By Matteo Loizzo
Plug and Abandonment is the last step in a well’s life cycle. When the structure is decommissioned, incremented tubulars are recovered, and steel is cut below the ground (or seabed) level. Then the site is restored. Initially, the goal of P&A was to prevent draining or flooding the neighbor’s reservoir, but soon resource protection - drinking water sources, but also future use for CO2 geological storage (CCUS) or geothermal power - became the driving force. Nowadays, methane emissions are a major concern. Whereas, on average, wells may emit a few tons per year of methane (less than 50 cows’ worth), they do so unevenly: 2% of wells are responsible for 98% of emissions.
When you’re planning to seal wells for the foreseeable future, a 1,000 years or so, only cement and rock have been deemed acceptable. Though, in recent years, a flurry of new materials has been tested. By and large, geological conditions determine how many plugs must be set and where. That’s why requirements have evolved from compliance with fixed rules specific to each jurisdiction, to a need to explicitly qualify a set of barriers that are as close as possible to the initial natural isolation. We may soon witness a further evolution, with regulations requiring proof of no leaks: from a stance of “justify your choice” to “show that it works”.
Even if the P&A is the last step in the life cycle, it shouldn't be our last thought. We design wells with the end in mind and the P&A schematic is ready before the well is even drilled. This will not only reduce final decommissioning costs, but saves us from future regrets (“I should have really run that log”) and helps protect the environment.
Given the global interest in the last phase of Well Integrity, and differences in the business ecosystem, a new technical section was created in March to focus on well abandonment, the P&A Technical Section. We maintain a close relationship with our cousins from the new Technical Section and are already discussing joint initiatives.