Basic Petroleum Technology Essay Example

rewards, turning companies, nations, and individuals into millionaires in a short period. The petroleum industry continues to attract individuals and companies willing to take on the challenge of risk, in hopes of reaping substantial benefits. Upon completing this course, non-technical participants will have a comprehensive understanding and appreciation for the different processes involved in producing petroleum for eventual sale to customers. Two fundamental perspectives exist regarding the formation of petroleum located deep within the Earth's layers.

In the field, there are two main theories: the widely accepted organic theory and the less popular inorganic theory. The inorganic theory includes Dmitri Mendele'ev's deep-seated terrestrial hypothesis, proposed in 1877. Mendele'ev, a Russian scientist famous for creating the periodic table, suggested an inorganic origin for petroleum due to its widespread deposits around the world. According to his hypothesis, metallic carbides found deep within the Earth react with water at high temperatures, resulting in acetylene (C2H2) formation. This acetylene then condenses and transforms into heavier hydrocarbons. It is important to note that this reaction can be replicated under controlled laboratory conditions. Berthelot modified this theory in 1860 and Mendele'ev further refined it in 1902.

The hypothesis of the earth's mantle containing iron carbide (FeC2) that reacts with water (H2O) to produce methane (CH4) and iron dioxide (FeO2), known as the deep-seated terrestrial hypothesis, lacks supporting evidence. In 1890, Sokoloff presented an alternative theory called the extraterrestrial hypothesis, which proposes a cosmic source for petroleum.

According to his theory, hydrocarbons originated from the original nebular matter that formed the solar system and were then released from the Earth's interior onto its surface rocks in the form of precipitation. The significance of this inorganic

theory grew in the 20th Century due to two notable discoveries. One was the identification of carbonaceous chondrites (meteorites), and the other was the observation of celestial bodies, like Saturn, Titan, and Jupiter, having atmospheres containing methane. Inorganic reactions are believed to be the sole source of methane. It has been proposed that the initial atmosphere of the Earth comprised methane, ammonia, hydrogen, and water vapor, possibly resulting in the creation of a greasy, wax-like surface layer. This layer might have served as a habitat for various prebiotic compounds in development, including life's precursors caused by photochemical reactions induced by UV radiation.

The discovery in 1963 by Mueller led to a renewed interest in the inorganic creation of organic compounds, specifically carbonaceous chondrites, a type of meteorite. These chondritic meteorites contain over 6% organic matter (not graphite) and small amounts of various hydrocarbons, including amino acids. The main evidence supporting an inorganic origin for these compounds is the repeated creation of methane, ethane, acetylene, and benzene from inorganic sources. For instance, congealed magma with gaseous and liquid hydrocarbons (90% methane, traces of ethane, propane, isobutane) has been discovered on the Kola Peninsula in Russia (Petersil'ye, 1962).

There is concern about the inorganic origins of paraffinic hydrocarbons found in igneous rocks (Evans, Morton, and Cooper, 1964). The source of organic material discovered in chondritic meteorites is uncertain, as it is unclear if it came from an inorganic or originally organic source. This uncertainty also applies to other celestial bodies. Furthermore, there is no field evidence supporting naturally occurring inorganic processes; however, evidence indicating an organic origin continues to increase.

White and Waring (1963) state that if hydrocarbons are formed

inorganically, volcanoes, congealed magma, and other igneous rocks should emit significant amounts of hydrocarbons. The most commonly observed gaseous hydrocarbon released from volcanoes is methane (CH4). Although these emissions usually represent less than 1% of the total volume, there have been instances where levels reached as high as 15%. Nevertheless, it is important to mention that igneous rocks do not contain substantial reserves of hydrocarbons.

Oil accumulations in igneous rocks are not common and typically occur in rocks intruded or covered by sedimentary materials, indicating that the hydrocarbons originated in sedimentary sequences and migrated into the igneous material. However, there are rare instances where oil forms within magmatic material. Conversely, petroleum is not naturally present in igneous or metamorphic rocks. Gas chromatography can illustrate that organic matter found in shales closely resembles that found in nearby petroleum pools. Therefore, the prevailing theory suggests that most petroleum is generated through the thermal maturation of organic matter, resulting in significant reserves of oil and gas. There are multiple compelling reasons that support this hypothesis.

The most important aspect is the connection between carbon, hydrogen, and organic matter. Carbon and hydrogen make up the majority of both plants and animals' composition, which are also the main components of organic material. Furthermore, carbon, hydrogen, and hydrocarbons are continuously produced by plants and animals throughout their life processes. A significant discovery has shown that various organisms retain preserved hydrocarbons and related compounds in sediments without much change over time. Another observation relates to the chemical properties of petroleum reservoirs where nitrogen and porphyrins (which come from chlorophyll in plants and blood in animals) can be found in all types of organic matter

as well as many sources of petroleum.

The presence of porphyrins in petroleum suggests that anaerobic conditions were present during its early formation. Porphyrins can be easily decomposed by oxidation in the presence of oxygen, indicating a lack thereof. This low oxygen content further supports the notion of a reducing environment. Therefore, it is highly likely that petroleum originates from an environment characterized by both anaerobic conditions and reduction. Lastly, physical characteristics were also observed.

The majority of petroleum is found in marine sediments, while petroleum found in non-marine sediments likely originated from nearby marine materials. Additionally, petroleum reservoirs at deeper levels generally have temperatures below 300oF (141oC). However, the presence of porphyrins prevents temperatures from exceeding 392oF (200oC) as they are destroyed beyond this point. Thus, the origin of petroleum is most likely associated with lower temperatures.

In summary, it is possible that time requirements for the development of liquid petroleum may be less than 1MM years due to recent oil discoveries in Pliocene sediments. However, it should be noted that Earth's physical conditions may have been different in the past, potentially causing a longer development time for petroleum. [pic] Figure 1A showcases the Organic Hypothesis, which emerged as the accepted theory around the turn of the century when the oil and gas industry was advancing and geologists were searching for new deposits. The organic theory suggests that the carbon and hydrogen needed for oil and gas formation originated from early marine life forms, particularly marine plankton that existed during the geological past.

Plankton make up over 95% of living matter in the ocean despite being microscopic. Plankton and other marine life rely on the Sun's energy for

survival (Fig. 1 ; 1A). When these early life forms die, erosion and sedimentation capture their remains (Fig 2). Layers of organic-rich mud and silt gradually cover previous layers of organic rich sediments, forming fossil-rich layers on the sea floor over time (Fig. 3).

The organic matter underwent thermal maturation processes such as decay, heat, and pressure, gradually transforming into oil and gas. These sediments, which were rich in organic material, then went through geological changes over millions of years and formed rock layers. Over time, these layers experienced deformation, buckling, breaking, and uplift. Throughout this process, liquid petroleum moved upwards through porous rock until it reached a point where it could no longer flow. This led to the creation of oil and gas reservoirs that are currently being explored (see Fig. 4). However, the hydrocarbons found in the final product (oil and gas) differ somewhat from those present in living organisms.

The process of creating petroleum, also known as oil or gas, involves a series of changes and transformations that occur between the deposition of organic remains and the formation of the final product. According to the organic theory, petroleum is formed by altering organic material derived from small plant and animal life. These materials are transported in large quantities by rivers and streams to lakes or the ocean, where they settle in areas with deltaic, lacustrine, and marine conditions along with fine clastic sediments. These environments also host their own microscopic plant and animal life that coexist with the organic material brought by rivers and streams. As these materials are deposited in these environments, they become buried and protected by clay and silt, preventing decomposition

and aiding in accumulation. The conversion of this organic material is known as catagenesis, which occurs over long periods of geological time.

Assistance in the process occurs due to various factors. Burial, temperature, thermal alteration, and degradation all contribute to creating pressure. These factors are influenced by depth, bacterial action in a closed nonoxidising chemical system, radioactivity, and catalysis. Temperature plays a significant role in thermogenic activity, being the primary criterion. Other factors also assist depending on the context. Bacterial action accompanies the accumulation of organic and clastic material on the bottom of a sea or lake.

If there is plenty of oxygen, aerobic bacteria will break down organic matter. Both plants and animal remains contain carbon and hydrogen, which are essential components of petroleum. Shale and certain carbonates also contain organic material that contains hydrocarbons similar to those found in petroleum. Although not reservoir rocks, these rocks could eventually be considered as source beds. The hydrocarbons found in them are identical to those present in living plants and animals, and they exist in the form of asphalt, kerogen, and liquid.

The most ideal source rocks are black-coloured shales that are rich in organic matter. These shales are deposited in a marine environment that lacks oxygen and is calm. The generation of crude oil is depicted in Figure 5 through the organic composition found in shales. Organic material makes up around 1% of the volume of shale rock, while the remaining 99% consists of clay mineral constituents. Kerogen, which is insoluble and has a high molecular weight, makes up approximately 90% of the organic material in shale. The remaining 10% consists of varying compositions of bitumens, which some

researchers believe are thermally altered forms of kerogen.

As temperature increases in the closed system, alteration leads to the development of kerogen. The depth is directly proportional to the temperature increase. The earth's crust experiences a normal heat flow that generates an average geothermal gradient of around 1.5 oF for every 100 feet of depth.

Maturation studies have shown that oil is formed at depths ranging from approximately 5,000 feet to 20,000 feet under normal heat-flow conditions. Pressure, similar to temperature, is determined by depth and increases by 1 psi for every foot of depth. The weight of sedimentary overburden causes this pressure. Bacterial activity plays a significant role in converting organic matter to petroleum at shallow depths. This process involves breaking down the original material into hydrocarbon compounds that eventually transform into biogenic gas. The formation of bitumens, which contribute to the accumulation of crude oil, is primarily influenced by kerogen.

The thermal conversion of kerogen to bitumen is a crucial process in the formation of crude oil. This process increases the carbon content of migratable hydrocarbons, leaving behind unmigratable kerogen components. The maturation of kerogen occurs as it becomes buried at greater depths and experiences higher temperatures, resulting in chemical changes. As kerogen matures thermally and increases in carbon content, its color changes from an immature light greenish-yellow to an overmature black, indicating a higher coal rank. Natural gas is generated through the formation of biogenic gas and thermogenic gas, each with distinct characteristics based on their origin conditions. Biogenic gas forms at low temperatures, typically at depths below 3,000 feet, in anaerobic environments or during periods of high rates of marine sediment accumulation.

Oxygen in the

sediments is consumed or depleted first, before the reduction of sulfates in the system. Methane, which is the most common component of natural gas, is formed after the sulfates are eliminated through the hydrogen reduction of carbon dioxide. The anaerobic oxidation of carbon dioxide results in the production of methane.

Approximately 20 percent of the world's known natural gas is believed to be biogenic. Water molecules, for instance, are identical and possess the qualities of water. However, individual hydrogen and oxygen atoms lack the characteristics of water. Crude oils consist of numerous substances, making separation challenging, and are the source of various petroleum products like gasoline, kerosene, propane, fuel oil, lubricating oil, wax, and asphalt. These substances primarily consist of compounds with only carbon (C) and hydrogen (H) elements and are referred to as hydrocarbons.

Refining crude oil involves two types of processes to create the products necessary for modern society. The first type includes physical processes that refine the crude oil into useful products like lubricating oil or fuel oil, without changing its molecular structure. The second type consists of chemical or other processes that modify the molecular structure and yield various products, including petrochemicals. Hydrocarbons exist in gaseous, liquid, or solid form under normal temperature and pressure, depending on the arrangement and quantity of carbon atoms within their molecules.

Substances with up to 4 carbon atoms are in gaseous form, while those with 20 or more are in solid form. Those with carbon atoms in between are in liquid form. Crude oils, which are generally liquid, can contain both gaseous and solid compounds in solution. As the number of carbon atoms in a crude oil increases,

making it heavier, it becomes more solid-like, which becomes more pronounced as its temperature decreases. On the other hand, lighter oils will remain in liquid form even at extremely low temperatures.

Hydrocarbons, which consist of carbon and hydrogen, exhibit a wide variety of types and quantities due to the capability of carbon atoms to form lengthy chains. Classification of hydrocarbons is based on their composition (number and type of atoms) as well as the molecular structure (arrangement of atoms in space). The four main types of hydrocarbons are paraffin, unsaturated, naphtene, and aromatic. The paraffin series, also referred to as the alkane series, is characterized by open chains of carbon atoms joined by single bonds, rather than closed rings.

The paraffin hydrocarbons are completely saturated (containing only single bonds between carbon atoms) and have the general formula CnH2n+2. The simplest hydrocarbon is methane, which is a gas composed of one carbon atom and four hydrogen atoms. [pic] Figure 6 shows the molecular structure of methane. Carbon atoms have the unique ability to form four bonds with other carbon atoms or atoms of different elements. Hydrogen atoms, on the other hand, can only form a single bond with another atom. Larger hydrocarbon molecules consist of multiple carbon atoms connected to each other and hydrogen atoms. These carbon atoms can be arranged in a straight chain, a branched chain, or a ring. The first three members of the paraffin series, methane, propane, and butane, have distinct but single structural formulas.

Examples include propane (C3H8), a straight chain molecule, shown below: [pic] Figure 7 – Molecular structure of propane. The remaining members of the hydrocarbons may have two or more structural

formulas for the same chemical formula. This phenomenon, known as isomerism, has a significant impact on the thermodynamic properties. An example of a branched chain is isobutane (C4H10), shown below: [pic] Figure 7 – Molecular structure of isobutane. Isobutene has a boiling point of 109 oF, while normal butane boils at 31.

The paraffin series is comprised of important components of crude oil. Some types of crude oil primarily consist of hydrocarbons from this series, while others have a smaller amount. Natural gas is mainly made up of the more volatile members of the paraffin series, with carbon atom counts ranging from one to four per molecule. The paraffin series is known for its chemical inertness.

They do not react with concentrated sulphuric or nitric acid at room temperature. However, when exposed to air or oxygen and ignited, they release a significant amount of heat. This combustion can be explosive under certain conditions. The reaction with oxygen only occurs at higher temperatures. The paraffin hydrocarbons' inertness is the reason for their presence in petroleum. Their ability to exist for long periods of time geologically requires a high level of stability. Unsaturated Hydrocarbons, on the other hand, have double or triple bonds between carbon atoms. These multiple bonds allow the addition of hydrogen atoms, given the appropriate conditions, hence the name unsaturated.

The hydrocarbons in the olefin series have a double bond in the molecule and are represented by the general formula CnH2n. The first three members (n=1…4) of this series, ethene, propane, and butene, are commonly known as ethylene, propylene, and butylene. Isomerism occurs with the olefins due to the branching of the carbon chains and the

position of the double bond. Another series of unsaturated hydrocarbons known as diolefins has two double bonds in the molecule. The general formula for this series is CnH2n-2.

The acetylene series is a significant group of unsaturated hydrocarbons that are characterized by having a triple bond and a general formula of CnH2n -2 . These compounds are isomers with the diolefins and the first three members of this series (n=2…4) are ethine (commonly known as acetylene), propine, and butine. [pic] Figure 8 - Molecular structure of Ethine. Unlike the members of the paraffin series, the unsaturated hydrocarbons are highly reactive.

Olefins, which react quickly with chlorine to produce oily liquids, are named for their ability to form oil. Under the proper conditions, they easily react with hydrogen, saturating the double bonds and creating paraffins. Due to their high reactivity, these unsaturated hydrocarbons are not typically present in significant quantities in crude oil. Nevertheless, they are produced extensively through petroleum cracking processes and hold significant industrial importance. Naphthene hydrocarbons, also known as cycloparaffins, are saturated hydrocarbons with carbon chains that form closed rings.

The general formula for cycloalkanes is CnH2n (n > 2) and they are isometric with the olefins. To name them, add the prefix "cyclo" before the corresponding paraffin hydrocarbon's name. The first members of this series (n=3...6) are cyclopropane, cyclobutane, and cyclohexane, and so on. These compounds are saturated and relatively stable, making them significant components of crude oil. Overall, the chemical properties of these hydrocarbons closely resemble those of the paraffins.

Aromatic hydrocarbons, which are cyclic compounds and can be seen as variations of benzene (C6H6) with the general formula CnH2n-6 (where n is

larger than 5), are quite common in organic chemistry. The structure of benzene is characterized by a six-membered ring with alternating single and double bonds. In fact, the hexagon with a circle in the center has become a special symbol for representing the benzene molecule. Certain simpler members of this group feature benzene with one or more alkyl groups attached as side chains.

Methylbenzene, also referred to as toluene, is an example that exemplifies the need for a common name. Despite the fact that the benzene ring possesses three double bonds, suggesting potential high reactivity, the members of this series do not display the same level of reactivity as olefins. While not as stable as the paraffins, they still fall short of the high reactivity characteristic of olefins. Crude oil contains compounds from this series, making petroleum a significant source of these vital hydrocarbons.

[pic] Figure 9 – Molecular structure of Aromatics The aromatic hydrocarbons can exist as either liquids or solids at standard temperature and pressure. Benzene, a colorless liquid, has a boiling point of 176°F. The aromatic series is characterized by fragrant odors, which is why it is called "aromatic." Crude oils exhibit a wide range of appearances and viscosities depending on the oil field. They differ in color, odor, and properties. Although all crude oils consist mainly of hydrocarbons, the variations in molecular structure lead to differences in ease of production, transportation via pipeline, and refining.

The variations in crude oil can impact its suitability for specific products and the quality of those products. Crudes are categorized into three groups based on the hydrocarbons they contain. Paraffin-based crude oils have higher molecular

weight paraffins that are solid at room temperature and typically lack asphaltic (bituminous) matter. These crudes have the ability to produce high-grade lubricating oils.

Asphaltic Based Crude Oils have high levels of asphaltic matter and minimal paraffin content. Certain types are mainly composed of naphthenes, making their lubricating oil more susceptible to temperature fluctuations compared to paraffin-based crudes. Mixed Base Crude Oils fall within the intermediate category, containing both paraffins and naphthenes, along with aromatic hydrocarbons.

Most crudes fall into this category. Crude oils typically have small quantities of oxygen, nitrogen, and sulphur combined. Crude oils obtained from different locations have varying characteristics, suggesting that the hydrocarbons possess distinct properties.