Horizontal
Multi-Lateral Drilling

Oil well productivity is a function of surface area. The greater the surface area, the greater the instantaneous production potential (holding the reservoir characteristics constant).
Over the past 30 years operators have learned how to use different technologies depending on the reservoir characteristics of their targeted oil-bearing rock.
Vertical Well
Vertical Well
Vertical wellbore technology allowed for the production of conventional oil reservoirs. High permeability, good oil viscosity, thicker reservoirs and good porosity rock are the necessary requirements for vertical conventional reservoirs to be economic. An average vertical well may contact up to 30 feet of reservoir that it produces from. These reservoir characteristics allow the vertical wellbore to drain a wide area of oil-bearing rock. The downside of vertical well production is the limited drainage radius around the wellbore. This reduces the ability to produce economically from marginal permeable reservoirs. Vertical wells are often uneconomic to use in the production of thinner or poor permeability rock.
Horizontal Well
Horizontal Well
The next advancement was horizontal wells. Horizontal hydraulically fractured technology allows for the production from unconventional oil reservoirs by increasing the drainage radius though the creating of fractures. Low permeability, poor to good viscosity, thinner reservoirs and marginal porosity are the characteristics of an unconventional reservoir, The average hydraulically fractured well may contact up to 3,000 feet of reservoir that it produces from. Hydraulic fracturing increases wellbore permeability and that allows for unconventional reservoirs to be produced economically. The downside to fracturing technology is the high cost to complete the horizontal well, often representing one half of the total well cost.
Horizontal Multilateral Well
Horizontal Multilateral Well (Birds Eye View)
Multilateral Open Hole (MLOH) horizontal technology allows the for production from reservoirs with characteristics between unconventional and conventional. MLOH projects tend to have low to medium permeability, poor to good oil viscosity, thinner reservoirs and marginal to good porosity. An average MLOH , with 6 legs, may contact up to >18,000 feet of reservoir. The 6 or more lateral legs decrease the drainage radius needed to facilitate production of from marginal permeability and porosity oil-bearing reservoirs by placing an adjacent wellbore (leg) in an evenly spaced pattern. Due to its open-hole design, these wells do not require expensive completions or steel casing in the lateral portion of the wellbore. The well design allows MLOH horizontals to access significantly higher surface area and increase the total area of drainage versus hydraulically fractured horizontals while achieving this at a lower per well cost.