Hydrocarbon Exploration - Terms Used in Petroleum Evaluation

Terms Used in Petroleum Evaluation

  • Bright spot - On a seismic section, coda that have high amplitudes due to a formation containing hydrocarbons.
  • 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.
  • Dry hole - A formation that contains brine instead of oil.
  • Flat spot - Possibly an oil-water, gas-water or gas-oil contact on a seismic section; flat due to gravity.
  • 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 - proportion 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
  • Lead - a structure which may contain hydrocarbons
  • Play - A particular combination of reservoir, seal, source and trap associated with proven hydrocarbon accumulations
  • Prospect - a lead which has been fully evaluated and is ready to drill
  • 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.

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