N80 Tubing and Burning Gas from Oil Production Wells

You are wanting to use Well Casing pipe to "burn off" excess gasses from an oil well?

Why not use those gasses somewhere else?

If it is flamable it could produce power to run your operation.

Hello, thank you for your a quick reply.

I have mentioned in my previous email that we want use tubing well not casing well in order to burn off gases however this operation must be done before any well operations ( acidification,kick off,boulhead,work over etc.....).

IF you need some highlighting i am really happy to do that.

Thanks a lot.

Instead of flaring it you really should be reinjecting it into the formation to increase production and to prevent the formation drive energy from falling off and causing you to have to resort to tertiary production equipment (esp's etc.). Flaring everything is very "Old School" these days. Sure some flaring is necessary, but you should work to minimize it.

N80 is a medium carbon steel with a carbon content in the neighborhood of about .30 if memory serves (I don't have access to the API standards at the moment.) that means it will be thermally sensitive. it will develop a HAZ near the hot end. You may even see "ringworm" type corrosion in the HAZ. Also the 80KSI Yield will drop considerably as the steel gets hot so you need to look at it's yield when hot for your design strength.

A better possible answer is to use Inconel 600 for your burner and put a radiant heat shield around the N80 that feeds the burner to minimize the heat radiated into the pipe.

Dear Rorschach, Firstly I would like to thank you for your comment.

Pipe specification API 5CT grade N80 doesn't specify chemical requirements other than phosphorous (0.030 wt %) and sulphur (0.030 wt % maximum) and the following tensile requirements: Yield strength :80.000~ 110.000Psi , Tensile strength : 100.000Psi minimum. As you said tubing N80 is a medium carbon steel with a carbon content in the neighborhood of range between 0.30 wt % and 0.5wt%.

Steel tubing pipe microstructure are typically designed to be either, ferrite and pearlite or tempered martensite dependant on composition and thermo-mechanical processing.

Tubing N80 must has less % carbon than L80 Tubing ( 0.4 : 0.5 ) regarding API 5 CT Table 2.

N80 will be affected by heat environment and their mechanical properties change consequently as both yield strength and tensile strength .

Could you please explain your ideas with more details trough chosen and preferential data?

Thanks a lot

Do you know how heat treating works? do you know what happens to medium carbon steel when you get it hot? it changes from Martensite to Austenite with an associated crystalline structure change. When it cools back down again you get untempered martensite in the transition area where the temperature gradient is, you will have a transition from martensite to untempered martensite which is brittle, hard, and prone to corrosion attack. This is known as the Heat Affected Zone (HAZ). and it is not at all unlike the HAZ you would see adjacent to a weld. Ringworm corrosion is most commonly seen in upset drill pipe in the area of the upset when the pipe is not full length normalized but only normalized at the ends to save time/money. at the edge of the area that was normalized you have a HAZ. That HAZ is prone to corrosive attack so you can get a circumferential ring of corrosion right at the HAZ.

Steel loses strength as it gets hot, 80KSI yield at room temp may drop to as little as 60ksi at 150C, depending on the alloy. You need to determine the yield at the expected operating temp. to determine what your design strength will truly be. You won't be able to use a catalog specification to determine that, it will have to be empirical.

Only the part that gets hot mattters - usually near the tip. If you use well casing it will probably distort. You should really consult a flare supplier but some will use a refractory stainless such as 310 or incolloy 825 for the last metre ( or 3 ft) near the area where the flame is. You must be sure the flow and environment will not allow the flame to lick down the tube. You must also ensure noise and radiation from the flame at the tip will not cause a problem in the surrounding area and that everything coming out burns. If it does not burn,what happens to it - can it drift into an area where people might be? Will it drop to the ground as droplets (possibly in flames) like raining oil drops?