Bottom hole pressure, also called flow pressure, is the pressure measured at the bottom of the well during production. Bottom hole pressure is a key indicator for producing wells. The oil and gas flowing into the bottom of the well is lifted to the ground by the bottom-hole pressure, so the bottom-hole pressure is an important indicator of the self-blowing capability of the oil and gas well.

Different types of oil reservoirs have certain rules in the production of oil wells at different development stages. Maximizing the potential of oil wells is the fundamental need for oilfield development, and the most important parameter that determines oil well production is bottom hole pressure.

Bottom hole pressure can be expressed by the following formula:

Pwf = Po+ Pm+Pf


Pwf——bottom hole pressure;

Po ——wellhead pressure (tubing pressure);

Pm ——the pressure of the flowing fluid column in the wellbore;

Pf – the pressure lost by fluid flow in the wellbore.


When the bottom hole pressure (flow pressure) is higher than the saturation pressure, the flow pressure of the oil well decreases and the production increases linearly;

When the flow pressure is lower than the saturation pressure and further reduced, the production rate of increase slows down;

When it is reduced to a certain extent, the phenomenon that the output decreases with the increase of the production pressure difference will appear.

Therefore, maintaining a reasonable bottom hole pressure is very important for the well to maintain high production. In the case of single-phase liquid flow and oil and gas two-phase liquid flow in oil wells, the principle of reducing bottom-hole flow pressure to the maximum extent is to improve the single-well production of oil wells; When the oil well is in the three-phase seepage state of oil, gas and water, it is more complicated to determine the minimum allowable flow pressure of the oil well. Various factors such as sand, wax, well deviation, well depth and technological level must be considered to maximize the potential of the oil well.


At the production site, the back pressure of the pipeline is too high, which has a serious impact on the normal production of the oil well. One is that the oil well fluid volume and water content are low, the liquid supply is seriously insufficient, and the oil wells cannot be produced normally; the second is that the back pressure is often increased; the third is that the pipeline is perforated.

At present, some tubing valves of old wellheads in oil fields cannot be opened due to rust or other reasons. Therefore, the residual pressure in the tubings cannot be effectively controlled. If the valves or wellheads are directly replaced, there are certain safety risks. The existing punching device with pressure cannot observe the pressure change in the tubing during the punching process, nor can it effectively control the pressure in the tubing after the punching is completed.


Therefore, Sanjack Company has developed a punching device under pressure, which can observe the pressure change in the tubing during the punching process, and can effectively control the pressure in the tubing after the punching is completed.


The device consists of oil well tubing (1), nipple(2), control valve (3), drill bit (4), check valve (5), pressure gauge (6), pressure control pipeline (7), extension rod sleeve ( 8), extension rod (9), extension rod seal (10), fixed ring (11), fixed sleeve (12), torque joint (13), etc.

Working principle: Weld the nipple with the outer wall of the oil well tubing, open the control valve, rotate the torque joint, and drive the drill bit to punch pipe through the extension rod. When the hole is punched through, the oil and gas pressure in the tubing will enter the extension sleeve, pressure control pipeline, check valve, pressure gauge. Since the extension rod sleeve is equipped with an extension rod seal, the extension rod sleeve is a sealed space. When the drill bit penetrates the tubing under pressure, the pressure gauge through pressure change tell whether the hole is open, and there will be no gas or liquid overflow, so as to ensure the safety of operation. When the punching is completed, withdraw the drill bit from the control valve and close the control valve. The pressure in the extension rod sleeve can be evacuated through the check valve, and the extension rod sleeve can be unloaded from the control valve to complete the such operation. Since then, the pressure inside the tubing can be controlled by the control valve to ensure the safety during subsequent operations such as replacing the valve or replacing the wellhead.

The structure developed by Sanjack can observe the pressure change in the tubing during the punching process, and can also effectively control the pressure in the tubing after the punching is completed, ensuring the safety of operation.。