The Difference Between Conventional Wells and Unconventional Wells
Published on September 26, 2023
Oil and gas wells extract valuable resources from deep beneath the Earth's surface. These reservoirs can be categorized as either conventional or unconventional. When it comes to exploring for oil and natural gas, three critical geological factors come into play: porosity, hydrocarbon saturation, and permeability. In simple terms, porosity refers to a rock's ability to hold liquids or gases, hydrocarbon saturation indicates how much of the pore space is filled with hydrocarbons, and permeability pertains to the rock's capacity to allow the flow of liquids or gases.
Conventional Wells:
Conventional wells are typically drilled straight down or at a slight angle.
They target reservoirs, like sandstone or limestone, with ample porosity, hydrocarbon saturation, and permeability.
Porous rock can store and transport hydrocarbons effectively, and this is why conventional wells have historically been successful.
Once drilled, the hydrocarbons, previously trapped under high pressure, naturally flow up the wellbore to the Earth's surface due to the pressure difference between the reservoir and the surface. This process is described by petroleum engineers using scientific equations.
Unconventional Wells:
Unconventional wells, on the other hand, are more complex and require advanced techniques.
They often involve horizontal drilling and hydraulic fracturing.
Unconventional reservoirs, like shale formations, have sufficient porosity and hydrocarbon saturation but lack permeability.
This means that while they contain substantial oil and natural gas, these resources don't flow freely through the rock pores, making production challenging.
In the 1990s, innovations like horizontal drilling and hydraulic fracturing made it economically viable to create artificial permeability in unconventional wells, allowing for the extraction of these resources.
Unconventional well production is usually isolated and independent from nearby wells, assuming no external interference, making it suitable for AI-assisted statistical forecasting.
In summary, conventional wells tap into naturally permeable reservoirs, facilitating the extraction of hydrocarbons, while unconventional wells use advanced methods to overcome low permeability in reservoirs, enabling the production of valuable resources.
