Importance of knowing the nature of the invading fluid in the drilling of an petroleum well

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The nature of a fluid that is different from the drilling fluid is considered invasive, an example of this is gas and/or oil that come from the producing formation and that enter the well in an invasive way and migrate from the bottom of the well to the surface because the pressure exerted by the drilling fluid on the walls of the well at some point ends up being less than the formation pressure (pressure with which invasive fluids enter the well).

By nature we understand the behavior that these invasive fluids may have once they enter the well while we are exercising the well drilling activities, such behavior will depend on some factors such as the geometry of the well and also the physical properties of the drilling fluid that in this case is responsible for generating a backpressure to hold these invasive fluids out of the well.

Why should the nature of an upwelling of fluids such as gas and/or oil into the well be understood?

If personnel such as petroleum engineers, workers and other supervisors do not know how an expanding gas behaves and how flammable it can be in the presence of oxygen and the friction generated in the drilling of a well, then most likely they will not know how to control the well and divert the influx out of the well, especially bearing in mind that with the knowledge of the behavior and nature of the influx it will be possible to determine the control method to be applied in the well to divert the gas from the influx and thus avoid a possible blowout on the surface, and thus saving human lives and avoiding economic losses due to all that would be burned if this were to happen.

The first thing is to know which is the invading fluid that has entered the well, if it is oil, or if it is oil and water, if it is gas and oil or a combination of the three, this will allow to plan the control and deviation of the influx out of the well through a technique that allows the control of pressures inside the well, because if for example it is an expanding gas, we cannot close the well because it would increase the pressures inside the well, the most convenient is to gradually relieve pressure until we have removed all the formation gas from the well.

The conclusion of the case is that knowing the nature of the influx is very important to know the mode of action, since it even allows us to diagnose the technique and even the equations that we are going to use, since for example if it is a gas and we want to know the volume of that gas, then we know that we have as an option to apply the laws of real gases and the law of ideal gases (Boyle's law, Charles, combined law).