Continuous circulation drilling technology suitable for gas-liquid two-phase flow drilling

Abstract

The invention discloses a continuous circulation drilling technology suitable for gas-liquid two-phase flow drilling. The technology comprises a gas injection unit, a safe pressure relief mechanism, a gas-liquid mixing device and a gate valve control system; and the gas injection unit, the safe pressure relief mechanism, the gas-liquid mixing device and the gate valve control system are connected in sequence in operation. Then, a main circulation channel leaded out from the gate valve control system is connected into a vertical pipe, a collateral circulation channel with a pressure gauge is connected to a drill stand for future use, and a pressure relief channel is connected to a circulation tank. In normal drilling operation, a gas phase and a liquid phase are evenly mixed through the gas-liquid mixing device to enter the gate valve control system for circulating through a main circulation channel; and in single connection or round trip, a gas-liquid two-phase flow enters a drill for circulating through the gate valve control system by the collateral circulation channel. The technology solves such problems as great underground pressure fluctuation, low drilling efficiency and blockage of drilling due to fall back of chips caused by stop of single connection and round trip circulation in the large effluent stratum gas-liquid two-phase flow drilling process, and largely improves the gas drilling efficiency and safety.

Description

technical field [0001] The invention relates to a continuous circulation drilling technology suitable for gas-liquid two-phase flow drilling, which is used for drilling construction operations and belongs to the technical field of oil and gas drilling technology. Background technique [0002] In recent years, the domestic gas-based fluid drilling technology is developing rapidly with its unique advantages, and the application footage and well times have been increasing year by year, which has played an important role in improving the mechanical penetration rate, controlling lost circulation, and discovering and protecting oil and gas layers. However, in terms of overall application, formation water is the bottleneck that restricts the application of gas-based fluid drilling technology. Except for Sichuan, Chongqing and some areas in Xinjiang, other areas have not been popularized and applied on a large scale. [0003] The atomization, foam and air-filled drilling technology ...

AI Technical Summary

Problems solved by technology

[0004] 1. After the large water-yield formation is connected to the column, the pressure fluctuates greatly due to the fluid accumulation at the bottom of the well. The pressure first rises and then fluctuates and drops. The drilling speed is slow before it stabilizes again, which seriously affects the gas drilling efficiency and ground safety.

[0005] 2. For formations with poor well wall stability after water outflow, stop the circulation and connect a single root, local slight block loss and large-grain cuttings that have not been brought out of the wellbore will fall back and accumulate, and there will be a greater downhole risk

[0006] 3. Bottomhole pressure fluctuates greatly after the formation with large water yield is connected to the column, and the equivalent density of the downhole fluid is unstable, and the buoyancy generated by it on the drill string is correspondingly unstable, resulting in large fluctuations in the bottomhole pressure on bit

[0007] 4. After the gas-filled drilling well is connected to a single pipe, the pressure fluctuates greatly and the liquid level is unstable. It is difficult to judge whether there is an overflow in the well, and there are potential safety hazards

[0009] Chinese patent 201210561390.0 discloses a continuous circulation drilling process suitable for air drilling. This process first connects the supercharger to the air supply pipeline of the air supply control device, and then connects to the continuous circulation short circuit in two ways, which can realize air drilling. However, the process lacks a gas-liquid mixing process, and its sealing parts can only seal pure air, and cannot realize continuous circulation drilling under gas-liquid two-phase flow drilling conditions such as atomization, foam, and aeration.

The short joint sealing part can only seal the liquid phase, but cannot seal the gas phase and the gas-liquid mixed phase, and cannot bear the air pressure, so the short joint is only suitable for mud drilling, not for gas-liquid two-phase flow drilling, and the short joint is not There is a pressure relief valve, and the pressure trapped inside the drill pipe cannot be released when other valves fail, which poses a safety hazard

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