A kind of downhole blowout preventer pressure maintaining drilling method

Abstract

The invention discloses a pressure-maintaining drilling method for an underground blowout prevention hole, which comprises the following steps: 1. Drilling and sealing the hole; 2. Installing a protective pipe and connecting a drilling fluid pressure-maintaining and returning mechanism; 3. Obtaining a pressure-maintaining pressure value; 4. Exhaust of the liquid storage chamber; 5. Pressure-holding drilling; 6. Continued rod drainage; The present invention obtains the holding pressure value according to the actual stress of the coal stratum, the physical and mechanical properties of the drilling surrounding rock and the gas pressure, uses the drilling fluid to cooperate with the pressure holding and return mechanism to balance the pressure in the drilling hole, and uses the high-pressure return pipe to maintain the pressure of the drilling fluid. The pressure return mechanism transports the mixture of gas, liquid and drill cuttings that flow back from the drilling gap and discharges them. The pressure maintaining drill mechanism is formed by connecting multiple joints of drill pipes through independent drill pipes, so as to realize the pressure maintenance of the drilling holes and prevent the holes from spraying and collapsing. and drilling fluid ejection.

Description

technical field [0001] The invention belongs to the technical field of pressure-maintaining drilling for downhole blowout prevention holes, and in particular relates to a method for pressure-maintaining drilling of downhole blowout prevention holes. Background technique [0002] When drilling coal rock layers with high gas content and high gas pressure in underground coal mines, as the coal body of the drilled hole is exposed, the stress of the coal rock mass on the wall of the drilled hole is redistributed, the pressure in the drill hole is low, and the coal rock mass in the coal rock layer is exposed. When high-pressure gas and other gases flow into the borehole, the coal body is prone to spray holes under the joint action of gas pressure, ground stress and borehole disturbance stress, and even induce outburst. The holes forming the boreholes are large, which affects the shape and stability of the boreholes, and is unfavorable to the reformation of coal and rock mass fissu...

AI Technical Summary

Problems solved by technology

[0002] When drilling coal rock layers with high gas content and high gas pressure in coal mines, as the coal body of the drilled hole is exposed, the stress of the coal rock mass on the wall of the drilled hole is redistributed, the pressure inside the drill hole is low, and the coal rock mass in the coal rock layer is exposed. When high-pressure gas and other gases flow into the borehole, the coal body is prone to spray holes under the joint action of gas pressure, ground stress and borehole disturbance stress, and even induce outburst. The holes forming the boreholes are relatively large, which affects the shape and stability of the boreholes, and is unfavorable to the reformation of coal and rock mass fissures by methods such as fracturing in the later stage, which is not conducive to gas drainage; The mixture of coal, drilling fluid and drilling cuttings affects the safety of the operation, and a large amount of gas and other gases gushing out may easily cause the gas to exceed the limit, which may easily lead to gas suffocation, gas explosion and other accidents

When a drilling rig is used to drill holes in coal mines, the existing boreholes cannot match the drilling fluid to balance the pressure in the borehole. When the drill is withdrawn, the previously injected drilling fluid will spray holes, which will change the integrity of the coal and rock mass and increase the management of the mining roof. Difficulty, thus affecting safe production

When drilling in weak rock, it is easy to cause the borehole to collapse under the joint action of the ground stress and the borehole disturbance stress, which affects the stability and shape of the borehole

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