Each of these different deposits requires a different production technology. The easiest is when you have a nice accumulation, and this accumulation is under a cap rock and it is on-shore. This is what we find in many parts of the world, but especially in the Middle East. In places like Saudi Arabia, Abu Dhabi, Kuwait. There, you have huge accumulations of oil and it's very easy to produce it. All you need to do is to drill a well, perforate the cap rock, and then you reach the level where oil is contained. Because oil down there is under pressure and it is hot, it will come out spontaneously. So in the past when people were drilling wells, they were reaching a deposit of oil, they were very happy and you had what they call at the time a gusher, an oil well that had a fountain of oil coming out, and you can see a picture that looked for, it's a picture from the 19 twenties. This is the field of Baba Gurgur, which is the first major discovery in Iraq. Look at the way in which the oil comes out like a fountain, and people would be very happy. You can see perhaps a little river coming from the well and that river is a river of oil, and in other cases that have been leaks of oil created by this phenomenon. Today we would call this an environmental disaster. At the time, they were very happy. Today we call this a blowout and we want to avoid at all conditions blowout, we want to make sure that there is no oil that escapes into the environment. That we control every drop of oil that comes out of the well. When it comes to deep offshore, if instead of operating on the ground, we are operating at sea, then the matter becomes more complicated. If we are deep offshore where we cannot have a platform with legs that reach to the bottom of the sea, then we need to use a ship. These are very special ships, you see an image of a ship of this kind, which are capable with propellers. They have generally at least six propellers that can be directed in all directions so that the ship is capable of sitting immobile on top of the place where they want to drill the well, and this is out in the ocean where there are hurricanes, where the sea can be very bad, and it's very difficult to operate, and yet we are capable of keeping a ship absolutely steady on top of a well and drill in this well. So imagine you have 3,000 meters of tubes going through the water, then reaching the bottom, then starting drilling and going further another maybe 3,4,5, or 6,000 meters. It's a very complex technology. It's a very difficult thing. The opposite case is when we have oil that has not found a cap rock and comes to the ground or very close to the ground. That is the situation with tar sands in Canada. Then you use methods like strip mining. The oil is basically solid. It's mixed with sand and you have to scoop it up and then wash it in order to separate the sand from the oil. You do that with a lot of water, generally hot water. Because the hot water facilitates the process of separating the oil from the sand. Of course, that is an expensive and challenging process. But the challenge is entirely different from producing oil in the deep offshore. Finally, we have something that has become better-known recently because there is a boom of that in the United States, and that is shale oil. Shale oil is oil which has formed in the crust of the earth but has being trapped in a rock which is not porous, and it cannot flow away from this rock. So if you just drill a conventional well in this rock, there will be very little oil going into the hole that you have drilled. So in order to increase the production and make this meaningful and profitable, you have to fracture the rock around the well, around the hole that is well. So that when you fracture it, there are veins that open in the rock and through these veins, the oil which is trapped in the rock can flow into the well, and will come to the surface. This is what we call hydraulic fracturing or fracking, which is a very controversial, has become a very controversial technology or technique. Although, it has been in use for many many years, and it has been in use much before even for conventional oil deposit, much before the recent developments. But the scale at which it's being used these days is without precedent. So in order to exploit a shale oil deposit, you need to drill a well. We have learned how to drill horizontally in the ground. Vertically first, then we reach the level where the oil is contained, and we continue horizontally. This allows us to have a well that has a large surface of contact with the oil reservoir. Because you have to keep in mind that the oil reservoir is not very thick. Maybe you are drilling 4 or 5,000 meters below, at least 3,000 meters below. You may have a few meters of oil baring rock or up to a few thousand meters in the major fields. In the Middle East, you may have 100 to 100 meters. But it's not a huge thickness. So in order to increase the contact, you have to drill horizontally into the formation so that more oil comes out of a single well. In the next unit, we have selected a few short videos to illustrate these different methods, and this will be more clear than I can tell you in words. I hope that you will find them clear and instructive. The important thing, remember the following. Drilling a well is always a risky matter. You never know what you will find. So it's risky because it's expensive. It's risky because when you come to the end of it and you have reached your target, the formation that you had seen with your exploration techniques, you may find out that there is nothing there. Maybe just contains water. There is no oil. Maybe it contains gas, which is much less valuable. So there is a significant economic risk. At the same time, there is an environmental risk. Because if the job is not done properly, a lot of damage can be made. If the job is done properly, then we know how to avoid damage. In theory, a well drilled well is not going to cause any damage. But this is the theory and then there is practice, and sometimes practice is not in line with the theory.