LECTURE 22

LECTURE 22

1. CHEMISTRY & NATURE OF PETROLEUM

   • Hydrocarbons
     • natural gas, crude oil, tar, asphalt (s), bitumen (s)
     • ~85% C, ~15% H, small amount S,O,N,metals
     • Isomers
       • same no. atoms, different structure
     • Types
       • aliphatic
         • Impurities
           • Sulfur: poisonous +corrosive
           • CO2: dilute HC, greenhouse, commercial exploitable
           • requires refining processes to separate different size HC, remove contanminations
         • saturated/ unsaturated, can compose of S,N,O instead of C.
       • aromatic
         • HC has specialised ring structures include both single + double bonds
       • Paraffin (alkane)
         • Only contain C +H, single bond, saturated
         • eg: methane
         • <4C: gas at Rtemp, >4 liquid
         • linear/branches
       • Naphtenes (cycloalkanes)
         • HC contain 1/more ring structures
         • eg: cyclopropane/cyclohexane
       • Unsaturated
         • double bonds (alkene)
         • triple bond (alkyne)
     • structure, H:C ratio -> properties
     • Crude oil
       • complex mixtures of HC molecules, varying amount of paraffins, naphthenes, aromatics, dissolved gas
     • Natural gas
       • Dry gas
         • almost pure methane
       • Wet gas
         • contain significant of ethane + propane...
       • LNG
         • liquified natural gas
   • Oil formation volume factor
     • Volume of oil at reservoir conditions required to produce 1 barrel of oil at stock tank condition (rb/stb)
   • Gas-oil ratio
     • ratio of produced gas to produced oil (cubic feet gas/stock tank barrel of oil)
   • Energy content of oil and gas
   • from decomposing of living materials
   • Pour point
     • temp at which liquid become semi-solid
   • API gravity
     • weight of petroleum:water

2. PETROLEUM SYSTEM

   • provide: unifying concept of necessary factors, elements
   • each component has to be assess for risks
     • no direct method to locate petroleum elements
     • data from indirect evaluation techniques
     • not guarantee hydrocarbons exist- dry hole
     • must balance betw. risk vs. reward
   • is a mature source of rock and all its generated hydrocarbon accummulation (elements + processes)
   • essential processes
     • trap formation - generation - migration - accumulation - preservation