MMM106
Educational Website
"(00:05) okay good afternoon everybody so today we will start a new chapter matrix acidizing as with it was said in previous chapter matrix acidizing is a uh one of the methods to remove or minimize the effect of formation damage here are the learning objectives of this chapter for what you have to concentrate on i'm not going to read this all out because you have it on your books so matrix acidization or matrix simulation because when we (01:12) acidize the matrix we stimulate the reservoir to p roduce more to increase permeability so it is a uh acidization is a type of stimulation there are many methods of uh stimulation like hydraulic fracturing methyl methoxization acid wash acid fracking and matrix acidization is a matrix here is the near world ball reservoir rock matrix and it is a world treatment it is not a reservoir treatment although we are injecting acid into the formation (02:18) but it is for near world war zone within the uh meter or two meters maximum area radius and this is kind of a considered as a part of world as a part of world performance attributes therefore it is a world treatment and it can be done at any stage of the world operations after the drilling to example to remove the effect of mud filtrate on the reservoir permeability near world war zone permeability and involves pumping a series of specially (03:21) uh designed uh fluids with the different uh various uh composite chemical compositions depending on the type of damage uh type of reservoir rock or lithology and it is injected under fracturing pressure so the idea here is not fracture the reservoir but the idea is to inject required amount of the acid to dissolve the damage to solve the solids or any fluids that are damaging that are reducing the permeability or relative permeability so and success here depends on the (04:29) what well is selected for the for the acidization because of course the maximum effect will be from the wells that are more severely affected by the type damage i n terms of production rate but there are some factors to be taken into account like remaining oil volumes or reserves around this well i will talk about that later choosing a correct type of the simulation treatment so what kind of injection we are going to uh to run and how we are going to operate these (05:36) these operations perform these operations what kind of a chemicals is going to be used and another important factor is injecting the treatment fluid or the chemical compositions into a p articular zone that is damaged or to provide smooth or the required amount of treatment fluids into the appropriate zones into the um as required as per the severity of the damage so the most damaged zones should you should (06:41) receive more treatment fluid and less damaged stones should be you should get more less treatment fluid and that is uh achieved by some [Music] diverters we'll talk about that later and so what is the aim of the wealth stimulation from the world inflow equation uh we know that [Music] production rate is directly depends on the relative permeability to oil or gas the thickness [Music] drawdown and viscosity so and skin of course so (07:49) this parameter uh so for different types of [Music] treatments uh the these parameters are to be increased like relative permeability uh thickness well thickness here is meant to be uh actual contributing thickness of the reservoir into the particular wall and drawdown as you know through increasing throwdown may lead to so me formation additional formation damages so the main increasing thickness is also sorry may require some reperforations or making additional perforations so main objective here is increase relative permeability in other words to (08:56) clean the pores that are blocked by the chemical injection and decreasing the skin [Music] here we our aim is formation damage skin increasing increasing relative uh sorry the effective wellbore diameter when we um expand the connection with the reservoir of the world war with the reservoir and the changing the viscosity of the produced or fluid to increase the mobility of the fluid this is the uh kind of chart for the (10:02) guideline for the uh remedy to remedy limited inflow performance where we have a natural wells and the formation damaged wells when we have particle plugging emulsions with ability chains fines migration and clays and different approach to a remedy or to remove the damage with the different methods and operations yes my question is relating to previous slides what the benefit of decreasing vo coefficient and is it possible to change bio coefficient by using stimulation i mean chemicals now did i say that we are trying to (11:02) decrease the uh view it's just a mathematical way and i was talking about only what we can do with this parameter so formation volume factor i didn't mention that uh metric sensitization is related to that so it is not possible and there is no benefit to change it or decreases from the mathemati cal point of view yes of course there is a benefit but how you can decrease it it is kind of a property of deployed here again for different roles yes does this parameter depends on the separated condition for example (12:06) temperature and pressure of the separators i mean the stage in the process of flash vaporization or differential liberation as i know is the fx's parameter if we are talking about formation volume factor then it is not affected by separator because it is a a ratio between t he stock tank barrel and reservoir barrels and stock tank barrel is the uh stockton conditions so zero atmosphere uh or one atmosphere absolute and uh 60 degree fahrenheit okay so your separated conditions will affect shrinkage of the oil (13:11) at this particular field with these particular separated conditions but total formation volume factor is uh calculated based on the standard kind sorry stock tank conditions which is the fear which is fixed is that clear uh yes it's clear but uh as we c hange this temperature and we flash it or we do some differential revolution this uh value of this parameter for this different pressures are changing that's why i'm asking that when we talk about uh sorry again you are uh you have to realize that when we say (14:12) vo in this case this is for the uh stock tank stock tank conditions so final uh value of this uh yes it is changing it depending on the bo but it's sort of pressure and temperature but when we talk when we put this value into this f ormula we use the uh ratio that is reservoir barrels over the uh stock tank bottles okay the all uh changes are between these two states two states okay between the reservoir pressure and the surface pressure you mean it is depends on the only initial condition and the final condition not the (15:15) past that uh do it okay well it is a uh [Music] i i suppose you you have seen this curve of uh bo against the pressure yes i have seen that yes so this is the last point on the curve which is the lo west point and at the 60 degree uh fahrenheit and zero gauge polish zero psi at gauge pressure or one psi uh sorry for 15 psi of absolute pressure at so this is the conditions uh this value for this formula is used okay thank you okay this uh (16:19) the change of the value is used when we consider the uh multiphase flow in the world board to see how at which depths of the well we will have how much gas we will have okay you get the point so as we go through from the surface from the reservoir t o the surface through the tubing this curve that you have seen or you refer to uh beo against the pressure is used to calculate uh multiphase flow conditions uh is in in the world so because as it goes up uh uh to the surface the the multiphase fluid goes up to the surface (17:15) the pressure change drastically at every inch of foot or meter and the change of po dictates how much gas is going to be released from this fluid and that allows us to calculate at each depth the [Music] hold up if you remember what is hold up so hold up is the liquid area of the pipe occupied by liquid over the area of the pipe cut off i mean if you look at the pipe the area pipe category so over the uh area that is occupied by gas and that's very important to calculate friction losses it's very important to (18:13) calculate a month phase flow regimes to identify the regimes and to calculate the pressure losses through the tweeting but in this case when we call when we consider why actually this parameter i s here because initially this formula was derived for the uh reservoir conditions so how much fluid we are producing from the reservoir but the fluid from the reservoir is not a financial kind of uh parameter value so therefore this was used this was inter in introduced into this uh formula to convert it to the stock tank barrels which is the fixed (19:06) conditions to to realize how much uh sellable oil we have okay how much market oil we have so this value is the last value of the at the fixe d stock tank virus stock tank conditions and stock tank conditions is fixed are fixed okay okay thank you yes can you please repeat what you have said about this radius ratio no in in the same on the same slide re over rw i mean [Music] yes yeah can you like um here you can see okay i see uh here you (20:10) can see that rw is the uh so as we decrease our w sorry as we increase our w the production rate should increase right yes okay so as we so therefore we our aim to increase the effective wor ld bore radius and we will see how we achieve it actually i talked about that during the perforating during the talking about the perforating techniques like uh extreme over balance or frank frack packing uh and other other techniques when we increase the uh connection of the world war (21:12) with the uh reservoir and by that we increase the effective or apparent wellbore radius and matrix stimulation is also uh contributes to this increase we will see it later okay okay did you get answer to y our question well yes you said like increasing re will um will contribute only increasing increase re is increasing re will decrease the production rate and it is a kind of purely mathematical effect it's not a reservoir effect okay but decreasing rw will increase the production rate (22:18) and the increasing rw are different question that we will try to answer well partially we are we have seen the effect of some preparation techniques to increase rw uh effective radius and later we will see h ow the symmetric stimulation is affecting okay so and this again some description of mechanical methods chemical methods biological combined thermal and uh what is the objective uh to how it it will affect the which parameter it will affect here you can see a combined mechanical chemical message for carbon information acid fracking (23:14) including proper acid fracturing closed fracture or wormhole this will increase rw substantially here for example another example uh profit hydraulic fracturi ng when you fracture the wall and reservoir and increase the contact area with the reservoir explosive fracturing under leaning and additional perforating increasing the thickness as i said so these are the and you have it on your in your book i hope and you can go through it and memorize it or try to understand and if you have any questions i will be happy to answer okay (24:11) and these are the global guidelines to select a simulation treatment for clastic and carbonate reservoirs what is cla eral uh terms classic reservoirs clastic formations are the sandstones uh usually sandstones with the sequencing with the shales so it means it's a kind of deposited or sedimented as a particles okay as opposed to carbonates that are created by mostly um high pressure over (26:23) and this from these from the uh carbons mostly are generated dieting nested from the uh organic materials okay and this this table is also two tables are also present in your book so you can go through so there is a cl okay uh so as we uh talked through all the um time uh last semester this semester as well the most uh vulnerable or most affected area or zone within the well drainage area is the near wallboard zone because as we said in the near world war zone we have a uh reduced area to flow (28:24) and uh the uh from the from on the other hand this near world war zone is uh mostly um affected by the formation damage because of these uh drilling fluids compare the completion fluids work over fluids and ther loss might be even killing the well so no production or production will be affected by times okay so to remedy this we have to treat near world war to restore the natural uh oil production capacity in ideal case uh again uh mentioning the uh hawkins formula that we um talked about uh in uh previous chapter again uh just reminding (30:20) you that from the previous chapter you have seen different exposition of these charts when we have a different radius and uh effect of this and the percentage o he effect of this will be much less than effect of uh damage so again therefore it's better to prevent the damage rather than remedy damage another issue is the effect of damage collar it happens when we do a matrix acidization and so initially the damage is around (32:38) the world bore and then when we do this matrix acidization then there might be some damage color left over in the reservoir and this damage the distance to this damage color and the uh kind of a width of the damaged collar is lor then the damage then it is almost 45 only of the original productivity if we uh move it to the four feet like a meter away from the world ball so we have damaged zone here and we have clean zone here relatively then the damage might be 20 percent okay and for different uh color thickness the color thickness is also is important because again uh the thickness of this color (34:40) it is a damaged zone and thickness of damaged zone is uh will be affecting the productivity okay yes can you say under pressure okay and uh sometimes the volume that we inject is not enough to cover all these damage radius and we only clean this area this radius and also pushing some damage or uh damage to the fluid that is damaging the formation further from the uh world war okay and that is the case when this damage caller is created damage color is not created uh initially okay it's not possible uh having this color with the clean area (36:42) around the world if you mean that the other world is that wh s of acid treatment and these acid treatment treatments are acid washing matrix acidizing and fracture acidizing in this course we will talk about mostly matrix acidizing when we inject a chemical compositions at matrix pressures or at pressures of the formation exceeding formation pressure and below the fracturing pressure to dissolve or remove the damage or bypass the damage okay and uh acid washing is the we will talk about that to mention it uh when we pour some acid into the world bore (38: no i did change can can the others see the change now in the impact of the location of tasonia they will bore there is also one graph three curves one graph about the color thickness i think after this graph which graph you are seeing now uh i am think uh 10 mountain uh the page thing okay it's not the the one that you want yes it's not uh won't i want 11 the page 11 can you (41:02) return the page 11 okay i'm on the penis uh yes the in the color sickness uh what's the color sickness i didn't un can you see this yes i can see yes i understand and the fracture acidizing is a acid treatment uh compo combined with the fracturing when we inject the acid at the pressures exceeding the formation for fracturing pressure so it's a having even more effect on the uh increasing the effective uh world war radius (43:06) however we don't need always this we may only we may get the results with just a matrix acidizing so it it will depend on the lithology it will depend on the formation damage stabi d removing the damage so main aim is to dissolve or remove the uh chemical uh precipitations or solid particles that are soluble and or plugging the perforations and the distal plug into perforations again through the chemical effect chemical reactions and only in this case the sandstone (45:16) acidizing will have an effect and the acids commonly used here are hydrophobic hydrochloric acidic and formic so mostly used is hydrophobic we decombine with in combination with hydrochloric hydrochloric ese damage by the dissolving those particles uh chemical precipitations results of chemical precipitations or fines that migrated or entrained by the [Music] mud fluid or competition fluids is that clear yes okay in the carbonate formation the aim is a little bit different because carbonate formations are [Music] (47:17) consists of calcium carbonate and it is a very reactive with the hcl and acidic and formic acids and as it gets contact with hcl then it will dissolve the cementing material the ball and bypass the damage rather than the uh removing it and by as as we have these wormholes you can see all these effective world war radius is increased okay because now fluid is inflowing into the world board through this (49:26) network of the wormholes okay do you understand what's wormhole wormholes are these small channels or it's not fractures it is exactly how whole holes or the channels created by the acid in the carbonates okay as we said it is important for the uh success uh chanc chemicals cost of the operation and the other for example just a salary of the people who involved into these operations so therefore identifying a candidate (51:20) well is the first task because if you pick the wrong well you will get ineffective results or you will get uh low economics economic results uh of course the net income from as i said additional hydrocarbons produced should should cover the cost so therefore we have to first identify the world economics we'll talk about that on our so chemically we create wormholes right yes matrix sensitizing is acid chemical creation so this uh do you know what's (53:11) wormhole yes it's just a kind of uh conductive channel let's see no in in in a very simple world in general you know what's warm so warm is [Music] oh the aim of this term here is that this wormholes are created under pressure that is lower than fracture pressure and the these wormholes are created only by the chemical effect not by the injection effect okay so the aim i r through the farm through the near world war zone of the reservoir okay (55:16) it's not chatting planting is concentrated flow high pressure flow of some solids like it might be sand might be water but uh it should be high pressure and very narrow kind of injection okay this is not getting this is wormhole can we say that it kind of solves the part of formation rock not kinds of exactly dissolving the formation rock yeah so the same principle as the sandstone sandstone formation no no in sands ud itself should be dissolvable by the acids so we can clean it after the drilling uh by the acidization in this case we dissolve the matrix the rock itself that clear therefore we say (57:29) here we are trying to bypass the damage okay we are creating this wormhole network which bypassing the damage we are increasing the effective wall more radius effective inflow radius yes sure i mean if you still have a question if there is any uh on clarity please ask no that was what i meant actually yeah 'll do that okay okay uh thanks very much see you next week uh next week or maybe at the uh tutorials you one of the tutorials (59:39) you uh may have a quizzes that will be again uh part of your final uh grading for this course okay i'm preparing the questions for the quizzes and for the kind of uh midterm it's not a exam but it will be quiz during the tutorials so no pressure but just want ideas how you are getting on the course okay okay thank you thank you you're w"