Drilling 101

Photo Courtesy of All-star Energy Services

 

Along with most people, whenever I entered the oil & gas industry, I had no clue as to how oil was extracted from the ground.  This morning my goal is to give you the elevator pitch version.  Considering that many of the easily extracted prospects have already been exploited, the days of the Beverly Hill Billy's is long over...

 

The technology needed to drill these modern day wells is really quite complex.  However, the overall process is quite basic and that's what I plan to talk about today.  To keep it simple, the processes I will discuss will be in reference to the drilling of a land well.  So let's dive in...



Roller Cone Bits, Photo Courtesy of Smith Bits

 

Once the site has been chosen, the land must be cleared.  A level ground is needed to bring in the rig.  A pit is dug next to the location.  This pit will be where the cuttings are discarded.  In many cases, the cuttings will be used to fertilize the farmer's, or property owner's, land.  The cuttings are high in mineral content, one of which is nitrogen.  This makes for great fertilizer!

Once the location has been set, the rig crews begin to dig a giant rectangular pit where the well will go.  This pit is known as the cellar.  The cellar will be where the Blow Out Preventer (BOP) is placed and also provides a place for the rig crews to work on the well.  After the cellar has been put in place, the crew will bring a small drill truck to drill the initial surface hole.  Next the conductor casing will be put into place. 

Hercules 205 in the Gulf of Mexico.  I spent 5 weeks on this rig in 2011

 

On a side note... Casing is large diameter steel pipe that provides the barrier between the formation and the well. By the time the well is completed, several layers of casing will be in place.  The casing schematic will almost resemble something of a telescope.  Please see the image below for an example...

 

Photo Courtesy of Range Resources



Following the prepping of the site, the rig is brought in.  Once the rig is brought in and all the necessary equipment is on site, the crew begins the drilling process.  The actual drilling process is pretty basic.  The formation you are drilling into has a natural static pressure.  This pressure comes from what pressure it takes to keep the formation from collapsing, along with holding back any gases/liquids from coming to surface.  To hold this natural pressure back, the wells are drilled using drilling fluids (known as mud in the industry).  The idea is that the mud weight will be heavy enough to hold back any gases/liquids and help keep the formation from collapsing.  This is called drilling "over balanced."

If the mud weight is lighter than that of the natural pressures, then this is referred to as drilling "under balanced."  In this scenario a seal is placed at the top of the well to prevent any gases from leaking out. 

The mud also serves several other benefits besides what's listed above.  The mud also helps to bring the cuttings to surface and to keep the drill bit cool.  The mud is cycled through the well continuously.  Mud is pumped down the inside of the drill pipe and out from the drill bit.  From there, the mud passes on the outside of the drill pipe (known as the annulus), and up to surface.  The mud is then passed through what is called a "shaker."  The shaker is a high vibration machine that shakes out an cuttings from mud.  Once all the cuttings are shaken out, the mud is pumped back down the drill pipe and the process repeats all over again!

Once the new hole is drilled, smaller casing is placed inside of the existing casing and cemented into place.  This casing will go all the way down to the bottom of the hole.  Following this, the whole process will be completed over again until the desired depth is reached.  The sequence of events below provides the different sections in the drilling process (this represents a simple land well so the casing diagrams can get more complex than this and include multiple sections).   

• Surface Hole, followed by Surface Casing
• Intermediate Hole, followed by Intermediate Casing
   
• Production Hole, followed by the Production Casing

Once the production casing is set, depending on what play the well is in, they will begin to prep the well for production.  The production casing is the conduit, or piping, that the oil company will use to pull the oil out of the ground.  Once the well has been prepped, the rig will place a well head on the well and hand it over.  The completions group will then follow the drilling group, and prep the well for production.  And that's it! Sound's simple right?

 

As I said before, this a very vague overview of the process.  As we begin to deplete these easily accessible resources, and the demand continues to grow, the technology to drill these wells will become ever more complex.  As the technology increases, we will be able to access plays that people had never before even dreamed of.  Who knows where we will be in 50 years... Perfect evidence of this scenario is the evolution of horizontal drilling and the fracking process.  From the implementation of these processes many people in the Energy Industry believe that the United States of America will reach Energy independence before 2020, not to mention a major natural gas exporter.  10 years ago economists thought that energy independence would never be possible!

 

Again, thanks for stopping by. Hopefully you were able to pull something educational from this post.  If you have any questions, or would like to make any comments, send me a contact inquiry! 

-Bormann