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How Hydrocarbons Break Out Of Oil Base Mud vs Water Base Mud

Does anyone have any information on how gas reacts with oil base mud compared to water base mud in terms of deliverability, absorption, and release at surface.  Any differences in molecular phase changes vs depth of the hydrocarbons from pressure and temperature.  It seems everyone agrees there is a difference, especially how gas breaks out at surface, but no one seems to know just why.

Thanks

Tags: Base, Break, How, Hydrocarbons, Mud, Of, Oil, Out, Water, vs

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Hey Stephen, this is a VERY good topic!! We have just started to look into this. I am excited to learn anything about this. I will try and share anything I've found out in the upcoming days. Please keep me posted....
Will do...Thanks...
OK, here goes. I just got out of well control school today, ( aced the test ). This topic was discussed pretty well. Gas enters the wellbore in a liquid state asit is under tremendous pressure. As it migrates up the hole in WBM it turns into a gas and expands as it moves up the annulus. We circulate it out, naturally. In OBM, the mud is already hydrocarbon based, is extremely hot, and actually mixes with the liquid gas as it enters the wellbore.That is why it is difficult to actually tell the size and type of the influx, because it doesn't break out of OBM like it does WBM. Therefore the gas migration is really non existan until you get the influx closer to the surface. Are ya as confused as I am ? LOL. If ya need more info on this let me know & I'll put ya in touch with Taylor, the instructor for WWCI. He is REALLY sharp on this and is more than willing to give you good information on it. Be safe, Brothers. Jim.
Thanks for the info and congrats on acing the test! I understand the concept but am confused on specifics, like does the gas in solution lighten the mud down hole significantly, and does all the gas break out or does some remain in solution even at surface, especially if heavies are present. From a mudlogging standpoint, how is gas readings affected.

I would really appreciate if you could put me in touch with your instructor. I'm trying to develop something meaningful to put in a presentation (and give credit to all contributors) and also try to develop a useful tool for predicting a kick.

Thanks very much,
Steve
The amount of gas soluble in water is much less than in oil at equal temps and pressure...gas is in a liquid state under a hydrostatic load/pressure or in other words "soluble"...once the pressure is reduced...I.E. circulated to about 3000ft TVD with even as much as 14.0 ppg SBM...it then starts breaking out as gas bubbles rapidly/violently dependant upon hydrostatic pressure it was under prior to starting up the hole...

Being on several volatile blowouts on HPHT wells it is easy to see the liquid gas changing rapidly to gas and it is more a force of pressure than anything...but temperature affects it greatly as to when "bubble point" is reached...I.E. the higher the temperature the faster it reaches bubble point...

Also while testing high pressure wells I have seen almost 100 API liquid which is crystal clear liquified natural gas at surface...we actually caught several bottles of it and could not put the tops on it due to the volatile eruption if it was slightly shaken any at all...the evaporation rate was so fast you could literally see the liquid disappearing from the plastic bottles...this was out of Condensate Wells where Gas Injection to the tune of 100mm cuft/day was being injected into the upper reservoir for maintenance of the lower condensate bearing reservoir...

Another factor is the "base" oil that is being utilized for the OBM/SBM...the Ester Base oil seemed to be much more susceptible to gas solubilizing as well as Diesel base oil...while Mentor base oil was less...so the type of base oil does have a bearing on the solubilization...

Another laymans fact would be that while you could dissolve/solubilize 5 bbls of gas into a SBM or OBM, taking the same 5 bbls of Gas if you tried to solubilize it into WBM at same pressure and temperature only 0.05 gallons of gas would solubilize out of the 5 gallons you started with...the other 4.95 gallons of gas would remain gas... so hopefully this explains a little to what we actually see here in the field...

The most challenging wells we worked were 3000ft TVD where the pressure was equivalent to 13.5 ppg at this shallow depth and utilising SBM...if the well looked as if it was flowing don't look again...shut the BOP...because the next time you looked you would be wearing a #3 rotary bushing for a neck collar....4 small blowouts...all successful kills...I can tell story after story and quite a few most probably wouldn't believe so they remain untold...when you work for Mobil Drilling you had better know your business...no excuses...
Thanks so much,
That explains why some of the Haynesville wells (especially in the beginning) would kick suddenly and without any real warning. One question, given all factors equal with OBM, the greater the pressure down hole the more the solubilization so the more violent the reaction at the bubble point. Is the gas solubilized equally or in variuos stages and when it goes thru phase changes, is it always rapid or can it be gradual as it nears the bubble point.

I wonder , from a mudlogging standpoint, is it possible to develop a useful tool that would give some indication of a kick. For instance, if bottoms up and annular velocity is known exactly (as possible) and the bubble point is known for the parameters in place, would it be possible to know that an increase in gas at a given time would be significant.. For example, if BU is 60 minutes and bu from 3000' TVD is known, would a gas increase in 50 minutes after starting circulation be a reliable indicator.

Thanks again, i really appreciate the info.

Steve
Each well is usually different in geometry/profile...this changes many aspects...

Several things that can be done...

Drilling into a known reservoir:

Drilling short intervals 10-30ft and circulate out so there is not enough gas to cause an underbalance/kick in the annulus at one time...you can vary the length drilled once you see the amount of gas at surface and stay within limits to control well...

Stopping to flow check when bottoms up gas is half way out of hole then again each 1000ft the bottoms up moves up the hole...

Flow check thru Choke Manifold into Trip Tank...this requires closing well and opening thru Choke Manifold to Trip Tank to monitor, but is safe and effective...

Also note that when utilizing SBM mud weight is not as great a factor concerning ROP...mainly losses or ballooning is more of a concern...so SBM can be ran at much higher ppg and not affect the ROP...this will help control the gas influx into the well bore...the drilled gas is the only problem when you drill too much of it at once and then it gets close to surface and breaks out of the mud violently...in turn it reduces hydrostatic and then the well starts kicking due to underbalance...
BUT there are many times that the gas will break out and blow the top portion of the mud out of the hole I.E. 20-50 bbls and this will still not put the well in an underbalance condition so this must be noted also...these are usually reconized/labeled as kicks when actually they are just bubbles breaking out at surface from "drilled formation" that contains gas...

Just this year we took this type of blow at surface and usually by the time the BOP's are shut the pressure is "0" psi or 10-40 psi...
The big problem here is a Drill Crew the doesn't understand how to open an Annular safely will then open the well and it will blow again thru the rotary due to poor practices and then complicating the situation as everyone gets gunshy...

Can someone list the proper steps of opening a surface BOP after gas or a kick has been taken? This would be interesting as I was working with a rig in Jan 2010 and MOST of the "Drillers" were Toolpushers or Rig Managers/OIMs from other rigs that were stacked...I was surprised at their lack of knowledge on this simple procedure and this is not the first time I have seen it happen, but several times from highly experienced veterans in the field...

Their are many other critical mistakes made during well control situations and I can label quite a few more THAT are not taught in Well Control...

The last guy that told me he made a 100% on Well Control (An OIM)...lost a $15,000,000 well while I was on days off and we tracked it back to him on the choke panel...that simple...a lack of field knowledge and very basic understanding of well control...BUT he did make a 100% on his Well Control "written" test...

Went to IWCF Well Control last Sept 2009...saw a DSV with 30 yrs experience fail his hands on Choke Panel test...he was given a pre-printed chart to cover his error...and return to Egypt to continue as Sr DSV....

Sorry for the rant...just a lot of people think that because they have 30 yrs experience and can pass well control it makes them "quallified"...it doesn't...as the old adage states: the proof is in the puddin'...
As a 14 year mudlogger in the Permian Basin of SE New Mexico and West Texas,I have seen a huge decline in gas kicks over the past several years.One reason for this is the operators in our area have been drilling for oil VS. natural gas due to low NG prices,and number two is the New Mexico pit rule which forces operators to haul off cuttings instead of using reserve pits for cuttings which is less expensive.
Not wanting to get off topic I wanted to reply to Stephen on how to acknowledge a gas kick.With your parameters in place,any drilling break has the opportunity to kick.If your bottoms up comes in early like your 50 minute scenario then absolutely but at the same time it is operator responsibility to check flow and if need be shut the well in.All you can do is have good correlation to offset wells(more than one offset) and forwarn your company man that there is the possibility of taking a kick! In my experience in the patch I feel like I have saved several wells from blowouts,but what really counts is people giving a damn about what we do out there from the company man to the NEW-HAND-ON-RIG! Be safe out there,ALL!!
It is serious business opening a BOP after a well kill. Much more critical in deep-water drilling, but your question was concerning a surface stack. If the annular preventer was used during a kill there can always be some gas trapped under the annular element (BAG). This is for the simple fact the choke lines leave the BOP stack at a lower level. Therefore gas can be trapped above the level of the HCRs. The main thing is to be sure there is no recordable pressure. No SIDPP or SICP no pressure anywhere. (Always take in to account if you have a drill string float also) if you do then SIDPP may not be a true reading. Ensure all HCR valves and chokes are in fact open to the surface and going to a mini trip tank, MGS etc. Before opening the BOP (preventer) monitor the well for 15 minutes on open chokes to make sure it is dead. (NO FLOW). If you just finished a well kill another few minutes is not going to be a problem. Always make sure you have LOCKED the drilling (#3) bushings into the master bushings. ( A rig was lost once because the bushings blew out and landed on top of the Koomey system and destroyed the manifold.) They will always be the first thing to get blown to the monkey board if there is actually trapped gas. Make sure there is no ignition sources around the rig floor. If you are running diesel engines then kill them. If gas is released the exhaust can ignite it or the gas can enter the motor intakes and send them into over-speed. (HORIZON) Shut off the derrick lighting if possible. Clear everyone away from the rotary table and rig floor. Line out on the trip tank and be prepared to monitor if the hole is gaining or losing. Open the annular preventer. If the hole is stable and not gaining or losing all is good and you are back in business for doing a bottoms up on an open well bore. Start string movement, rotation and circulation keeping a close, close monitor for gains or losses. Line out your choke and kills correctly for drilling. Do a bottoms up to condition mud and watch and monitor for any gas in the mud.
Opening Annular with gas trapped below:
Correct: Lock the bushings in Master's and #3's if they both have locks

Open Annular by bleeding the Annular Regulator to "0" psi slowly...this will allow the gas to escape slowly and alleviate the pressure...then increase the Annular Pressure back to normal and open it up...fill up the hole and monitor on trip tank...if you just open the bag up after a kill, it will blow mud/hydrocarbons all over the rig floor/derrick and could even flash fire...

We also work the pipe thru the annular on well kills and have rotated at times knowing the condition of the annular...they can both be done safely with a "good" annular element, but if it is fairly worn...do not rotate pipe with the annular closed...
That is a great reply about lowering the annular pressure to reduce the opening speed. There is another way also on a surface BOP. You can close off the accumulator bottles and open the bag using only the air or electric pumps. This greatly reduces the speed of opening or closing. It is also a good way to control rod movement when working on the BOP or changing out rams.
when using the latest generation, deepwater drilling fluids called isomeric oil-fins, c1-c5 breakout at the shakers but a large quantity remains dissolved in the mud. The mud works it's way through the pits (a lot faster than one would think given the volume) and is recycled, being circulated through the bit or boosting the riser. Recycled gas will be noticed for at least three 'true' circulations before a fairly constant background reading can be established. I say 'true' circulation because the when the contaminated mud crosses the shakers, it is not long before it goes back down-hole, despite having 2000 barrels in the active pits. Fractions above c5, for the most part, remain in the mud as background readings. It should be noted that these muds breakdown over time into c5 and above fractions. The longer you utilize the same mud, the higher these concentrations will climb, while the c1-c5's tend to breakout within 3 or more circulations.

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