How To Choose The Right Drill Pipe for Different Drilling Depths?

Consider the strength of the drill pipe

1. Shallow drilling (depth less than 500 meters)

For shallow drilling depths, the formation pressure and friction are relatively small. Generally, a drill pipe with slightly lower strength can be selected. For example, ordinary carbon steel drill pipes can usually meet the requirements. The yield strength of this type of drill pipe may be between 300-500MPa, which is enough to withstand the pressure of shallow formations. At the same time, its cost is relatively low, and it is more suitable for some small building foundation drilling or shallow geological exploration projects.

2. Medium drilling (depth 500-2000 meters)

As the drilling depth increases, the formation pressure and friction also increase accordingly. At this time, a drill pipe with higher strength, such as an alloy steel drill pipe, is required. The yield strength of an alloy steel drill pipe can reach about 700-900MPa. This type of drill pipe can effectively resist the lateral pressure of the formation and prevent the drill pipe from bending or breaking during drilling. It is often used in the exploration of oil and gas in the middle layer or in the drilling of medium-sized mines.

3. Deep drilling (depth greater than 2000 meters)

For ultra-deep drilling, the drill pipe has to withstand huge pressure and tension. It is necessary to use high-strength and high-toughness drill pipes. For example, some drill pipes made of special alloy steel have a yield strength of more than 1000MPa. Moreover, this type of drill pipe also needs to have good fatigue resistance, because in the long-term deep drilling process, the drill pipe will be subjected to countless tensile and torsion cycles. In projects such as deep-sea oil drilling or ultra-deep geothermal well drilling, this high-performance drill pipe is indispensable.

Pay attention to the size and weight of the drill pipe

1. Shallow drilling

Small-sized drill pipes can be used for shallow drilling, such as drill pipes with an outer diameter of 50-73mm. The smaller size makes the drill pipe lighter and easier to operate and transport. At the same time, when drilling in shallow formations, the required lifting force and torque of lighter drill pipes are relatively small, and general drilling equipment can meet the requirements. For example, in the drilling of some agricultural irrigation wells, this small-sized drill pipe can efficiently complete the task.

2. Medium drilling

When the drilling depth increases to a certain extent, the drill pipe size needs to be appropriately increased to ensure its stability and strength. Usually, drill pipes with an outer diameter of 73-127mm are more suitable. These drill pipes are moderately heavy and can provide sufficient drilling pressure without placing too much burden on the drilling equipment. Moreover, a reasonable size can ensure that there is enough space inside the drill pipe for the circulation of drilling fluid, which is essential for cooling the drill bit and carrying cuttings. In the drilling of medium-layer oil wells or medium-depth water wells, such a drill pipe size is a common choice.

3. Deep drilling

For deep drilling, large-sized drill pipes are necessary. Drill pipes with an outer diameter of 127-219mm can withstand the huge pressure of deep formations. However, large-size drill pipes also mean increased weight, which requires drilling equipment to have higher lifting capacity. When selecting the size of the drill pipe, the weight distribution of the entire drill string must also be considered to ensure the stability of the drilling process. In deep-sea oil drilling and other projects with greater depth, the instability of the drill string can be effectively avoided by reasonably selecting the size and weight of the drill pipe.

Consider the connection method and sealing of the drill pipe

1. Shallow drilling

In shallow drilling, a simple threaded connection drill pipe can usually meet the requirements. This connection method is easy to operate, and the tightness of the connection can also ensure that the drilling fluid will not leak in large quantities under the pressure of the shallow formation. For example, the common triangular threaded connection drill pipe is widely used in some shallow geotechnical engineering drilling.

2. Medium drilling

With the increase of drilling depth and pressure, a connection method with better sealing and higher connection strength is required. For example, a trapezoidal thread connection or a joint with a special sealing structure is used. These connection methods can effectively prevent the leakage of drilling fluid under high pressure, and also ensure that the drill pipe will not be disconnected under large torque and tension. In the mid-layer drilling of oil and gas, this high-performance connection method is very important to ensure the smooth progress of drilling operations.

3. Deep drilling

For deep drilling, the connection method and sealing of the drill pipe are crucial. Usually, joints with multiple sealing structures are used, such as a combination of metal-to-metal seals and elastic seals. This joint can ensure the effective circulation of drilling fluid and the reliable connection of the drill pipe in the deep formation environment of high temperature and high pressure. For example, in the drilling of ultra-deep geothermal wells, the high temperature and high pressure environment puts extremely high demands on the connection and sealing of the drill pipe. Only by using advanced sealing and connection technologies can the success of drilling be guaranteed.