The process of extracting oil is extremely expensive and time-consuming. It requires a number of measurements, tests, sampling and finally boring wells to confirm the presence of the raw material. Of course, there are a number of difficulties, such as porosity of the rock or the viscosity of the substrate itself. In the past, only 10% of the raw material was mined from the discovered deposit, leaving the rest underground. Thanks to modern mining technologies, the degree of recovery of crude oil and natural gas has increased to over 60%.
Extraction of natural gas
Natural gas occurs in the outer layer of the Earth’s crust, i.e. the lithosphere. It was created as a result of the transformation of organic substances under different pressure and temperature conditions, which have been going on for many millions of years. Natural gas consists mainly of methane (CH4) and its homologs (C3-C4). Its composition is strongly dependent on the type of deposit from which it is extracted. Of course, apart from methane and its homologues, natural gas also contains a number of undesirable components, such as nitrogen, water, hydrogen sulphide or carbon dioxide.
Under natural conditions, gas can accompany crude oil or occur separately. It occurs mainly in two forms: as a gas freely dissolved in water or oil, or in the form absorbed in rocks or coal.
Gas produced by industrial methods
Several types of gases can be obtained using industrial methods:
a) Liquid gases – popularly referred to as LPG (Liquefied Petroleum Gas). Their main components are propane (C3H8), butane and isobutane (C4H10). They are obtained mainly by stabilizing raw gasoline, crude oil or by processing refinery gases from reforming, cracking and pyrolysis processes.
b) Town gas – obtained in the conditions of low- and medium-temperature carbonization of coal.
c) Coal gas – produced in the process of high-temperature coal degassing.
d) Gas from coal gasification – it is obtained by acting on brown coal or black coal with a mixture of water vapor and oxygen at temperatures above 900°C. Its composition depends on the gasification technology used. The most important economic factor is the production of a mixture of CO and H2 (so-called syngas).
Application and advantages of gas fuels
Gas fuels have a number of advantages. They are characterized primarily by high energy efficiency. In addition, they provide a constant combustion temperature, do not require storage for the user and burn without smoke (without ash and emissions of sulfur oxides). Natural gas is a valuable energy carrier and an important raw material in the industry: chemical (production of syngas), energy (piston combustion engines, gas turbines, generators), construction (production, glass, cement and building ceramics) and metallurgy (heating furnaces).
Extraction of oil
Choosing the location of a new oil field is a very complicated and expensive process. It starts with the performance of seismic surveys in order to search for appropriate geological structures that can create oil deposits. Two research methods are used for this purpose. The first involves making underground explosions near the deposit and observing the seismic reactions that allow you to get information about its location and size. The second method is to obtain this data from naturally occurring seismic waves.
The first stage of oil extraction is to bore a deep hole in the ground. Next, a casing (steel tube) is placed in the drilled hole, ensuring stability of the entire structure. In the further stage, more holes are made to allow increased flow of the extracted oil. In order to dissolve pollutants in the bored well, hydrochloric acid is often used, which effectively acidifies the carbonate and lime formations and removes deposits of scale, rust and carbonite. Hydrochloric acid is also used to remove residual cement remaining after the drilling process. In the next stage, a special installation is placed at the top of the well, sometimes called a “Christmas tree”. It is a set of combined valves, pipes and fittings that are designed to regulate the pressure and flow of oil and gas.
After connection of the entire apparatus, the primary recovery stage takes place. In order to extract oil in this process, many natural mechanisms are used, for example gravity drainage. The recovery rate in the primary stage usually does not exceed 15%. With further extraction, the underground pressure drops and becomes insufficient to continue to displace the oil to the surface. At this point the secondary recovery step begins.
There are many techniques for the secondary recovery of petroleum. They usually involve the supply of external energy to the deposit by injecting fluids (e.g., water) or gases (e.g., air, carbon dioxide) to increase the pressure underground. The average recovery rate after primary and secondary oil recovery operations usually does not exceed 45%. The last stage of the extraction process is the so-called third order recovery, which can be obtained using various techniques. The first of them reduces the viscosity of oil through thermal heating. The second is the injection of gas into the deposit (injection of carbon dioxide). The last method is called chemical floods. They consist in mixing dense, insoluble polymers with water and injecting them underground. Tertiary recovery allows for an additional 15% of oil production from the deposit.
Due to the ending reserves of land oil deposits, the search for its resources under the seabed has begun. For this purpose, drilling platforms are being built, which is a complicated, expensive and time-consuming process – the construction of the mining platform usually lasts for 2 years. They can be fixed permanently to the bottom (depth up to 90 m) or drift on special floats, fixed with an anchor system. Offshore drilling platforms are usually connected to a network of several dozens of wells that extract oil in porous rocks. In addition to extracting oil on the drilling platform, it is also separated from the gas. The raw material thus obtained is transported through a pipeline system to a refinery or to a mining and transhipping vessel. Then oil and gas are sent to the tanker, which transports it ashore.
Of course, the amount of oil recovered does not depend only on the drilling techniques used. The key factors in this case are geological aspects, such as rock permeability, the strength of natural drives, the porosity of the deposit or the viscosity of the oil itself.
Processing of crude oil
The extracted crude oil is processed in refineries to obtain fuels, oils, lubricants, asphalts and other products. Most often, crude oil is separated into fractions without a chemical change of its components. In this way, refinery gases volatile at room temperature, petroleum ether with a boiling point of 35-60°C, light and heavy petrol, kerosene, diesel with different boiling points and mazut (i.e. a residue with a boiling point above 350°C) are obtained.
Crude oil undergoes various processes, such as:
a) Cracking – consists in the decomposition of long aliphatic hydrocarbons found in heavy mazut and oil fractions, into compounds with shorter chains found in petrol and diesel oil. In addition to short-chain aliphatic hydrocarbons, methane, LPG, unsaturated hydrocarbons and coke are also formed in the process. Cracking can be initiated by thermal, catalytic or radiation methods.
b) Reforming – this is a process applied to light petroleum fractions or products obtained from cracking in order to obtain fuels with a high octane number. The process is carried out in the presence of hydrogen using very expensive platinum catalysts. The reforming process produces hydrogen, refinery gas, LPG as well as isobutane and n-butane.
c) Distillation – is aimed at separating crude oil into fractions boiling in various temperature ranges. Thanks to this process, basic fractions are obtained, such as: dry and wet gas, light and heavy petrol, kerosene, diesel oil, mazut and gudron.
d) Alkylation – this is the reaction of olefins with isobutane, resulting in the formation of isoparaffins with higher molecular weight and octane number. In the alkylation process, sulfuric acid can be used as the catalyst.
e) Pyrolysis – degradation process carried out without oxygen at very high temperatures. It is used to break down heavy oil fractions to pyrolytic gasoline, oils and tar.
The PCC Group’s offer for the mining industry
In order to improve the oil extraction and its processing, the use of various chemicals is of key importance. Soda lye is used in the refining of crude oil, mineral oils, pitch and bitumen and shale gas extraction. Sodium hydroxide in the PCC Group is produced by a membrane electrolysis process and supplied in the form of a solution with a concentration of approx. 50%. Another application of sodium hydroxide in the mining industry is the treatment of sewage and liquid coking products.
An important group of products that are of great use in the extraction and production of oil and gas are surfactants. Surfactants reduce the interfacial tension between crude oil and rock. This reduces adhesion forces and additional oil can be released from the oil field. Surfactants are also used as a means to reduce ecological damage resulting from oil and other petroleum leaching. They can also be used to clean tanks and vessels needed for transporting the extracted raw material.
One of the most important groups of surfactants used in cleaning preparations are the alkyl ether sulphates offered by the PCC Group in the SULFOROKAnol series. These products, due to their anionic character, will work well in formulations with other anionic, non-ionic and amphoteric surfactants. Their washing, emulsifying and foaming properties make them useful as ingredients in formulas that clean different surfaces. Alkylbenzenesulfonic acid (ABS) and its salts, e.g. ABSNa, also have similar use. The ABS/1 acid belongs to the group of anionic surfactants. Due to its solubility in crude oil, it may be an element of auxiliary agents used for oil extraction and processing. In addition, ABS/1 acid, thanks to its detergent properties, is used for cleaning and degreasing processes, e.g. of tanks and ships. Cleaning products used in the oil industry may also include ROKAmid series of products. They are characterized by the ability to create dense and stable foam, even in a small concentration. Thanks to their liquid form, ROKAmid products significantly facilitate all operations related to their storage, transport and dispensing.
The next group of products necessary in the processes of oil and gas extraction are emulsifiers. They are used in industrial methods of oil dewatering and desalination. These processes rely on oil heating with the addition of emulsifiers in a device called electro-dehydrator. The mixture thus heated is forced through the space of the concentric electrode system. Drops of water are deformed, loose their load and are easier to combine with each other, thus they separate from oil. Dehydrated and desalinated crude oil can be subjected to further processing. Ideal as emulsifiers in industrial dewatering and desalination processes are ROKAnol products. These are non-ionic surfactants belonging to the group of alkoxy fatty alcohols. ROKAnol products can be used in a very wide range of temperatures, as well as in acidic, neutral and slightly alkaline environments. They can also be part of degreasing cleaning agents used in the oil industry.
Very good emulsifying properties are also exhibited by ethoxylated sorbitan ester derivatives, such as ROKwinol 60 and ROKwinol 80. These products can be components of drilling fluids used in oil production. On the other hand, sorbitan esters, such as ROKwin 60 and ROKwin 80, can be used in the leakage of petroleum substances to waters as dispersing agents.