structure; ⑹ Confirm that the frame material has been allocated into the cave; ~200 meters, reserve 250 meters of filling material in the water hole of the drilling tool; (8) Make the lower end of the drilling tool reach the top of the plugging filling material, and lift it up to the safe well section after circulation, and turn off the pump for static plugging. The comprehensive plugging method can form an effective bridging structure in the karst cave and improve the success rate of plugging.

Description

technical field [0001] The invention relates to a plugging method for oil drilling, in particular to a comprehensive plugging method for karst-cavity leakage, and belongs to the technical field of oil drilling. Background technique [0002] Loss of circulation is a common worldwide problem in drilling engineering, especially serious leakage when drilling faults, large fractures and karst caves, which often manifests as the loss of drilling fluid and the inability to continue drilling. A large amount of plugging materials, and the success rate of one-time plugging is low, it often takes a long time to process, and sometimes even causes wellbore collapse, sticking, overflow, blowout, etc., and some can only abandon the wells that have been drilled and re-arrange wells , causing huge losses. [0003] Due to the complex and changeable underground conditions, there are relatively few plugging technologies and materials that can effectively deal with cave-type leakage. Cement sl...

AI Technical Summary

Problems solved by technology

[0011] To sum up, there are few plugging technologies and materials that can effectively deal with karst vug leakage, and their versatility is not strong.

Although high-concentration conventional plugging slurry, bridge plugging, cement slurry plugging and chemical gel plugging technologies are usually combined and applied repeatedly, it has a certain effect on small cracks and karst cavities, but it is not effective for larger fractures. The plugging effect is not obvious, not only consumes a lot of expensive plugging materials, but also takes a long time to process, resulting in huge economic losses

The main reason is that the plugging material is easily taken away by the lost drilling fluid, and it is difficult to stay at the lost channel, so an effective sealing wall cannot be formed at the lost channel, resulting in a low plugging success rate

[0012] After the large-grained plugging materials dropped from the wellhead to the bottom of the well, they will gradually accumulate upwards with the bottom of the well as the center of a circle, forming a cone. The subsequent injection of plugging materials such as slurry, cement slurry, and gel with appropriate concentration cannot It successfully enters the karst cave around the wellbore, but accumulates at the mouth of the karst cave at the bottom of the well to form a sealing wall, and cannot form an effective bridging structure at the leakage channel around the wellbore. When drilling, the sealing wall in the wellbore will be destroyed, and the probability of re-leakage is very high

[0013] At present, there is no special setting tool for large-grained LCM. Drill bits and male cones are usually used, which are not only easy to damage the drill bit and male cone, but also have no special design for the large-grained LCM. The throwing effect at the bottom of the well is not good, and it cannot form an effective bridging structure in the leakage channel around the wellbore, resulting in a low plugging success rate

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