Gas Condensate Reservoirs

1
Gas Condensate Reservoirs

• Characteristics
• GOR 3000 200 000 scf/STB
• OGR 300 5 STB/MMscf
• C7 0.5 12 mol
• Tc lt TR lt Tcricondentherm
• Retrograde condensation
• (liquid dropout).
• Condensate blockage
• (productivity loss).
• Condensate revenues.

Whats special about gas condensate reservoirs?
Units
Unit Conversion
Fluid types

• Gas Condensate engineering ? Dry Gas engineering
  except
• A retrograde liquid phase forms in the
  reservoir as pressure falls below dewpoint. This
  liquid HC phase usually has zero or very low
  mobility except near-well. Retrograde
  condensation impacts condensate recovery and well
  deliverability (i.e. economics).
• A significant part of the income of a field may
  come from surface condensate (liquid) production.
  Surface condensate comes from the produced
  reservoir gas when it is processed at the
  surface.
• Most gas condensate reservoirs are produced by
  depletion. Typical depletion recoveries are 60 to
  80 for gas and 20 to 40 for condensate.
• Gas cycling can increase condensate recoveries,
  but will delay gas sales and/or require purchase
  of injection gas -- and therefore is often
  uneconomic.
• When Well BHP falls below the dewpoint,
  productivity can be reduced by the accumulation
  of liquid around the wellbore -- condensate
  blockage. This is an important consideration
  for most low and medium permeability condensate
  reservoirs.

2

• References
• Craft and Hawkins, Petroleum Reservoir
  Engineering, Ch.2
• Muskat, Gas Condensate Ch. 13.
• Gas Condensate PVT Whats Really Important and
  Why?
• SPE Phase Behavior Monograph Chapter 2.

• Examples
• Value of Gas and Liquids CGR - Cn relationship
• Simulation example Depletion and Gas Cycling

Notes