• Drilling (narrow sense)

Use a drill bit to directly break the rock. When drilling, use enough pressure to press the drill bit onto the bottom rock and let the edge of the drill bit eat into the rock. The drill string is connected to the drill bit, and the drill bit is driven to rotate the drill bit to break the rock, and the well is gradually deepened. The pressure applied to the drill bit is called the weight-on-bit.


The drill string transmits the power on the ground to the drill bit, so the drill string extends from the ground to the bottom of the well. As the well deepens, the drill pipe is continuously increased, the drill string is gradually increasing, and its weight is gradually increasing, so as to exceed the required drilling pressure. Excessive weight-on-bit will cause damage to the drill bit, drill pipe and equipment, and the weight of the portion of the drill pipe that is greater than the required weight-on-bit must be suspended so that it does not act on the drill bit. During the drilling, the pressure applied to the drill bit is controlled by the driller in a timely manner to effectively drill evenly.


  • Cycle

The bottom rock is broken by the drill bit to form small pieces called drill cuttings (also often referred to as sand). The accumulation of drill cuttings will affect the drill bit to drill a new bottom, causing the rate of mechanical drilling to drop. Therefore, the cuttings must be removed from the bottom of the well in time and carried to the ground. The drilling fluid is injected through the inner hole of the drill pipe and flows out of the water hole of the drill bit to clean the drill bit and rush toward the bottom of the well.


The cuttings are washed away from the bottom of the well, and the cuttings enter the annular space between the well wall and the drill string along with the drilling fluid, and return to the ground until the ground.


The cuttings are separated from the drilling fluid on the ground and removed. This is called sand removal. The drilling fluid from which the cuttings have been removed is pumped into the well for repeated use. While drilling, the washing and crushing of the rock are carried out simultaneously. In order to ensure uninterrupted circulation of drilling fluid, it is necessary to continuously pump in with a drilling pump.


  • Take the single root

During the drilling process, as the well continues to deepen, the drill string must be lengthened in time, and a drill pipe is called a single root.


  • Drill down 

In order to replace the worn drill bit, all the drill string must be taken out of the well, replaced with a new drill bit and then returned to the well to continue work. This is called drilling and drilling (referred to as the drill down). A well needs a lot of drill bits to drill, so the number of trips is many. In order to improve efficiency and save time, the drill is not carried out in units of a single drill pipe, but the three drill pipes are a loading and unloading unit called a standpipe (or column). Each drill rod is 8 to 10 meters long and the length of the root is generally 26 to 30 meters. In order to match such a long stand, the height of the derrick is generally about 40 meters.


For other reasons, such as salvaging wells, logging, etc., it is also necessary to drill down.


Drilling Progress:

From the beginning to the completion of a well, it is necessary to go through preparatory work, drilling, cementing, and other operations.



  • Fixed well position. The bottom hole position is determined according to the needs of geology or production, and the design is made. 

  • Repair the road. In order to transport various equipment and materials into the well site, roads need to be repaired. Since the drilling equipment is heavy material, the road should ensure that heavy vehicles can pass.

  • Pingjingchang. A square land is flattened near the wellhead for construction. The area of the well site varies with the rig and is roughly rectangular in shape. The large rig covers an area of about 120 meters and a width of 90 meters. The medium rig covers an area of about 100 meters and a width of 60 meters. The size of the rig can be adapted to local conditions. 

  • lay the foundation. In order to ensure that the equipment will not sag or skew during the drilling process, it is necessary to lay the foundation (or called the base). The small foundation can be made of square wood or prefabricated parts, and the large foundation is watered on the site with concrete.

  • Installation. Shaft rigs, installation of drilling equipment, placement or excavation of drilling fluid tanks (pools), etc.

The generalized drilling refers to the process from drilling to drilling a section of the formation or drilling a well. Drilling by rotary drilling can be roughly divided into the following processes.


● Cementing

Cementing is an important process in drilling engineering. Its basic purpose can be summarized as two points: strengthening the wall (to prevent collapse of the shallow wall) and isolating the oil, gas and water layers of the well (to prevent mutual interference between layers) . The method of cementing is to put a seamless steel pipe called casing into the well, and grout the cement slurry between the wellbore and the casing to fix the casing, and close the annular space between the casing and the well wall, and separate Some formations. This is the casing and cementing operation. From the beginning to the completion of a well, it is often necessary to enter a multi-layer casing and grout cement, which requires several cementing operations (Figure 6.2).


In some areas, although the well is deep, the formation conditions are better, and the technical casing can be omitted, only the casing and the oil casing are in the lower layer; in some areas, the well is not too deep. If the shallow formation conditions permit, the deep oil and gas water The pressure on the layer is not high, and the surface casing can be omitted. In the whole well, there is only one layer of oil casing. In short, the cementing should be determined according to the actual geological conditions, not only to ensure drilling safety and well quality, but also to save casing and cement as much as possible to reduce drilling costs and improve economic efficiency.


Usually, the cement slurry should be coagulated for about 2 days, and the well quality should be detected by logging methods such as well temperature or acoustic amplitude. The cement return height, cement cementation and sealing status, etc. Quality standards.


Other Work

During the drilling process, operations such as logging, geophysical logging, and formation testing are also performed.


Once a well is drilled, if there is no special situation, it should be constructed according to the construction design, and the design depth can be drilled. However, exploratory wells may be based on new conditions emerging in the ground, or drilled ahead of time, or continue to deepen.