Aging Well Infrastructure

William Hart drilled the first successful natural gas well in the United States in 1821.¹ A few years later in 1859, Edwin Drake completed the first commercially viable oil well in the United States, which is largely credited with sparking the country’s first oil boom.² Fewer than 50 years later in 1901, the “Lucas gusher” opened a new frontier for oil and gas exploration along the Texas Gulf Coast.³ However, these are just examples of famous and productive wells. Operators drilled hundreds of thousands of other wells across the country without finding hydrocarbons.

In the hundred or so years before record-keeping regulations and best practices, operators often abandoned these uneconomic wells without properly plugging them or mapping their location. Operators may have filled early wells with trash, unconsolidated cuttings or other materials, failing to seal them properly. These practices increase the chances of hydrocarbon migration and groundwater or surface contamination. The problem of abandoned wells becomes even more difficult when the drilling company folds or otherwise ceases to exist. In this case, many agencies classify these wells as orphaned wells.

Because there is no national regulation of exploration and production, the responsibility for mapping and monitoring abandoned or orphaned wells falls to state agencies. However, through no fault of their own, the agencies’ maps and list of wells are usually woefully incomplete. In Pennsylvania alone, researchers who focus on the issue of abandoned wells and their relationship with greenhouse gas emissions, recently increased the estimated number of abandoned wells from between 300,000 and 500,000 to between 475,000 and 700,000.⁴ In states less well-studied, the estimation of number of abandoned oil wells is far less accurate. For example, the Colorado Oil and Gas Conservation Commission keeps track of 35,000 abandoned wells state-wide.⁵ Coast to coast, there may over 1 million abandoned wells, both known and unknown.⁶

One of our experts explains the importance of monitoring aging wells and the hazards of unknown wells in terms of impact on operations and the environment.

Transcript

Aging Well Infrastructure – Alfred William Eustes III – Colorado School of Mines

The first successful natural gas well in the United States was dug in 1821 in Fredonia, New York. Early wells were dug using a cable tool rig. The cable was actually a hemp rope used to raise and lower the drill bit using gravity to hammer the rocks. This is called percussive drilling because of the impacts delivered to the rock by the bit. At that time, the operator’s focus was getting the petroleum out of the ground as fast as they could. Things like hydraulic isolation, preventing one formation from flowing into another, and long term well integrity were most definitely not high on their list of concerns. As the industry matured, increasing importance was placed on well integrity to better protect the environment and the health and safety of all stakeholders.

By the early 1900’s, engineers were experimenting with cement placement techniques. Many of those are still in use today. But at that time, there was no standard protocol for taking wells out of service. When wells were abandoned, they were often used as trashcans. They were rarely sealed properly. The record keeping was poor or even missing. Today, the location of many of these old wells is unknown.

There are many risks associated with abandoned wells and one of the most serious is fluid migration. Fluid migration can contaminate groundwater in the event of gas emissions air and the site if the surface containment is compromised. Regardless of age, any well can be a conduit for fluid migration. That’s why it’s important to employ the proper fluid barriers and identify potential leak paths in order to seal those paths. The purpose of a barrier is to prevent a formation’s liquid or gas from flowing to the surface or another formation.

The hydrostatic pressure head of a wellbore fluid is a classic example of a barrier. For well bores, this is accomplished primarily with casing and cement. Steel casing and cement are both considered passive static barriers. They work as long as they remain in place and their integrity is not compromised.

But time is the enemy of any engineered structure. Seismic activity, pressure and temperature variations and exposure to brines, acids or naturally occurring chemicals can all weaken cement and casings. Over time, casing can corrode and cement can weaken. This increases the likelihood of a failure.

There are two types of failure: potential and catastrophic. Potential barrier failure is the breakdown of a single or of multiple barriers in a wellbore that doesn’t result in contamination. Potential failures require remediation of the failed barrier. If this isn’t done, it can become a catastrophic failure, which is the breakdown of a combination of wellbore barriers resulting in contamination of freshwater aquifers or surface soil.

The problem when dealing with abandoned wells is that we may not even know where they are. In the early days of petroleum production, there was little regulation and record keeping. Today, there are hundreds of thousands of orphaned wells, abandoned wells without owners, across the U.S. in some states, scientists, regulators and volunteers are working together using old records, ground penetrating radar and aerial surveys to locate orphaned wells.

But what about the aging or abandoned wells that we know of? What risks do they pose? The answer is that we don’t know the risks without examining the wells. That’s why regular inspection, observation and integrity testing is critical to identifying wells in need of workover, or proper plugging.

We now have data showing the failure rates for various well construction processes. This allows us to focus our attention on the types of wells that are more likely to leak or fail. It should be noted that even with the data we have about failure rates, there are no hard and fast rules that can predict how long a particular well will maintain its integrity. It’s true that cement will deteriorate over time, but well planned and executed cement engineering can last a long time. The world’s largest un-reinforced concrete dome is the Pantheon in Rome. It’s almost 2,000 years old and it’s still structurally sound.

With advances in technology and techniques and better regulations, modern wells are far less likely to leak or fail over their lifetime. A 2013 study found the risk of integrity failure in modern wells to be extremely low for most quality operations, but this does not make regular testing in monitoring any less important.

Citations

1. American Public Gas Association, 2015, A Brief History of Natural Gas, http://www.apga.org/apgamainsite/aboutus/facts/history-of-natural-gas (accessed February 27, 2017)

2. Drake Well Museum & Park, 2015, About Us, http://www.drakewell.org/about-us (accessed February 27, 2017)

3. Texas State Historical Association, 2010, Handbook of Texas Online, Robert Wooster and Christine Moore Sanders (eds.), “Spindletop Oilfield,” https://tshaonline.org/handbook/online/articles/dos03 (accessed February 27, 2017)

4. Ker Than, Stanford study of abandoned oil and gas wells reveals new ways of identifying and fixing the worst methane emitters, http://news.stanford.edu/2016/11/14/study-abandoned-oil-gas-wells-reveals-new-ways-fixing-worst-methane-emitters/ (accessed February 27, 2017)

5. Jordan Wirfs-Brock, 2016, “Where People Meet Oil And Gas: A Colorado Story In 3 Maps,” Inside Energy, http://insideenergy.org/2016/02/09/where-people-meet-oil-and-gas-a-colorado-story-in-3-maps/ (accessed February 27, 2017)

6. Stephanie Joyce, 2016, “Danger Below? New Properties Hide Abandoned Oil And Gas Wells,” NPR Morning Edition, http://www.npr.org/2016/05/30/474100388/hidden-abandoned-dangerous-old-gas-and-oil-wells-in-neighborhoods (accessed February 27, 2017)

Images: “Explore PA History” by Drake Well Museum