The working mode of the single roller cone bit to rock stratum

Single roller cone bit is the most widely used bit in petroleum drilling engineering. It has the characteristics of a wide bottom layer and high ROP. So how does the single roller cone bit work? What is its rock-breaking principle? Next, we will focus on the above problems to introduce the single roll cone bit.

Here is the content list:

• The working mode of the single roller cone bit.

• Impact crushing effect of the single roller cone bit.

• Shear action of the single roller cone bit.

The working mode of the single roller cone bit.

When the single roller cone bit works at the bottom of the well, the bit rotates around the bit axis as a whole. The WOB of a single roller cone bit acts on the rock through the teeth to break it (crushing). In the rolling process, the change of the position of the tooth center of the single roller cone bit causes the longitudinal vibration of the bit. This longitudinal vibration compresses and stretches the drill string. The lower drill string converts this periodic elastic deformation energy into impact force, which generates impact force on the formation through the teeth and breaks the rock. This impact crushing action is the main way of rock crushing by a single roller cone bit.

Impact crushing effect of the single roller cone bit.

As the single roller cone bit drills are a combination of dynamic and static load breaking, they are more efficient and are now widely used for drilling into hard rock formations. It works on the following principle:

The teeth of a single roller cone bit have a certain speed when rolling and make the teeth impact the rock under the action of dynamic load, which causes the rock to undergo volume crushing and a crushing pit is formed. This action exceeds the hydrostatic action, i.e. the axial load acting on the rock by the single roller cone bit consists of two parts: hydrostatic and impact load, while the impact crushing action is the main way in which the tooth wheel bit crushes the rock.

The impact action is related to the impact velocity, i.e. the greater the impact velocity, the greater the impact action. The following conclusions can be drawn from rock-crushing engineering.

(1) The impact force of a single roller cone bit is inversely proportional to T0. For brittle rocks, T0 is very small and thus a large impact force can be obtained; for plastic rocks, T0 is large and only a small impact force can be obtained. Therefore, the impact effect on the crushing of plastic rocks is not significant.

(2) The size of the impact force of a single roller cone bit is only related to the cross-sectional area of the lower drill collar, but not to the length of the pressurized drill collar, so to increase the impact force, a large size drill collar should be used.

(3) The impact force of a single roller cone bit is proportional to the radius of the bit's tooth wheel and inversely proportional to the square of the number of external teeth. Therefore, increasing the diameter of the toothed wheel and reducing the number of teeth can increase the impact power.

In addition, for hard rocks, to increase the impact breaking effect, the toothed wheel of single roller cone bits is often made into a single cone, without sliding.

8 1/2" IADC637 Rotary Drilling Single Roller Cone Bit

8 1/2" IADC637 Rotary Drilling Single Roller Cone Bit

Shear action of the single roller cone bit.

The shearing effect is mainly three-fold: one is the shearing effect of the teeth as they eat into the rock; its second is the shearing effect of the single roller cone bit as it rotates; and the third is due to the sliding of the single roller cone bit's tooth wheel as it rotates, the greater the sliding amount, the greater the shearing effect.

There are three ways to increase the sliding amount of the toothed wheel of a single roller cone drill bit: i.e. using over-top, shifting shaft, and compound cone tooth wheel.

Overtopping: the tapered top of the wheel of a single roller cone bit exceeds the centerline of the bit.

Shifting the axis: the axis of the toothed wheel of a single roller cone bit is shifted by a distance in the horizontal direction.

Compound cone: the toothed wheel of a single roller cone bit consists of two or more cones of different tapers. The distance between the cone tops is called the cone top distance. The larger the cone top distance, the greater the sliding of the toothed wheel.

We are obliged to produce high specification and high-quality single roller cone bits to ensure that there are no accidents caused by product quality in the process of exploration drilling. Hejian Hengji Bit Manufacture Co., Ltd. conducted several tests on the single roller cone bit before leaving the factory to ensure the quality qualification rate of the outgoing equipment. If you are interested in using this device, please contact us.