60 Percent of Statistics are Made Up
Writing in The New York Times on Christmas Day 2012, none other than Yoko Ono declared that 60 percent of wells producing natural gas from shale will fail – perhaps surprising those who weren’t previously familiar with Ms. Ono’s background and experience as a petroleum engineer. Expertise (or lack thereof) aside, could it really be the case that more than half of all wells will be “poisoning drinking water” sometime in the not too distant future?
First of all, this isn’t a new claim. Opponents of responsible shale development have been using that “60 percent fail” statistic ever since Cornell professor (and anti-natural gas activist) Anthony Ingraffea invented it and passed it along to Josh Fox, Yoko Ono, and numerous other anti-shale audiences, including some among our friends to the north. Ingraffea even claims to have “industry documents” as his source, but as with so much bandied about by folks dedicated to shutting down hydraulic fracturing, the claim is pure fabrication.
Let’s start by taking a look at these “industry documents” that opponents would have us believe are the Holy Grail of anti-shale activism. The main source is a decade-old article in Oilfield Review examining what’s known as sustained casing pressure, or SCP. There is indeed a graph on the second page detailing that, over a 30 year time span, 60 percent of wells will be affected by SCP.
But what’s listed in the caption – and what no activist ever mentions – is just as if not more important: the graph refers to offshore wells in the Gulf of Mexico. The data came directly from the now-defunct Minerals Management Service, which was the federal agency tasked with regulating offshore oil and gas development in federal waters.
The caption also states clearly: “These data do not include wells in state waters or land locations.”
So, right off the bat, we can see that opponents are trying to pull the wool over the public’s eyes by pretending that casing pressure in offshore wells is actually referring to wells developed onshore in deep shale formations. Even worse, the documentation explicitly states it does not refer to onshore production, which is where shale development is actually occurring!
Do they not understand the difference? Or do they refuse to disclose this information because they fear the public actually would? Either way, the statistic is misleading, if not completely meaningless.
Now let’s dig a little deeper into the specific claim that 60 percent of wells are “leaking” or “failing” based on the Minerals Management Service data in the Oilfield Review article. In reality, sustained casing pressure (SCP) is a much more complex issue, and simply saying that the presence of SCP is evidence of a leaking well reflects an incredibly poor understanding of even basic facts about well construction.
Some quick background: As this handy diagram from Encana shows, a typical well includes many layers (casings), each with its own specific purpose.
The outer layers – the conductor and surface casings – are typically the ones designed to protect groundwater, while the inner casings are designed to protect against any other potential abnormalities (some have even said the intermediate casing is run “as an insurance” against unforeseen problems). The innermost layer, the production casing, is what provides the pathway for oil and natural gas to flow from the target formation underground to the surface – through tubing that is inserted into the casing itself. Cement fills the space between the casing strings, providing yet another layer of protection between what’s inside the pipe and everything that’s outside of it. You can learn more about the well construction process by clicking here.
Sustained casing pressure, meanwhile, is essentially the buildup of pressure in an annulus — the space between the casings. This occurs because of “inadequate zonal isolation” – meaning a gas bearing zone deep underground is not fully sealed off from one of the layers of the well. Of course, this doesn’t mean the well is fatally flawed, and it certainly doesn’t mean that methane inside the pipe is leaking into water supplies (more on that in a moment). Indeed, the purpose of the Oilfield Review article in question was to highlight the options available to the industry not only to prevent SCP, including better cementing procedures and other well construction techniques, but also how it can be reduced and mitigated.
The upshot: SCP is preventable, but when SCP is detected, there are a variety of technologies and processes that can address it – directly contradicting Ms. Ono’s claim that “no one can be sent thousands of feet under the earth to make repairs once this happens.”
According to the article, 47.1 percent of SCP is detected in the production string, and 16.3 percent is in the intermediate string. That means 63.4 percent of the supposed “leaks” that opponents are referencing are actually pressure abnormalities that are limited to inner layers within the well. And since the conductor and surface casings are installed specifically to protect groundwater, there are still multiple layers of concrete and steel separating water from the affected area.
Does that mean SCP is not a problem in these 63.4 percent of cases? Absolutely not. But the good news is that a combination of improved industry practices and new government regulations has helped reduce the occurrence of SCP, and when it is detected, there are a variety of remediation tools available to the operators. As mentioned, the purpose of the article in Oilfield Review was to highlight the steps that the industry has been taking to address and mitigate SCP.
Of course, that still leaves us with 35 to 40 percent of SCP cases – at least according to this MMS data from 2003 – affecting the conductor or surface casing. The lowest percentage by far is the conductor string, for which the data show SCP impacting about ten percent of the time. In many cases, the conductor casing is what actually isolates onshore wells from shallow drinking water resources, so we can already see how the “60 percent of all wells leak” suggestion has been, based on the facts, mostly reduced to “ten percent of 63 percent of offshore wells in 2003 experienced sustained casing pressure in the outer layer of the well.”
After a little arithmetic, we find the incidence rate is actually six percent — dramatically better than 60 percent, and certainly much less alarming.
But even this is based on the assumption that pressure data for offshore wells is materially relevant to onshore shale development. We know, for instance, that offshore wells typically have higher pressure readings than onshore wells – a product of the many differences between a deep shale well and one drilled thousands of feet below the sea floor. And there’s also that inconvenient fact mentioned in the Oilfield Review article: the MMS data do not refer to onshore wells.
Thankfully, there are data available that show the actual failure risk of onshore wells – and it’s far below what Yoko and the Incredible Hulk would like us all to believe.
An August 2011 report from the Ground Water Protection Council examined more than 34,000 wells drilled and completed in the state of Ohio between 1983 and 2007. The data show only 12 incidents related to failures of (or graduate erosions to) casing or cement – a failure rate of 0.03 percent. Most of those incidents (more than 80 percent) occurred in the 1980s and 1990s, too, before modern technology and updated state regulations came online over the past decade.
That same GWPC report also looked at more than 187,000 wells drilled and completed in Texas. The Lone Star State is the largest oil and natural gas producing state in the country by far, so it stands to reason that high failure rates – if they existed – would be present there. As it turns out, there were only 21 incidents related to well integrity, which works out to an error rate of 0.01 percent.
So, if we’re interested in understanding well integrity for shale development, which should we trust more: Data from 15,500 shut-in and temporarily abandoned offshore wells, or an analysis of more than 200,000 onshore wells, including tens of thousands of wells that were stimulated with hydraulic fracturing? The answer is clearly the latter – unless, of course, your interests lie in cherry picking and misrepresenting data to craft a pre-determined narrative.
None of this is to suggest, however, that well integrity issues should be ignored; they absolutely should not, and even an error rate registering in the hundredths of a percent shows room for improvement. But the industry continues to address those problems head on, and states have strong rules and regulations regarding construction standards, casing strength and pressure requirements (Colorado’s are here, Pennsylvania recently updated its rules, Texas regulators have proposed updated wellbore integrity regulations, and Ohio’s standards are among the most robust in the country, just to name a few). Many of these rules have been supported or even encouraged by the industry itself.
The suggestion that 60 percent of shale wells will leak may draw media attention and even scare the general public, but it has no real basis in fact. It’s not science, and it’s certainly not based on “industry documents” that opponents believe have validated their claims. Data that are more relevant to shale development reveal an industry that is committed to safe operations, including maintaining well integrity. That commitment is further supported by strong state regulations, which have been and continue to be crafted in an open and transparent manner.
They may not make for a catchy headline, but hopefully the facts provide a degree of comfort to the general public that shale development is — and will continue to be — a safe process.