History and Chemistry of Petroleum Extraction

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From searching for oil to utilizing it, there are roughly four main stages: exploration, extraction, transportation, and processing. These four stages are generally referred to as “oil exploration,” “oil field development,” “oil and gas transportation,” and “oil refining” respectively. Let’s trace the development history of the oil industry through these four stages. “There are many methods for oil exploration, but whether there is oil underground must ultimately be confirmed through drilling. The degree of progress in drilling technology often reflects the development status of the oil industry; therefore, some countries compete to announce that they have drilled the world’s first oil well, as a way to show that they were among the first to make advances in this industry. “\"Oilfield development\" refers to the process of using drilling to determine the distribution of oil and gas, and to having wells that can be put into operation to achieve a certain level of production. In this sense, the development of the Ziliujing gas field in Fushun County, Sichuan, in 1821 was the world’s earliest natural gas field. “The technology of oil and gas transportation also emerged as oil and gas exploration progressed. Around 1875, the Ziliujing gas field utilized locally abundant bamboo as raw material; the bamboo was stripped of its nodes, wrapped in burlap and coated with tung oil to create what we now call \"gas pipelines.\" These pipelines had a total length of two to three hundred miles. In the Ziliujing area at that time, these interconnected pipelines crossed hills and flowed through valleys, forming a gas transmission network that allowed natural gas to be used not only near the wells but also at distant salt production sites. This facilitated the development of the gas fields, resulting in an annual production of over 70 million cubic meters of natural gas. As for \"oil refining,\" its origins go even further back; the \"Commentary on the Waterways,\" written during the Northern Wei Dynasty around 512–518 AD, describes the process of extracting lubricants from oil. British scientist Joseph stated in a related paper: “By the 10th century, China already had oil and used it in large quantities.” It can be seen that the Chinese were already distilling oil long before this. This shows that the technology for refining oil emerged in our country as early as the 6th century AD. Oil exploration refers to the study of geological history and geological patterns in order to locate oil and gas fields. It mainly involves four steps, namely: determining the extent of ancient lakes and oceans (ancient basins) ； Then, the deep depressions that could produce oil are identified from these; the third step is to look for geological traps around such oil-producing depressions that are conducive to the accumulation of oil and gas; finally, drilling is carried out on the most promising traps to determine whether there is oil or gas present and to ascertain their reserve volume. The following describes the tasks involved in these four steps. (Specific oil exploration techniques will be discussed in detail later.) (1) Determining the extent of ancient lakes and oceans: As mentioned earlier, oil is formed in the sediments of ancient lakes or oceans, and oil fields also develop in these areas. Therefore, determining the location and extent of ancient lakes and seas (i.e., ancient basins) is of primary importance. The geological basis for determining ancient lakes and seas mainly comes from the study of rocks and fossils (the remains or impressions, traces, etc. of organisms preserved in ancient strata). Through the research of geologists, there are now a great many types of rocks on Earth, but they can be broadly divided into three categories. The first is igneous rocks (also known as magmatic rocks), which form when magma from deep within the Earth erupts to shallower layers or the surface and then solidifies. The spectacular scenes of modern volcanic eruptions have been reported on television many times, making it easy to understand the origin and formation of such rocks. The second are sedimentary rocks; their origin and formation process were discussed earlier in the context of oil and gas formation, and they serve as the primary material basis for identifying ancient lakes and seas. In other words, where there are sedimentary rocks, there were ancient lakes or oceans, without a doubt. Third are metamorphic rocks, which are various types of rocks (including igneous and sedimentary rocks) that have undergone changes in their original properties due to high temperatures and pressures during the transformations in the Earth’s crust, resulting in another type of rock that is both hard and dense. So, how are ancient lakes distinguished from ancient oceans? This is mainly determined and differentiated through fossils. Because the biological characteristics of lakes and oceans are very different. Furthermore, even among the same sedimentary rocks, the physicochemical properties of lake and marine rocks differ. Simply put, it is classified based on the salinity of the water at that time: fresh water corresponds to lakes, while salt water corresponds to seas... The preservation status of ancient lakes and seas is of great importance for oil and gas exploration; during subsequent geological changes, they may have suffered from weathering and erosion, resulting in incomplete conditions ； or be damaged by the intrusion of igneous rocks ； Or through severe metamorphic processes, etc.; in all such cases, it is necessary to determine their formation process by examining aspects such as the properties of the rocks and the degree of preservation of the strata. (II) Determining the location of the oil-generating basins: Whether they are lake basins or sea basins, their area is very large, usually exceeding tens of thousands of square kilometers. Basins as large as China’s Tarim Basin cover more than 500,000 square kilometers. The shape of the basin floor is also uneven and irregular, with variations in height and depth. The lower areas are referred to as depressions, while the higher areas are called elevations or protrusions. Generally, the remains of aquatic organisms tend to accumulate in the lower parts of the basin floor; therefore, depressions are considered to be areas within the basin that are favorable for oil formation. Of course, deeper depressions are preferable. Thus, after determining the boundaries of the basin, the next step is to identify the locations of the deepest depressions, that is, the places where more oil and gas can be formed. (III) Searching for geological traps – Searching for geological traps is the key step in locating oil fields. Any oil exploration department attaches great importance to this work. Geological traps vary in size and depth, and come in various shapes. For example, the Daqing Changyuan structure in the Daqing Oil Field has an enclosed area of over a thousand square kilometers, making it the largest oil reservoir structure discovered in China to date. Of course, there are also those that are less than one square kilometer in size; some individual oil reservoirs consist of just one oil well. Some geological traps can be partially exposed above the surface; even a mountain can constitute a complete geological trap ； Some are buried very deep, and they are completely invisible from the surface. At present, the depth at which traps can be detected in our country is around five to six kilometers. At such depths, it is possible to determine their location with relative accuracy using artificial seismic methods, and drilling can also be used to reach them. Finding traps is also a process that progresses from the shallow to the deep, and from the large to the small. It is of course very difficult to locate deep and small traps, as it requires a much higher level of technical precision and complexity than in ordinary cases. After identifying a geological trap, it is also necessary to conduct research and evaluation to determine whether the trap possesses the conditions for oil storage. Generally speaking, geological traps near oil-generating depressions are conducive to the migration of oil and gas, making them promising oil fields, while traps in other locations are assessed as being of lower quality. Furthermore, factors such as the integrity of preservation of each trap itself and the amount of oil it can store also need to be studied and evaluated. (IV) Drilling oil and gas fields: It is generally difficult to draw a conclusion as to whether oil or gas is stored in the geological traps that have been identified, without drilling to verify them. Therefore, drilling geological traps is the final step in searching for oil fields, and it is an extremely important and crucial step. Its importance and significance lie in the fact that all the techniques and methods employed in this step are related to whether an oil field can be successfully developed and what its ultimate fate will be. There have been many such cases in the history of oil field discovery: a reservoir that was originally filled with oil failed to yield its hydrocarbons due to improper drilling techniques and methods; it wasn’t until years later, when people recognized it again and drilled there once more, that it was confirmed to be an oil field ； In some cases, oil layers were discovered during the first drilling attempts, but the oil and gas could not be extracted or the production levels were very low; as a result, these sites were deemed to have no industrial value and were abandoned. However, subsequent re-drilling or the application of certain technical measures enabled high-volume oil and gas flows to be produced. It is evident that drilling is a crucial step in discovering oil and gas fields; its relationship to the preceding tasks is akin to nine months of pregnancy followed by childbirth, so it must be taken very seriously. Determining the location where the first exploration well or wells should be drilled within a basin or an enclosure requires taking various types of data into consideration. In fact, the possibility of discovering an oil field with the first well drilled is relatively low. For example, in Karamay, Xinjiang, oil could be seen due to the presence of Heiyou Mountain, and it was from that first exploration well that oil was produced. As for searching for oil fields in the coverage area in eastern China, it is not so easy; the first oil-producing well at the Daqing Oil Field was Well Songji 3, which indicates that there were at least two other wells there prior to that ； Hu8 was the first oil-producing exploration well in the Shengli Oilfield, indicating that at least 7 dry wells had been drilled prior to it ； The Dagang Oil Field was discovered only after drilling nearly 20 exploration wells ； The first oil-producing well in the Renqiu oil field was Well Ren 4; before it, more than 5 wells had failed to produce oil. Of course, determining the location of exploration wells is not done without any guidelines or in a completely random manner. Simply put, exploration wells aimed at finding oil (while wells intended to identify geological formations are called reference wells or parameter wells) are always located as high as possible within an accumulation, and the reason for this is that oil and gas always float on top of water. The so-called “height” here refers to the height of the oil-bearing layer. The geological structure is extremely complex, so \"high\" is not an absolute term. To put it vividly: if the structural feature to be drilled resembles an upside-down bowl or basin, the first drilling site will be located at the bottom of that bowl or basin; if it resembles a fish lying vertically, then the first well will be drilled at the height of its back ； If the trap resembles an inclined plate (like in Karamay), the exploration well is located above it. There are also very few exceptions; for instance, in most people’s hair is thickest at the top of the head, while those who are bald have hair only around the edges of their head. Attempting to cut hair from the top of the head is pointless. There is an example from the Junggar Basin in Xinjiang: in the 1950s, a drilling well was built at its highest point, but no oil was found. In the 1980s, wells were drilled at lower points around that area, and oil was discovered there. Using the analogy of hair around a \"bald spot,\" there is indeed a similarity. There are indeed cases where oil has been found in the \"pelvic floor\" area; it’s like adding some oil to a wok used for cooking – the oil can’t stay at the rim of the wok. This is because there is almost no water in the strata here, and oil doesn’t have the advantage of density differences to allow it to float, so it has to \"sink to the bottom.\" Such cases are rare, which is why \"looking for oil in higher areas\" remains the principle that should be followed first. When a geological trap is drilled and a well produces oil or gas of industrial extraction value, an oil field has been discovered. However, it is still necessary to further clarify the specific scope of this oil field and its oil production capacity. Therefore, once oil and gas are detected during drilling, it is necessary to immediately determine the number of oil layers, their depth and thickness. The lithology and other physical properties of these oil layers must also be identified, in addition to testing their oil and gas production capacity and analyzing the properties of the crude oil. Then, expanded drilling is carried out to further determine the oil and gas presence within the trap, and to calculate the amount of oil and gas reserves underground. In this way, for an individual oil field, its preliminary exploration work is considered complete. Finally, it should be noted here that in the actual process of searching for oil fields, these steps cannot be carried out completely separately; rather, they are always interrelated and take place simultaneously. In the process of searching for structures conducive to oil generation, geological traps are often discovered simultaneously; while looking for such geological traps, new sedimentary layers or new structures capable of oil generation are also found. During drilling in these traps, new oil-bearing layers and reservoirs are discovered as well, thereby providing people with many new insights. Overall, the process of searching for oil fields is, on the one hand, a process of continuously gathering information and deepening understanding of underground conditions, and on the other hand, a process of continuous improvement in oil exploration technologies. Oil field development: After geological exploration identifies oil fields of industrial value, preparations can begin for their development. The development of any mineral resource must take its economic viability into account. In other words, it is necessary to achieve low input costs (i.e., spend less money), high output (i.e., extract more ore), and ultimately a high recovery rate. For the development of an oil field, the goal of ensuring effectiveness is to extend as much as possible the period during which the field can produce oil at high levels, so that the maximum amount of crude oil can be extracted from it, resulting in a high final recovery rate and good economic outcomes. However, achieving this goal is not easy. Due to the differences in the geological conditions of various oil fields, the levels of natural energy present, and the properties of the crude oil, it is necessary to determine what development methods should be employed for each oil field. Additionally, it is important to decide how to strategically locate the production wells. What should be the annual production volume of an oil field? These are all fundamental issues that must be carefully studied and determined before starting the development of an oil field. Furthermore, since oil fields are buried underground and constitute hidden entities, during extraction the oil, gas, and water within them are in constant motion and change; this fluidity is a characteristic that other solid mineral deposits do not possess. Therefore, to develop oil fields effectively, it is necessary to continuously adjust various measures during the development process to adapt to changing circumstances ； At the same time, it is also necessary to continuously modify the oil layer so that it can change and develop in a direction predetermined by people and conducive to exploitation. This is an issue that needs to be continuously studied and resolved during oil field development. Furthermore, during oil field development, it is always necessary to have engineering technologies capable of adapting to changes in underground conditions in order to achieve effective development goals. That is, advanced oil extraction technology is required ； Advanced monitoring and observation technologies ； Advanced reservoir modification technologies and sophisticated management methods are used to ensure the implementation of development projects. Overall, the process of oil field development is one of continuous understanding and adjustment; advanced methods of understanding and transformation techniques are required to enable its effective development. The following provides an introduction to the basic tasks involved in oil field development. (The specific oilfield extraction methods will be discussed in detail later.) (1) Identifying the type of reservoir and selecting the appropriate development method are prerequisite conditions for the effective development of an oilfield. The type of reservoir serves as the basis for determining the development method, and this method must not only suit the various characteristics of the reservoir but also change as the development process progresses. Therefore, before a oil field is put into development, these two issues must be taken seriously. It should be briefly explained here that a reservoir refers to an oil-bearing body that is worth developing as a single unit; it can be a single oil layer, or it can be a group of several oil layers with similar properties. A reservoir can be an oil field, and an oil field can also comprise several reservoirs. For example, Renqiu Oil Field in our country has a carbonate rock reservoir beneath it and a sandstone reservoir above it; it is an oil field with multiple reservoirs. Oilfield development projects are generally considered on a reservoir basis. Because sometimes the geological conditions and crude oil properties of several reservoirs within the same oil field vary greatly, and since they are different types of reservoirs, they should be treated differently; various extraction methods and development well patterns should be applied to each reservoir. Of course, if several reservoirs with similar burial depths and geological conditions can also be developed using the same extraction methods and well patterns together, that would naturally be better; however, it is necessary to first clarify the geological conditions of each reservoir as a separate unit. Reservoir types are classified primarily based on the morphology of oil bodies, into stratified reservoirs and massive reservoirs. Based on trapping conditions, they can be classified into structural reservoirs, stratigraphic reservoirs, and lithological reservoirs. The basic characteristic of structurally formed reservoirs is that the traps in which oil and gas accumulate are created as a result of rock strata being deformed and displaced by tectonic movements. Its types can also be further subdivided, with the most important ones being anticline reservoirs and fault reservoirs. A stratigraphic reservoir refers to a reservoir in which oil and gas accumulate due to obstruction conditions caused by stratigraphic factors. Among the stratigraphic reservoir types, there are further distinctions between stratigraphically overlying reservoirs and stratigraphically unconformity reservoirs. Lithologic reservoirs are primarily those in which sandstone is surrounded by shale, forming lithologic pinch-out traps and lensoid traps, within which oil and gas accumulate to form reservoirs. Oil transportation and gathering: What was discussed earlier in the section on oil field development relates to a set of underground engineering techniques aimed at ensuring that oil and gas can flow smoothly from the oil and gas reservoirs to the bottom of the wells, and from there to the surface. As for what happens after oil and gas flow to the surface from the oil wells, how they are gathered from these wells, how oil and gas are separated from each other, and how they are initially processed into suitable crude oil and natural gas for storage or transportation to refineries – this is what is commonly referred to as \"oil field gathering and transportation technology\" and \"oil field surface engineering projects\". The collection and transportation technologies as well as the construction of oil fields are determined and vary depending on the geological characteristics and properties of the crude oil in each field, the geographical and climatic conditions, and the progress of oil field development. For example, differences in crude oil viscosity and freezing point, as well as variations between cold and hot regions, have a significant impact on the technologies used for transporting crude oil ； For example, some crude oils and natural gases contain hydrogen sulfide, and therefore must be desulfurized before they can be stored and transported; this requires corresponding desulfurization technologies and infrastructure ； For another example, when oil field development enters the middle and later stages, oil wells contain both oil and gas as well as large amounts of water. It is necessary not only to separate oil and gas from each other but also to remove the water. The oil and gas must be processed into qualified products, and the water must also be treated properly to prevent environmental pollution… Numerous such problems involve a wide range of technologies and engineering tasks, all of which are part of the core aspects of oil field construction. Crude oil gathering and transportation refers to the process of collecting, transporting, and processing the oil and gas produced by oil wells into qualified crude oil. This process begins at the oil well head, where the crude oil produced by the well along with the associated natural gas products are gathered and subjected to necessary treatment or preliminary processing on the oil field. After it is made into qualified crude oil, it is sent for export at the first station of the long-distance oil pipeline, or to the oil depot at the mine site from where it is transported by other means to refineries or transfer terminals ； Qualified natural gas is gathered at the initial station of the pipeline and then sent to petrochemical plants, liquefied gas plants, or other users. In general, the scope of oil and gas gathering and transportation refers to the operations at a mining site that start from oil wells and end at the crude oil storage tanks at the site or at the initial stations of the oil and gas transmission pipelines. A typical oil and gas gathering system includes oil wells, metering stations, transfer stations, and centralized processing stations; this is referred to as a three-stage layout. In some cases, it goes directly from the metering station to the centralized treatment station; this is called secondary station layout. A facility where centralized processing, water injection, wastewater treatment, and power transformation are combined is called a combined station. Oil wells, metering stations, and centralized processing stations are the main locations where oil and gas are collected and initially processed; they are connected to each other through pipelines for the collection and transportation of oil and gas. (1) Surface facilities for oil wells: Oil production wells are of two types: artesian wells and mechanically extracted wells. The equipment at the surface of a self-priming well typically includes a production tree, wax removal equipment (such as winches, wires, and wax scraping tools), nozzles, a water-jacketed heater, and an oil-gas metering and separation unit. Whether a surface building and a duty room are necessary depends on local climate conditions and social factors. Currently, mechanical oil production wells generally use four methods of extraction: deep well pumps (i.e., tubular pumps), hydraulic piston pumps, electric submersible pumps, and jet pumps. The process equipment and auxiliary equipment in mechanical oil production fields mainly include: production trees, oil and gas metering and separation units, heating and wax removal equipment, as well as oil production machinery. Due to the different methods of mechanical oil extraction, the surface engineering at the wellhead also varies. Hydraulic piston pump technology is a relatively advanced method of mechanical oil extraction; below, we will discuss the aspects related to the construction of the wellhead facility. Hydraulic piston pump oil production is a rodless pumping system that uses high-pressure liquid as the power source for the downhole pump. It is mainly used for relatively deep wells, cluster wells, waxed wells, heavy oil wells, as well as oil wells with complex operating conditions. The hydraulic piston pump oil extraction system consists of a surface pump unit, wellhead equipment and pipeline systems, a water jacket heater, a sedimentation tank, and downhole hydraulic piston pump units. Hydraulic piston pumps generally use light oil as the power fluid. Crude oil from this well or adjacent wells can be degassed using a separator, then heated to around 60°C in a water-jacketed heater (or heat exchanger). It subsequently enters a sedimentation tank and is drawn into a high-pressure three-plunger pump. The pressurized crude oil (acting as the hydraulic fluid) is injected into the tubing through a four-way valve at the wellhead, thereby causing the hydraulic piston pump assembly to move up and down. A connecting rod then drives the pumping unit to extract oil from the well. The hydraulic fluid that has been used in the well, along with the crude oil extracted, rise to the surface through the annular space between the tubing and the casing, and then enter the oil-gas separator via a four-way valve. The degassed oil returns to the sedimentation tank; after sedimentation, part of it goes back into the surface pump for reuse, while the other part enters the main oil collection line. (II) Installation and construction of metering stations. The main function of metering stations is to measure the oil and gas production from oil wells, collect the oil and gas from a certain number of wells (7–14), and then transport it via pipelines to the oil and gas processing station. In addition, the metering station also supplies fuel and other items to the wellhead heating equipment. Based on the building structure, the types of metering stations include brick-concrete structure, monolithic slab structure, and train-type structure ； Classified by the process flow, they include single-tube metering stations, double-tube metering stations, and triple-tube metering stations. The facilities of a metering station typically include the inlet manifolds for each well (also known as the main control unit), metering separators, heating furnaces, and metering instruments. The oil and gas gathering and transportation process is the core component of field surface engineering. The process to be adopted mainly depends on the geological conditions of various oil fields, oil well production rates, the physical properties of crude oil, natural conditions, as well as the development level of the national economy and science and technology. The development trends in oil and gas gathering and transportation processes, both domestically and internationally, are generally toward metering at small stations, centralized processing at large stations, sealed transportation, and the full utilization of natural resources. There are generally two processes: 1. The heating and transportation process for heavy and viscous crude oils: With the development of the petroleum industry, the proportion of heavy and viscous crude oils in the total oil production is increasing steadily. For this type of crude oil, heating is generally used for transportation both domestically and internationally. Heated conveying is divided into direct heated conveying and indirect heated conveying. Direct heating transportation involves using a furnace for heating, or heating the liquid mixed with the oil, gas, and water at the wellhead to facilitate transportation ； Indirect heating transportation involves using heating methods such as hot water, steam, or the electrodermal effect for transportation. In some oil fields in our country, such as the Shengli Oil Field, Jianghan Oil Field, Fuyu Oil Field, and Liaohe Oil Field, a small-scale oil and gas transfer station process using wellhead heating for insulation and single-pipe oil output is employed in certain areas ； There are also process designs for small oil-gas transfer stations that utilize double-tube liquid injection for heat preservation ； There is also a three-tube hot water system with a small station process. ⒉ Single-tube or double-tube unheated closed transfer process: This process is used in most oil fields in Europe and the United States. The reason is the good physical properties of the crude oil, or the favorable natural conditions of the oil field, resulting in a high oil production temperature from the wells. In some oil fields in our country, the unheated wellhead process is also adopted depending on the properties of the crude oil and the natural conditions of the oil field, but there are still some fields where this process cannot be used. (III) Construction of centralized treatment stations (combined stations) Centralized treatment stations are an important part of the oil and gas gathering and transportation process in oil fields. Its assigned tasks, construction scale, and location within the oil field are generally determined by the overall plan through comprehensive comparison based on information provided by the development department. The centralized processing station includes: oil and gas process systems, utility systems (power supply, water supply and drainage, heating, communications, ventilation, roads, civil engineering, etc.), water injection, wastewater treatment, fire protection, substation facilities, as well as necessary production equipment. The main equipment in the centralized treatment station includes: separators, water-containing oil buffer tanks, dewatering pumps, dewatering heaters, dehydrators, crude oil buffer tanks, feed pumps for the stabilizer tower, the stabilizer tower itself, stabilizer tower heaters, stabilized crude oil storage tanks, export pumps, flow meters, wastewater buffer tanks, and wastewater pumps. Pipelines within the station should be kept above the ground as much as possible (cables and instrument wires can be installed on the same structure), which facilitates maintenance and management and reduces the risk of corrosion. Off-station pipelines should be laid along roads as much as possible to facilitate construction, maintenance, and management. The following focuses on crude oil dehydration and crude oil stabilization: 1. Crude oil dehydration – All oil fields go through a stage of water contamination during production, especially those with high oil extraction rates or those where water injection is used to enhance production. The period of water-free oil production is generally short, with water appearing in the oil wells early on, leading to a rapid increase in the water content of the crude oil. Crude oil water content not only increases the load on equipment during storage, transportation, and refining processes. Moreover, it increases fuel consumption during heating, and even causes scaling or corrosion of equipment and pipelines due to salts and other substances present in the water. Therefore, high water content in crude oil is entirely harmful with no benefits at all. However, during oil field development, water is almost an inevitable companion of crude oil, especially in the middle and later stages of development; without pumping water from the oil wells, there will be no oil. Therefore, crude oil dehydration has become an essential part of the oil field development process and has always received considerable attention. Through years of repeated experimentation, various crude oil dehydration processes that have been successfully developed include sedimentation separation dehydration. This takes advantage of the principle that water is heavier than oil; as crude oil passes through a specific device, the water sinks and the oil and water are separated. This is also the basic process for dehydrating all crude oils. Chemical demulsification and dehydration. That is, chemical agents are used to separate oil and water in an emulsified state. Chemical demulsification is a commonly used method for water removal from crude oil. Electrodemulsification dehydration. High-intensity electric fields used for electrical demulsification include alternating current, direct current, AC-DC electricity, and pulsed power supply, among others. Its basic principle is to promote the separation of oil and water ions through the action of electric ions. Wetting, coalescence, demulsification. During crude oil dehydration and stabilization, heating helps to reduce the viscosity of the crude oil and increase the volatility of its light components. This also facilitates the separation of oil and water. Dehydrating crude oil requires a lot of energy; to make full use of this energy, crude oil dehydration units and crude oil stabilization units are usually placed together. To save energy and reduce losses due to oil and gas volatilization, by stabilizing crude oil to recover light hydrocarbons, the dehydration process for crude oil in oil fields is moving toward a tankless, sealed system. The prominent feature of the tankless process is its high level of sealing, which prevents any volatilization and loss of oil and gas. During the process sealing, sealing the crude oil dehydration process is a critical step, as it operates at high temperatures and for long periods of time, which makes it easy for oil and gas to evaporate and be lost. It has been determined that, in an open-flow process, the oil and gas loss during the dehydration stage accounts for approximately 50% of the total loss. Crude oil dehydration equipment represents dehydration technology, and it plays an important role in the process of crude oil dehydration. The rationality of the structure of a dehydration device is directly related to the effectiveness and efficiency of dehydration, as well as the quality of crude oil and the production costs; this in turn affects the overall economic benefits of crude oil dehydration processing. Therefore, in conjunction with oil and gas gathering, transportation, and processing processes, there has been a gradual shift toward a \"tank-free\" approach – that is, storage tank-based sedimentation and separation equipment is no longer used, and pressure-resistant sedimentation and separation equipment is more commonly employed, along with the development of advanced, large-scale pressure-resistant dehydrating containers. The electric dehydrator is an advanced device that remains the most efficient and capable to date for dehydrating crude oil, relying on the action of an electric field. There are various types of electric dehydrators, such as pipeline-type, tank-type, vertical cylindrical type, spherical type, etc. With the development of the oil industry, through continuous practice and experience, there is a trend toward the widespread use of horizontal cylindrical electric dehydrators. Its processing capacity and production quality have both reached high levels; the processing capacity of each unit per hour can be several times the volume of the unit itself, and the water content in the purified oil can be reduced to below 0.03%. To accelerate the construction of oil fields and increase the degree of prefabrication in the installation of dewatering equipment, four types of devices – horizontal electric dehydrators, oil-gas separators, flame tube heaters, and sedimentation dehydrators – have been integrated into one unit. This combined device not only features a compact structure but also reduces the need for numerous pipelines, valves, and power equipment. Especially in situations where the scale of oil fields varies, this integrated device allows the number of units to be increased or decreased according to the production requirements, thus offering high flexibility. ⒉ Crude oil stabilization refers to the process of treating crude oil that has been collected in a sealed manner from oil fields; during this process, light hydrocarbons such as methane, ethane, propane, butane, etc., are separated from the crude oil and recovered for reuse. In this way, the volatilization of crude oil is reduced, and losses caused by evaporation are minimized, thereby stabilizing it. Stabilizing crude oil is a solution to reduce evaporation losses. However, even for stable crude oil, necessary measures must still be taken during storage and transportation, such as sealed transportation and storage in floating roof tanks. Stabilizing crude oil offers significant economic benefits, as it allows for the recovery of large amounts of light hydrocarbons to be used as raw materials in the chemical industry. At the same time, it enables the safe storage and transportation of crude oil, thereby reducing environmental pollution. There are many methods for stabilizing crude oil, and the four main methods currently used at home and abroad are as follows: First is the negative pressure separation stabilization method. After oil and gas separation and dehydration, the crude oil enters the crude oil stabilizer, where it undergoes flash evaporation under negative pressure to remove volatile light hydrocarbons, thereby stabilizing the crude oil. The negative pressure separation and stabilization method is mainly used for crude oils with low levels of light hydrocarbons. Second is the heating and flash stabilization method. This stabilization method involves first heating the crude oil after oil and gas separation and dehydration, and then subjecting it to flash separation under slightly positive pressure to achieve flash stabilization. Third is the fractional stabilization method. After oil and gas separation and dehydration, the crude oil passes through a distillation tower, where it is vaporized and condensed multiple times at different temperatures to separate light and heavy components. This process of separating light and heavy components is called fractional stabilization. The stable quality of crude oil obtained with this method is better than that achieved by other methods. This stabilization method is mainly suitable for crude oils containing a high amount of light hydrocarbons (this method works best when the degassing volume per ton of crude oil reaches 10 cubic meters or more). Fourth is the multi-stage separation stabilization method. This stabilization method is applied to oil fields mined under high pressure. Generally, 3 to 4 stages of separation are used, with a maximum of 6 to 7 separation stages. The more stages of separation there are, the greater the investment required. The choice of stabilization method is based on a comprehensive consideration of specific conditions, and the two methods can also be combined if necessary. (IV) Construction of crude oil depots: A facility used for receiving, storing, and distributing crude oil is called a crude oil depot. Crude oil depots are characterized by storing a single type of oil, handling large volumes of oil in both receipt and dispatch, and having frequent turnover. They serve as an important link in the normal operation of oil fields and in the transportation of crude oil outside these fields. Based on different methods of transporting crude oil, crude oil depots can be classified into the following types. Railway-based crude oil export depot: The depot is equipped with dedicated railway lines and relevant oil loading equipment. In the 1960s, the Daqing Oil Field relied mainly on railways for transporting its crude oil; oil tank trains, forming long queues, carried the crude oil continuously from the oil depots to various refineries across the country. Crude oil export pipeline depot: It uses pipelines to transport crude oil to various users. However, oil fields that use pipeline transportation do not necessarily all have crude oil storage tanks; for example, the North China Oil Field does not have any such tanks. Crude oil from North China is transported north to Shilou, and south to the refineries in Cangzhou and Shijiazhuang, all by pipeline. Depending on factors such as the transmission distance and oil volume, heating and pressurization stations should also be installed along the transmission pipeline. Joint crude oil transportation depot: Crude oil is delivered to end-users using railway tank cars and pipelines. Previously, the crude oil from the Shengli Oilfield was transported by pipeline to Xindian, and from there it was shipped outward using railway tank cars; later, an oil pipeline was built from Dongying to Huangdao for transporting the crude oil. For oil fields located near the sea or rivers, it is also possible to consider using ships to deliver crude oil to the users. Additionally, for some remote oil fields that are small in size and produce little oil, or for newly developed oil fields that yet have no established transportation systems, oil can also be transported by truck. For example, in the Arxan Oil Field in Erenhot, crude oil was transported by truck from the very beginning of its development. In some areas of the Jizhong Oil Field, the construction principle is to build stations first and then pipelines, to transport oil first and then carry it via pipelines. A crude oil depot generally consists of equipment for receiving, storing, and dispensing oil, as well as utility systems and facilities for production and living. Oil collection equipment mainly refers to the valve assemblies used for oil collection. The equipment used for storing crude oil is mainly storage tanks. The crude oil storage tanks at oil fields are mainly vertical cylindrical metal tanks. Commonly used types include momentless tanks, dome tanks, and floating roof tanks. In terms of reducing the evaporation losses of crude oil, floating roof tanks are superior to tanks with other structural designs. Equipment for distribution refers to the equipment required for transporting crude oil outside. When using railway transportation, it is necessary to build dedicated railway lines, oil loading nozzles, trestles, oil loading pumps, and metering equipment. When using external pipeline transportation, it is necessary to install external transfer pumps, external valve assemblies, heating equipment, and metering equipment. The dispensing equipment for combined external transportation oil depots is a combination of the dispensing equipment for the above two types of oil depots. Where possible, the elevation differences in the terrain should be fully utilized for loading in order to save energy. The utility systems of the oil depot are basically the same as those of the crude oil processing station. It is important to emphasize the safety and fire protection of oil depots. Once a fire or explosion occurs in a crude oil depot, the consequences are unimaginable. Petroleum refining: Petroleum is composed of various hydrocarbons, and there are few ways to use it directly; it can only be used as fuel to power boilers. Using oil in this way is a huge waste. Processing oil into different products allows it to be utilized to the fullest, enabling its full potential to be realized. The pre-treated crude oil is sent to a kerosene plant for processing, to produce gasoline, kerosene, diesel, lubricants, and asphalt, among other products. The overall processes in various kerosene plants vary; some are simpler while others are more complex. In the oil refining process for producing fuel oils, there are three units: distillation, cracking, and coking units. There are mainly four units for producing lubricating oil, namely propane deasphalting, solvent dewaxing, solvent refining, and clay refining. Oil does not have a fixed boiling point. The boiling point range of ordinary oil is around 30 degrees Celsius to 600 degrees Celsius. It is a mixture of **small hydrocarbons with different boiling points**, the boiling point of these hydrocarbons increasing as the number of carbon atoms increases. For example, a hydrocarbon with 5 carbon atoms (called heptane) boils at just 36 degrees Celsius; whereas a hydrocarbon with 12 carbon atoms (called dodecane) requires heating to 216 degrees Celsius to boil. In this way, by heating the oil, the various hydrocarbons can evaporate in sequence according to their different boiling points. Refineries, which process oil, take advantage of these properties of oil by subjecting large amounts of it to different temperatures, thereby producing various products. In refineries, there are two vertical units, one tall and slender and the other short and stout; these are called distillation towers. Those that are tall and thin are called atmospheric distillation columns (abbreviated as atmospheric columns); those that are short and stout are called vacuum distillation columns (abbreviated as vacuum columns). After being heated in a heating furnace, the oil is first sent to an atmospheric pressure tower; the products from the bottom of this tower are then reheated in a heating furnace before being fed into a reduced pressure tower. This process is called distillation in refineries. Under normal conditions, oil is heated to 350 degrees Celsius and fed into a atmospheric pressure tower, where the hydrocarbons with lower boiling points vaporize and rise, passing through layer after layer of trays until they reach the top of the tower. Since the temperature of the tower decreases from bottom to top, as oil vapor passes upward through the trays, different hydrocarbons condense into liquids at different tray temperatures according to their respective boiling points. In this way, the hydrocarbon members of the oil \"family\" experienced their first \"separation\". People obtain different products from it. What remains at the bottom of the tower is the heavy oil that has not been vaporized and has a boiling point above 300 degrees Celsius. For the heavy oils at the bottom of atmospheric pressure towers, since they are all hydrocarbons with very high boiling points, increasing the temperature further under atmospheric pressure can also break them down, but they cannot turn into vapor and evaporate. As we all know, the boiling point of water can be reduced at high altitudes. In other words, the lower the atmospheric pressure, the lower the boiling point of water. By the same logic, it is not possible to reduce the pressure in the heating furnaces and distillation towers in order to lower the boiling point of the heavy oil, thereby allowing the various hydrocarbon \"components\" within it to be separated. Thus, the lubricating oil product is obtained. Since the wax content in this portion of the product is high, it is also known as wax oil. The product obtained from the distillation process is commonly referred to as a straight-run product; it represents the first generation of products resulting from the first division of the petroleum \"family\". There is a limited supply of these products. In terms of the oil components in our country, generally 25–40% light crude oils obtained through straight distillation and 20–30% wax oils can be obtained. In other words, to refine 100 tons of oil, only 25 to 40 tons of light oil products and 20 to 30 tons of wax oil can be obtained. The residue left after distillation can be used as fuel in boilers, power plants, etc.; however, it is clear that this does not represent an efficient and adequate utilization of the valuable petroleum resources. Changes in the petroleum \"family\": In order to obtain more light hydrocarbons from petroleum, as well as to improve the quality of oil products and increase the variety of products, various methods have been developed to modify the existing hydrocarbons. These methods allow the hydrocarbons within the petroleum \"family\" to change their original characteristics, so as to meet the requirements regarding product yield, quality, and variety, by transforming them into new hydrocarbons or by recombining them. In other words, by implementing the new method, second-generation petroleum products can be obtained from the petroleum \"family\". So, what are the methods available now? The first method is cracking. As the name suggests, it involves breaking down the long-chain hydrocarbons in oil (the main components of heavy oil) into short-chain hydrocarbons (the main components of light oil); it’s like cutting a very long chain into several shorter chains. By using this method, many new members of low-molecular-weight hydrocarbons can be added to the petroleum \"family\", which not only increases the production of light oils but also represents an important route for producing olefins in today’s petrochemical industry; for example, octane cracking can yield ethylene and hexane. For refineries, there are three different types of cracking: the first is thermal cracking. It relies entirely on heating for cracking. The equipment for thermal cracking is relatively simple and low in cost; the main raw material used for cracking is the waxy oil obtained from the production of vacuum distillation towers. Through thermal cracking, light oils such as gasoline, kerosene, and diesel can also be obtained. However, the quality of the products obtained through thermal cracking is not good enough. The second is catalytic cracking. That is, during cracking, not only is heating applied but a catalyst is also added. Since catalysts, just like yeast added when steaming buns, can **accelerate the reaction rate**, catalytic cracking produces more light oils than thermal cracking (with a gasoline yield of around 60%), and the quality of the products is also better. Third is hydrogenation catalysis. It is catalytic cracking carried out in the presence of hydrogen. The advantage of this method is that it yields a higher yield of light oil of better quality, and there are no strict requirements for the raw materials – both crude oil and residue can be used. The disadvantage is that the equipment must be made of special steel, resulting in high investment costs. The second approach is to change the composition of the three major groups within the oil \"family\" – alkanes, cycloalkanes, and aromatics – in the products, in order to improve product quality. For example, the straight-run gasoline obtained during the first separation of petroleum contains a high amount of straight-chain alkanes, and its properties are not sufficient to meet the requirements of aircraft and automobiles; therefore, the \"reforming\" process was used to address this issue. Reorganization means to reorganize something. In other words, straight-chain hydrocarbons are reorganized into hydrocarbons with side chains or cyclic hydrocarbons. The quality of reformed gasoline can be **significantly improved. Moreover, important chemical raw materials such as benzene, toluene, and xylene can also be obtained from the aromatic hydrocarbons in reformed oil. The third method is to remove the harmful substances from the products obtained during the first “splitting,” in order to improve product quality. In refineries, this is called refining. For example, oils such as straight-run gasoline and diesel contain sulfides, which give them corrosive properties; therefore they must be refined before they can be used. Similarly, various lubricating oils obtained from vacuum distillation towers are also only semi-finished products, and they too must be refined to become suitable for use. The fourth method is to obtain large quantities of important chemical raw materials and products by taking measures of separation and combination on the hydrocarbons within the oil \"family\". When long-chain hydrocarbons are shortened using thermal cracking and catalytic cracking methods, a large amount of short-chain alkenes are produced; these alkenes are then combined with each other under certain conditions, forming a chain similar to links in a chain. This is called a polymerization reaction in chemistry. For example, isobutylene is a colorless gas that consists of 4 carbon atoms and 8 hydrogen atoms. However, through the polymerization reaction, thousands of isobutylene molecules join together to form a polymer containing 6,000 to 8,000 carbon atoms and 1,200 to 16,000 hydrogen atoms; this polymer is known as polyisobutylene. Such compounds are also known as high-molecular-weight organic compounds. At this point, its properties are completely different from those of the original isobutylene; it is no longer a gas, but rather a rubber-like substance. In petroleum processing, people bring the true value of oil into play as a \"treasure trove\" by carrying out the first division of the petroleum \"family\" and making subsequent changes to it.