Wednesday, March 9, 2016

What Was The Daily Magnitude Of Methane (That Leaked) Out Of Aliso Canyon?

In the aftermath of the leaking methane well at the Aliso Canyon Gas Storage Facility, questions are still being asked about the damage done both to the environment and the citizens that live within the area (Porter Ranch).  Recently, in the science news, there was a statistic reported regarding the leak near Porter Ranch of methane.  Specifically, the amount per day was reported by comparison to filling up a known volume -- the Rose Bowl in Pasadena in California -- with gas.  Here is a quick post to verify that amount.  Additionally, the intention is to bridge earlier posts with an upcoming post on the bill SB 380 -- requiring the Aliso Canyon Facility to be inspected before resuming operation.

How Much Methane Leaked Per Day?

The calculated answer from a previous blog is 25 million cubic feet of methane gas.  The more complicated (and long) answer to this question is not easily answered due to fluctuating conditions underneath ground.  Normally, I would not rely on such an immediate answer like this.  But the reality of the situation over the course of months (in which the well leaked), the reports are 'averages' and have significant variations.  Why?

In my earlier posts on the gas leak near Porter Ranch (Post 1 and Post 2), there was a comment by a reader who had previously worked at a gas facility in Wyoming.  I do not claim to be a person with personal experience in such matters.  I only went off of the popular news accounts of the leak.  In the popular news, there were reports of fluctuations in the flow rate as the pressure of the 'reservoir' changed over time (due to the corresponding volume change).

Part of me agrees with this idea.  Although, only in the approximation of a large reservoir.  According to the reader who commented, the pressures are pretty high.  Here is what he wrote:

Think about it, the natural gas is naturally occurring, it will only build up to the point the reservoir can contain it. After that point the gas would migrate to another reservoir pocket, or, of it finds a way, to the surface and atmosphere. 

After working with the Department of Environmental Quality on Wyoming for several years, I have seen natural gas reservoirs that naturally hold pressures from 350psi, all the way up to 13,000psi.

The premise of the comment was that I made a gross approximation of the 'void space' of the underground gas reservoir -- 87 billion cubic feet.  Reports in the news stated that the amount of gas stored underneath ground was 87 billion cubic feet.  Of course, in my last post on the volume, the actual volume stored is much greater.  The reader was simply stating that the volume is much smaller than I led the readers of the blog to believe.

Part of that is true.  But only to the extent that I was illustrating the volume (magnitude) of the amount of gas stored underneath ground.  I was referring to the volume as if the amount I was speaking of was equivalent to the space underground.  That could not be true taking into account the reported pressures that the reader speaks of.  With an increased pressure (such as his), the volume would be much smaller (in order to drive up the pressure -- the two are inversely proportional to one another).

Realistically, I was referring to the volume of gas under the conditions of 'standard temperature and pressure' -- which are more comparable to the flowing gas that the public saw coming out of the ground represented by 'infrared imaging.'   Therefore, I am completely comfortable with my representation.

Especially, after reading the following statistic from a website 'Laboratory Equipment.'  The title of the brief was "California Gas Blowout Well Caused Nation's Largest Methane Leak" and the statistic regarding the daily amount of methane leaked from the broken well was stated as follows:

The University of California, Irvine joined the National Oceanic & Atmospheric Administration, UC Davis and others to show that during the peak of the Aliso Canyon disaster, enough methane poured into the air every day to fill a balloon the size of the Rose Bowl.

I am continuously surprised at the amount of readers who read such articles and blow right past these statistics.  In my previous blog regarding the amount of gas stored at Aliso Canyon, I calculated on the side that the amount of methane leaked out of the well in 1 hour would fill 4 Goodyear Blimps.  The calculation is shown below assuming that a 1 Goodyear Blimp would hold a volume of 250 thousand cubic feet of gas:

That is the amount of blimps which could be filled in a single hour with the reported flow rates from the Environmental Protection Agency on the Aliso Canyon Storage Facility.  The flow rates varied with the pressure adjusting underneath ground.  I pulled the value for the flow rate from the table shown below provided by the EPA:

The flow rate used was recorded by the EPA and reported for the 21st of January 2016.  Given the flow amount of gas for an hour to be 1.05 million cubic feet, for a 24 hour period of time, the total volume would be equal to 25 million cubic feet.  In order to calculate the percentage of volume occupied by the gas (in this case the volume is the Rose Bowl), the volume of the Rose Bowl needs to be known.  I had trouble finding the dimensions for the height.  In the end, I asked a search engine and the answer I received was from the website '' given as 20 million cubic feet.

If this answer is correct, which we can take it to be (supposedly for now), then according to the volume of gas that is known over a 24 hour period of time, 120% of the Rose Bowl will be filled.  At least 1 Rose Bowl will be filled along with 20% of the second Rose Bowl.  This raises a couple of questions:

1) What volume was being used in the calculation which resulted in the reported value?

2) Can we guess to see if we come close to the approximation?

What do I mean by the last statement?

How would a person check the calculation?

I stated earlier that I had trouble finding the dimensions of the Rose Bowl on line.  Which raises questions as to the assumed dimensions to arrive at the reported values.  I was able to find an area of the 79,136 square feet for the Rose Bowl.  Using the approximation of a cylinder, we can write the volume as a product of the area and height of the Rose Bowl as follows:

Does the answer make sense?  We could divide the answer by 100 yards (300 feet) to get 84%.  This means that the height of the surrounding walls of the Rose Bowl stadium are 84% the length of the field.  Take a look at a picture of the Rose Bowl below:

Clearly, the height of the wall is not equal to 84% of the length of the field.  In order to compensate for the change, we need to revisit the equation above.  One of two possibilities can be changed to correct the value.  Either the volume is smaller than 20 million cubic feet or the area reported is much greater than 79 thousand square feet.  I would go with the volume being smaller.


Either way, the amount spilled or spewed of methane from the Aliso Canyon Storage Facility was large and possibly the worst ever.  Hopefully, a leak of this magnitude is the last.  In order to ensure that is the case, the California government should enact SB 380.  I did not have much time to go into that in this post.  That can be for another post.

We (Southern California residents) should not forget the magnitude of this disaster.  We should demand more from our elected officials to demand more in turn from SoCalGas.  At the very least, every well should be inspected before operations resume at the storage facility.

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