How is an Oil and gas well plugged

Yes.  Chapter 1509 of the Ohio Revised Code “Ohio Oil and Gas Law,” and  Chapter 1501 of the Ohio Administrative Code “Rules of the Division of  Oil and Gas” govern oil and gas development including oil and gas well  plugging. 

Typically, the tank battery is removed first.  Any fluids in the tanks  must be removed and disposed in a lawful way.  The wellhead is taken  apart and removed.  The well bore is then cleaned out to the bottom of  the well, if possible.  All tubing and casing strings that can be  removed are removed except the surface casing at the top of the well.   Plugs are then set across all potable water zones.  A permanent Well I.  D. cap is welded on top of the surface casing to mark the location of  the plugged well. 

Before the creation of ODNR, there were few legal requirements.  The  oldest wells were plugged with dirt, logs, and fire clay.  Some wells  were not plugged at all and just covered over.  Modern wells are plugged  with Class “A” Portland cement, nine sack grout mix, prepared clay  and/or Bentonite gel. 

Shallow  wells can be plugged by filling the entire well bore.  Deeper wells are  typically plugged with a series of cement plugs across all potable  water zones.  Cement is heavy, typically 15.6 pounds per gallon.  If the  well bore was filled from bottom to top, hydrostatic pressure could  cause damage (cement leaking into) the very water zones that are being  safeguarded.

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For example, GonzOil plugged  the Thoreau #1 well that was originally drilled 2800’ deep to the  Clinton Sandstone Formation.  Starting at the bottom of the well bore,  five plugs were placed as follows:

• 150’ plug from 2800’ to 2650’ (to isolate the Clinton Sandstone Formation)
   
• 400’ plug from 2500’ to 2100’ (to isolate the Newburg Formation)
   
• 400’ plug from 1300’ to 900’ (to isolate the Big Lime Formation)
   
• 300’ plug from 500’ to 200’ (to isolate the Ohio Shale Formation)
   
• 200’ plug from 200’ to 0’ (to protect the freshwater aquifer) 
   

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            That is a total of  1450 feet of cement plugs in a 2800 foot well which means the Thoreau #1  well bore was filled 52% with cement.

Yes, if the well was plugged in compliance with ODNR regulations within  the last fifty years.  The top surface casing was likely cut off at  least 30” below surface grade and a steel well identification plate was  welded in place.  The plate is usually inscribed “ODNR” with the four  digit well id number on the 1/2” steel plate. 

Gaining  access to the well site by a service rig can be a problem.  The lease  road may be in disrepair or blocked.  Sometimes the area around the well  is cluttered with junk that must be moved.

There may be pollution outside of the dikes that must be cleaned up when the tank battery and wellhead are removed.

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However, the major concern when  plugging a well is the ability to have access to the formation that is  producing oil and gas.  This requires an open, unobstructed hole from  top to bottom.  Obstructions can be caused by mechanical failure of the  casing and/or tubing.  Unfortunately, some wells have been used to  dispose of steel cable, chain, drill bits (the worst), and other metal  pieces.  If the well has been plugged previously and is now leaking,  re-plugging can be much more difficult and expensive.  In order to  properly plug a well, all obstructions need to be removed so the  producing formation can be cemented off.

Some wells can be properly plugged but begin to leak.  This means that,  even though the well was properly plugged, it was not effectively  plugged. Depending on the specific situation for the well, ODNR may  require that the well be drilled-out and re-plugged.  In some  situations, ODNR will require a vault and vent to be placed over the  well. 

Some wells cannot be stopped from leaking.  Although this is unusual,  steps must be taken to make the well as safe as possible.  In this  situation ODNR would like a vault placed over the well.  In the event of  a leak, fluids would be contained in the vault.  A vent pipe is  installed with the vault to direct any leaking gas to a safe area.   Vaults are about 5’ x 5’ and 4’ tall.  They resemble the cement box  culverts that you see at new road construction projects.  The vault  usually has a manhole to allow inspection of the well.  The vault should  be installed in such a way that it can be removed if a service rig must  be brought in to repair an unsafe situation. 

Then probably nothing will change.