How is an Oil & Gas Well Plugged
Are there rules and regulations that govern oil and gas well plugging in Ohio?
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.
How is a well plugged?
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.
What material is used to plug wells?
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.
Is the well bore filled with plugging material from bottom to top?
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.
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)
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.
Is there a marker to indicate where the well was located?
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.
What can go wrong when plugging a well?
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.
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.
After a well is plugged, can it start leaking?
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.
What is vaulting and venting?
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.
What if I do nothing about the well?
Then probably nothing will change.