Terms used in petroleum evaluation

• Lead - a structure which may contain hydrocarbons
  Dry Hole - Counter-intuitively, a formation that contains brine instead of oil.
  Flat Spot - An oil-water contact on a seismic section; flat due to gravity.
  Bright Spot - On a seismic section, coda that have high amplitudes due to a formation containing hydrocarbons.
  Prospect - a lead which has been fully evaluated and is ready to drill
  Play - A particular combination of reservoir, seal, source and trap associated with proven hydrocarbon accumulations
  Chance of Success - An estimate of the chance of all the elements (see above) within a prospect working, described as a probability. High risk prospects have a less than 10% chance of working, medium risk prospects 10-20%, low risk prospects over 20%. Typically about 40% of wells recently drilled find commercial hydrocarbons.
  Hydrocarbon in Place - amount of hydrocarbon likely to be contained in the prospect. This is calculated using the volumetric equation - GRV x N/G x Porosity x Sh x FVF
  GRV - Gross Rock volume - amount of rock in the trap above the hydrocarbon water contact
  N/G - net/gross ratio - percentage of the GRV formed by the reservoir rock ( range is 0 to 1)
  Porosity - percentage of the net reservoir rock occupied by pores (typically 5-35%)
  Sh - hydrocarbon saturation - some of the pore space is filled with water - this must be discounted
  FVF - formation volume factor - oil shrinks and gas expands when brought to the surface. The FVF converts volumes at reservoir conditions (high pressure and high temperature) to storage and sale conditions
  Recoverable hydrocarbons - amount of hydrocarbon likely to be recovered during production. This is typically 10-50% in an oil field and 50-80% in a gas field.