Natural gas is a crucial source of energy in today's world, and understanding its extraction methods is essential. In this article, we will review the processes involved in natural gas extraction. From the formation of natural gas to traditional drilling techniques and modern extraction methods such as hydraulic fracturing and horizontal drilling, we will cover everything, so keep reading to find out more!
Introduction to Natural Gas Extraction
Before diving into the details of natural gas extraction methods, it is important to understand what natural gas is. Natural gas is a hydrocarbon compound primarily composed of methane (CH4) and is found underground in reservoirs beneath the Earth's surface. It is a fossil fuel formed over millions of years from the remains of plants and animals.
In today's world, natural gas plays a vital role in meeting global energy demands. It is used for heating, cooking, electricity generation, and powering various industries. It is the cleanest burning fossil fuel, making it a preferred choice.
The Science Behind Natural Gas Formation
Understanding the process of natural gas formation is essential in comprehending extraction methods. It begins with the decomposition of organic material over millions of years through heat and pressure. This organic material, such as dead plants and animals, accumulates in layers of sediment on the ocean floor and in ancient lakes.
As these layers of sediment continue to build up, they create immense pressure on the organic material trapped within. The weight of the sediment, combined with the heat from the Earth's core, gradually increases the temperature within the layers. This rise in temperature triggers a series of complex chemical reactions that transform the organic material into hydrocarbons, primarily natural gas and oil.
After the hydrocarbons are created, they start moving through the rocks around them. This happens because they feel pressure from the layers of sediment above them. The gas moves through small spaces in the rocks and eventually moves upward towards the surface.
However, not all hydrocarbons reach the surface. Along their journey, they encounter various geological formations that act as barriers, trapping the gas in underground reservoirs. Today, we tap into these reservoirs using various methods to extract and utilize the natural gas trapped inside them.
Types of Natural Gas Deposits
Natural gas deposits come in different forms. When natural gas forms, some of it may travel up through layers and eventually get trapped by layers of rock. This is typically referred to as conventional natural gas. If this trapping takes place in small pores in sandstone, shale, or other sedimentary rocks, it is referred to as shale or tight gas.
Natural gas also occurs on top of oil reservoirs. This type of gas is called associated natural gas. Furthermore, natural gas is often found along coal deposits and referred to as coalbed methane.
Overview of Natural Gas Extraction Methods
Traditional Drilling Techniques
Traditional drilling techniques, also known as vertical drilling, have been used for decades to extract natural gas. This method involves drilling a well vertically into the ground until the target reservoir is reached. Once the reservoir is accessed, the natural gas flows up the wellbore to the surface due to the pressure difference.
This technique has presented numerous success stories but is limited to conventional reservoirs where the natural gas is easily accessible. As technology advances, new extraction methods have emerged to access unconventional reservoirs and increase production efficiency.
Modern Extraction Techniques
New extraction methods have greatly changed the natural gas industry by making it possible to access huge reserves of gas that were once thought to be unreachable. One of these methods is called hydraulic fracturing or fracking.
The Process of Hydraulic Fracturing
In hydraulic fracturing, a mixture of water, sand, and chemical additives is pumped into a wellbore under high pressure. This creates fractures in the surrounding rock formations, allowing the extraction of natural gas. The sand props open the fractures, enabling the gas to flow freely to the wellbore.
Horizontal Drilling: An Innovative Approach
In this technique, they start by drilling a wellbore down into the ground to a specific depth. Then, they gradually turn the wellbore sideways to reach the desired gas reservoir.
By drilling horizontally through the gas reservoir, the wellbore gets to cover a bigger area, which leads to more gas being produced. Horizontal drilling allows the wellbore to make better contact with the reservoir, making the process of extracting natural gas more efficient.
Benefits and Challenges of Horizontal Drilling
The benefits of horizontal drilling include improved productivity, reduced environmental impact, and enhanced exploration potential. It allows access to reservoirs that would otherwise be difficult to reach using traditional vertical drilling techniques.
Despite its advantages, horizontal drilling also poses challenges. It requires advanced drilling techniques and technologies, making it more costly and technically demanding. Additionally, the potential for wellbore instability and formation damage must be carefully managed.
Regardless of how the gas is extracted, it always contains impurities that need to be removed. The type and level of impurities depend on the related geology of the source. After extraction, gas is sent to gas refinery plants. Gas refineries prepare the gas to be injected into the gas pipelines.
Gas refineries perform several important tasks. First of all, they remove some of the heavier hydrocarbons from the mixture. These valuable liquids are called NGL (Natural Gas Liquids) and are sold as fuel for many applications.
When they take out the heavier hydrocarbons from natural gas, it also lowers something called the hydrocarbon dew point (HCDP). HCDP is the temperature at which the gas will turn into liquids under a specific pressure. You can find more information about why this parameter is important and how to measure it in other blogs.
Before the gas is put into the pipeline, there are rules and fees based on the HCDP. Pipeline engineers set these rules to make sure the pipeline operates safely and efficiently without any problems.
Gas refineries also reduce the levels of moisture, hydrogen sulfide and carbon dioxide in natural gas. In refined gas that goes into pipelines, there are usually agreements about how much of each contaminant is allowed to be present. These agreements set limits on the amount of impurities that the gas can have to ensure it meets the required quality for safe transportation through the pipeline.
The level of allowed moisture is very important and has implications on the safe operation of the pipeline. The level of water is specified by either specifying what its dew point can be, or it can also be specified by how much moisture (expressed in ppm or other units) is in the gas. Please see a blog titled “Water Content or Water Dew Point” for further information.
Hydrogen sulfide is a corrosive which can damage the pipelines and also pose safety concerns for the users of the gas, thus the need for reducing its level. Carbon dioxide can also be corrosive in the presence of liquid water.
Once natural gas has been sufficiently refined, it is injected into pipelines for transport to customers.
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