Onshore oil and gas extraction is the process of recovering hydrocarbon resources from reservoirs beneath the Earth’s surface on dry land. This distinguishes it from offshore operations, which use specialized platforms in marine environments. Onshore activities are the oldest form of hydrocarbon production and provide the bulk of the world’s oil and natural gas supply. Land-based sites are generally more accessible, making these operations less logistically complex and more cost-effective than deep-water projects. The entire lifecycle involves a distinct set of legal, engineering, and logistical challenges, from securing land access to handling the final product.
Defining Onshore: Location and Access
The term “onshore” encompasses extraction activity conducted on the mainland, including inland waters, marshes, and swamps accessible by conventional land-based drilling equipment. Operations are governed by the ownership of subsurface mineral rights, which may belong to private individuals, state governments, or the federal government. This structure dictates how energy companies secure the right to drill.
Access to these resources is secured through an oil and gas lease, a contract permitting the company (lessee) to explore and produce hydrocarbons from the mineral owner’s property (lessor). In the United States, the “split estate” is a common legal concept where mineral rights are legally separated from surface rights. This means one party may own the land while another owns the oil and gas beneath it. The mineral estate is often considered “dominant,” granting the mineral owner the implied right to use the surface as reasonably necessary for extraction.
The permitting process varies based on land ownership. Operations on private or state-owned lands often have a streamlined regulatory process, with permits sometimes processed quickly. Conversely, projects on federal lands, managed by agencies like the Bureau of Land Management, are subjected to an extensive review process that lengthens the timeline for obtaining a permit. This difference in regulatory oversight influences where companies focus their development efforts.
The Extraction and Production Lifecycle
The physical process of bringing onshore oil and gas to the surface is a multi-stage endeavor that begins before drilling. The first step involves preparing the site, which includes clearing vegetation, leveling the ground, constructing access roads, and digging a cellar—a shallow pit around the wellhead for specialized equipment. Once ready, the drilling rig, transported in sections, is assembled for operation.
The drilling phase creates a borehole extending thousands of feet below the surface to reach the target reservoir rock. Modern technology incorporates directional drilling, where the wellbore is steered to run horizontally through the hydrocarbon formation. This technique increases the contact area with the reservoir, maximizing the volume of resources recovered from one surface location.
After drilling, the next phase is well completion, which prepares the borehole for production. Steel casing, a series of concentric pipes, is run into the hole to prevent wall collapse and protect freshwater aquifers. A specialized cement slurry is then pumped down the well and forced up the annular space between the casing and the rock formation. It hardens to provide structural support and permanently isolate the various underground layers.
For certain “unconventional” reservoirs, such as tight sand or shale formations, a well stimulation technique is required to initiate flow. This technique, known as hydraulic fracturing, involves injecting a high-pressure fluid mixture, primarily water and sand, into the horizontal wellbore. The pressure fractures the dense reservoir rock, creating thousands of tiny fissures. The sand, or proppant, holds these fractures open once the pressure is released. This process increases the rock’s permeability, allowing the trapped oil or natural gas to flow into the wellbore and up to the surface.
The Difference Between Onshore Oil and Onshore Gas
Although both are extracted using similar drilling and completion processes, crude oil and natural gas require different handling procedures once they reach the surface. Crude oil is a complex liquid mixture of hydrocarbons, while natural gas is primarily gaseous methane. This distinction drives the design of the surface infrastructure needed to prepare each resource for market.
For crude oil production, the initial surface facility contains separators, which divide the raw well stream into its three main components: oil, gas, and water. The separated crude oil often contains impurities like water and salt, requiring further treatment in heaters and treaters to meet quality specifications for transport. The oil is then routed to storage tanks before being shipped via truck, rail, or pipeline to a refinery.
Natural gas, upon separation, is channeled into a system for purification and compression. The gas must first pass through dehydration units to remove water vapor, as excessive moisture can freeze or cause corrosion in transmission pipelines. After purification, the gas (primarily dry methane) is compressed to high pressures for efficient movement through the pipeline network. These pipelines require intermittent compression stations along the route to maintain the necessary pressure for long-distance delivery to utility companies and end-users.