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For the seventh day, we had a lecture by engineers. We learned from him that Oil Rocks is exploited with two deposits( Neft Dashlari and Palciq Pilpilesi), there are 514 wells now and 492 of them are active, 21 of them are not active, just one well is at the appropriation stage, and the average amount of oil extracted from one well is about 5.5 tonnes. Furthermore, we knew that there are seven oilfields and just two of them are stationary sea oilfield( 1887 and 2585 numbered).
Additionally, for now, there are 72 oil-gas extraction platforms and 31 of them are isolated from the land and are quite in the sea. It is also distinct to us that until now 2280 wells were drilled. We also talked about the types of wells. For example, all wells in Oil Rocks are divided into three types of group. First one is active wells, the second one is nonactive wells, and the last group is called appropriation. The first group itself is divided into two parts, wells that are active now and wells that are not active temporary.
The next one also divided into two parts, nonactive from this year and from last year. If we are not able to extract oil from a temporary nonactive well during 45 days it means this well belongs to nonactive group from this year, if this process is continued for one year it means that it belongs to the nonactive wells group`s last year part. Until we get oil from well it belongs to the group of appropriation.
During this stage, different processes are ongoing for the well in order to get oil from it. They also said that some wells may be canceled for some reasons.If there are not any productive layers of the well, in this case, it is canceled. Furthermore, if any platform was destroyed, and the amount of money that is important for the recreation of that platform is more than the money that we can earn from it in the future, it means, wells that were active there, must be canceled.
If the height of the cylindrical hole is quite bigger than its diameter, and creates a relationship between different layers and surface, in this case, it is called well.
Now, we also know that there are three types of exploitation. First one is natural(fountain), Gas Lift(by injecting gas), by special apparatus(pump). Actually, in Oil Rocks, 44 wells are exploiting by the first method, 8 ones with the third method, and others by means of the second method and this is carried out by the pressure of the gas that gathered behind the pipe and forces the fluid to go up. After extracting oil by the first way, oil is committed to separators and here gas released form oil, then it is going to oil collection area and connected separator devices. In the case of the second way(most using way) product is going to technological block, gas is released, water is going down, and oil is collected by the pump and is pumping to collectors.
Furthermore, almost all platforms are provided with drainage tank located under them, that all waste fluids are going there.
Today, we went to 418a area again in order to monitor the wellhead construction and the process itself after the lecture of engineers. After that, we had a lecture about types of logging that utilized in there, in the room of the department. Geophysical research methods are based on the lithology of rocks, collector characteristics, water-oil-gas saturation and a number of physical properties. Consequently, geophysical surveys are underway in the wells. They introduced us mainly three types of it. Electrical, radioactive, and acoustic logging. For the first one, it is important to measure the resistivity of layers by creating an artificial electric field in the well and examine the characteristics of the electric current that occurs naturally around it. It is obvious that oil does not transmit electric current and it is one of the main principles of this method. If we know the specific resistance and conductivity of a well’s rocks, we can judge about the lithology of different layers on the logging diagram. Methods of radioactive logging are studied in natural and artificial radioactive areas of the environment. Natural radioactivity is called the process of splitting atomic nuclei. As a result of this process, ?-?-? rays and some elementary particles are formed. Artificial radioactivity determines the nuclei of atoms with electrons, protons, neutrons, and so on. The intensity of the emission radiation resulting from exposure to artificial irradiation is measured. When studying these areas, the natural radioactivity of rocks determines the interaction of neutrons with the ? rays of rocks. As a result, the choice of collectors, density, porosity and lithology of the layers is determined. In addition to other geophysical complexes, it is possible to determine the porosity, oil and gas saturation, water-oil, gas and oil, gas-liquid contact and residual oil and gas saturation.
Furthermore, we also learned a type of logging that is called gamma-ray logging(GRL). A special device is putting into the well and is raising with stable speed from down to up. The main objective here is to study the intrinsic nature of the naturally occurring ?-radiation field along the cross-section. The intensity of this naturally occurring area depends on the radioactive elements in the rocks. By studying this area, it is possible to divide the well cut into clayey and clay-free layers.As a rule, in the GRL method diagram appears the maximum curve in front of the clay layer and the minimum values in front of the sand layers. The primary logic for this is that the clay layers contain a potassium isotope (Ca). Another reson for this is that sandy layers which contain oil have high reisitivity, while layers with water have low resistivity.
We also talked briefly about the last one, the physical principle of the acoustic logging is based on the speed of the kinematic and dynamic specifications of elastic waves and time period for the extinction of them. Generally, speaking the most using method in Oil Rocks is GRL and electrical logging.
Our tutor engineers also gave us some information about the process of the casing and cementing.
Every well drilled is in need of casing and cementing. The casing is a steel pipe and prevents the hole from formations(which can cause many problems). Generally, there are four types of pipes, Conductor, Surface, Intermediate, and production casing. The main purpose of the first pipe is to block off the well from the water of the sea, and it is the biggest part in terms of the diameter of the hole, while is the shortest one in terms of the height. After that, there is surface casing, it protects the zone from damage by additional drilling operations. Following this, we have the longest section of the casing in the well which is called intermediate, and it disconnects formations that can cause a lot of problems for the process. It also may be located in the abnormally pressurized zones. Finally, production casing(the smallest one in terms of the diameter) that isolates producing zone and also protect the special device that is using for the perforation process. Usually, this action is used to form a path for the passage of oil. To accomplish this process, perforators are set to the wanted depth, and when they are fired, the casing or formation is perforated.
The casing has to be cemented and for this aim a type fo device pump cement down inside of the casing and up the annulus.This safeguards installed pipes from external dangers.
In that day, we had a lecture with an engineer from the department of geology. Firstly he talked about the types of rocks(it was the first lecture that we had learned this in our university as second-year petroleum students). Generally, there are three types of rocks, Igneous, Sedimentary, and Metamorphic rocks. Igneous rocks are constructed as a result of solidification of the liquefied rocks. These substances come from the bowels of the earth. Igneous rocks are divided into two types that are formed by the expulsion of volcanoes onto the surface of the Earth (extrusive) and those that penetrate into previously formed rocks (intrusive).Sedimentary rocks are assembled as a result of the amassing of particles.Following the action of transportation, by the help of compaction buried substances accumulate. It has three types, namely Clastic, Chemical, and Organic. The first type is usually established by the help of erosion of rocks that were existing in old periods. After that, there is a process of transportation of little substances by the help of water or air, and finally, they accumulate and our sedimentary rock is ready.The second one is usually developed straightly by the chemical process in which a solid substance is produced from a liquid.The last type consists of the remnants of old members of fauna and flora.Additionally, he told and we also know that oil is extracted mainly from sedimentary rocks. We also discussed the Rock Cycle that all types of rock can be formed from each other. Metamorphic rocks are created by the process which is called metamorphism. This process is going with two ways, by heating or compaction with heating. Generally, it is resolidification of previous rocks.
He also talked about the different periods of exploitation of an oil field in Oil Rocks. There are different stages from the beginning to the end of the operation. He divided the whole process into five periods. In the first stage, the rate of extraction is increasing until the maximum value of it, and it is the end of the first period. During the next period, this value is stable but not exactly, because, it can decrease by about ten percent of the maximum rate, and this can take one to ten years. During the third period, it is decreasing, despite the actions that applied for stabilization of its value, and it is quite possible to say that the main reason is a decrease in the amount of energy of different layers. It continuously decreases during also IVa period and it is the longest one. In that time, the extraction rate of oil is quite poor, because of the low energy of layers, some problems related to watering and sandy plug in the well. After that, by the help of some actions with new technology and injecting some chemicals(with the aim of increasing the extraction rate) it can be again increased for some period of time. And the last period is called IVb, and in this period rates are again not sufficient.
It is required quite much time for the creation of oil, and there are some theorems about it, however, our tutor engineer said that he believes mostly organic theorem. What is organic theorem? for this, animals or plants that were existing in old times, died or destroyed, and their bodies were mixed with land, and after many years(thousands or millions years) they were covered by different layers and help of the pressure and heating there, our oil is formed.
In the last day, we had again a type of lecture, and during that time we mainly discussed our knowledge that we had gained in Oil Rocks from engineers that are working in different departments. In addition to that, they talked about the problems that appear during different periods of the process in that area. For example, during the process of exploitation in many wells, there is a quite distinct manifestation of sand, water. Despite the fact that many actions are applied in order to solve these problems, for example, cementation of the bottom of well, injecting some chemicals, and by using some new technologies, however, they complicate the process and those actions cause some extra expenses.
Furthermore, in some areas(mostly in 46 wells), the extracted oil contains some amount of sulfur and it is deteriorated the condition of pipes and after some period of times, those pipes must be changed. They said that some new apparatus and chemicals are using for this problem(“PADUS”, and “SNPX-2005” respectively), but they did not say anything about the main working principles of them.
In the second half of that day, we had a meeting with the chief of Oil Rocks. He talked about the profit of ten days of practice for us, then he asked some questions from us, about the condition in the dormitory, parks, cafe, quality of the visits and lectures, behavior of engineers with us, and finally he also asked from us our plans about working there in the future.
In conclusion, it is quite tangible to say that we have finished our internship quite successfully and profitably. It is undeniable fact that I am a second-year student and we had not learned theory part of these processes, that is why it was quite difficult for me to understand the whole process that acting on there, however, by the help of clear explanations of engineers, and by visiting different fields, and platforms we were able to see by our eyes and understood the crucial processes. Furthermore, we could get the chance to see the life of workers in that area. I strongly believe that during the next years, it will have a quite positive effect on the process of learning university materials, and will give a strong motivation to learn as much as I can in order to be a professional petroleum engineer.
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