This month’s Oil & Gas Measurement Podcast episode features Kevin Warner, of Mustang Sampling, discussing the challenges in obtaining representative gas samples of wet gas and rich gas, particularly when the gas is delivered at high temperatures.
In this month’s episode, you will learn the importance of proper design and installation of the sampling system, along with some of the common pitfalls of cutting corners with high GPM shale gas.
Rich Gas Sampling Show Notes, Links, and Insider Terms:
- KevinWarner has been working in the measurement industry since 1994 when he joined Daniel Industries to promote ultrasonic gas flow metering. He has earned several patents and has published a multitude of papers on subjects including cryogenics, speed-of-sound measurement techniques, formation evaluation, nuclear experimentation, and ultrasonic flow metering. Currently, Kevin serves as the Chief Technology Officer for Mustang Sampling, Inc. Connect with Kevin on LinkedIn.
- Mustang Sampling, LLC is the innovator of Analytically Accurate® solutions within sample conditioning systems. Mustang provides custom solutions of products and services globally to the Natural Gas, Natural Gas Liquids (NGL), and Liquefied Natural Gas (LNG) industries.
- Mustang Sampling Owner, Founder, and CEO, Ken Thompson, believes if you work hard, you should play hard…and in the case of Mustang Sampling, that also means DRIVE HARD, in the Mustang Sampling IMSA Prototype Challenge car. More on IMSA Racing.
- Ultrasonic Flow Meters are non-contact flow meters that use sound waves to determine the velocity of a fluid moving through a pipe.
- AGA-9 – American Gas Association Report No. 9 is an industry standards document relating to the design, installation, and use of Ultrasonic Flow Meters for natural gas custody transfer measurement.
- IMSA VP Racing Sportscar Challenge is a North American auto racing series for LMP3 and GT4 (run as the GSX class) vehicles.
- RNG – Renewable Natural Gas is natural gas produced by capturing and processing the gasses produced from a variety of renewable processes, such as landfills, sewage treatment plants, and large scale agricultural operations.. The RNG must be processed and filtered to achieve pipeline-quality standards, so it becomes “interchangeable” with geo-sourced natural gas. The methane content must be concentrated to approximately 90%, inserts reduced to acceptable limits, and toxic and\or damaging contaminants removed.
- Hydrogen Gas is a clean energy carrier that can be used to store, move, and deliver energy produced from other sources. Hydrogen can be produced from a variety of domestic resources, such as natural gas, nuclear power, biomass, and renewable power like solar and wind. These qualities make it an attractive fuel option for transportation and electricity generation applications. It can be used in cars, in houses, for portable power, and in many more applications.
- Hydrogen Injection or Hydrogen Blending is the concept of adding Hydrogen gas to existing natural gas pipelines, and delivering a carefully controlled blend of gasses to the customer, with the goal of reducing the carbon intensity of the fuel. While simple in concept, this is a complex and potentially deadly process, since hydrogen may embrittle certain steel pipes, resulting in catastrophic failure. On a volume basis, at a given pressure, Hydrogen provides only a small fraction of the energy that is provided by natural gas, which can cause difficulty in end use devices.
- BTU (British Thermal Unit) is a measure of the heat content of fuels or energy sources. It is the quantity of heat required to raise the temperature of one pound of liquid water by 1 degree Fahrenheit at the temperature that water has its greatest density (approximately 39 degrees Fahrenheit).
- NGL – Natural Gas Liquids are components of natural gas that are separated from the gas state in the form of liquids. This separation occurs in a field facility or a gas processing plant through absorption, condensation, or other methods.
- Rich Gas is natural gas containing a large amount of valuable natural gas liquids. Rich gas is not suitable for direct use by residential or industrial customers and must first be processed to remove most of the NGLs. Sampling and analysis of Rich Gas is extremely difficult, since phase changes can occur with changes to pressure or temperature.
- Shale Gas refers to natural gas extracted from the tiny pores in shale sedimentary rock formations. The composition of the gas extracted from different shale formations varies, but is generally high in NGL content.
- GPM or Gallons Per Thousand Cubic Feet, is a unit of measure used to describe the concentration of Natural Gas Liquids (NGL) present in natural gas.
- C1 – C6: A shorthand used to refer to individual hydrocarbon compounds by the number of hydrocarbon atoms. C1 represents Methane. C6 represents hexane.
- A C6 analysis refers to a GC analysis that stops separating the sample components at C6, grouping all hydrocarbons C6 and larger into a single value.
- Shale gas is natural gas found in shale deposits, where it is trapped in microscopic or submicroscopic pores. This natural gas is a mixture of naturally occurring hydrocarbon gasses produced from the decomposition of organic matter (plant and animal remains). The composition of the gas extracted from different shale formations varies, but is generally high in NGL content.
- Upstream is the operation stage in the oil and gas industry that involves exploration and production.
- Downstream is the process involved in converting oil and gas into the finished product, including refining crude oil into gasoline, natural gas liquids, diesel, and a variety of other energy sources. The closer an oil and gas company is to the process of providing consumers with petroleum products, the further downstream the company is said to be.
- Probe or Sample Probe is a special pipe fitting designed to allow withdrawal of small amounts of the gas or liquid from a pipeline for analysis. The design and length of sample probes vary with the product and pipe size.
- Phase Envelope is a diagram that plots the relationship between temperature and pressure for a compound, showing the equilibrium phase (solid, liquid, gas) .
- Phase Boundary – a temperature – pressure equilibrium point, where two phases of matter exist together (solid-liquid, liquid-gas).
- 2-phase flow occurs when both Gaseous and Liquids are present
- Bubble Point is the temperature (at a given pressure) where the first bubble of vapor is formed, when heating a liquid consisting of two or more components.
- Coalescing filter – A filter designed to capture and separate liquid aerosols by allowing them to form larger droplets, which are large enough to be drained away gravitationally. While used in natural gas sampling systems to protect analyzers from liquids, these filters change the composition of the sample.
- Joule–Thomson effect – the cooling that occurs when real gasses (except Hydrogen and Helium) expand, from a drop in pressure.
Rich Gas Sampling Full Episode Transcript:
Weldon Wright: Welcome to episode 18 of “The Oil and Gas Measurement Podcast”, sponsored by GCI, the Gas Certification Institute, which has been providing measurement training, standard operating procedures, and consulting services to the oil and gas industry for over 20 years.
GCI proudly partners with Muddy Boots Online, offering measurement professionals a true cloud based field operations option. Visit GasCertification.com to find out how Muddy Boots can streamline your meter testing, witnessing, and sample tracking.
Announcer: Welcome to The Oil and Gas Measurement Podcast, where measurement professionals, Bubba geeks, and gurus share their knowledge, experience, and likely a tall tale or two on measurement topics for the oil and gas industry.
Now, your host, Weldon Wright.
Weldon: Hello, and welcome to episode 18 of The Oil and Gas Measurement Podcast. I’m here with Kevin Warner today from Mustang Sampling. He’s the chief technology officer over there.
Kevin, tell us a little bit about what a chief technology officer does, how you got to be there at Mustang, and what you all are up to these days.
Kevin Warner: I’d be happy to, Weldon. Thank you for having me. I’m not sure what a chief technology officer does at Mustang Sampling. I think mainly whatever interests me is usually what I’m doing, to be quite honest.
We have a very rapidly evolving industry with natural gas, and so, our products are always changing. Our customers come to us with different requirements pretty much on a continual basis. We’re always trying to develop new products for new applications. We just go wherever the customer takes us. That’s really where we go.
The way I became involved with Mustang Sampling was 30 plus years ago I met Ken Thompson, who owns the company. At the time, I was promoting ultrasonic metering, which was a brand new technology back in the ’90s for natural gas measurement.
I was working for Daniel Measurement and Control. Very few people would give me the time of day to talk about ultrasonic metering. Ken Thompson was one of the few people who would.
I spent a lot of time with Ken, just talking about ultrasonic metering. We met his customers. Pretty soon, they were using the technology. I’ve had a close relationship with Ken ever since.
Ken’s interests were more along the lines of gas analysis. 20 plus years went by. I had spent time at Emerson and then I spent time with Elster Instromet doing mainly metering, but when Honeywell purchased Elster I was looking for something to do. I talked to Ken about doing something together.
He said, “Yeah, we’ll figure something out.” That’s how you become a chief technology officer at Mustang Sampling. It’s mainly through those relationships that we had built over the years, mainly through the evolution of ultrasonic metering. That’s how it came to be.
Weldon: That’s great. In that time frame, ultrasonic metering, you were almost a snake oil salesman in the industry, weren’t you in the beginning?
Kevin: We absolutely were. We spent…I joined with Daniel in, I think, 1993. It took us until 1998 to get the first version of AGA-9 published, with a white paper prior to that. It was difficult to get people to really take us seriously for almost five years.
Weldon: Now, today, you don’t see a big custody transfer metering station being put in with anything other than ultrasonics these days.
Kevin: That’s right. Every so often I get pulled right back into it, which is fine. I never know what I’m going to do from day to day.
Weldon: What we wanted to talk about today was sampling challenges, specifically questions I’ve been getting from some of the listeners about challenges out there with rich, hot gas.
Before we do that, you mentioned something when we were setting up a time for this call that made me take a step back. What is this I hear about Ken not having a race car this year, this season?
Kevin: That’s a fact. We’ve been racing in the IMSA series for prototype sports car racing for, I guess, the past seven years. About every three or four years the standards change, the cars change, and so you’re required to get a new car, which runs with a completely different platform.
This was the first year that hybrids came into being for IMSA motorsports. To make a long story short, there were a limited number of cars. The car that we had ordered was delayed. It was delayed into the middle of the season, and so we’re on the outside looking in without a car this year. We expect to be back next year, but for the 2023 season we’re on the outside looking in without a car. That’s a fact.
Weldon: Wow. Supply chain problems in the race car industry. Man.
Kevin: That’s correct.
Weldon: Getting back to the topic at hand, here, as I mentioned earlier I guess I originally talked to Ken a year ago about talking about RNG sampling. We’ve had listeners that come to us with challenges.
We all know it’s a challenge. What they’re asking for is information about the current answer to their challenges. We have folks out there in some of these production fields, especially, that are dealing with high BTU rich gas, sometimes 1,300 BTUs plus, six GPM plus gas, one percent, one and a half, even two percent C6 pluses in that stuff.
Some of them are taking that gas at low pressures and fairly high temperatures, 100 degree plus temperatures. Of course, they have a few sampling problems, don’t they?
Kevin: Yes, they do. We’ve had, I would say…I may have mentioned earlier that customer requirements and the industry is rapidly evolving. If I think about the last three big changes that we have had to find solutions for, the most recent would be hydrogen, hydrogen injection into the pipelines and distribution systems.
Before that, we had renewable natural gas coming into the pipeline and distribution systems. Before that, we had shale gas. Really, the shale gas and the shale revolution, which is now going back 12 or 13 years, that’s really where we started to see the composition of gas change dramatically, especially with gas fields that are not associated with oil.
Absolutely, the gas that we’re trying to analyze today is much hotter, much richer than what we would have seen 20 years ago. The sample conditioning systems and the analysis itself required to deal with those compositions is completely different than what we’ve dealt with traditionally.
Weldon, it starts at the probe itself and works its way all the way through to the analyzer. There’s not one part of our business that’s not impacted.
Weldon: I can see that. Kevin, I think that we sometimes stick our heads in the sand, right? In our standards, and our trainings, and in our standard operating procedures it’s easy to say we’ve got to keep that sample in a gaseous state. We can’t transform it in any manner. The realities of what that really takes… it’s tough, right?
Kevin: Yes, it is. We usually talk about three things that have to happen correctly in order to understand your process.
The first thing you have to do is you have to be able to obtain a representative sample. The second thing you have to be able to do is to be able to transport that representative sample and prepare it for introduction into an analyzer. The third thing you need to be able to do is you need to be able to analyze it.
Like I said earlier, it’s all three of those. All three steps are significantly impacted when you’re dealing with rich gas.
Weldon: What does the process look like, Kevin? When you get a call from a customer and they say, “Hey, we’ve got trouble. Our results are all over the place. The other party is not convinced that we’re sampling right,” or they flat out say, “We’ve got two samples with widely differing analyses.”
Where do you start that conversation with the customer? What does information gathering look like?
Kevin: Typically, we start with, “Give us your best estimate of the gas composition.” If they really knew that, if they knew that very, very well they wouldn’t be calling us. That’s where we start, “Tell us what you think you have. Tell us your operating temperature, your operating pressure,” and try to talk through enough information to understand if the gas is flowing and where we think it might lie.
Then, we’ll put together some kind of a phase curve. Again, it’s an estimate. We’ll try to create a phase curve that we can use to at least look for bubble points and understand where they’re operating with respect to phase boundaries.
From there, we’ll get into deeper discussions about what does your current sample conditioning system look like? What kind of analyzers are you using? How many are there? Why do you think your…Where are you seeing a problem? What kind of problem do you think you’re seeing? Do you have any other comparisons that we can use from other types of samples?
We really go down the line. We always start with, “What do you think the composition is?” Oftentimes, that’s enough to find the real root of the problem.
Weldon: It seems like sometimes it may not be as much as what they think the composition is as what they hope or what they want the composition to be, right? Depending upon which side of that meter on, the desires may be a little different, right?
Kevin: Yeah. The desires are definitely different. I think over the past five or six years we’ve seen a significant change in the mindset of, how do we handle things that are liquids at ambient conditions? What do we do with natural gas liquids that are diluted in a high pressure gas line?
The way in which people have historically conditioned their samples was created from the process itself and how the industry was ultimately allocating resources and who was taking what out of the pipeline and in which order.
That’s, of course, still true today, but yeah, if you’re selling gas, you want to know everything that’s in that gas stream, not just the gas, but also the heavier components. It goes back to how it can create a situation where it’s a lot harder to get a representative sample.
Weldon: I’ve been out on several audits out in the field looking at production facilities. All shale gas. Two of the three were actually very low pressure deliveries, but one of the things you walk up is I walked up to one site where there’s a membrane probe trying to reject liquids inside the pipe.
There’s literally a liquid separator, a coalescent filter, sitting on top of the sample probe. Then, they were still getting liquids into their chromatograph added on the site. Their concern was, “How do we get these liquids out so we can analyze the sample?” That was really the wrong question, wasn’t it?
Kevin: That’s right. It’s the wrong question altogether.
Weldon: Those liquids are actually part of the composition of that gas. That wasn’t liquids gurgling down the pipeline. They were condensing liquids out of that natural gas stream. As you said before, they were not getting a representative sample of the equipment.
Talk about how you all approach that. What does someone need as the standards or what you begin with, I should say, when you start looking at sample systems for this low pressure, hot thermally, and high GPM gas?
Kevin: I think where we start is if someone has a…Again, to your point, that people who are producing the gas, who have ownership of the gas are oftentimes more concerned that you’re missing some of those heavies. One of the places where we like to start is we want to determine whether a representative sample can be obtained using a conventional sampling system or a conventional probe with a membrane.
Sometimes it simply isn’t. That’s the very first thing we have to ask people, is tell us exactly what you want to sample. If it’s a two phase gas, we’re going to have a real problem. Are you willing to take the steps necessary to separate that two phase gas or to get it into a different state where we can get a representative sample?
If we can’t do that, we can never expect to get a proper analysis. That’s the kind of difficult conversation that we often start with, “Do you believe we can ever get to the point where a representative sample will be available?”
If you’re trying to take something out of a process that’s in the two phase region, we really can’t guarantee that it’s ever going to be consistent. If you don’t believe that, just look at the repeatability of the gas chromatograph over a function of hours, or days, or weeks. It will pretty much prove itself.
Weldon: I think I see that quite a bit. I see the results of what you’re talking about there. Every time, both parties are usually fairly convinced that they’re delivering single phase gas, but it may be single phase gas that is so close to the edge that a single degree of temperature drop may change the state of that gas.
Kevin: That’s right. Most of the standards that we have for natural gas analysis assume that you’re starting with a fairly dry, high pressure gas. Some of the biggest issues you’re going to have are going to be associated with Joule Thomson cooling.
That simply isn’t the case when your starting point is a rich, low pressure gas. The problems are different. You’re not going to see issues from regulating the gas to a pressure that you can get to the analyzer because it’s already at low pressure.
It’s a completely different type of problem. If people are truly interested in getting the value of that gas, we start with, “Let’s talk about what it’s going to take to obtain a representative sample and to be able to transport that to an analyzer. Can you do it simply as a gas or can you do it simply as a liquid? Do we need to separate it? What’s it going to take?”
A lot of times it’s not a matter of just putting a probe into the line and hoping for the best. That’s simply not a solution. Removing a membrane is not a solution. You still don’t get a representative sample.
It’s a difficult problem, but we really have to take each one of them on a case by case basis and try to understand exactly where the process needs to go in order to obtain a proper sample point.
If you want to think about an analogy, in flow measurement if someone is two diameters downstream of a couple of elbows and they point to that position and say, “I want you to give me good flow measurement right there,” we would have a long discussion about why that’s not a particularly good place to put a flow meter.
A lot of times you have to have that same conversation when it comes to analysis. Instead of talking about a position, perhaps you’re talking about a region of pressure and temperature on the phase curve or upstream or downstream of certain types of equipment.
Again, it’s really a conversation about what you can do at that particular point. Are you trying to do something that’s possible, or are you trying to do something that’s not possible? That’s where the conversation starts. Usually, people are fairly agreeable to get to that end.
The other piece of this, of course, is when we sample, the other part of sampling is we always ask people why they are sampling. Compliance, safety, the things that aren’t about custody transfer also come into play.
We have to make sure that people are in compliance with what they’re being asked to do, and they’re doing things in a safe manner. Those things are also important in determining the entire system.
Weldon: Makes sense. For simpletons like me and I’m sure a lot of the bubba geeks out there that know just enough to be dangerous about our business, when I hear getting that representative sample of rich gas to the analyzer, the little voice in the back of my head immediately screams, “Heat, heat, heat.”
Is more heat, is maintaining temperature, is that always the solution? I suspect it’s not. I suspect there’s other approaches, too.
Kevin: It’s definitely not always the answer. If putting adequate heat into the sample is the solution, then we can simply vaporize…We can employ vaporizers. The vaporizers will raise the temperature of the gas significantly higher. From that point, we can maintain the temperature.
The upper limit on that is normally determined by the lowest temperature specification of the analyzers that you’re using. There’s certainly a limit. Otherwise, we would just simply raise the temperature like you’re suggesting.
That’s not always possible. It’s also more of a…It’s a tool in the second part of the process, in the transportation of the sample, because if it’s at a temperature and pressure in that pipeline getting the representative sample to begin with…That can be a real challenge. It’s not always the answer. More heat is not always the answer, that’s correct.
Weldon: You’ve mentioned quite a bit about obtaining that sample and a little bit about analyzing it. You’ve mentioned twice about transporting that sample. Transporting that sample, of course, the first thing you think of is, “I’m going to get it in a sample cylinder and carry it to a lab.”
That’s one piece of the puzzle, but also what we do with that online or that local analyzer, that always fits into the equation as some of the more complex work we need to do on the overall system in the field.
Let’s talk just a little bit about samples being transported back to a lab, about being analyzed off site. I suspect there’s some concerns there that we need to be aware of with this really rich gas.
Kevin: That’s really not an area that I have a lot of experience with, Weldon. We’re normally operating online analyzers first than trying to bring a sample back into the laboratory. It has a lot of challenges, as you’ve noted. I think that there are probably people who know a lot more about that than I do.
Weldon: I just know I see quite a bit. We know that there’s a problem with an online analyzer. We’re working on sampling systems. We’re working on the analyzer. We’re looking at the calibration standards. All of that stuff is being done, but then the question always asked, “Now, prove to us that this is right by sending a sample to the lab.”
What I was really getting at with the other question is that sometimes getting that sample to the lab and it being representative can be harder than getting it to a local online analyzer.
Kevin: Absolutely. Again, I think any time you have a sample and the pressure and the temperature conditions are changing, trying to restore that sample back to where it was at any point in time can be challenging.
I usually talk to people about if you go to the store, and you buy ice cream, and you put it in your car, and you go to the shopping mall. Three hours later, you take that ice cream and put it in your freezer. It’s refrozen after a while. You really don’t have ice cream anymore.
We get a little bit of that in the gas world. It’s really never an acceptable practice to simply allow things to change phase significantly over periods of time, and then try to recreate the pipeline conditions and say everything is good. It might be. It might not be, but time is certainly an element. Volumes are an element of getting it right. Again, it’s a very, very tricky business.
Weldon: I think the one take away I have from what you’ve said so far, Kevin, is that there’s not a one size fits all answer here. I’ve heard you repeat over and over here that you want to take a look at, you want to understand, you want to review what’s coming from the information coming from the customer.
I think that’s the takeaway here, is that you can’t look at a book and find a one size fits all sampling and analyzing scenario for everything that’s out there. You can’t just say that casing head gas is not the same as shale gas.
Shale gas is not the same as shale gas depending on when you’re looking at it, where you’re looking at it, right?
Kevin: That’s right.
Weldon: The differences in delivery pressure and temperature actually enter so much into the equation. They really need somebody like a Mustang looking at this and telling them, “Hey. Here, from our experience, is how we address these particular problems.” Does that sound correct in your book?
Kevin: Yeah, that’s absolutely correct. People have very different practices, depending on where you go. If you’re talking to a pipeline customer versus, a producer, versus a BLM producer, versus someone in Mexico just over a span of a couple hundred miles, the requirements may be very, very different, and the practices may be very, very different.
It does seem like we constantly reinvent sample conditioning systems and sampling systems because each one is unique. It’s hard to believe, but they are, and that’s the way we treat them.
Weldon: That’s a lot to think about, lot of good information there, Kevin. Kevin, before I let you go, what is your gut reaction to the customer that says, “We need to analyze this gas on site. It’s low pressure, it’s high temperature, and, oh, by the way, I don’t have utility power out there. I want to do it with a solar panel”? Other than laugh, what do you do?
Kevin: When we have power limitations, then things that we would normally employ into the solution, things like heat trace tubing, a lot of those things go out the window. We may start using vacuum jacketed tubing, and things that we can use to provide very good insulation to at least keep the temperature from changing very much.
If you’re limited on power, then heat becomes more and more difficult, and we just have to do the best that we can. We really look hard at fluctuations with the analysis as a function of ambient temperature, night and day in particular. If we see significant changes on a daily basis, then that’s a big clue to us that we haven’t gotten it right yet.
In those situations, we do the best that we can to provide enough power using solar. It’s somewhat scalable, so we can generally get more power if we need it, but it’s always a challenge.
Weldon: One of the most interesting things I’ve seen from y’all is that y’all had a setup with an online analyzer, one of the small footprint analyzers, actually sitting in a very small enclosure, literally on top of the sample probe. That’s getting outside the box for a lot of people, but some ventures like that, I’m sure, help in the low power area.
Kevin: Absolutely, and the wetter the gas, the less…We don’t want to transport that sample 12 feet or 20 feet, so the closer we can get, the happier we are.
Weldon: Kevin, I want to be respectful of your time. Anything you want to say before we part ways here?
Kevin: Just thank you very much for the opportunity, Weldon. We’re excited at Mustang Sampling for all of the challenges that we have ahead. I mentioned renewable natural gas, and I mentioned hydrogen. As the gas supplies become more and more diverse and coming from different directions, it certainly complicates sampling.
A lot of the things that people have taken for granted as not changing for the past several decades, all of a sudden, are changing. We’re excited about the future. We love challenges. Again, appreciate the time here today to talk about one of them, and be happy to talk about any others in the future that you’d like to talk about, so thank you again.
Weldon: Thanks, Kevin. We’ll have your contact information, your LinkedIn info, we’ll have it on the show notes when we put that up. Thank you for being on.
Kevin: Great, thank you.
Weldon: Have a good one.
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