transcript

"(00:01) hello everyone uh welcome to uh the third week the first uh webinar this is me ahmad al gerhy and today i will be your moderator for this session let me introduce my friend dr ahmed ghomah ahmed is currently a fracturing fluid engineer for you know unconventional reservoirs in bp united states ahmed previously worked as petroleum engineer for saudi aramco for one year also ahmad worked as a research scientist for baker hughes for more than five years his measure is you know including hyd raulic fracturing fluid acid stimulation fluid diversion and (00:50) engineering treatment design in general he holds a bachelor degree and mastery degree from cairo university in egypt and also a phd from texas a m university in united states all in petroleum engineering ahmed published 10 granted patents u.s patents and 15 patent applications 13 journal publications and 70 conference papers dr ahmed we are happy to have you today please uh you know we we are waiting for your presentation you c asset simulation is too hard it is like unsteady type of injection so it's not this state is actually honestly state it's non-isothermal so (02:16) actually temperature will change as you are injecting your fluid as the fluid is reacting and oxford is a 3d type of fluid it's not linear flow it's not radial flow actually is almost like if you have a perforation you are talking about spherical flow so we have a flow in the 3d pattern and as a as it mean we have a chemical so we are injecting a che factor by removing or bypassing any near world bore damage so that's like a quick definition about this stimulation however the main question that you should ask yourself like when the asset treatment is needed like uh is my existing well need to have a (04:09) nicer treatment or not uh a lot of people will ask themselves this one and a lot of people need to know exactly when they apply the acid for their wells i said we do not bump it just to increase the productivity no i said only bump it whe not really high and that's happened in the cases like when you have a calcium carbonate scale and this can be a very building slowly with time and the decline that you have in the oil and gas production will be slowly styled a second one can be really rapid can happen suddenly and that's happened when you are blocking your formation plugging information or (06:00) plugging your perforation or actually plugging your tubing this can happen very quick and very extensively a second one when you star ere this water coming from and what is the source of the damage that can water happening to us so what type of acid simulation we are talking about mainly we have two type of asset simulations that a lot of people when you mention this simulation they talk about either matrix surviving or fracturing less advising and that the main key factor is how you're actually bombing your job in case of matrix exercising you are injecting at a rate under pressure usually (07:50) less than the fracture gradi g and the acid will actually react (08:58) with the surface of the frank not inside divorce there is definitely some leak of the classes were acting divorce but the main job here is the acid to react with the surface of the frag trying to etching the surface of the frag and create what we called redundant heterogeneous surface etching that's will help after the how can i say the closure this heterogeneity will not make it completely sealed when the frac is closed after the treatment and will cre at been in the industry can dissolve in the sandstone except the hf therefore any sandstone treatment must have somehow a way that contain (10:56) an hf then we have another asset based on the chemistry origin which is organic acid which came from organic components like acetic forming citric acid and other engineer we are really good at blending we like a lot of blends we like to blend different acid to get a better results and to get a more optimized system so you can have a blend of hcl hdf a ne however we just use them very narrow usage but under special condition only so let's cover the main assets that we usually pump in in oil field industry the first one and the most popular one is the hcl it has a lot of advantage and (13:03) we like this asset a lot first the concentration you can have a wide range of concentration from three percent up to 28 so you have that you have a like how can i say a border type of design of concentrations that you can use hcl being delivered to the fie is the reaction product when hcl reacts with the calcium carbonate or calcium or doramite which is calcium magnesium carbonate all the reaction product is water (14:58) soluble as we can see here the reaction product so i have here the reaction rate between hcl and calcium carbonate and the reaction product will be calcium chloride which is sold and that can be dissolved quickly co2 which is gas and h2o which is water so we don't have anything that can cause any damaging or precipitation again w you are bombing is consumed and as we are saying there is no damage there is nothing can be accusing any precipitation or anything however it is a tricky to design with hcl because a lot of things first corrosion corrosion hcl also can eat your vibes especially at really high (16:58) temperature so you need to have additional additives with hcl to reduce any corrosion for the wives that you are injecting with second faster activity hcl react in seconds very high reactivity so sometimes if you li id for you and also if you have iron especially is in the formation when inside your clay like if you have iron hydroxide that's one of the concern that you'll have was iron and as feltine will kill the sludge and lose some some damage that hcl will not remove the only to remove it using solvent so in this case we need to have also additional additives like iron control (18:58) agent to be able to to overcome any concerns we have from the compatibility issue and as you can see like additives add both hf and hcl the reason i will discuss them is my next slides because hf is a good asset to dissolve however hf developed a lot of reaction product insoluble reaction products that's actually is not good and can significantly reduce your procedure permeability and can significantly how can i say it make the job that you are trying to improve your production give you the opposite direction therefore when you are talking about something so necessary you need to be (21:07) really careful about 3) and that's also the how we are trying the best way to write the concentration of the hclhf system and we usually call it mud asset 12 hcl and 3 hf it dissolves 0.27.217 bound of sand just remember like each 15 hcl can dissolve 1.7 bound of calcium carbonate but that's another type of formation just to highlight how this material is and we are talking here about three percent of hcf to dissolve 0. (23:08) 217 so we're actually having good dissolving power for this type of material this is some t thing when the hcl reacts with the sand itself it it produces what's called flow flow select acid and the same it's happening when it's react with clay like for example i've been told in tonight it produced the same acid the fluorosarco then this acid will react with the sodium and potassium either exist in the clay or actually exist in your formation water choosing some sodium flow circuit or potassium flow circuit and this is the material actually that will precipitate so in each if you have ill be diluted and the ph will start to increase above two at that time there will be a (26:31) precipitation but this precipitation will be will not happen near world war area it will happen far away from your world area and this case the negative effect you will have from this precipitation will be very minimized and overall you will get a good success from fashion hf treatment also what if your sandstone formation have a slight amount of carbonate not really high but you still having some amo ganic assets as we discussed early we have a main three type of acid that we called organic acid formic acid acetic acid and citric acid and this is we can call the organic (28:40) version of hcl it do what what what hcl can do so this one also can dissolve carbonate only it does not does not have any ability to dissolve silica so it actually dissolves carbonate or any carbonate or bromide calcium magnesium carbonate it has a much better than the hcl first it has a low corrosion rate so it does c acid and a lot of time you are you are mixing the hcl with organic acids because actually organic acids like to control thyroid organic acid can sometimes can cleat zion you don't so you don't have any damaging coming from diagon from your case one of the things like (30:46) iron also can precipitate and can significantly reduce can significantly cure your damage to the formation and then back the result of your treatment so having an organic acid will reduce the the precipitation happened fro this is the main topic like i would i will just quickly highlight it but that's actually is is the main reason you select different companies so you have a different surface company for example like schlumberger haliburton baker whether ford whatever company you have the main difference between these companies is actually what additives they can provide to you hcl hf formic aesthetic citric acid all (32:58) these acids as thunder assets so there is no much difference between them however the mai er between your assets and the pipe so the acid cannot react directly with the surface of the vipe casing or or whatever by call tubing that you are injecting with and you will find based on the acid there is different corrosion hyper so you will find there is a corrosion hebrew word for hcl there is corrosion have to work for organic acid and there is acceptance corrosion after work for hf so it's not one corrosion having to work for everything and the the best way to select the corrosion inhib ou will ask surface company to run different corrosion inhibitor at (35:55) different concentration and you will select the one that will always give you less than 0.05 pound per square feet that's like a standard amount and just to highlight it this is will dissolve around 0.031 millimeter of your tubing so 0.05 bound per square feet is the thickness that i'm the thickness of the tubing that will be dissolved is a very small thickness 0. (36:24) 03 one millimeter of the tubing and that is accep if you are really have a special (37:44) material or or or your contact time is too high in this case we can use it at lower temperature but for example if your formation temperature is 150 and you see corrosion hyperintense fire you need to request it from the surface company why you are adding this one because usually antennas fire need it at a higher temperature third additives what we call iron plating agent as we said there early like iron is one of the yeah mineral that exists in your form d calcium carbonate react extremely fast however we notice that is like hcl does not be able to dissolve the calcium carbonate and we will not be sure why until we see (39:40) the actual sample we see like the calcium carbonate has been covered by an organic material maybe asphaltine maybe barafin maybe any organic component that can actually that work as a barrier between hcl and the calcium carbonate or the material that we'd like to solve so that's why it came we need to have a solvent and a h a natural gas try to reduce the reaction rate component i'm not sure if uh if you have any question or anything we can we can have it at the end of the session for the discussion moving to another part which is acid treatment what type of treatment that we (41:40) usually bomb basic for so we have a different type of treatment that we typically use acids the first one called bickling treatment soaking or scale removal treatment acid breakdown job matrix as a diving which is a boss like one for be is not that completely clean so we do what we call bickling and the objective is to remove any irons out from the silhoue from the welds before we are bumping the fluid inside the formation and usually we do this one before any acid treatment so this is one of the recommended treatment that we do before bumping the acids inside the (43:36) formation backlink we are talking about a weak acid so usually from three to five percent hcl and as additives usually you are having two only additives co g acid just to remove this one and restore it to the original part it can help also to remove any scale from perforation and sometimes some of this care will be in the formation phase so we can bump we can bomb the acid this formation phase again when we are doing acid washing our intention to not bomb it inside the formation we are just like as a maximum or the the maximum location is just the formation phase because we have scale we have a calcium carbonate asset concentration will be go (45:3 ugh the perforation like perfection cleaning can be from (46:56) scale or from debris after after you have your perforation so you are in intentionally bombings assets inside the formation you will have a little bit of acid that can go inside the formation and that's why you still like as always inhibitor is one of your main additives you're still having some formation compatibility and someone will call diverting agent as you can see like you will have in this case i have a horizontal wheel wit lighting in red improving the prostate and the permeability and if there is any fines or any particles that causing the damage (48:47) hchf will be dissolving this amount restoring your permeability to the original value again that the best way that you are inject that inside the stone you start again with hcl to remove any carbonate then you pump your main acid which is the mixture between hcl hf and then the finally over flush with hcl to keep the ph low and bumping your eliminate any precipit use of the precipitation parts it's a little bit difficult to deal with the higher concentration of (50:35) a gif another type of oxidizing called carbonate acidizing which in this case we mainly were talking about either hcl acetic formic or a blend of these assets and the objective when we are talking about as dies and carbon excising we are not removing damage we are not stabilizing damage what actually bypassing this damage and the way that why we are bypassing it because hcl is a pretty agg to get the best uh wormhole so i'm having here going from left to right in the injection rate part so so if you are injecting at low rate what will be happening what we call (52:40) phase distribution at a lower injection rate acid reacts very fast usually so if you are if you are not injecting at a really high rate so the hcn will merely dissolve the surface of the core will not be able to been treat deeper so if you do a little bit higher rate you have what we call conical which is still acid assets but only how can i say it you create a certain lens that you you need for for the homework to be dissolving so you do not get any additional benefit all the acid that dissolve more you remove the oil you remove the rock but you actually do not get additional benefit in the permeability part the final type of the acid fracturing is (54:36) the fun type of the acid treatment is acid fracturing and here we are injecting the acid to actually uh to create a frag and and bombing at higher press he frac become like everything will be closed again and you'll have a really small area that will open for the flow so in acid the amount of acid that you inject and the way that you're injecting it's pretty important to have the good etching part and to have a good channeling you don't want to have the acid react with the whole surface area you would like to be selective in a small area to to get the maximum benefit of doesn't (56:27) the way that we bump the acid we do it in three ways the fir eterogeneity (57:37) impermeability so imagine if you have a case that you have like the bottom part will be the hypermobility then the top part the permeability will go low and the lowest one will have it like the lower the lowest permeability and usually you are injecting from the surface and you don't have a control acid like a liquid fluid like water will go in the less resistance path what's happening the acid will will inject and will go only to the high permeability formation and will kee al acids and just like cold tubings that's a picture of cold tubing in this case you are actually go with the cold tubing (59:24) to whatever dips that you are actually interested to treat and bump acids there then move cold tubing to another area and bomb that is there and move the culture into what the third area and bomb that is there so use a cold tubing to support the acid in each location through the whole world a second one like parker in this case you set the walker in the zone that you of acid however it has a lot of disadvantage first it it only control the fluid inside of the wellbore so if the fluid would go inside the formation you don't have any control where the flow will go after about the (1:01:08) perforation second most of the time you need to have a casing and perforation type of treatment so if you have an open whole type of treatment usually mechanical method is a pretty tricky to be used and the third and the most important part the expensive it's a pretty expen be high so the viscosity will be low so it's easier to bump however when it's to go inside the formation because you are moving in the radial part your injection rate or your velocity inside the formation will go down so the viscosity will go become higher and higher as as you go away from the wordpull area as (1:03:00) if this goes to go higher it will block the zone that you are you are bombing in and actually will will allow the nexus to change make its acid stage to go to a certain one i wil her viscosity there is no flow will be able to go here so the acid the next stage will try to go to the lower permeability and again you inject your chemical that will block the formation here forcing the acid to go to the top part so at the end of the treatment you will find all this viscosity will be higher for a certain time it will break and when you have the flow back you're treating the whole zone actually this is with my last slide (1:04:57) if you have any question i would like happily t ng would try (1:06:17) to actually moving from the lower curve to the upper curve and restoring to the original permeability however we are bombing the acid in almost three to five feet if we're talking about as advising in a matrix as dying that's a maximum that you can reach so you will not be able to enhance the permeability of the whole reservoir so you are mainly around the world area and this is will enhance the productivity around the willpower area only but to the original value of the r ng the tubing and that can happen for all type of of formation type yes okay so um uh another question about uh uh mud acid (1:08:14) some asking someone asking why we use mud acid in sandstone and why we do mixing mud acid is a definition meaning you have an hf and hf is the only acidizing that dissolves sandstone so without haf you'll not be able to dissolve any sandstone so if you keep bumping hcl in a sandstone formation it will not do anything assembly hcl does not dissolve silica or sand s d and does not precipitate so iron control can be either cleating or reducing part like collecting it make it a complex with iron and keep its globalization or reducing it from ferret to ferrous and in this case will not will not be (1:10:13) damaging okay so um there's one more question someone asking in in the uh chat section why everybody in egypt do you have an answer for that sorry why everyone in egypt named ahmed it seems like he noticed there's a lot of ah"