Negative pressure well cementing system and control method thereof

Abstract

The invention discloses a vacuum cementing system as well as a relevant control method; the invention comprises: A drill rod, a liner suspension, a liner, a filling device and a well-sealing device; wherein, the drill rod, the liner suspension and the liner are connected in sequence; the filling device is linked to the drill rod; the drill rod also comprises: A sonar sounder, a fluid flow meter, a gas flow meter and a pressure transducer, a pressure relief valve, a gas compression device and a computer; the sonar sounder is placed on the ground near the well opening; the fluid flow meter is arranged on the pipeline between the filling device and the drill rod; the pressure relief valve, the gas compression device, the gas flow meter and the pressure transducer are connected in sequence through pipelines; the gas flow meter and the pressure transducer are connected in sequence with the well-sealing device through pipelines; the filling device, the fluid flow meter, the sonar sounder, the gas flow meter and the pressure transducer, the pressure relief valve and the gas compression device are respectively with the computer through cables. The invention effectively fulfills cementing operation in case of leakage, so as to improve cementing quality abd solve the cementing problem in leakage.

Description

technical field [0001] The invention relates to a negative pressure well cementing system for petroleum drilling engineering, in particular to a negative pressure well cementing system and a control method thereof. Background technique [0002] Well cementing is a very important process in petroleum drilling engineering. Its main method is to put the casing (a special steel pipe) down the well, pump the cement slurry from the casing, and the cement slurry from the gap between the outside of the casing and the well wall. After returning, the cement slurry stays in this annular gap and solidifies into cement stone, which fixes the unstable well wall or separates the fluid (oil, gas and water) in the deep formation, which is convenient for layered production during oil production. [0003] However, due to the inhomogeneity of formation pressure at different depths, lost circulation is very easy to occur during drilling. After lost circulation, it is difficult for the cement slu...

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Problems solved by technology

[0005] However, if there is a leakage zone 14 or a pressure-sensitive formation in the open hole section 13, it is difficult for the cement slurry 16 to flow back to the liner hanger 2. However, after well leakage occurs, the formation pressure P of the lost zone 14 is lower than the pressure generated by the mud column in the entire wellbore, and the static liquid level of the mud in the wellbore should be lower than the position of the sealing device 5. , its height from the ground is H1, its distance from the bottom of the well is H2, and the false high mud density is R1, then P=R1*H2, in this case cementing, the cement slurry 16 is suspended from the lost zone 14 to the liner Difficulty will be encountered when device 2 returns

[0006] As shown in Figure 2, when it is lost circulation, the cement slurry in the prior art cannot return to the ideal height. When the cement slurry is pumped to the annulus 12 between the loss zone 14 and the liner 3 and reaches the height of the loss zone 14 Finally, at this time, if the cement continues to go up, the static liquid level of the mud in the wellbore must rise. If the dynamic liquid level of the mud in the wellbore rises to the height H3 from the ground during the cement slurry injection process, the distance from it to the bottom of the well is H4, because H3 is smaller than H1, H4 is larger than H2, and the formation pressure of the lost zone 14 is P=R1*H2, obviously P<R1*H4, that is to say, if the cement slurry 16 continues to return, the annular space 12 The liquid surface pressure in the lost circulation zone 14 will be greater than the formation pressure in the lost circulation zone 14, so the fluid in the annular space 12 will leak into the lost circulation zone 14, which is equivalent to that the cement slurry will be directly pumped into the deep formation in the lost circulation zone 14, and the cement The slurry 16 cannot be returned to the upper position of the liner hanger 2 at all, that is, the distance from the liner hanger 2 to the bottom of the well is above the position of H5, and the purpose of cementing the liner 3 cannot be achieved. This is what the current conventional cementing operation faces a difficulty of

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