Recovery
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"Recent years' dramatic changes in technology are making existing energy reserves stretch further while keeping long-term energy costs lower than they otherwise would have been." Testimony of Chairman Alan Greenspan before the Committee on Energy and Commerce, U.S. House of Representatives - June 10, 2003
Recovery is the process of extracting, or "recovering," oil and gas from a reservoir. When a well is drilled, natural pressures within the reservoir often cause the well to flow on its own. This is called Primary Recovery. However, when the pressure drops and the well stops flowing, about two-thirds of the original oil in place is still underground. To extract the oil and/or gas after initial pressures have dropped off, companies use Secondary Recovery processes. Secondary oil recovery techniques increase pressure in depleted or low-pressure reservoirs. A variety of techniques are used, such as waterflooding, steam injection and gas injection.
In formations characterized by low porosity and permeability, newly drilled wells are often unable to flow on their own. The oil or natural gas is trapped within the reservoir. Well stimulation techniques such as fracing, or frac jobs, are used to initiate production. Frac jobs create fractures within the reservoir so the oil or gas can flow to the wellbore. This is accomplished by injecting fluid at very high-pressures which causes the reservoir to crack, or fracture. Fracture fluid can be oil-based, water-based, acid-based or foam. Prolonged exposure to fluid injection expands the length and width of the fracture, making it easier for more oil, gas, or both to flow into the wellbore. Hydraulic fracturing and acidizing are two of the most common frac treatments used. Hydraulic fracturing injects fresh or salt water. Like its name suggests, acidizing injects acid to dissolve the rock.
Enhanced Oil Recovery (EOR) techniques are becoming increasingly important in making drilling projects economically attractive. Sometimes referred to as Secondary or Tertiary Recovery, EOR is essential to the economic viability of exploration and development in both conventional and unconventional settings.