Introduction to Open Hole Logging, Dr. Moustafa Oraby

0:00 Welcome to the second week of the Arab oil and gas Academy. We hope you had a good weekend. And without any further ado, I would like to introduce our speaker for the for today. And basically the best kickoff to the week, we're having Dr. Mostafa Oraby back. And if you don't already know, Dr. Mostafa Oraby is the master of simplifying technical knowledge. The petroleum technology to the students. So, Dr. Mostafa, it's always to have you back. Let me just introduce him very quickly. Dr. Mostafa Oraby is has a 25 years of experience in petroleum industry. He holds a PhD degree from North Carolina

0:46 State University. And the master's and a bachelor degree from Alexandria University in Egypt. Dr. Oraby has also joined Alexandria University in his early career as an assistant lecturer. Till he obtained his master degree. He also used to teach at community college in USA. In the industry, Dr. Oraby had many many positions in all aspects of petroleum industry. And lived in many countries around the globe. Basically, the guy is a living legend. So, please make the most out of this lecture today. Dr. Mostafa, over to you. Thank you, Ms. Nehan. Thank you very much. Good morning, everybody. Or good afternoon. Or good night. It depends on where where you are. So, today actually I'll talk about the

1:31 introduction to well logging. I know that you you actually had another or previous lecture on well logging. The reason we thought about this one is I need to link this one with the coming or the upcoming unconventional reservoir. Because the unconventional reservoir will will be based on some understanding of the well logging. I just want to make sure that you guys are very much aware of what we need to know from well logging to really start talking about the unconventional reservoir. So, that's that's not a a new or a different presentation. Just a continuation on the previous one to try to stress on a few facts, a few properties, a few observations that you need to make sure

2:16 you understand it fully. Because that will help us in on Wednesday where we will will start talking about the unconventional reservoirs, okay? All right. So, let me start. You remember we started the previous week on the introduction to oil and gas industry. And we made a we made a review. I just want to link all the lectures that we have in the webinars, including my lectures, to the same distribution and same divisions that we distributed and divided the the industry into different segments. These segments that has multiple things, all these operations, all these processes, and all of them actually are connected to each other. So, if you remember the slide that we discussed in

3:02 the introduction to oil and gas industry, we looked at the industry all in all and we said that the industry actually is a circle of multiple connected none or none of them is isolated from each other. All of them are connected to each other. And we put three different or three major different segments. The first segment is the identification, drilling, and evaluation. If you still remember this lecture. Second segment is the completion and production. The third segment is the field management. Once you drill, we evaluate, you complete wells, then you have multiple multiple of wells that you need to understand how to manage these wells and how to manage the field in general. And put different aspects of all of these. And one of them actually we call logging

3:49 wireline and and LWD. That's the one we're going to stress on today. It's part of the whole sequence, the whole chain of operations, all all chain of connected as I'm repeating this again, it's an integration and a teamwork. None of these is isolated from any any others. All of them are very much linked together. As you will see that why you study so many webinars and all of them has to be connected together to see where each one fits in the puzzle of the oil and gas industry, So, from logging and and and and operation, it's part of the identification drilling and evaluation. From the evaluation side, we do logging. Logging can be in two types. Either in wireline or in LWD. Now, the

4:34 question is what is wireline? What is LWD? Wireline operation happens after you drill the well and you pull the bottom hole assembly that we talked about before. Once you pull the bottom hole assembly, the only thing that exists in the wellbore is the drilling fluid. The drilling fluid is the only one is in the wellbore now before you do the logging operation as wireline logging, okay? Here is a video from a video I just took for about two from about two months ago or so. With a Schlumberger truck in one of the Egypt fields. It is how it looks. Here is the Schlumberger. Let me just shut this down. So, here is the truck and let me stop

5:21 here. You can see you can see right there. This is the wire. That's why we call it wireline. See, here is the truck and there is a wire coming out of the truck. This wire contains some conductors that sends and receives information from and to the get the information to the tools and receive information from from the tools. We give orders to the tools and receive information from the tools. Here is the wire the wire that does this operation. That's why we call this wireline logging. Because we use a wire a multiple conductors, normally seven conductors in this wire. And we acquire data and we communicate with the tools from the surface here to the bottom hole and we communicate with the with these tools with sending

6:06 orders and receive information out of these tools, okay? We'll continue on this. As you can see, here is the wire going all the way to the rig. And from the rig, the wire will the wire will go down to the wellbore and acquire the information, okay? The information will be brought back all the way to the truck where the truck it has computers in there to store the information and proceed with printing and making tapes and making data. All of these for for the for the data of the well. We call this wireline. So, wireline happens after you finish drilling the well, you pulling everything out of the wellbore except for the for the fluid. That's before you do any casing, before

6:51 you do any cementing. That's why you call it open hole wireline logging. It's an open hole wireline logging. No casing. Nothing in the wellbore but the mud or the drilling fluid. Then you go with the tools inside this wellbore with the drilling fluids in there, okay? The other type we call it LWD or logging while drilling. Logging while drilling, you actually do the logging while you are drilling. So, this means your tools are not on wire. Your tools is part of the bottom hole assembly, okay? So, let me also start this video here. I'm going to just going to run through this quickly. We don't need those, okay? Here is how it goes. And you can see here is the

7:37 where you're going to hang the bottom hole assembly. All right. Here is the tools. The tools will be connected to the bottom hole assembly as you see. All these operators, they are connecting the tools and then you're putting the tool inside the wellbore as as part of the bottom hole assembly. So, you're not waiting for finishing the drilling, no. You acquire the data while you are drilling. And you keep adding tools and so on until you put all the tools that you require, all the tools that you need to evaluate your reservoir while drilling. So, there are two of them. Either wireline or LWD. When do we use wireline? When do you use LWD? It depends on the situation. Most of the time we do we use the LWD while we're

8:22 doing wells like horizontal wells, highly deviated wells, multilateral wells. Vertical wells, we don't really do LWD in vertical wells. Normally in vertical wells, we do the wireline logging, okay? And because of the wireline will be difficult to go for deviated well, high angle wells, horizontal wells, we prefer to go with the logging while drilling, But they both have the same tools. They acquire same data with different type of data or different analysis of data, let's put it this way. But they are all have the same type of technology that we will talk about in a second. You will understand that now. Okay. So, what do we really measure with all these tools that we're going to be talking about? What are we measuring

9:09 there okay? First of all, when you drill a well, you drill a cylindrical shape well, right? But because we're actually drilling in an unknown formation, we use motors, we use bits, we use mud. So, we're not really expecting that the hole will be in that very nice, very clean shape cylindrical shape. This is that's not the case. This very nice nothing in here, no washout, no changes, very straight line. That that doesn't happen in in nature in the reality. Reality, what we will get will get this shape. Okay? You will see a regular shape of the wellbore. Yes, it is cylindrical in all, but the diameter

9:54 of the wellbore will be different based on how your mud how your drilling actually reacted with the formation that you are drilling. Not all the formations are alike. The mud sometimes does does actually deteriorate the wellbore. So, the wellbore will interact with the mud. The cuttings will not be in in the in the cuttings that you like to have. The pressure from the mud is not highly equivalent to the pressure from the formation. There are so many factors that you study in drilling that will affect the wellbore. It's not going to be as nice as you expect it to be. That will be the actual shape of the wellbore. So, actually we need to know what is the shape of that wellbore. What

10:40 is the diameter at each depth? For example, if this is the 10,000 ft, what is the diameter at 10,000 ft? What is the diameter at 10,001? What is the diameter at 10,002? Because it can actually change on a foot-by-foot basis when you drill a well. So, the first thing we need to know is what is the diameter of this wellbore. Okay. So, this this operation will actually end up having a wellbore with that shape. So, this is the shape actual shape of any wellbore that that we drill. It's not going to be a straight line side cylindrical wellbore at all. That's expected, right? So, the diameter here is different from the diameter there and we need to know that. Why do we need to know that? Because that tell us so many things about wellbore stability. Also,

11:27 the most important part is when you start cementing when you start the cementing operation, you need to cement between the casing and the wellbore. So, you need to know what is this this diff distances between the casing side and the wellbore side because the wellbore side is not a straight line. So, it's not a straight line equation that you're going to put. There is an irregular shape of the wellbore that will affect the cementing volume that you need to use. So many reason that we need to know what is the bore hole diameter that we are dealing with. So, the first thing is bore hole size. Bore hole size is one of the major most important parameter that we need to measure for our wellbore. So, bore hole size, okay? Second,

12:13 here is the formation that you drilled through. So, this is your wellbore and here is the formation that you drilled through. Remember when you talked about the formation structure and the reservoir structure in the introduction to oil and gas industry, we said that the the whole formation is composed of of grains and these grains are sorted in a way. That sort sorting of of the grains create what we call porosity. So, how much porosity do we have in our formation is a very important parameter that we need to know. So, we have to know the diameter first of the wellbore. Second, we need to know how much porosity do I have. The pores is the void between the arrangement of

12:59 of these grains, okay? In reality, if you remember this before, here is the reality. Here are the grains arranged in reality. This is an ideal case just for the explanation. But, this is reality. Here is the porosity right there. Okay? So, we need to know how much porosity do we have. Why? Because our hydrocarbon will migrate from the source rock to our pores. So, I need to know how much of pores do I have to find out how much volume of hydrocarbon do I have later on. So, the first thing to measure is the bore hole size. Second thing to measure in the formation itself, how much porosity do I have, okay? Third, these grains are different for different lithology. For example, if I

13:46 am working in a sandstone formation or a limestone formation or a dolomite formation, the grains are different. The density of the grains are different. That's why we need to know what type of formation are we dealing with. Am I dealing with sandstone or limestone or dolomite? This is very important in our interpretation as well. So, what type of lithology do we have? Type of lithology do we have? We would get it from from the density tool. So, I have a tool that measure the density of these grains, okay? And the density of the total bulk of the rock. So, first one is bore hole size. Second one, how much porosity do I have? Third one, what type of formation am I

14:32 dealing with? Am I dealing with sandstone or limestone or dolomite? I need to know that because they are different in property, okay? Going back to we call this one lithology. We'll talk about this in some details later. Now, going back to the pores, what does live in the pore? I mean, what are the fluids that live in these in in these pores, okay? Actually, originally everything was water. Then, the hydrocarbon moved in. So, our expectation is to find water and hydrocarbon in our pores. Okay? We need to find how much water do I have and how much hydrocarbon do I have. So, actually we call it fluid saturation. Fluid saturation, what are the fluids that saturates my pores and

15:18 how much of it is water, how much of it is oil. The more oil, the better. The more water, bad news. So, we need to find out if my reservoir has oil or gas or water. How much of water, how much of oil, how much of gas. This is what we call fluid saturation. So, bore hole size is important. Porosity of my rock is very important. Lithology of my rock is very important. How much fluids do I do I have in my pore space is one of the most important parameters that I need to find out. Okay? So, these are the measurements that we ask for fluid saturation. We talk about water or hydrocarbon okay? Is it clear now? Everybody is is following. Now, let me go back to the

16:05 same distribution of of operation or sequential of operation that we do. One thing that we actually talked about in the petroleum industry overview, something was very important as well. We call this one production enhancement. What is production enhancement enhancement? I think you guys got introduced a little bit on fracturing. We have what we do with fracturing and we increase conductivity of the rock or make paths for the hydrocarbon to flow when there is no permeability in the rock that allows the hydrocarbon to flow. If there is no permeability in the rock that allows hydrocarbon to flow, I'm having a problem. So, I need to intervene and make path or in or create

16:51 conductivity for my hydrocarbon to flow from the formation into the wellbore. Here is part. How can we how can we do this operation? It depends on how strong how strong my rock is. How can I break this rock, okay? How can I break this rock? All this information we getting we get this information from the logging. Logging will get give us information which which we call the the the one that we used to create the fracs, we call it rock mechanics. So, the rock mechanics or the properties of how how solid this rock is. What the the strength of the rock. What is needed to break this rock and create these fractures for my my hydrocarbon to

17:38 flow, we get this information from logging. So, we get the bore hole sizes from logging. We get the porosity from logging. We get the lithology from logging. We get the fluid saturation from from logging, either water or hydrocarbon. And we get the rock mechanics or the rock mechanical properties. The rock mechanical properties also we get this from logging. So, logging is so crucial. That's why we call it evaluation side. This is how you evaluate your reservoir from all the properties that defines how important this zone to you. So, you need to go and do something for this zone. You need to produce it or is not economic enough and you need to walk away and end the operation, okay? So,

18:25 logging is a the very determinant type of operation. You determine the continuation of your drilling, continuation of your management of the field, continuation of of how you're going to handle this zone. That will be determined based on the information you get from from the logging tools. Okay? Everybody is following this. Okay. One more thing that I need you guys to be very very very aware and I said three very in this sentence. It's a very important thing. Clay and shale, okay? We need to really spend some time to talk about this. It's very important thing specially when you start talking about unconventional reservoir. So, understand

19:11 this slide very well because it will be very determinant in the way we look at the unconventional reservoir later on, okay? What is clay and what is shale, right? First of all, when we looked at this piece of rock, remember when we talked about the thin section and we came we looked at the distribution of grains and the distribution of pores between the grains, okay? And we zoomed into this zone and we found here is the here is the here are the grains and here is the porosity. And you can see porosity is very clean. It means there is nothing here but fluids. And it should be originally filled with water and when the hydrocarbon migrates, it pushes the water down because it's higher than

19:57 density and the hydrocarbon lives instead of the water lives inside the pore. Okay? Is the situation that good all the time? No. Nature is not that nice to us all the time. Let me give another example. So, the the expectation now is the hydrocarbon will live here. Let me give you another example. Here is another another piece of rock that we took a thin section, we put it under the microscope. Okay? Now, let's just look at a certain zone here and zoom it. Look at this. Here are the grains. Here is the porosity. Is this porosity empty or it is filled with something else? It's filled with something else. So, there is no room for the hydrocarbon. When it actually leaves the

20:42 source rock, there is no room for the hydrocarbon to live in. So, the pores are very much controlled by some other material that actually lived inside my pore space. This material we call it clay minerals. So, clay minerals is very dangerous. Okay? Clay minerals are very very dangerous because they live inside my pores. And when they live inside my pores, they reduce my porosity. When they reduce my porosity, there is no room for my hydrocarbon to live. If there is no room for my hydrocarbon to live, I don't have a reservoir. Simple and clear. So, clays are very

21:27 critical to know what are these clays because they live inside my pores. You're already clear on this okay? So, clays actually are minerals, certain type of minerals without going into details, that actually loves to live in my pore space. All right? And clogged my pore space. No room for my for my hydrocarbon to come and live in here. All right? Every clay we call it shale. Listen listen listen to what I'm saying here carefully. Every clay is a shale geologically. So, when you look at the geological distribution of minerals and of grains, all clays are

22:12 considered shale. And listen to this. Every clay is a shale, but not every shale is clay. Take this and write it down if you have a piece of paper and a pen. Every clay is a shale, but not every shale is clay. What does it mean? We have a family of five. Okay? Call one of your brother and sisters, call him clay. So, that clay, that member is part of the family, but not all the family called clay. That specific person is called shale, but not all the family are called clay, okay? So, every clay is a shale. It's in the shale family, but not all the shale family are clays.

22:59 Am I clear on this? It's a very very very important point to understand before you get into unconventional reservoir, okay? The word shale gas, the word shale oil, we use it now as, you know, everybody call it shale gas and shale oil, but do we understand the difference? That's the most important. When you hear the word shale, it doesn't mean it's clay, but when you hear the word clay, it means shale. Okay? So, every clay is a shale, but not every shale is clay. Am I clear on this point? It's a very important thing but for at least for for Wednesday when we start talking about the unconventional reservoirs. Okay? Clear to everybody?

23:45 All right. Porosity, if you have clays in the pore space, I'm not going to call this shale anymore. In conventional reservoir, I'll call this clay minerals, okay? So, we understand this now. We call this one clay minerals. We're not going to call it shale because shale will will reserve this word to the unconventional reservoir. So, when the clay lives inside the pore space, my porosity becomes close to none. There is no porosity and that's actually harm my reservoir. Clays, which is part of the shale family. Clay is part of the shale family, but not all shale are clays. Yeah, I'm repeating myself multiple times because this is a very subtle problem. Uh sub You have to understand

24:31 it very clearly before you even touch the word unconventional reservoir, okay? So, clay minerals very harming to our to reservoirs because they reduce my porosity, they clog my porosity, there is no room for my hydro my hydrocarbon to migrate and live inside my pores. What are the basic wireline and LWD logging tools? What are these two? First of all, we talked about the wellbore. This is this is the well this is an actual wellbore shape here that was drilled in Egypt, unfortunately, and you can see here is a very very bad wellbore yeah? Okay, this wellbore is should be cylindrical wellbore, but there's lots of deterioration. You can see the wellbore diameter is changing from one foot to the other. Okay? We measure this

25:18 with what we call caliper tools. We'll talk about the caliper tools in details later. Caliper tool is the tool that we measure or that we use to measure the diameter of the wellbore. So, the diameter of the wellbore is measured by a caliper tool. Okay? Everybody understand that. How about the clays and the the clay which is a shale member? How can we find the clay in our reservoir? Well, we find this with a tool called gamma ray tool. So, we measure the diameter of the wellbore with a caliper. We measure the clays with the gamma ray tool. Everybody understand that. We need to know how we measure this. Third, reservoir porosity. We measure

26:06 reservoir porosity by a tool called neutron porosity tool. So, we measure the reservoir porosity by a neutron porosity tool. Okay? We we measure the rock lithology by a tool called density tool. Okay? I will review this again. We measure the wellbore diameter with a caliper. We measure the clay with a gamma ray tool. We measure reservoir porosity with a neutron porosity tool. We measure the lithology with the density tool. We measure the fluid saturation with the resistivity tool. Okay? We measure the rock mechanical properties with the sonic tool. It's a family of tools. And you choose these tools based on what

26:54 do you want to measure? What are you interested in? Am I interested in rock mechanics? Then I use the sonic. If I'm not interested in rock mechanics, my my reservoir has very good permeability, I'm not going to use the sonic. Okay? I'm my wellbore is in a very in a very good shape, probably I will reduce somehow the the the use of caliper, which nobody did, but yeah, assume that this is the case. Okay? I have a very clean reservoir, then I don't need the gamma ray. I'm just giving you an example. It may not may not be real examples, but at least my point is you decide on the tools that you use based on the problem that you have and the measurement that you want to measure.

27:40 Okay? You have a you have a a box of tools that you pick and choose from these tools whatever you want. Normally normally, we run caliper, we run gamma ray, we run neutron, and we run density. And our density and resistivity. Okay? So, we run this group almost in every well. We call this basic logs and we call them triple combo. Triple combo is neutron, density, and resistivity. Okay? Nobody's counting the gamma ray as a tool because it's a basic tool okay? So, the triple combo is the neutron, density, and resistivity. Now, if you add to them the sonic, we call him the quad combo. Quad combo is four tools, neutron, density,

28:27 resistivity, and sonic. Okay? So, these are the box of tools that we have that we actually choose depending on which property I need to measure. All right. Now, as engineers and as we agreed previously, engineers always ask questions. Engineers always ask why. Okay? And to be a good engineer, you have to keep asking why and you have to understand why we're doing this why are we why you're doing that. If you cannot find someone to to answer, go to the textbooks. You will find answers for sure, okay? So, the first question, how does each tool work? This is a very basic question.

29:14 Second, what does each tool measure? So, how does it work? What does it measure? Okay? Very important to know how does it work and what does it measure. Okay? So, there are two very basic questions. Actually, these two questions will be asked based on your knowledge of physics. Physics is very important in formation evaluation. That's why in the industry, we call the people who are working in formation evaluation, we call them petrophysicists. It means they are the petroleum engineers who actually understand physics to come up with the measurement. That's why we call them petrophysicist. Petrophysics is the link between

29:59 petroleum engineering and physics. I'm very sure everyone who graduates for petroleum engineering or any engineering will study two or three courses of physics. Please go review your physics courses because that'll be very helpful for you to understand the logging operations, understand the logging measurements, understand the logging interpretation because if you don't have that strength you may not actually know exactly how each tool work and what does each tool measure. Okay? We'll go through each one of these tool, try to find out what are the physics behind it and what do we measure. And what we can extract information from each one of these two. Right?

30:45 So, these tools are very, very important. Physics and petrophysics are very much linked together. Okay? Understand this. What do we need to understand? First of all, each tool has to have two things. Each tool has to have two things to understand the tool. First, a physical property to measure that relates to the rock property. I have a rock property. I need to measure porosity. How can I measure porosity? Then I have to find a physical property that relates to my porosity to measure it. I need to measure the clay content. Okay? I need to find a physical property that is is unique to the clay that I can measure which will relate to clays.

31:33 Okay? I need to measure oil or gas, hydrocarbon. I need to find out a physical property that's unique to the hydrocarbon that I can use to actually give an indication of existence of hydrocarbon. That's what it means. Physical property. Physical property is what the tool physics is based on. So, the tool physics is based on a physical property that relates to the rock property. Okay? Second, a detection method. How can I detect this property? How can I measure this? It's exactly like we do in the physics lab. In the physics lab, you do something and you detect it. And from the initiation and detection, you find the property. That's exactly what this one of these

32:18 each tool do. You have a physical property and you have a detection method which we call the tool detection. So, two very important thing, physical property and detection method. Every tool will have to have has to have a physical property and a detection method. And we will go through all of these tools one by one to discuss this and what do we measure. Okay? Caliper. Caliper, we need to measure what? We need to measure borehole size. Okay? First of all, why do we have different borehole sizes on a foot by foot basis? Washout while drilling. Okay? Because when we drill, that they can break actually the the rock and gives you what you call washout. Washout

33:04 after drilling. When you leave the mud in the wellbore, the rock will react with the mud and some deterioration will happen. We call it washout after drilling. Some of the clays, even when they see water, they swell. Swelling will affect the diameter of the wellbore. Rock deterioration, some of the rocks actually falls down at the bottom of the wellbore. That will also deteriorate the wellbore. So, actually these are the reasons why do we need to have caliper. Caliper is the tool that we use to measure the borehole size of our reservoirs. Okay? Originally, that's what we really like to have our our borehole diameter would look like, which is not the case

33:50 unfortunately because nature is not nice all the time. Which means the diameter in any direction is the same. If you have this and you are lucky one way or another, your rock is very stable, okay, which I doubt that is in any reservoir you see something like this. But any any any way, if you do have a well that's very highly stable and you can see only can see the diameter in every direction is the same. Or you can have actually an oval hole. Oval hole will have two diameters, a long diameter and a short diameter. Okay? How can we handle this? How can we handle that? Actually, in reality, you may not see this and you not see that. You may see something like this, absolutely irregular that actually have

34:37 diameters different in direction, multiple directions. All right? So, either this one or this one or that one. If we have this type of hole, so a caliper with two arms but here is the caliper. The caliper have arms. This arm open and closes when it goes into the wellbore. And the distance between every two arms that make 180° for example, this arm and this arm, they making 180°. When they open, they measure the distance between these two arms which is actually equivalent to the wellbore that open and sticks to the wellbore. And when you move it up and down, it actually measures the diameter of the wellbore. So, if you have a hole like this one, two arms is good enough. How

35:24 about this hole? Four arm will do the job. I need two arms to measure two arms to measure this diameter and two arms to measure that diameter. How about this one will be six arms. Six arms, two diameters in 180° and the other one may be a you move another 120° and then when you move another another 120°. We'll we'll show you an example of this. So, the whole idea is you bring a tool that has arms. These arms have springs and the springs will open and close based on the diameter of of the wellbore. Now, you can have two arms for this type of of wells. You have four arms caliper for this type of wells and you have six arm

36:11 caliper for this type of wells. Okay? So, the caliper will change based on what is the expectations that you see in your reservoir requires two arms, four arms or six arms. Okay. Here is how we plot this. Here is the caliper. As you can see here, caliper. Caliper goes from 6 to 16. Means 6 in to 16 in. Can we change this scale? No, you cannot. This is an API scale. What's the API? API is the American Petroleum Institute that actually puts the scales for us. So, the scales are controlled by the American Petroleum Institute which is told us for the standard for all

36:58 companies. The the the 6 to 16 is the scale of the caliper. For example, at this depth for example, 3600 m. This is meters, huh? 3600 m, what is the diameter of the wellbore at this point? I can say it is 6 to 16. So, the so the span is 10 divided by five. Because this is 1 2 3 4 5. So, each one of these is actually two. So, this is 6 + 2 is 8 + 1/2. So, it's 8 and 1/2 in hole. So, I can find out the diameter of my borehole at any depth. For sure, if I go at that depth, my diameter will be high. So, I know there is a washout happened here. There is a

37:45 washout out happened there. There is a washout washout here. So, I can actually see how my wellbore look like. Okay? So, by using the caliper, I can determine the borehole irregularity, how irregular my wellbore look like. Okay? All right. Give me Let me give you an example of the six arms. Here is an example of example of the six arms. Here is caliper number one that measure from angle 60 to angle 240. The span is 180°. The second caliper from 120 to 300. The third caliper from 180 to 360. So, I have three three caliper or six arms. Every two arms will measure certain diameter. And

38:30 if you see for example, if you look at this depth, the caliper here reads very high. Yeah? The caliper number one. How about caliper number two? It doesn't read very high. How about caliper number three? It's a little bit of high but it's not as high as the caliper one. So, it's very irregular wellbore. Okay? Very irregular wellbore. That's why in this well, they use the six arms. Why? Because they can are expecting to see an irregular wellbore with the shape that we look at here. If you look at that at that depth for example, you see caliper number three, caliper three reads very high while caliper two does not and caliper one does not. So, the hole is very, very irregular. That's why two arm

39:16 will not do the job. Four arm will not do the job we need to have six arms caliper. Okay? So, as I said, the the tool that you pick and you use depends on your expectation and the situation where your field is, which is mainly the stresses of the field. Okay? Clay zone evaluation. So, we now we understood how we measure the wellbore diameter. How do we measure the clays? And again, I'm not going to call it shale anymore. I'm going to call it clay. Okay? Clay mineral. Yes, clay is a shale, but not every shale is clay. But we will call it clay. For the For For the conventional reservoir, don't call it shale anymore. Shale is not a bad word anymore. Okay? Let's just

40:02 call it clay minerals to make sure we put the names properly. So, clay zone evaluation. Now, we need some physics. What is the physics that we will use to measure the clay zone? First of all, we'll say clays are radioactive. That's a property of the clay. All clays are radioactive. It means they emit gamma rays. Okay? So, the clay zones, you should see high gamma ray. Why? Because all clays are radioactive. They have radioactive elements. Okay? That That's a very good property that will actually make us able to identify the clay zones. Okay?

40:50 They contain radioactive elements. What are these elements? They told us two main elements, potassium and thorium. Okay? So, all clays contain potassium and thorium. Potassium is radioactive. It emits gamma ray. Thorium is radioactive and it emits gamma ray. And all clays, they have potassium and they have thorium with different percentage and different components from one clay type to another clay type. But they all have potassium and they all have thorium. Everybody understand that. Now, we got the physical point here. The physical point is all clays have potassium and thorium. Now, they emit gamma ray.

41:38 So, what is the detection? Well, let's just go and measure the gamma ray. Let's just bring a gamma ray detector. Put the gamma ray detector in the well bore. If the gamma ray detector reads high gamma ray, that's an indication of clay zone. If the If the gamma ray detector does not read high gamma ray, it means it is a clean zone and very very low clay components. Everybody understood this? So, the physics that we will measure is the radioactivity of the clays. We measure the radioactivity of the clay. Whenever we see high gamma ray, we actually raise a flag. This is a clay zone. Okay? So, how does it look? Here is our reservoir and here are the

42:23 gamma rays coming from where? Coming from the clays. All you need to do is you know that there is a gamma ray coming here. Then, here is your tool. What is the tool? It's a gamma ray detector. That's the whole thing. So, you have gamma ray coming from the formation. All you need to do is to put a gamma ray detector in here and you count the gamma ray. Okay? So, when you count the gamma ray with the gamma ray detector and here is the gamma rays. You count the gamma ray. When you see a high gamma ray, hey, that's a flag. This is a clay zone. When I see low gamma ray, well, you know that your reservoir does not have much of clays, which means that clays will not destroy your porosity. Okay? Here is an example.

43:09 Clays here, this is the gamma ray from 0 to 150. Okay? API. I don't want to go into the details of the A or the API or the you will study this information evaluation in the classroom. Okay? So, the scale that the API put together is from 0 to 150 measure. Now, look at this zone. Is it high value or low value? This is high value. What do you make out of this? This is a clay zone. How about this zone? It's a low value. What do you make of this? This is not a clay zone. High value in here, well, a little bit of clay. High value in there, clay. Low value here, less clay and so on. So, from the behavior of the gamma ray, I know where is the clay and where

43:57 is no clay. Where is the clay zones? Where is the clean zones? Okay? And if the clean zones, they contain porosity, that's a possibility of a good reservoir. Okay? So, look at this zone. It's what? It's low gamma ray activity. Look at that at that zone. It's a high gamma ray activity. This means it's a clean zone in the top and it's a clay zone at here. Very simple. So, what did we use? We used a physics property. What is the physics property? That all clays, they contain radioactive elements, which is potassium and thorium. If I count the high gamma ray activity from the potassium and from the thorium, I can clearly identify my clay zones.

44:45 Everybody understand that? Okay. So, this is how the gamma ray works and this how the gamma ray identifies the clay minerals. Porosity measure. We need to you know, somehow understand how we measure porosity. Because it's it's a different thing. Right? And let's let's concentrate on this. Porosity measure. Okay? Let's just look at the composition of the pores. What is actually in the pores? One by one. I have either water or oil or gas. Correct? In my pore space, porosity, this is my pore space. What should be there? Fluids. Correct? What type of fluids do we have? We have hydrocarbon or or water.

45:33 That's the This is the two fluids or these are the two fluids expected in my pore space. Okay? What is water? Water is H2O. Correct? So, it is actually composed of hydrogen and oxygen. Everybody agrees? So, it consists of hydrogen and oxygen. Okay? What's oil and gas? We call this hydrocarbon. Hydrocarbon. What does it mean? It means it composed of hydrogen and carbon. So, the water is hydrogen and oxygen. Hydrocarbon is hydrogen and carbon. Mm, something very important here. The The water and oil, they share what?

46:20 They share that they both have hydrogen. Uh? Look at Look at how people think now. The water includes hydrogen or has hydrogen. Oil and gas, they have hydrogen. Now, if I can measure the amount of hydrogen in my rock, this will relate to the amount of porosity I have. Why? Because the water and the hydrocarbon live where? In my pores. Everybody understand that now? So, the physical property that you need to look at here is that both water and hydrocarbon, they have hydrogen. Now, if I can measure the hydrogen, then that measurement will relate to how much

47:06 porosity do I have in my rock. Okay? Why? Because water and hydrocarbon lives inside or both live inside my my pores. Okay? So, both water and hydrocarbon have a common atom, which is hydrogen. So, the conclusion is if you measure hydrogen atoms, this can be translated to porosity. Very simple. All right? So, we found the physical property here. The physical property that we need to measure that relates to porosity is the amount of hydrogen in my pore space. Okay? Let's just play some of the physics that we used to play before, which is the

47:51 collision. Okay? We can actually say this into mechanics. But mechanics and physics are very much related. If I have an atom here, which is a formation atom, any formation atom. Okay? That atom can be in clastics, in carbonates, in dolomite, in clays, whatever it is. You have an atom here. And you brought a neutron. Listen to this. That's where the word neutron comes in. You brought a neutron. What is the mass of the neutron? The mass of the neutron is one. Okay? The atomic atomic mass is one. The atomic mass of any atom can be A. A or A can be any number. Okay? For example, A for oxygen is is what? Okay? A of oxygen is 16, exactly. A of carbon is 12 and so

48:38 on. So, the amount A is relates to the mass of the atom. Now, if I give energy to my neutron, I give it a very high energy. That neutron will move and hit with the atom. So, I will send neutrons into the formation. The neutron with high energy will hit the atom and the collision will happen. What will happen? Some of the energy will be given to the atom, so it will actually move around itself. And the other one will be taken from the neutron. So, the neutron with the energy E initial, it will have a final energy E final. I'm not actually fond of putting equations into these simple lectures, but I just want to put this one single equation and

49:24 don't worry about that. There will be no more equations. Okay? I just want to give you give you the concept what's really happening here. Now, the question is what is the final energy of the neutron? Okay? After the collision. They gave us this in an equation says the final uh energy of the neutron after the collision, it will be A2, which is this A2 of the atom, minus one, which is the one of the neutron, divided by A2 plus one squared E initial. Okay? So, if it if the A2 is, let's say, 20, it will be 20 minus one over 20 plus one squared and E initial gives you the E final. Okay? Let me ask you a question. What if this atom is hydrogen?

50:13 Okay? And everybody answer the question now. What is the if this atom is hydrogen, what is the atomic mass number of hydrogen? It's one. The atomic mass number of hydrogen is one. Now, let's just calculate the E final if the neutron hits a hydrogen. If the neutron hits a hydrogen, it will be 1 minus 1. Okay? Divided by 1 plus 1. So, what is the final? Zero. This means if the neutron hits a hydrogen, it will die. It will lose its energy. Everybody understand that? Now, if the neutron that you sent to the formation sees a hydrogen, it will hit it and stops and dies. Okay? What does

51:02 it mean? It means you will lose that neutron. Okay? Let me give you an example. Let's say see my sent a thousand neutrons into the formation and I get only a hundred back. What does it mean? It means that 900 died. It means they collided with 900 hydrogen atoms. It means there are lots of porosity in my pore space. But what if I sent a thousand and I got back 900? This means I have only a hundred hydrogens. This means my porosity is low. Everybody understand that now? You send a certain number of of neutrons into the formation and you count what's coming back. If the coming

51:49 back is very low number, this means there are lots of hydrogen there. This means you have good porosity there. If the number coming back to you is very high, this means less hydrogen is in the formation, which means less porosity. Everybody understand that now? So, that's why we put this equation to understand what will happen if the neutron hits a hydrogen. Okay? So, the neutron tool physics is use a neutron source, let the neutrons collide with atoms. Okay? Detection is count the number of of neutrons coming back. So, here here you go. Here is use a neutron source and a neutron detector. Here is the neutron source. Here are the detectors. So, this is the

52:36 neutron source. Here is the neutron detectors. Send Here is Here are the atoms. Send neutrons. Neutrons will interact with these atoms and it will actually go back and will be detected by the neutron detectors. Here is the it's a whole thing. If I have less hydrogen, then I will count much of the neutrons. Why? Because the only one that kills the neutron is a hydrogen. Now, if I have less hydrogen, I will have high counts in my in my detector. It means low porosity. What if I have more hydrogen in my formation? This means I'm not getting much of the counts because what the hydrogen will do to my

53:21 neutrons? It will kill the neutrons. Okay? And it will not be able to come back. Right? So, less hydrogen, it means more counts, it means low porosity. More hydrogen, it means fewer counts, it means high porosity. Okay? Everybody understand that? Okay. Here is actually the neutron tool. It goes from -15 to 45. Okay? 45 is the maximum porosity. It means 45% porosity or -15% porosity. I will ask you a question as an engineer. I'm not going to answer this question because if I answer this question, I need two more lectures. And I think uh Dr. It's not going to give me that much time to to answer the question.

54:08 Is anybody in whoever is watching this lecture expecting to have a negative porosity in your reservoir? No. Minimum porosity in our reservoir will be zero. So, why the American Petroleum Institute put a -15 here? Go ask about it. Go read in the textbook to find out why the American Petroleum Institute put a negative porosity in here. If you can't find this out, contact me. I'll probably will give you an answer. Okay? But it will take some time to really understand that. Okay? Now, the scale is from -15 to 45. Why 45? Because if you study reservoir rock properties, you know that the maximum porosity for the idealistic

54:54 idealistic structure, which is the cubical, is 47%. That's why our maximum porosity is 45%. Now, if I ask you, what is the porosity at that depth? All you need to do is you go from -15 to 45, it's 60. Divided by 10 to each one of these is six. You say it's -15. You add six, it will be -9. Uh correct. You add six, it will be -3 and so on. You add six, it will be three. It will be nine. It will be about 12 or so. It's about 12%. So, the porosity at that depth is 12%. That's how we measure the porosity in our reservoir. Okay? Fluid saturation. Okay?

55:39 Now, we we measure the borehole size. We measure the clay content. We measure the porosity and everywhere we need to find a physical property to to measure. How about the fluid saturation? Fluid saturation is hydrocarbon or what? So, we need to find the physical property to measure. Okay? Let's ask a question. Water is conductive or resistive? Water is very conductive. It means if you put electric current in water, the current will flow. How about if you pass electric current in oil? Will it flow? No. Okay? So, hydrocarbon is hydrocarbon is resistive. So, that's a very important physical

56:26 property. Water is conductive, but hydrocarbon is resistive. So, how can I differentiate between water and hydrocarbon? Go measure the resistivity. That's all. Okay? So, fluid saturation is measured by resistivity. Why? Because we can differentiate clearly. If I measure the resistivity and the resistivity is low, that's bad news because this means it is conductive. Which fluid is conductive? Water. So, this means it's a water zone. How about if I measure the resistivity and it became very high? Then it should be very high. When it shows to be very high, it means that's good news. Why? Because it contains

57:12 hydrocarbon. So, it's as simple as such. Go measure the resistivity. So, the detection is measuring resistivity will differentiate between water and oil. So, to find out your your fluid saturation, do I have oil or gas or or water, go measure the resistivity. All right? Now, let us understand this resistivity thing. We all know Ohm's law. Every one of us know Ohm's law. What's Ohm's law? Okay? If I have a piece of rock and you put a battery, uh just a theoretically, you put a battery, and you put an ammeter here to measure the the current. You know the voltage, you know the current. What will happen? You can actually say the current will go through it if it has water.

58:00 Okay? And you will say that Ohm's law will say I, current, equals voltage over R or I can measure the resistivity as voltage over current. Very simple. So, all you need to do is to pass a current into the formation. And you measure the resistivity. As simple as such. All right? Okay? So, if hydrocarbon exists, what's going to happen? If the hydrocarbon here exists, uh in this case, your current will be less and your resistivity will be high. Very simple. Do actually they did this? Yes, they did. And let's see how the how the tool works. Here is your well bore and here is your tool. The tool is composed of a current source Okay? And emits a current into the

58:48 formation. And there is a current receiver or current return. You send the current and it returns to to the current receiver. All right? So, you know the current, you can measure the voltage, and you can say in this case, I can calculate my resistivity. But you need the current to flow from the tool to the formation. That's why the mud has to be conductive. What What about if the mud is resistive? Well, we'll talk about this in a second. But you need the mud I need a conductive mud. So, when should I apply this tool? I should apply this tool if I am drilling with a conductive mud. Okay? I'm very sure in the drilling fluids, you heard about oil-based mud.

59:35 What's an oil-based mud? You drill with certain type of oil or synthetic oil, whatever it is, which is resistant. So, in case of oil-based mud, this tool is not going to work. We will find a different way of measuring the resistivity. Okay? Everybody understand that? All right. So, you have a current source, you send the current, and you receive the current at the other side. All right? Here is the conductivity. Then, we call this lateral resistivity. When you hear the word lateral resistivity, it means the resistivity that works with Ohm's law. You send the current, you receive the current, and then you measure the resistivity. Okay? Here is the resistivity. It's actually on a logarithmic scale. Resistivity can be as high as a thousand

1:00:22 ohms, two thousand ohms. So, we have to put them on logarithmic scale. So, the reason for the logarithmic scale is because they are very high values. Okay? All right. And you can see right here. Here is from 0.2 to 2,000 as resistivity. Here is a lower resistivity than this zone. Okay? So, what do you make out of this zone? This zone has high resistivity or low resistivity? It has low resistivity. It means this zone has high resistivity. This means this zone has low hydrocarbon volume. This zone has high hydrocarbon volume. No question asked. Okay? Okay. At the same time, if you look at the gamma ray here, is it high gamma ray or low gamma ray? It's low gamma ray. So, is there any clay in there? No, not that

1:01:10 much clay. Clay means high gamma ray. So, this actually low gamma ray has very high resistivity. This means this zone is a potential reservoir. Why? I have pores that does not contain clays and is very resistant. Come on. Pores that doesn't have clay and very resistant, that's an excellent reservoir. So, that's how I define my reservoir. I look at the gamma ray. If my gamma ray reads low, then I look at my resistivity. If my resistivity reads high, good news. Why? This means I have a clean zone that has high resistivity. Okay? And we'll talk about the the

1:01:55 porosity as well. You can also check the porosity value and see how much porosity do you have. So, if I have low gamma ray and high resistivity and good porosity, it's my excellent news of the day. I have a good reservoir. How about this zone? This zone has high gamma ray. Is it a reservoir? No. How about the resistivity? It reads low. So, when I see high gamma ray, it's not a reservoir. Resistivity will not read high. When I see high Why? Resistivity is decreasing. How about this zone? It's the same. You see high gamma ray, you see low resistivity. Okay? Resistivity is decreasing and so on. Okay? So, expectation is when you see high gamma ray, you don't see high resistivity

1:02:40 because it's not reservoir, it's clay minerals. High gamma ray means clay minerals. Everybody understand that. Okay. All right. So, never forget this. What's the reservoir properties on logs? Low gamma ray. That's a reservoir. High resistivity, reservoir, and porosity. Okay? Okay? Non-reservoir property is what? High gamma ray, low resistivity. That's very important. When you look at any of these logs, look first at the gamma ray. Is it low or high? If you If you see low gamma ray, look and look at the resistivity. If it's high gamma ray, here you must actually highlight this zone as a potential of being a

1:03:27 reservoir. Okay? All right. Okay? We talked about the resistivity in conductive mud. I think I will I will I will cover this one and then quit because the uh um taking too much time, I guess. So, how about the the resistive mud? How about How can I measure the resistivity of a resistive mud? I cannot use Ohm's law. Everybody understand that? Because I need to inject current. You cannot inject current in oil. It's not going to go. Okay? Oil does not conduct current. Okay? What do you need to do? It's a very interesting idea. Actually, we put a tool that uses electromagnetic wave. Uh so, this is the property now that we will look at. We use electromagnetic

1:04:15 wave. What this electromagnetic wave will do? We need to understand first of all, what's the electromagnetic wave. Okay? If you look at this this tool here, it has these three line red red lines here or red uh uh sections here. We call these transmitters. They transmit electromagnetic wave. What happens? Electromagnetic wave is actually takes this form from the physics. This what the electromagnetic wave form is a sinusoidal wave. Okay? Every electromagnetic wave is denoted by two things. The first one on the x-axis is an angle. The angle here for every cycle. Here is zero, and here is 360, and go for the

1:05:02 second cycle, third cycles, and so on. So, this is an angle. We call this angle phase. So, the word phase in physics means angle. Okay? Okay. How about the y-axis? Y-axis is the amplitude of the wave. The amplitude of the So, every wave has two things. Has amplitude and it has an angle. All right? They found Look at this. If you send this wave into the formation, the wave will change. It will actually some shift will happen. That shift that happens on the wave relates to the resistivity. What do you mean What do I mean by this? Let Let me Let me see this.

1:05:47 Here is this the wave after it was sent to the formation. What happened to this? First of all, what happened is the the amplitude is reduced, reduction in amplitude. And at the same time, there is a change in the angle. So, there's a reduction in the amplitude and a shift in the angle. That reduction The amount of reduction of the of the amplitude and the amount of shift that happens at takes place to the wave depends on the resistivity of the rock. Everybody understand that? So, you send the electromagnetic wave, then you measure it coming back. Okay? You measure what? You measure the

1:06:33 change in the amplitude. Okay? And you measure the change in the angle. The change in the amplitude and the change in the angle will relate to how resistive your formation is. Everybody understand that? So, you send the electromagnetic wave, and you receive the electromagnetic wave in the receiver. Okay? So, you send them from the transmitters, right there. Here are the transmitters. If I can If I can point to this. Where is Where is it Where is it Where is it? Here are the transmitters, and here are the receivers. You send the wave from the transmitter, and you receive them from the receiver. And you receive the wave, and you see how much shift it happens and how much reduction in

1:07:18 amplitude it happens. Then you take these values, and you measure them. You actually have attenuation resistivity coming from the change in the amplitude, and you have phase resistivity coming from the change of the angle. Okay? What you do, you measure the phase shift, and you translate it to resistivity. And you measure the the attenuation, which is the amplitude, and you change it to to resistivity. And as I said, we call this tool induction tool. So, you have two tools. Lateral tool that follows Ohm's law, induction tool that uses electromagnetic waves. Okay? And I think uh I probably need to stop here

1:08:04 uh because it's already overdo the time. Am I okay on time, or should I continue, or how's it coming? Should I continue on this, Mr. Ahmed? Hello? I think we can do 5 minutes more or so. Yeah, yeah. We we can do like 10 minutes, and we can keep the questions for a different session, like uh a Perfect. Okay. Thank you. So, uh now, if we move to the density tool, again, for any tool, you have to have a physics property, physical property to measure, and a detection methodology. Okay? The physical property should What is density? From the definition is density is

1:08:51 actually mass over volume. Correct? True. What if I assume that the volume is one? So, you're actually getting the density of cubic foot or cubic centimeter, whatever you like. Okay? So, if I take the volume as one, then the density relates to mass. Okay? So, if I need to measure the density, then look at the mass of unit volume. The mass of unit volume is related or relates to density. Excellent. Okay? Now, measuring the mass will relate to density. That's what the physical property that we need to measure, okay? Yeah. If you look at any atom, where is the mass? Is the mass in the electrons or the mass in the nucleus?

1:09:37 The mass is in the nucleus. Okay? So, if I actually look at the nucleus, this is where the mass of the the atom is, which if you come and all the atoms together through this is what the total mass is all about. Okay? But, let's look at this. In any rock, number of electrons equal number of protons because the atom has to be neutral. In our rock, because our rock is not radioactive, what is the radioactive rock? Clays. But, our reservoir is not radioactive. So, if you are if your rock is not radioactive, we call it a stable rock. Stable rock, number of electrons equal number of protons equal number of neutrons. This means,

1:10:23 if I measure electrons, multiplying by two, that will relate to the mass. Why? Because the mass is in the nucleus. What's in the nucleus? Neutrons and protons. But, the protons number equal to the electrons. And the neutron numbers equal to the protons as as as as we said in our rock, because it's not radioactive, okay? This means, if I measure the number of electrons, multiplying by two, that gives you the number of all the element in the nucleus, which relates to the mass of the nucleus, which will relate to the density of the nucleus. So, the whole idea here, can you measure the number of electrons? If you measure the number of electrons, multiplying by two,

1:11:09 okay? They will relate to the mass of the nucleus, which will relate to the total mass of the material. That's what the mass is. Mass is coming from these components, okay? All right. So, the whole idea, measure the number of electrons. So, detection is electrons measurement. That's what the density tool is all about. So, what does the density tool measure? Measure electrons. Why the tool measure electrons? What's the relationship between density and electrons? It's simply because if you multiply the number of electrons by two, it's equivalent to the number of constituents of the nucleus, which is where the mass is. Okay? The mass is the number of protons and the number of of neutrons okay?

1:11:54 How do we measure electrons? Here how it goes. Here are the atoms where the where the electrons are rotating around the nucleus. So, what we do, we get a gamma ray source at low energy. Why is low energy? Because we don't need the gamma ray to go deeper. So, we send the gamma ray to interact with the electrons. If you have too much electrons, the gamma ray will lose a lot of energy. If you have less electrons, gamma ray will lose less energy. So, we send the gamma ray and we count the gamma ray coming back. If the gamma ray loses too much energy, this means this element is heavy and we can relate this to density. If the gamma ray didn't lose much energy, this means this element

1:12:41 does not have much of protons, does not have much of neutrons, okay? So, it is light element and the gamma ray energy will be will be a little high, okay? So, that's the whole idea. You just send this and you measure measure the gamma ray. So, again, source, which is the gamma ray source, you send the gamma ray source and you receive it into a detector, yeah? And the gamma ray collide with formation electrons, their energy is reduced and the reduction of energy is inversely related to density. It means, if the reduction energy is high, if it loses a lot of energy, so, loss high loss of energy means high density. Low loss of energy means low density. Okay? All right. So, that's how

1:13:28 we measure the density. And again, here is the neutron tool that we put from -15 to 45. The scale of the density, which is the red color, here is the red color. This is the density from 1.95 to 2.95. There is a reason for this is for that

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