(This article is the second installment in a two-part series. Read Part 1, “Where Is All This Methane in the L.A. Basin Coming From?“)
In 1985, a methane pocket ignited under a Ross department store causing an explosion at 3rd Street and Fairfax Avenue and injuring at least 21 people. The property was situated atop the Salt Lake oil field.
This field, discovered in 1902, was one of the most prolific in the L.A. basin, producing more than 50 million barrels of oil from approximately 400 wells by 1917. By the 1930s, production had begun to decline precipitously and surrounding land values had increased sufficiently that most of the wells were abandoned in favor of real estate development. The field runs from the Beverly Center and the Cedars Sinai Hospital complex on the Western edge, to Melrose and Vine on the East, and South to Wilshire Boulevard – some of the most prime real estate in the L.A. area.
In 1985, the city estimated that there were approximately 528 abandoned wells in this field.
Subsequent to the Ross explosion, the city commissioned a study to analyze the cause of the methane buildup and make recommendations to address any problems identified in the report. What became known as Task Force I blamed the methane buildup on naturally occurring methane leakage – swamp gas, from ancient near-surface seeps, similar to the La Brea tar pits – that was biogenic in origin. They discounted the possibility that the methane came from abandoned wells in the area, citing no evidence of thermogenic gas.
A subsequent methane buildup event near the corner of 3rd and Ogden, also within the Salt Lake oil field, did not explode, but was of significant concern that a second Task Force was created to investigate the incident. The resulting Task Force II report mildly backpedaled on the prior 1985 Task Force’s conclusion that all the methane was of biogenic origin. The report acknowledged that the event could have been the result of pressure building in the underlying oil field (forcing methane to migrate to the surface through paths of least resistance), and that some of this gas could have been from abandoned wells and thus thermogenic. They cited the results from a more sophisticated chemical gas analysis subsequently utilized to analyze the gas.
An independent study, done by geologists Douglas H. Hamilton and Richard L. Meehan of Stanford in 1992, arrived at a number of suppositions which they felt better explained the origin and cause for the presence of gas that caused the 1985 Ross explosion, and the subsequent 1989 discovery of explosive levels of methane in the buildings at 3rd and Ogden.
In the 1960s, enhanced oil extraction techniques were introduced into the Salt Lake field an attempt to revive this moribund oil field, using water injection and gas injection, from strategically located “islands,” using slant drilling techniques. In the early 1980s, the operator of the field, McFarlan Energy, sought and received permission from the then Department of Oil & Gas (DOG), to increase injection pressure from 200 psi to 770 psi. Hamilton and Meehan believed that high pressure water was injected into at least one converted production to injection well, without the authorization of DOG.
They believe that this high pressure water injected into producing strata fractured the surrounding geologic formation, creating pathways for the oil and gas to migrate to the surface. These pathways most probably included the long abandoned and poorly plugged wells in the area. Meehan and Hamilton concluded that there was evidence that unreported injection had occurred and that the criteria employed by [CDOG] and the industry relating to fluid injection were inadequate to protect against future such incidents.
The Haphazard Manner of Plugging Wells
With little knowledge or concern of proper well plugging practices in the early part of the 20th century, and lax oversight, many of the wells in the area were simply abandoned or remedially plugged. In the early days of drilling, abandonment and plugging procedures were for the most part haphazard and primitive, sometimes entailing nothing more than throwing old rags, tree stumps, mud and other junk down the hole. Prior to 1952, when the American Petroleum Institute standardized procedures, there were no industry standards for plugging wells.
In 1915, when the Department of Oil and Gas was created, it was playing catch up, trying to inventory existing wells and permit new wells. They readily acknowledged that their enforcement of well abandonment procedures was lax at best, and that there were many abandoned oil wells whose location and status were unknown to them. Often DOG waived the formal plugging requirements, remarking that the presence of oil or gas was so marginal as to have little commercial value or present a threat to ground water, not envisioning future well enhancement techniques that might be implemented.
Even in recent history, the high cost of proper plugging and abandonment has seen many small operators often choose to idle a well and then abandon it years later without proper plugging. In some cases, major operators have sold or transferred ownership of low producing wells, “stripper wells,” to small operators, thus evading responsibility for plugging and abandonment costs. The increase or decrease of idling or abandonment of wells tends to follow the price of oil, and in California, with high real estate values, urban development has become an additional consideration and impact.
Studying L.A.’s Air
In a 2008 study measuring methane levels in the L.A. basin, overseen by Paul Wennberg, a Caltech professor of Atmospheric Chemistry and Environmental Science and Engineering, preliminary results indicated that a significant amount of methane measured bore the chemical signature (i.e., ratios of methane and ethane) characteristic of the natural gas provided by Southern California Gas Company to its customers, and similar to natural gas that might escape from operating gas wells.
Southern California Gas reported very low losses in the delivery of natural gas (approximately 0.1 percent), and yet atmospheric data suggested that the source of methane from either the natural-gas infrastructure or petroleum production, represented up to 2 percent of the total gas measured in the basin. Leakage from homes and businesses might explain some of these measurements but would have to be excessive to support these numbers. Biogenic sources of methane (such as livestock, landfill gas, and wastewater), though present, were overshadowed by the thermogenic sources.
Another group of researchers in 2012 released a paper in the Journal of Geophysical Research titled “Isotopic measurements of atmospheric methane in Los Angeles, California, USA: Influence of ‘fugitive’ fossil fuel emissions,” which echoed the findings of the 2008 study (i.e., data indicated that the dominant source of CH4 [methane] is leakage of fossil fuels, such as from geologic formations, natural gas pipelines, oil refining, and/or power plants). Caltech’s findings have led to the NASA/JPL led “Megacities Carbon Project,” a far reaching project to measure and analyze data on carbon emissions in the world’s major metropolitan cities.
The Well Leakage Problem
Even with today’s knowledge and technological advances in well cementing and plugging, leakage appears to be a major problem. A 1980 study of 250 casing jobs over a 15-month period with new cements, found 15 percent of the wells leaked, according to a paper given by L.T. Watters and F.L Sabins at an oil and gas conference in Dallas, Texas. Another 2013 study out of Cornell University, which looked at 41,381 oil and gas wells drilled between 2000 and 2012, both conventional and unconventional, estimated that 5.7 percent of the conventional wells drilled prior to 2009 had well integrity problems.
This compared to only 2.27 percent for wells drilled after 2009 (unconventional wells had significantly higher integrity problems, almost 10 percent for wells prior to 2009 and nine percent for post-2009).
In a 2003 article in Oil Field Review, “From Mud to Cement – Building Gas Wells,” uncontrolled gas migration in well bores was cited as a major challenge for the industry. The paper graphically showed incidents of gas migration in studied fields increasing over time, from five percent in the early years, increasing to over 50 percent in later years. Another paper published in 2014 by the University of Waterloo and Geofirma Engineering, Ltd. also cited well bore leakage as a common problem in the industry. Looking at data from across Canada, they found that 10 percent of the wells in British Columbia leaked, 20 percent in Saskatchewan and Ontario, and almost 50 percent in Quebec.
Other studies of methane leakage from abandoned and plugged wells have confirmed leakage from both unplugged and plugged abandoned wells as a significant source of methane venting to the atmosphere. A 2013 study 2013 study out of Princeton University found significant leakage from both abandoned and plugged wells in Pennsylvania, with little discernible difference between the two as to high emitter or low emitter leakage rates. Though based upon a small sample of wells, the investigators saw a wide range of leakage variation between the 19 wells measured, from a low of 0.9 to a high of 210 mg/h/well. Using a mean leakage rates from abandoned wells to be 0.27/kg/d/ well, they extrapolated that leakage from abandoned wells to be equal to four-to-seven percent of estimated total anthropogenic methane emissions in Pennsylvania. Most disturbing, is they found leakage from all wells measured. There are an estimated 200,000 abandoned wells across the state, making the potential emissions from these abandoned wells a factor to be taken into consideration when inventorying methane emitters and levels for the state.
There are an estimated 200,000 abandoned wells across the state, making the potential emissions from these abandoned wells a factor to be taken into consideration when inventorying methane emitters and levels for the state.
In a 2003 article by G.V. Chilingar and Æ B. Endres, “Environmental hazards posed by the Los Angeles Basin urban oilfields: an historical perspective of lessons learned,” they identified methane leakage from abandoned or poorly plugged wells as an enormous hazard, citing their evaluation of hundreds of documented well leaks, attributing “virtually all well leaks to the poor well completion and/or abandonment procedures (e.g., poor cementing practices).”
Even the oil and gas industry admits that poor plugging and abandonment practices represent a shameful environmental legacy. Quoting from a September 2011 White Paper published as part of the “Working Document of the National Petroleum Council (NPC) North American Resource Development Study:
“The plugging and abandoning (P&A) of oil and gas wells that are no longer economically viable for production, or which have wellbore issues that require closure, has historically been conducted as an afterthought in the oil and gas production business… Most wells are plugged at the lowest cost possible following the minimum requirements set forth by the oil and gas regulating agencies.”
Enhanced Extraction Technology and Abandoned Wells
Wells in oil fields that were either plugged or simply abandoned – then subjected to enhanced production techniques, such as water flooding, steam injection, gas injection or various fracking technologies – become pathways for migration of methane. Early plugging techniques never anticipated having to handle the increased pressures such activities generate.
The September 2011 White Paper published by NPC further identified poor plugging and abandonment practices as historically endemic within the industry and a potential major future problem for the industry.
“As these old fields are reentered to apply newer technologies such as solvent or CO2 flooding,” the authors write, “the reservoir pressure is increased due to the injection of fluids for oil recovery. When this higher pressure is applied to unplugged or poorly plugged wells, there is a chance that the formation fluids will bypass the plugging materials and migrate uphole.”
Corrosion also plays a factor in well integrity failures. Both steel and cement can and do erode over time in the corrosive environment found in oil fields, losing integrity subjecting them to a high likelihood of leakage over time.
Earth Movement and Abandoned Wells
Earthquakes (either naturally occurring or attributable to oil and gas production activity) and ground subsidence (resulting from oil and gas extraction), present other potential risks for well bore shifting, such as damaging the integrity of the well casing.
The many earthquakes in L.A. have caused considerable damage to oil and gas fields, as well as distribution infrastructure. The 1983 6.4 magnitude Coalinga earthquake damaged nearby oil field infrastructure, collapsing pipes and separating well casings. The 1994 Northridge earthquake caused similar damage to oil fields in the area. No doubt the dozen or so 4.0-plus earthquakes over the last 100 years in the LA basin have caused earth movement sufficient to affect the integrity of abandoned and capped oil wells in the area.
Though methane leakage from abandoned and even active wells is an industry wide problem for the L.A. basin, it could be particularly acute, due to the large number of wells abandoned prior to the institution of modern industry standards for plugging and abandoning wells. There is no doubt a certain amount of methane emanating from difficult to control near surface seeps, but the legacy of abandoned wells from oil’s glory days in the basin should not be ignored.
So in answer to the question posed at the beginning of this series of articles, “Where is all this methane in the LA basin coming from?” it may partly be a legacy of abandoned and poorly plugged wells, as well as the existing aging oil and gas wells that are scattered throughout the region. It’s not a matter of shutting down an industry. It’s holding it to a high standard of best practices and cleaning up a legacy of poor practices.