Abstract
In empty well killing, in order to save the time and cost of killing the well, the dynamic replacement method is often used to kill the well. The main problem of the dynamic replacement method for killing wells is how to avoid terrible working conditions caused by flooding, such as gas carrying fluid, killing fluid being brought to the wellhead. Based on the principle of flooding formation and the basic tenets of flooding correlation experiment and dynamic replacement method, this paper incorporates the kill fluid viscosity, surface tension, droplet diameter, inclination angle, drill pipe joint outer diameter, and drill pipe eccentricity into the calculation range and establishes a new mathematical model suitable for dynamic replacement kill. Based on the calculation results, the influencing factors of flooding are analyzed, and the following conclusions are drawn: the increase of dynamic viscosity, gas density in the well, casing pressure, well angle, the outside diameter of drill pipe, the outer diameter of drill pipe joint, and eccentricity of drill pipe can promote the occurrence of flooding; The increase of surface tension, well-killing fluid density, and casing inner diameter have an obstacle to flooding.
Highlights
During the drilling process, when the liquid column pressure in the wellbore is lower than the formation pressure, the fluid in the formation will invade the wellbore
The premise of the conventional well killing method is to shut in the well, the drilling tools in the wellbore are at the bottom of the well, and the circulation of killing fluid can be realized
We summarize the influence law and influence degree of the related flooding parameters on the engineering parameters of empty well killing
Summary
During the drilling process, when the liquid column pressure in the wellbore is lower than the formation pressure, the fluid in the formation will invade the wellbore. In the dynamic displacement method kill, since the injection and exhaust are performed at the same time, the kill fluid enters the well and flows downward under the action of gravity, and the gas in the well flows upward under the effect of the pressure difference at the exhaust port During this gas–liquid countercurrent contact process, it is very likely that the kill fluid will be carried out of the wellbore by gas. Yang et al (2013) pointed out that the casing pressure after shut-in is usually high in replacement killing, reaching about 50% of the casing internal pressure strength of the wellhead section, or about 50% of the rated pressure-bearing capacity of the wellhead and well control equipment At this time, it is necessary to take measures to reduce the casing pressure, try to prevent formation gas from entering the wellbore or less into the wellbore, and keep the annular liquid column pressure plus the casing pressure greater than the formation pressure. It guides selecting engineering parameters for the dynamic replacement method of empty well-killing to prevent flooding during the killing operation
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