Legal Definitions - surface casing

Surface casing refers to the first section of steel pipe, or "casing," that is installed into a newly drilled wellbore, typically in oil, gas, or geothermal operations. It is cemented into place to achieve several critical objectives:

• Protecting shallow groundwater: It isolates and protects freshwater aquifers from potential contamination by drilling fluids, oil, gas, or other substances from deeper formations.
• Providing structural integrity: It stabilizes the upper, often unconsolidated or unstable, sections of the wellbore, preventing collapse during drilling.
• Anchoring safety equipment: It provides a strong, secure foundation for the installation of blowout preventers (BOPs), which are essential safety devices designed to control well pressure and prevent uncontrolled releases of oil or gas.

Here are some examples illustrating the application of surface casing:

• Example 1: Agricultural Area Oil Well

  A company is drilling a new oil well in a rural area known for its fertile farmland, which relies heavily on underground aquifers for irrigation and drinking water. The initial drilling penetrates several hundred feet of topsoil and a significant freshwater aquifer. To prevent any drilling fluids or hydrocarbons from contaminating this vital water source, the company installs and cements surface casing through the entire depth of the aquifer. This creates an impermeable barrier, safeguarding the local environment and agricultural operations.

• Example 2: Urban Fringe Natural Gas Well

  An energy firm is developing a natural gas well on the outskirts of a rapidly growing city. The upper geological formations consist of loose, unconsolidated sands and unstable clay layers. To ensure the stability of the wellbore and provide a secure attachment point for the heavy drilling equipment and critical safety valves (like blowout preventers), surface casing is run and cemented into place. This not only prevents the wellbore from collapsing but also provides a robust foundation for pressure control, enhancing safety for the nearby residential population.

• Example 3: Geothermal Power Project

  A utility company is drilling a deep well to tap into geothermal energy for electricity generation. The initial drilling passes through various layers of soil and rock, including a shallow zone containing groundwater used by nearby communities. The installation of surface casing is crucial in this scenario to isolate this shallow groundwater from the deeper, hotter geothermal fluids and to provide a stable conduit for the drilling process. This ensures environmental protection and operational safety throughout the well's lifespan.