Consequences of lost circulation in petroleum well drilling

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Let's imagine for a moment what could happen to the human body if it begins to lose blood in the body, we could talk about a loss of blood circulation, which will not transport blood and nutrients to all organs of the body, therefore our body will be shutting down until death. Similarly the drilling fluid is important for the proper functioning of the drilling process of an oil well, so no matter what the reason is, there is a loss of circulation of drilling fluid in the well, then we are subject to have to deal with problems that will be aggravated until the death of the well and having to stop drilling and even having to lose the well as such.

In the drilling of oil and/or gas wells there is the eventuality that drilling fluid can be lost into the geological formations, since it is normal for the drilling fluid to be pumped by the mud pumps from the active tanks until it reaches the bottom of the hole where it exits through the jets of the drill bit, However, one of the indications that a loss of circulation may be occurring is that the volume of the active tanks is decreasing considerably and that there are no surface leaks.

Consequences of loss of circulation

The loss of drilling fluid circulation can have small consequences such as simply having a loss of drilling fluid costs, to even having very serious consequences from the operational point of view, where due to the total or partial loss of drilling fluid it can cause an explosion, resulting in material and human losses.

Because of these multiple undesirable consequences of lost circulation, it is necessary to monitor the volume levels of the active tanks, constantly evaluate the well in relation to how the well is flowing in terms of drilling fluid circulation.

The most important part of the well evaluation by the drilling operations engineer and field supervisors is that once lost circulation is detected, it is necessary to calculate the hydrostatic pressure that the drilling fluid is exerting with the existing fluid column, because if the level has dropped too much, the hydrostatic pressure may become lower than the formation pressure, and thus an influx of gas may enter and cause a blowout at the surface.

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Suppose that in spite of a total loss of drilling fluid, the formation pressure is not high enough for a formation influx to occur, it is most likely that drilling will continue but dry, i.e. without drilling fluid, However, the consequences are disastrous in the same way, since the drill bit will not cool down and the teeth will wear out, so the drilling will end up taking place, even collapse of the drill pipe may occur due to lack of cooling and subsequent wear due to frictional heating.

Conclusion

If we know the serious consequences of lost circulation, then it is essential to be able to act correctly to control a lost circulation while it is occurring, if for example we are going through a geological formation that is highly porous and permeable, it is likely that this is the cause of our lost circulation, so it is convenient to use chemical additives that can be added to the drilling fluid as anti-loss material, and of course monitor the volume levels in tanks to see if the additive is working as such.

References

[1] Petroleum Engineering Handbook, Volume II: Drilling Engineering. Society of Petroleum Engineers. 2007.

[2] Drilling engineering. Heriot watt university. 2005.

[3] Rabia, Hussain (1986). Oilwell Drilling Engineering : Principles and Practice. Springer.