Oil and natural gas extraction uses various methods to access hydrocarbon resources. Two primary approaches are conventional oil and gas extraction and hydraulic fracturing, often called fracking. These methods differ significantly in their techniques, geological targets, and operational requirements.
Conventional Oil and Gas Extraction
Conventional oil and gas extraction involves drilling vertical wells into reservoirs. These reservoirs typically consist of permeable rock formations, such as sandstone or limestone, where oil and natural gas have accumulated in pore spaces. Natural pressure within these formations allows hydrocarbons to flow freely to the wellbore.
When natural pressure declines, secondary recovery methods, like injecting water or natural gas, maintain production. This traditional approach targets large, easily accessible hydrocarbon accumulations. The process involves drilling a vertical shaft, casing it with steel and cement, and perforating the casing to allow hydrocarbons to enter the well.
The Process of Hydraulic Fracturing
Hydraulic fracturing, or fracking, is a well stimulation technique to extract oil and natural gas from low-permeability rock formations. The process typically begins by drilling a vertical wellbore, which then transitions into a horizontal section extending within the target formation. This horizontal drilling maximizes contact with the hydrocarbon-bearing rock.
Once the well is drilled and cased, perforations are made in the horizontal section. A high-pressure mixture, known as fracking fluid, is then injected. This fluid, typically composed of 90-99.5% water, 0.5-9.5% sand or ceramic proppants, and 0.5-2% chemical additives, creates and expands tiny cracks in the rock. The proppants keep these fractures open after injection pressure is released, allowing trapped oil and gas to flow to the wellbore.
Core Differences in Extraction Methodology
The fundamental mechanics of extraction differentiate conventional drilling from hydraulic fracturing. Conventional extraction primarily relies on the natural pressure of a permeable reservoir to push hydrocarbons to the surface. The drilling process creates a pathway, and natural conditions facilitate the flow of oil and gas. This method does not involve artificial modification of the rock formation beyond creating the wellbore.
In contrast, hydraulic fracturing actively modifies the rock structure to enable hydrocarbon flow. It uses induced hydraulic pressure to create new fractures or enlarge existing ones within low-permeability rock. While conventional wells are typically vertical, fracking often incorporates horizontal drilling to expose a larger section of the target formation, allowing access to a greater volume of hydrocarbons.
Targeted Geological Formations
The choice between conventional drilling and hydraulic fracturing is determined by the geological characteristics of the hydrocarbon-bearing rock. Conventional drilling targets permeable formations like sandstone and limestone, where oil and gas are concentrated in porous rock layers, allowing natural flow. These formations act as natural traps where hydrocarbons have migrated and accumulated.
Hydraulic fracturing, however, is designed for “tight” formations with low permeability, such as shale, tight sands, and coal beds. In these formations, hydrocarbons are trapped within the rock matrix and cannot flow freely without external stimulation. Fracking provides the necessary pathways by creating an interconnected network of fractures, making extraction of these resources viable.
Comparative Operational Requirements
The distinct methodologies of conventional and hydraulic fracturing operations lead to varying on-the-ground requirements. Fracking operations generally demand a larger land footprint for the well pad due to extensive equipment, including high-pressure pumps, blenders for fluid mixing, and storage tanks. The process requires large volumes of water, ranging from 1.5 million to 16 million gallons per well. Specialized trucks and equipment are necessary to transport and inject the fracking fluid and proppants.
Conversely, conventional drilling typically has a smaller surface footprint and less complex logistical demands. While both methods require drilling rigs and well completion equipment, conventional extraction relies less on high-pressure fluid injection systems and continuous delivery of water and proppant. Hydraulic fracturing has higher operational intensity and specialized equipment needs due to its engineered approach to rock modification.