# weights and measures for natural gas

Could someone PLEASE tell me what the exact numerical weight of a unit of natural gas? My brother-in-law was told of a 6000 unit kick on a natural gas rig. This in itself is an impressive number. But if a unit is a tablespoon this would be slightly less impressive than if a unit is one cubic foot. The National Office of Weights and Measures was unable (or unwilling) to answer, as was the Independent Association of Drilling Contractors. The boys won’t quit hounding me until I find an answer. HELP ME.

I know what a “kick” is w.r.t. natural gas wells, but I have no idea what a “unit” refers to in the way you are using it. I mean - a “kick” is when the gas pressure down at the bottom of the well is higher than the “mud column” (and you can find many web sites which give this terminology). From what I can tell, “unit” would refer to a unit of pressure or possibly length, not of mass or volume - I mean, it sounds like the natural gas pressure kicked the mud column up a certain number of units of length, or kicked up the mud column with a certain number of pressure units.

I think a “kick” as used in the OP simply refers to the gas units curve making an apparently significant excursion to the right. Mud logs are notoriously unreliable measurement tools. I have beside me a mud log that has numerous intervals showing 5000 gas unit curve excursions that mean nothing. And we have productive intervals that only showed 200-300 gas units.

Tight (impermeable) sands will give up gas shows, shales will give up gas shows, and there will often be a lag between gas shows and the penetration rate log (the left hand curve on a mud log) that is the curve that will be correct for depth. I would definitely NOT make an investment decision based on a mud log show.

So someone was saying to someone else “wow, there was a 6000 units gas kick on that well!” Or maybe they were saying “Have I got the deal for you, you can invest in this well and they’ve already had a 6000 unit gas kick.”

Ringo’s explanation of mudlogging puts it in the proper perspective - what may sound impressive is not really all that significant and not something to mortgage your house to invest in. The “kick” term may have been used to describe the twitch of the mudlogger’s graph, although a “kick” in the drilling business is as Anthricite describes, downhole pressure kicking some of the drilling mud up the hole.

As for gas units, “mcf” or thousand cubic feet is the usual unit for discussing natural gas. If someone said to me that a well had tested 6000 mcf per day that would be one hell of a good well…six million cubic feet a day. A well like that might give you revenue close to half a million dollars a month. I’d be happy to own a well that produces 600 mcf/day. A bunch of mediocre 400-600 mcf/d wells would be a nice little revenue generator for an energy company.

In summary, a “6000 units gas kick” doesn’t mean much but “flow tested at 6000 mcf/day” would mean someone hit the jackpot.

Okay, you lost me after “I think”. What does all this mean to someone who isn’t a driller?

I should let Ringo explain but…
When drilling for oil and gas, you use hollow drill pipe and a drill bit with jets on it or a hollow center, and pumps at the surface circulate drilling mud down the center of the drill pipe, out of the bit, and back to surface up the annulus, the area outside the drill pipe in the hole. The “mud” is a mixture of water and chemicals circulated through a big tank at surface. (Maintained by a professional “mudman”.) The mud composition varies a lot depending on what you want it to do. If you expect to encounter strong formation pressures you might use a very dense heavy mud that will hold it back and prevent a blowout. On the other hand, your gas might be in a delicate sandstone and you might want a mud that doesn’t damage or destroy the formation.

Anyway, many wells have a mudlogger on site while drilling. The mudlogger sets up sensors at surface where the drill mud is returning from its trip down the hole. The mudlogger then sits in a trailer or shack and monitors and records the sensor readings. He may also grab samples of the mud and seal it in cans. If the rig drills through oil or gas bearing zones the mudlogger picks it up and can often intepret information on the “show” that’s been penetrated. As Ringo said, shale or tight sand or coal beds might give bigger readings because they have hydrocarbons in them, but this doesn’t mean it’s economic.

After the well is drilled the mudlogger will have produced a log of the well which would show the mud gas readings, an interpetation of the geology, the rate of penetration (feet/minute), which is very useful to the mad scientists of the oil biz.

I’m at work and really don’t have time to address this now; I will explain my earlier post more fully this evening. Al Z has already made that job much easier.

To get back to the OP, I just picked up another mud log and noticed that the gas units curves are scaled in ppm (parts per million).

Although not directly mentioned in the OP, the use of “unit” clearly indicates a mud log response is being referred to.

As Al described, mud logs are often recorded as a well is drilled. You can think of a mud log as a graph where the vertical axis is depth, the depth values being displayed toward the center. On the left of the depth track will be the curve showing the rate of penetration and on the right will be one or more curves showing gas units. Detail logs often have a gas unit curve for methane, and a few more for “heavies” (hydrocarbons with more than one carbon molecule). Further over to the right may be a lithologic description that the mud logger compiles from samples.

When somebody says that a well kicked, it means what Anthracite and Al described. But the term “kick” is also used to describe a quick and notable movement of a curve on a graph. The same movement might also be called a “spike” if it is a high frequency movement wherein the curve returns or rebounds very quickly.

So, when you’re drilling through a shale and come to a sand, the drill rate (or rate of penetration) will likely increase and the corresponding curve will move to the left, away from the depth track. If the sand will yield gas over the background gas amount the gas units curve will move to the right, away from the depth track. When you encounter such a sand, the movements of these curves are liable to appear quite suddenly, over the space of one or two samples (typical sample rate might be one per foot). And that gives you a mud log kick.

As I said above, mud logs are notoriously unreliable. Their primary use in my world derive from the fact that often enough the drill rate - depth track - gas units display will very closely resemble the spontaneous potential (or gamma ray) - depth track - resistivity display of a typical electric log, and we can correlate the mud logs as they are recorded with electric logs from offset wells to guess (er, excuse me, “establish”) where we are (i.e., how much further to go until we’re through all of our objectives).

Hope that helps.

Thanks, Ringo and Al Zheimers, for the explanations. They’re as clear as mud.

(I actually understood the explanations. I just wanted to get that joke in.)

Thanks for all of the info so far but… I grew up in the patch, my husband is a derrick man and my brother in law is a driller. His father in law is a tower pusher in Saudi so the info I got back was old news. I just need an actual numerical measurement for a unit of gas. Does anyone know? Will anyone tell me? I just need a number and method of measurement. ie…10 lbs per sq in, 1000 cubic feet, 100 gallons, etc. Anything, even if it’s not the right answer, will get these guys off my back.

It seems to be a very difficult question to answer. Your “6000 unit kick” is not a clear definition. The “units” we’ve been discussing with regards to mudlogging are, as Ringo says, unreliable as a tangible measurement. The mudlogger would set his sensors, adjust his electronics to a baseline, and then monitor the mud as drilling progresses. If the drill bit penetrates just a trace of oil or gas it is going to show up as an increase in units or a “kick” on the mudlogger’s scale. If the drill bit goes through a thick porous oil zone a lot of oil will show up in the mud and really “kick”, a gas zone that mixes any quantity of gas into the mud is going to show up as a “kick” but if it’s a significant amount of gas going into the mud it’s going to lighten up the mud and suddenly we’re on our way to blowout city. Not good. The mudlogger’s units should really only ever be measured as traces in the mud. If you’re talking about a mudlogger’s 6000 unit “kick” then you are talking about an increase of “traces” of gas in the mud.

On the other hand, if you’re talking about generic units, then gas is measured in "mcf"s. Thousand cubic foot units. Deals are done to market millions and billions of mcfs. Wells produce so many mcfs per day. Pronounced em-cee-eff.

You can’t deduce anything about the mcfs in a well by a mudlogger’s units kick.

Over to you Ringo.

As Al Z has noted, a 6000 gas unit kick doesn’t represent any particular volume of gas. The gas detector will as often as not kick out to a few thousand units when you switch it on.

Above you’ll see that these gas units are reported in parts per million. I suppose if you were going to attempt a calculation of volume, at the least you’d need to know the volume of mud returns to conjure up a number.

But it wouldn’t necessarily represent anything real. As I said above, mud logs are notoriously unreliable and we often get mud log shows that amount to nothing. But drilling environments vary, and sometimes you trust the mud log more than other you do at other times.

I spend almost half of my time working in an environment where we run mud logs primarily for the correlative advantages mentioned above, and rarely get too excited about HUGE kicks - although we’ll at least note the more modest ones. And in the case of those, they’re usually depth lagged so we don’t really know where they came from anyway.

Other environments that are more black and white can yield mud logs that are more quantitatively useful, but it would be rare to see even the most optimistic (and we’re an optimistic bunch) explorationist try to claim a quantity of potential production from a mud log.

It’s far easier to wait and take a jug test (FT - formation test) when logging after the well is down. Or, to make production forecasts after a bona fide production test post-completion.

So, sorry, a real number is not attainable from the datum you have to offer. Notice, though, that you are now armed with the knowledge that the “kick” was 6000 parts per million, and you can tell your hounders that they need to supply you with the volume of mud returns before any calculation can be done.

And I’ll add that we probably can’t get to any kind of real-life meaningful number even if they do come up with mud return volumes.

Just curious Al; I’ve done no work in Canada - do y’all use mcf in your otherwise metric nation?