transcript

(00:00) hello everyone good morning good afternoon and good evening to everyone who's tuning in on behalf of pio petro arab oil and gas academy and spe egypt section i would like to welcome you to today's session my name is shahad bhajit i'm a third year petroleum engineering student at knu in kurdistan iraq my name is esmachendi i'm a petroleum engineer graduated from american university of prasad jaime and we will be your moderators for today before we start i'd like to remind you to please dr op your questions in the q a section (00:30) below please keep the chat box professional and ethical and please submit your quiz before the deadline now without further ado please give a warm welcome to dr ahmadil gahi who will be continuing his course on introduction to wealth stimulation dr ahmed is the director of the pio petro non-profit educational project he is an assistant professor at marietta college ohio usa where he teaches production and completion geomechanics and unconventional and conventional reservoir evaluation and development dr algerie holds a phd an msc (01:07) in petroleum engineering from texas tech university he also holds an msc in petroleum engineering natural gas engineering postgraduate diploma and bsc in mining engineering from cairo university in egypt dr ahmed al gerhay has over 11 years of experience in the oil and gas industry prior to work for marietta college he worked for advantech international inc ogs halda apache texas tech university and salman a nd associates ltd dr algeria published many journals and research papers on with elsevier spe sp wla and arma in addition he filed two u.s (01:49) patent applications to increase hydrocarbon recovery in both conventional and unconventional reservoirs dr ahmed thank you so much for coming and the mic is yours thank you thank you asmr for the introduction and today is a last lecture in this short course you know we will have the final exam next week and for sure at the end as matt will tell you ex actly when is the final exam so in this lecture today we will talk about uh you know we'll have like a short introduction about acidizing and acid fat you know acidizing and acid fact is (02:28) a very big topic so today just i will you know set the ground rules or you know give you a very basic stuff but for sure you need to learn more more to know what is exactly is acidizing and what is exactly is acid track okay so let's begin so uh before we start as you know again one more time pi operator blue this is a pipeline to uh there is a blue logo this is the student services and whenever you see the red logo this is services for companies so what we are working on right now is services for students and it is always (03:09) free of a charge so don't even ask about question is this course uh you know has a fee or registration fee or not all services for students is free of a charge and will stay free over charge forever okay so uh before we talk about acidizing and asset fraction last wee k in the last lecture in lecture number three three we get a question about what is the difference between defect and minifig and i promised last week that i will get you some detailed information about the difference but um as you know it is uh the difference (03:50) between defect minif leak of tests extend the deck of tests and micro fact is a long story is how to answer in one minute so this is why it was better to delay answering this question to uh today and i will try to summarize the mai n differences between the fed and minify before uh thinking about the difference between minific and effect both of them we use them to understand the behavior of a reservoir for example i want to know the closure pressure over frac i want to know the leak of uh you know behavior or leak of coefficient and after closure (04:34) i can get some information about the permeability and initial with the word bishop but to understand the difference ask yourself few questions first who's the company dev eloped that the test let's say manifrac this one developed by haliburton long time ago the second question you should ask yourself is when is it from 20 years ago or from five years ago or is it last year okay the last question ask yourself what is the fluid we are using in this test so for example maybe if you are doing leak of test and drilling you will use (05:17) drilling fluid and if you use defect if you are doing the fed before a fracture you will use just fresh water okay in minifrack we recommend to use the same frag fluid you will use let's say if you will use crosslinker gel we recommend to use crosslinker gel and mini frag but you will see many many companies these days they are using just linear gel okay for a reason i will mention it very soon so to know exactly what is the difference between the fed and minifrac ask yourself these three questions and i will try to (05:55) to show you uh the answer of these questions so that the company who developed let's say who the com hat test and many fracking data frack the almost the same thing okay except the the companies are different okay uh also you will notice that the fluid we are using in the test uh are different if you are doing let's say minifrack you will see crosslinker gel used in minifrac which is ever commended but most of the companies these days use linear gel linear gel because they don't want to wait long time because most of the jobs of the minifrac we do it right before that their main fraction so i d ou know for the same well you are collecting more information maybe the analysis you will do or the data you will collect for the minifrac (09:50) will not be that good maybe the data you will collect for the defeat will not be that good so at least you have two sets of data so you may get a better uh analysis okay so um this is very quickly what is the difference between you know defeat and minifac and uh let's begin our lecture again if if any of these things still not clear you can ask me aga idizing it means the injection pressure below the parting pressure of the formation when we say acid tract it means the injection pressure higher than the parting pressure of the formation and we break down the formation and we create a function okay so uh what is the purpose of the (12:39) objective of carbonate matrix acidizing you know we we can do oxidizing for carbonate formation or for uh sandy stone formation so we can do acidizing for both but the result is not the same and i will show y carbonate formation let's say like a limestone it will create these holes inside the carbonate formation what we call it wormhole effect so hcl if it is added to a carbonate formation will create these worm holes by nature okay and these wormholes will enhance the overall permeability and for sure will enhance productivity okay so here is i'm showing you the difference between using acidizing for sandstone formation and (15:35) acidizing for carbonate formation so that for the sandstone to the twork inside the formation connected (17:50) to the wool bore and i can produce more oil okay so to do that stimulation technique or need to check if you want to do a shallow stimulation or shallow oxidizing or shallow to moderate or moderate or deep stimulation and for example if you want to do deep stimulation most likely we do this if the permeability is too low okay and we do that we need to inject you big volume of acids and you need to inject maybe you have a higher injection rate okay if or acetic acid and we use organic acids mainly when we have a reservoir that has high temperature if you have a reservoir high temperature reservoir and you use hcl hcl will react (20:40) very quickly because you know when we increase the temperature the reaction rate will be higher so all the hcl whenever it enters the formation it will react immediately and there is no way to let that hcl go deeper inside the formation and you will start enlarging the world bore and not making a deep uh you kn is again you know um uh for the hcl there was different you know concentrations we can use and for sure there's different uh you know the it makes the acidity or the spin acid or the reaction rate will be different based on the concentration and here is the same thing for the acetic acid and the pka this is like a measure for (23:30) acidity something similar to the ph but you know it is uh you know different but it has the same objective and here's for example the ph is minus 0.64 remember that ause when we use when we have the high temperature it will make him active but not super active and uh like the hcl if it if there was too hot and the hcl will react immediately and there's no way to send this hcl deeper inside so this will work so here for example this is the formic acid and here's the difference between percent uh concentration of formic acid and ten percent concentration okay and in the other side this is the (26:32) same thing but for the ascetic and we do all this experimen cts of the reaction soluble in water (28:32) here is the dolomite i'm using four and one okay and the reaction the products of the reaction also soluble in water okay here is some equations this is how to calculate the gravimetric dissolving power of the gas of the acid here is a volume of the mineral which is let's say calcium carbonate for example here is the molecular weight of the mineral here is the volume of the acid there is a molecular weight of the acid and here is something we call fra about all of these parameters remember that the acids when we injected into carbonate it makes something like this is a worm holes something like branches of a tree see okay so i gave you a lot of numbers a lot of tables and (31:40) let's get you a problem to solve and this will help us to understand better okay so sandstone was a porosity of uh 20 containing 10 volume calcite this is a kind of confusing when you when we start by sensed information you get the feeling that i'm trying to acidize cite okay 10 i get this number then i will do i will i will calculate the initial uh for volume here is the initial for volume and i will get that then i will calculate beta the gravimetric dissolving power based on the equation we got before (34:48) and here is the equation here is the concentration of the asset 15 here is v m and v a one and two this is confusing what is one and two look here is one and two look at the equation one and two one and two okay so this is just one and two and here t even if it is matrix acidizing or acid frac you need to ask yourself what is the optimum injection rate why because if your injection rate is very low your acid will not go deep inside the formation and all what you will do is losing acid and enlarging the world bore most of the acidizing jobs it is open hole so most likely we don't have casing it is open most of them is open hole so (38:05) all what you will do is you are enlarging the wilbur okay because the acid weight is too low okay if th will you will have acid track (40:23) instead of matrix oxidizing so you need to understand the mechanical properties of the formation otherwise you will not know what should what is that value that you will you don't want to exceed okay here is the maximum pressure equal the fact pressure plus the friction plus minus the hydrostatic minus 200 psi as a safety factor okay so we can use you know simple equation like this to calculate the maximum pressure that i'm not allowed to exceed otherwise yo stimulating you keep acidizing the high chemical zone and no acids will go to that low permeable zone which is not correct this is not what we want to do maybe the formation that has local (43:04) mobility needs stimulation better than the formation has high permeability right so i need to distribute the all the acid in all zones surrounding the world bore in a uniform way i want my acid go to the high permeable zone and also go to the low permeable zone okay this is why we need to use something okay and flow into those parts of the formation with a higher permeability which is not what we want to do we want to stimulate everything stimulate both zones the high permeable and low permeable zones so i can use either physical diverter like a packer for example or a chemical diverter like uh some chemical additives to change uh (45:55) viscosity or whatever okay okay here is the schedule the sequence we use i may i should do a pre-flush before uh pumping the mean job okay and maybe this is need to have something we call soaking time okay okay here is a list of some acid uses you know as a acid use grade lines if you want to wash your perforation if you want to clean your profession maybe it has some scale deposition or any kind of formation damage to position you can use five percent acetic acid for example also you can use hcl who's in a low concentration also if you want to for the damaged perforation you can use here is the hcl often percent ascetic (49:08) or 10 percent formic a company you will use a lot of best effects because most likely to not (51:32) be the first well in this company you are acidizing but if you work in a lab in a research lab you need to think about what should be the optimum hcl concentration is it better to use 15 or 28 remember to prepare a volume at the same volume of 20 uh hcl concentration it would cost you more money is it worth to spend this money or not this is one of the most important questions you need to answer okay also um if the we get water in oil or oil in water so maybe i will get uh acid in acid in water or water in acid or acid and oil or oil and as something like that okay so it is emulsion there's external phase and internal phase (54:34) okay and using acid as an emulsion here is the external phase with oil this will control the reactivity i made the laser the activity for some time or until the acid reach specific depths okay and for foam foam means i have something more than 60 gas most likely nitrogen or may oves okay so the acid will make something called etching and i will show you how these edges look like okay so etching is one two is these womb holes will uh make us has no need to use propane okay also if you spoken the pokemon will embed inside the the the limestone or domite and you will lose any uh conductivity okay this is why we don't need or we we don't use popen in that okay (57:51) and acid track okay so the long time ago when i used to work for a petroleum company in egypt i remember o way (1:00:25) will make it similar to this look to this one this is after etching acid etching okay if you close the fracture again on each other still there are some gaps because of this etching and the acid the hydrocarbon and water can flow through these gaps okay so today i mentioned two things the wormhole effect and the etching effect okay to uh to do a good design for asset frag you need to collect all the available data information about perforations spacing between the horizontal wells in our in our software we will use in this design you will see one of the outputs is the lens of the etched sides in the function and i will show you an example let's this is the last thing i have for (1:03:23) you today i used to show you uh real cases okay so this is a real well this is a real world okay and as you see here we have a mineralogy okay because it is better to know exactly what is the formation you have if you have sandstone maybe i will go i will vote for hydraulic fracturing no the fracture okay to initiate the fracture so i would keep injecting without getting any problem during injecting so here i i filled the world ball with seven percent kcl then i injected a pad using this fluid okay then i start injecting acid and at the end i did we do something called flush okay so this is the design to written schedule for this well again you will find some (1:06:41) little differences between different service companies each company has their own technologies okay here is her 1:08:53) how it looks like very similar to the output we get here is our perforated zone very similar to the the output we get in the last lecture when we talked about the design for hydraulic fracturing and here is showing the mechanical properties the permeability stress youngest modulus and this is output of i believe this is a fact pro okay look here look at the mouse this is reservoir etched so i'm measuring the length of the etched sides etched face of the fracture how long is it okay also ing for sandstone but maybe in some cases i will not recommend that and i will recommend something else like doing hydraulic fracturing but we (1:13:19) can do it yes we can do it we can use hf and hcl to stim to acidize sandstone okay but i told you the maximum enhancement to um or decrease to the damage i can get it the skin factor down to zero but not to negative value or this is for sandstone okay we use hf alone to stimulate sense to information no i must use hf plus hcl hf alone cannot be bypassing the damage the damage by making let's say um acid flag for example and by passing the damage or (1:16:00) use another chemical that can dissolve the by light and the the products of the the chemical reaction products is still soluble in water so i can get it back during the flow back period yes go ahead okay next question uh if we make the fracturing in the cab rook what is the next action to avoid losing the oil or gas materials can you repeat this question because i did not get uh wh rowing outsides of the circle i wish this yeah you we answered this question uh next question can we use the measurement of the ph value of the flow back at the end of the job as an evaluation method for the treatment for sure yes yes this is actually what we do (1:18:47) when we get a flow back fluid we we know that it should be within a range let's say uh ph of two let's say to six for example okay maybe understanding that this will help me optimize the time of shutting because if i keep shutt a lot of science a lot of chemistry in in that so it is not something you can summarize in in one or two minutes so um also i will try to i did not see any example in my practical life that we acidize sandstone sorry uh yes we we all like the the jobs i attended personally which is not uh too much was acidizing limestone dolomite or generally carbonate formation and doing acid flag for carbonate formation and most of the jobs we do hydraulic (1:21:43) fact conventional effect we do it for sense den and horizontal stresses we get some damage to the formation which is maybe (1:23:44) happen but still that damage will be uh minor and productivity will stay uh you know after acidizing acid effect way better than without acidity uh doctor if you don't mind we have two more questions just they just okay someone is asking what happens when i frag beside a fold you said what a fold okay look if you flag beside a fort first most likely you your frag will be parallel to the fault your fact most or is not a chemistry if you are not a chemist there is no need to understand all the chemical details about these things just you you will be a good user for these things but if your major is a chem is chemistry (1:26:43) let's say chemical engineering not petrol imaging and one of your job is to work in the lab and produce this thing this is a different story then you need to know everything about the chemical reactions and additives and these things but what is important for us now is to know r last last thing uh they are they are asking if you can share the slides with them yes i was planning to show all the slides and i promise i will do that and maximum by tomorrow you will find the four lectures on and face in the facebook group also i will share them on the uh not on the facebook group let's do it professional and leave it on google classroom (1:29:33) i will leave it for you on your google classroom by tomorrow maximum great thank you dr ahmed and thank yo