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The Science of Extracting Oil and Gas: Why Do Unconventional Reservoirs Require Such Special Technologies?
In today's era of energy search, the extraction method of oil and gas reservoirs has undoubtedly become an important topic. The difference between conventional oil and gas reservoirs and unconventional oil and gas reservoirs lies not only in their geological characteristics, but also in the application of technology. As global demand for energy continues to grow, understanding the science and technology of these different types of oil and gas reservoirs is critical to the development of future energy sources.
Characteristics of conventional oil and gas reservoirs
Conventional oil and gas reservoirs refer to oil and gas naturally formed in strata about 4 to 5 kilometers deep. Because they are lighter than water, oil and gas are driven by buoyancy and gradually rise to the surface. In most cases, these oil and gas will also form reservoirs underground due to geological barriers, and sometimes even seep out naturally on the land or seabed.
If the reservoir has a higher porosity, it is called a conventional oil and gas reservoir.
When extraction techniques are applied to these reservoirs, conventional oil and gas reservoirs, as their name suggests, have characteristics that make the extraction process relatively simple, usually by allowing the oil and gas to naturally float to the surface through wells. When the pressure difference is large, the oil and gas will rise naturally, and can also be assisted by pumps or mechanical devices.
The emergence of unconventional oil and gas reservoirs
In the early 20th century, the demand for oil increased dramatically, prompting the industry to seek technologies to improve the efficiency of oil and gas recovery. As war and economic growth drive demand, new unconventional oil and gas resources have become critical.
The United States is beginning to turn to unconventional oil and gas reservoirs to achieve energy independence.
Unconventional oil and gas reservoirs include basin-centered gas, shale gas, coal-bed methane (CBM), gas hydrates, oil sands, light tight oil and oil shale, etc., which are mainly distributed in North America. Although these resources have been known for decades, they are often not taken seriously because of the high cost of extraction.
The difference between conventional and unconventional resources
The difference between conventional and unconventional reserves lies primarily in the characteristics of the reservoir and the physical properties of the oil and gas. Conventional oil and gas reservoirs basically rely on buoyancy mechanisms, forming obvious geological traps that are easy to detect and exploit. In contrast, unconventional oil and gas reservoirs are widely distributed and lack clear trap characteristics, which makes their prediction riskier and requires different extraction technologies.
Oil and gas in unconventional reservoirs are usually bound by strong capillary forces and cannot flow naturally.
Therefore, extracting unconventional oil and gas reservoirs requires changing the physical properties of the reservoir through methods such as hydraulic fracturing (fracking) or steam injection to facilitate the flow and extraction of oil and gas.
Comparison of environmental impacts
Whether conventional or unconventional oil and gas reservoirs, both face the problem of greenhouse gas emissions. However, there are significant differences in the carbon footprint of the two. The energy required for conventional oil and gas reservoirs is mainly natural energy, and oil and gas can rise freely, while unconventional oil and gas reservoirs require energy to be input underground, either through heat energy or pressure, which will generate greater pressure on the environment and water resources.
Extraction from unconventional oil and gas reservoirs requires large quantities of fresh water, creating supply and disposal problems.
In addition, the widespread distribution of resources also brings about land use issues, affecting the infrastructure and economic development of local communities. The impact of human activities on the environment is inevitable, but the difference in impact between conventional and unconventional oil and gas reservoirs is obvious and predictable.
Future Outlook
As the world places increasing emphasis on renewable energy, how will the oil and gas industry choose to develop different types of oil and gas reservoirs in the future?
