Well Abandonment & Reclamation Basics
What is well abandonment?
Well abandonment refers to the process in which assets on the surface and downhole are retired in a manner to protect health, safety and the environment. It first involves the identification and creation of an abandonment program.
The abandonment program is designed to identify wellbore integrity issues, producing and/or injecting formations, types of completions, groundwater zones, and the evaluation of cement behind the casing strings.
The next step is to remediate any issues present in the wellbore; this includes isolating porous zones, remediating gas migration and/or surface casing vent flows (SCVF), and isolating groundwater.
Once the downhole abandonment is completed, the wellbore is filled with non-saline or non-corrosive fluid and is assessed to ensure the long-term integrity of the well.
The final step is the surface abandonment and includes removing the wellhead, surface facilities and any pipelines on the lease.
At this time, the well license would be considered abandoned but it would still be the duty of the operator to ensure the lease was reclaimed to its original state
Why do we abandon wells?
Wells are abandoned because they are uneconomical to produce or an operator’s mineral lease has expired.
Regulatory bodies like the AER and BCOGC have created a set of rules and guidelines to follow while completing the abandonment of a well. These rules have been set in place to protect the health and safety of residents living near abandoned wells as well as the environment.
Wells are abandoned in a way that does not allow the communication of non-compatible formations within a well and to protect the groundwater near the surface.
How is a well abandoned?
There are a variety of ways to abandon a well. These methods depend on how the well was drilled or completed as well as the location of where the well was drilled.
For example, a vertical well penetrating the oil sands zone with a dual completion over multiple zones is going to be abandoned differently than the abandonment of an open hole, horizontal completion near Fort St. John.
The single most important aspect of abandonment is isolating different zones within a well. It is of upmost importance that abandoned wells are left in a state that contains fluids in their natural formations. Hydraulic isolation can be achieve through various techniques including bridge plugs, cement retainers, cement plugs, and perf and squeeze operations.
Once downhole abandonment is complete and another assessment of the wellbore confirms proper abandonment, the well is cut and capped below the ground level and the surface facilities removed.
What are some complications involved with well abandonment?
Abandonment operations can become complicated by the migration of fluids in or around the wellbore.
One of the major causes for this is a lack of good cement behind the production casing. This can cause gases or other fluids to flow up around the production or intermediate casing, either into the surface casing (surface casing vent flow or SCVF) or around the wellhead in the soil (gas migration). This can be serious to health, safety and the environment because these gases can be toxic (such as H2S) or they can contaminate ground water.
If a well is not abandoned properly, there is potential for the well to leak after the well has been cut and capped. Leaks could also be caused by corrosion or damage during excavation. If a leak is detected, the wellbore is usually re-entered so that the source of the leak can be identified and isolated.
What is reclamation?
Reclamation is the process of reconverting disturbed land to its former or other productive uses.
The lease reclamation process begins with pre-disturbance environmental site assessments. The assessments are collected prior to surface disturbances to collect historical data, review soil and vegetation details.
The site is then reclaimed to its original state and monitored to evaluate the progress and success of the reclamation program.
Once a lease has been deemed as reclaimed by the appropriate regulatory body, a reclamation certificate is awarded to the operator.