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Geology - Exploration terminalogy
Expert: Manoharan Kothandapani alias Manoharan - 11/5/2009
Question
"Hi, At present I am involved in the exploration study of some prospects. I don't belong to G%26G profession therefore I am interested to know a brief definitions of following terminologies used in the explorations: 1. Lead 2. Prospect 3. Prospect possibilities 4. Mature Province 5. Growth Area 6. Frontier 7. Large %26 Small prospects Plus one question in addition: How could / what criteria should we use to rank different prospects? what are best criteria? hydrocarbon size risk factor economic factor Regards, Kamal
Answer
Dear Kamal,
Thanks for your Question.
Lead and prospect are the terms used in petroleum evaluation
Lead a structure which may contain hydrocarbons.
Prospect is a lead which has been fully evaluated and is ready to drill.
Prospect possibility The parameters that determine the possibility for a prospect are:
1.A simple geological structure, 2. The existence, 3. Reserves, 4.storage conditions and 5. Exploitation values of oil and gas resources in an area, 6.Should have the need and will to exploit and utilize these resources, 6. Market competition, 7.economic partnership 8. Economic competition and 9.The current political and economic situation and in the world is favorable to oil and gas exploration at the place of interest.
Mature Province can be defined in terms of field the field life cycle in oil and gas production is characterized by a life cycle that begins with seismic exploration and is followed by the drilling of exploration wells. The field life cycle comprises five key stages namely seismic, drilling activities, field developmental activities, routine operations like mainainance and decommissioning etc., that bring oil and gas from their locations to the downstream market: Mature province is referred to the province that has almost in the stage of peak production and is in the stage of decline in production.
Growth Area Subsurface geology cannot be examined directly; indirect techniques are used to estimate the size and recoverability of the resource. New techniques have increased the reserves however, significant uncertainties still remain. This phenomenon is called reserves growth and that area or region is called growth area.
Frontier This term no refers to an undeveloped area or field for discovery or research. In oil and gas terminology these are used to define a basin. These basins are characterized by varied geology, age, tectonics, and depositional environments. Hydrocarbon shows in many of these basins are known, and in few basins oil and gas have flowed in commercial /non-commercial quantities. Always there is a continuous increase in area under active exploration in these basins and .normally the management introduce with multi-disciplinary teams and apply risk-reduction technologies to make these area a highly successful basin.
Large and Small prospects: It is also a relative terms on prospect and depend on the economic conditions of the area or operator.
The criteria for different prospect ranking are given below, however the rank varies form basin to basin and criteria also varies on the same basis. More the probability of discovery (POD) is the less Chance of Risk.
Geological risk analysis of individual prospects-the NPD procedure
The probability of discovery (POD )
POD=P1 x P2 x P3 x P4
P1-Probability of efficient reservoir
P2-Probability of efficient trap
P3-probability of efficient source and accumulation
P4-Probability of efficient retention after accumulation
Probability of efficient reservoir ( P1 )
P1=P1a (modified by P1b)
P1a = probability of existence of efficient reservoir facies with minimum net reservoir thickness ( net/gross-ratio, thickness ) as applied the resource assessment
P1b = probability of efficient porosity
Important factors
Well data
Type of facies and facies changes
Depth and diagenesis
Porosity and permeability plot
Porosity maps
Seismic velocities
Probability of efficient trap ( P2 )
P1a= P2b x P2b
P1a= probability of existence of the mapped structural/geometrical body with a
Minimum rock volume as presented the resource assessment.
P2b = probability of efficient seal of the mapped structural/geometrical body.
Probability of efficient source and accumulation ( P3 )
P3 = P3a x P3b
P3a = probability of existence of sufficient volume of mature source rock of necessary quality located in the drainage area for the mapped structure.
P3b = probability of efficient migration of hydrocarbons from the source rock to the mapped structure.
Efficient retention after accumulation ( P4 )
Probability of effective retention of hydrocarbons in the trap from the time of
Migration and until today.
Important factors:
Biodegradation
Erosion of the subsurface
Tilting
Reactivation of related faults
Hope these details would have covered your requirements,
Thanks,
Manoharan Kothandapani alias Manoharan
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