Secondary well Control 
On average there are 5 blowouts a year ?

Although the Blowout Preventors are the secondary well control I have decided to keep the subject as a separate section of the site.  Other than the hole itself there is no more important subject on the rig than well control. The first and foremost well control barrier (primary well control) is the drilling fluid, this is explained in the drilling fluid section. and also under well control. However should the unexpected happen or the primary well control fail we must turn to mechanical control, we call this the secondary well control.

Any valve installed on the pipe or wellhead to control the formation can be classed as a blowout preventer. (BOP) The objective, to secure a well should a need arise. They can be hydraulically, manual or air operated and in some cases a combination of all three.

Just to sum up or introduce people that have not been to the well control section Pressure control can be divided into three categories:

1. Primary control. The proper use of hydrostatic pressure to overbalance the formation and prevent unwanted formation fluids from entering the wellbore. The advantages of control at this level are self-evident

2. Secondary control. The use of equipment to control the well in the event primary control is lost. Formation fluids that have entered the annulus can cause a blowout quickly if not properly controlled.

3. Tertiary control. The use of equipment and hydrostatic pressure to regain control once a blowout has occurred. This could involve the drilling of a relief well. Although tertiary control is normally handled by experts, many things can be done during the planning and drilling of a relief well to simplify the final kill procedure and regain control of the well.

Failure of primary control. Any event or chain of events that create a negative differential pressure between the hydrostatic pressure of the drilling fluid and the formation pressure can cause "kick." A kick is an influx of formation an influx fluid into the well. The most common causes of a kick are:

1. Failure to keep the hole full of mud during trips.
2. Insufficient mud weight.
3. Lost circulation causing the hydrostatic pressure to be reduced. 
4. Swabbing in when pulling out of the hole.
5. Improper casing design and pore pressure prediction.

A  recent study of blowouts over a 10-year period lists the following primary causes of blowouts:

The study gave evidence showing that after the wells kicked, over 60% were not controlled for the following reasons:

Every drilling person worth there salt understands that time is money but if you take a close look at the figures shown you will note many of the problems stem from being in to much of a hurry or lack of proper maintenances. 

Not to long ago I put a rig on location. The choke and stack came from another operation and had been in use for the past 2 years. The operate was one of the top 5 operators world wide. The stack was opened and redressed with new ram rubbers and installed on a stump for testing. Even with all new ram nothing held. On the choke every valve leaked. There is no point in training people in well control if you have nothing to control the well with. Blowout don't come cheap nether do rigs and nothing can pay for the life of the Father or Husband. Don't dog house bop test. It not worth the time.

Now days you hear people talking about bop testing. Some are beginning to say they are not worth doing. What does this mean? Take another look at the figures 11% are improper casing and cementing program, Strange that in an industry the frowns on the use of computer for doing the work people are prepared to excepted and what's more stake their life on the output from a computer. A BOP test is only is only as good as the last test. Using worn part is an extremely expensive habit to get into in more ways than one. 

All secondary well control equipment must be included in the preventive maintenance program for the rig. This includes BOP's, and  Blowout Preventer Equipment "BOPE"  such as lines, valves. connections, check valves and what ever other equipment is installed one BOP and choke. and if equipment fails at the test It must be repaired there and then. Drilling out a shoe while waiting on parts to arrive at the rig is a sure way of getting into trouble.