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Research on Gas Drilling Technology

George Yang is a highly experienced professional in the field of borehole drilling machine manufacturing, with over a decade of hands-on expertise. Throughout his career, George has specialized in various drilling rig types, encompassing well drilling rigs, geothermal drilling rigs, DTH drilling rigs, and crawler drilling rigs.

George is deeply committed to sharing his extensive knowledge and data-driven insights with businesses in the drilling industry. His dedication to empowering professionals to make informed decisions has garnered recognition within the industry, and his expertise has been cited by reputable publications, solidifying his status as a trusted authority in the world of borehole drilling machines.

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Gas drilling is a drilling operation that uses gas instead of drilling fluid as the circulating flow medium. Gas has the characteristics of low density, low viscosity, and low pressure on the wellbore. It is the earliest developed underbalanced drilling technology. The use of gas drilling can greatly increase the mechanical speed and protect the production layer.

This technology is widely used in the drilling and development of oil and gas wells (including coalbed methane) in various places. Since the past, gas drilling has been mainly used in medium and low pressure formations, which can greatly increase the drilling speed and prevent lost circulation.

In recent years, with the development of a large number of low-permeability oil and gas reservoirs, how to protect such reservoirs has become the focus of attention. Gas drilling has obvious advantages over traditional drilling methods for protecting low-permeability oil and gas reservoirs. At the same time, gas drilling also has other characteristics such as greatly increasing drilling speed, reducing drilling cost, and less environmental pollution.

1. Overview of Gas Drilling

Topic Information
Wellhead Surface Control for Gas Drilling Effective wellbore fluid control at wellhead is vital in gas drilling; selection of wellhead, control device, and manifold must meet pressure and flow requirements, proven safety.
Installation of Gas Drilling Equipment Installing air drilling equipment involves connections (flow meter, relief valve), supply pipelines, drilling floor manifold.
Installation of Rotary Control Head Properly center rotary control head near turntable; ensure kelly and drill pipe surfaces are in good condition.
Installation of Discharge Pipeline Straight discharge line installation to prevent damage from high-speed debris; install pressure relief, sample capture, and ignition devices.
Gas Lift Gas lift preparations include casing pressure testing, bottom cleaning, replacing fluid with water, no power tools downhole.
Drilling Pre-drilling setup includes cock and check valve, open gate valves, and testing drilling parameters; monitor variables and report abnormalities during drilling.
Drilling Directional Wells Increase measurement frequency in easily deviated sections, lower inclinometer for measurement, monitor drilling tool movement during directional drilling.

Gas Drilling Is Especially Suitable for the Following Situations

Limitations of Gas Drilling

In terms of economic effects In other words, its value is equivalent to opening a new oil field in a fully constructed mine area. It is a technically feasible and more economically attractive method to use the original wellbore sidetracking horizontal wellbore for secondary completion in mature oilfields.

2. Gas Drilling Technology

Wellhead Surface Control for Gas Drilling

In conventional drilling, the entry of formation fluids into the wellbore is controlled, while in gas drilling, the formation is allowed to enter the wellbore. Therefore, in gas drilling, it is extremely important to effectively control the fluid entering the wellbore at the wellhead and on the ground. The selection of gas drilling wellhead, surface control diversion device and manifold must meet the following principles:

Installation of Gas Drilling Equipment

The installation of air drilling equipment mainly includes: the connection between equipment, including the connection of flow meter, pressure relief valve and bypass valve, etc.; the main supply pipeline from the equipment to the drilling rig; the drilling floor manifold includes the bypass pipeline and the discharge pipeline.

Oil supply system: mist pump – so that it can start working in the shortest time when needed.

Installation of Rotary Control Head

The rotary control head should be as close as possible to the turntable, and must be centered in line with the turntable. With top drives, the centering of the rotary control head is also critical. Make sure that the kelly and drill pipe surfaces are in good condition and free from pinch marks, as this will shorten the life of the insert.

Installation of Discharge Pipeline

Gas Lift


3. Matters Needing Attention to Gas Drilling Construction

Drilling Fluid Replacement and Wellbore Drying

The preparation work for gas drilling is to hollow out the wellbore and dry the wellbore. First, determine the lifting height according to the highest gas injection pressure and drilling fluid density that the gas injection equipment can provide; use the well control device to control the pressure during the gas lift process to ensure the safety of personnel and equipment, and thoroughly dry the well wall after replacement.

The purpose of drying the well wall is not only to ensure smooth circulation without the formation of new filter cakes, but also to ensure the stability of the well wall.


The main goal of the drilling stage is to increase the ROP and drilling time as much as possible under the condition of controlling the well deviation. There is no holding effect, and the ROP is obviously improved. With the increase of the WOB, the drilling time is obviously reduced; however, the effect is not obvious when the WOB increases to a certain value. Gas drilling generally adopts a tower drilling tool structure, which does not have the ability to correct and prevent deflection.

Therefore, in order to achieve the purpose of improving drilling efficiency, firstly, it is necessary to optimize the drilling parameters and drilling tool structure to ensure a high ROP; drilling to reduce the occurrence of well deviation, and at the same time strengthen the wellbore trajectory monitoring to ensure the wellbore trajectory control requirements.

Handling of Abnormal Situations

Formation Water

After the water came out of the strata, the cuttings returned had some changes, and the phenomenon of falling blocks was obvious. If there is no significant change in torque and gas injection pressure, it means that the water output is very limited, and you can observe it cyclically.

If everything is normal, you can continue drilling. If the water production is large, the torque and gas injection pressure will increase rapidly, and improper handling may cause downhole complex accidents such as pipe sticking.

Drill Sticking Phenomenon

There are three main causes of drill sticking:

4. Conclusion

Gas drilling should be combined with the actual production, based on the actual production of oilfields, from which valuable geological and experimental air drilling data can be obtained, which meets the needs of exploration and development work and conforms to the development trend of exploration and development, and is of practical significance and forward-looking

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