Oil well control

[3] Failure to manage and control these pressure effects can cause serious equipment damage and injury, or loss of life.

Improper handling of kicks in oil well control can result in blowouts with very grave consequences, including the loss of valuable resources and also lives of field personnel.

Even though the cost of a blowout (as a result of improper/no oil well control) can easily reach several millions of US dollars, the monetary loss is not as serious as the other damages that can occur: irreparable damage to the environment, waste of valuable resources, ruined equipment, and most importantly, the safety and lives of personnel on the drilling rig.

That is why oil well control procedures should be in place prior to the start of an abnormal situation noticed within the wellbore, and ideally when a new rig position is sited.

In other words, this includes the time the new location is picked, all drilling, completion, workover, snubbing and any other drilling-related operations that should be executed with proper oil well control in mind.

[6] This type of preparation involves widespread training of personnel, the development of strict operational guidelines and the design of drilling programs – maximizing the probability of successfully regaining hydrostatic control of a well after a significant influx of formation fluid has taken place.

Normally pressure is measured in the U.S. petroleum industry in units of pounds force per square inch of area, or psi.

The density of formation water in saline or marine environments, such as along the Gulf Coast, is about 9.0 ppg or 1078.43 kg/m3.

Excess pressure, called "overpressure" or "geopressure", can cause a well to blow out or become uncontrollable during drilling.

Annular capacity is given by : where Similarly and Fluid level drop is the distance the mud level will drop when a dry string(a bit that is not plugged) is being pulled from the wellbore and it is given by: or and the resulting loss of HSP is given by: where When pulling a wet string (the bit is plugged) and the fluid from the drillpipe is not returned to the hole.

An uncontrolled kick usually results from not deploying the proper equipment, using poor practices, or a lack of training of the rig crews.

Loss of oil well control may lead into blowout, which represents one of the most severe threats associated with the exploration of petroleum resources involving the risk of lives and environmental and economic consequences.

There are usually causes for kicks some of which are: Tripping is the complete operation of removing the drillstring from the wellbore and running it back in the hole.

During the tripping out of the hole, the space formed by the drillpipe, drill collar, or tubing (which are being removed) must be replaced by something, usually mud.

Lost circulation usually occurs when the hydrostatic pressure fractures an open formation.

When this occurs, there is loss in circulation, and the height of the fluid column decreases, leading to lower HSP in the wellbore.

Lost circulation can be caused by: If the density of the drilling fluid or mud in the well bore is not sufficient to keep the formation pressure in check, then a kick can occur.

If this occurs at a shallow depth, it is an extremely dangerous situation and could easily result in an uncontrolled blowout with little to no warning of the event.

During the course of the test, the bore hole or casing below the packer, and at least a portion of the drill pipe or tubing, is filled with formation fluid.

If there is an unexplained increase in the volume of surface mud in the pit (a large tank that holds drilling fluid on the rig), it could signify an impending kick.

It uses the mud weight to provide sufficient pressure to prevent an influx of formation fluid into the wellbore.

The following are examples of tertiary well control: Using shut-in procedures is one of the oil-well-control measures to curtail kicks and prevent a blowout from occurring.

Generally, a kill weight mud (KWM) mix, which provides just hydrostatic balance for formation pressure, is circulated.

Since we know the consequences of failed well control are severe, efforts should be made to prevent some human errors which are the root causes of these incidents.

Such a culture also requires personnel involved in oil well control to commit to following the right procedures at the right time.

Clearly communicated policies and procedures, credible training, competence assurance, and management support can minimize and mitigate well control incidents.

An effective well control culture is built upon technically competent personnel who are also trained and skilled in crew resource management (a discipline within human factors), which comprises situation awareness, decision-making (problem-solving), communication, teamwork, and leadership.

IADC, headquartered in Houston, TX, is a nonprofit industry association that accredits well control training through a program called WellSharp, which is aimed at providing the necessary knowledge and practical skills critical to successful well control.

This training comprises drilling and well servicing activities, as well as course levels applicable to everyone involved in supporting or conducting drilling operations—from the office support staff to the floorhands and drillers and up to the most-experienced supervisory personnel.

IWCF is an NGO, headquartered in Europe, whose main aim is to develop and administer well-control certification programs for personnel employed in oil-well drilling and for workover and well-intervention operations.