Podcast: Can You Explain the Joule-Thomson Effect? | Episode #9

Joule-Thomson Effect podcast
The Joule-Thomson Effect is a critical concept for oil and gas producers. In this episode of Stuff You Should Know About Oil and Gas Production, Kyle explains what it is, and how it explains freezing in oil and gas production.

Topics in A Simple Explanation of the Joule-Thomson Effect

  • How to calculate for the Joule-Thomson Effect
  • What problems freezing can cause
  • Solutions we recommend to prevent freezing 
Resources mentioned in this episode:

Joule-Thomson Effect, JT Effect Podcast

Transcript

Curtis: Hello, welcome to the Stuff You Should Know about Oil and Gas Production podcast. I’m your host Curtis Winkle here with Kyle Andrews. HeyKyle, how are you?  

Kyle: I’m doing good, Curtis.  

Curtis: Hey, we’re going to talk about the Joule-Thomson Effect today and freezing valves. Let’s start here: What causes freezing in oil and gas production?  

Kyle: The primary reason for this is due to the pressure drop of gas flowing through a valve. The Joule-Thomson Effect states that for every 100 PSI pressure cut across the valve, the gas will drop in temperature by degrees Fahrenheit. 

So the Joule-Thomson Effect, you hear this called “JT effect” as well. I’m going to say that one more time: For every 100 PSI cut across the valve, it’s going to experience a sevendegree drop in temperature Fahrenheit. So for example, let’s say you’re cutting the gas pressure from 350 pounds down to 150 pounds. 

So going across the valve, the temperature of that gas will drop by 14 degrees.  

Curtis: Okay. Alright. That math checks out. So is it the gas that’s freezing inside there?  

Kyle: It’s the moisture in the gas. All gas contains some amount of moisture. So this means when the temperature of that gas drops below freezing, below 32 degrees Fahrenheit, freezing is going to be an issue. 

Depending on the makeup of the gas, it can even begin to freeze before it gets to 32 degrees. If you’ve ever been on a site and seen a place where it looks like a freezer that needs defrosted, it could be just frost on the outside of the valve, or it could get to the point where there’s a block of ice around the valve.  

Curtis: Keep talking about that. What are some other problems that happen when the gas freezes?  

Kyle: So, if you do have that ice starts to freeze on the valve, it can keep the valve from moving. It can cause blockages. So that’s a lot of downtime to fix those problems, and it’s going to be a problem that’s going to be recurring. It’s not going to be something that, hey, once you clear this blockage, it’s fine. It’s just going to freeze again.  

Curtis: Yeah. I think that’s important to point out. Because, I mean, it’s mid-May here while we’re recording. And so people  sometimes think, well it’s almost summer, so I don’t have to worry about that. But ambient temperatures aren’t the only that cause freezing.

Kyle: Cold ambient temperatures don’t help with this issue, but it doesn’t have to be cold outside for this to take place. If you have a high enough pressure drop across the valve, it can freeze any time of year.  

Curtis: Now what kind of solutions are available for producers who are experiencing this? 

Kyle: A lot of people will use heat trace and insulation jackets. Heaters can also be used on the valves themselves. We like to use Catco heatersand a lot of producers find those helpful.  

Curtis: How does the Catco work?  

Kyle: The Catco heater goes around the valve body, where it’s most prone to freezing. And the radiant heat heats the body up. It doesn’t heat the gas; it just keeps the valve from freezing and keeps the valve operating. So the gas temperature is still going to be cold, but it will keep the valve working.  

It also has a door on it, a hinged door you can easily remove to do maintenance on the valve. If you’ve ever come across a, a valve wrapped in insulation and, you know, electrical tape or duct tape, it’s a mess. It’s a mess to get in there and work on the valve. So this allows easy access to it.  

Curtis: Yeah. Another option sometimes they’ll inject methanol, right? That seems like a more involved process.  

Kyle: Yeah. Overall, it can be a more costly and it’s also really hard on the elastomers in your valves. So the Catco would be a good recommendation for that. One thing to note is it’s really important to do those calculations to make sure what your pressure drops are going to be on the front end, otherwise freezing is going to be an issue for you. 

Curtis: Yeah. Great. We’ll have links to the products we mentioned and the resources in the show notes. We appreciate you joining us for this episode of the Stuff You Should Know about Oil and Gas Production podcast. We’ll catch you next time. 


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