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U. S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY

APPENDIX A
Input for Monte Carlo simulations of the Agbada Reservoir Assessment Unit
Date:…28 May 1998
Assessment Geologist:…Michele L. Tuttle, Michael Brownfield, Ronald Charpentier
Region (name, no.):…Sub-Saharan Africa/Antartica, Region 7
Province Name:…Niger Delta
Province Number:…7192
Priority or Boutique?… Priority
Total Petroleum System (name, no.):… Cenozoic Niger Delta, 719201
Assessment Unit (name, no.):…Agbada Deltaic Reservoirs, 71920101
* Notes from Assessor

CHARACTERISTICS OF ASSESSMENT UNIT
               
Oil or Gas (<20,000 cfg/bbl oil overall):…….     Oil 
               
What is the minimum field size?……….     1        mmboe grown (>1mmboe)
(the smallest field that has potential to be added to reserves in the next 30 years)
               
Number of discovered fields exceeding minimum size:…….....… ……….Oil:      481          Gas:      93     
Established (>13 fields)      X      Frontier (1-13 fields)              Hypothetical (no fields)            
               
Median size (grown) of discovered oil fields (mmboe):
1st 3rd     60      
2nd 3rd
     22      
3rd 3rd
   23    
Median size (grown) of discovered gas fields (bcfg):
1st 3rd     116    
2nd 3rd
     58      
3rd 3rd
    119   
               
Assessment-Unit Probabilities:
Attribute         Probability of occurrence (0-1.0)
1. CHARGE: Adequate petroleum charge for an undiscovered field >minimum size………………     1.0    
2. ROCKS: Adequate reservoirs, traps, and seals for an undiscovered field > minimum size……     1.0    
3. TIMING OF GEOLOGIC EVENTS: Favorable timing for an undiscovered field > minimum size     1.0    
               
Assessment-Unit GEOLOGIC Probability (Product of 1, 2, and 3):……...…….....….     1.0      
               
4. ACCESSIBILITY: Adequate location to allow exploration for an undiscovered field
> minimum size……………………………………………………..………………..……..…………     1.0    
 

 
UNDISCOVERED FIELDS
Number of Undiscovered Fields: How many undiscovered fields exist that are > minimum size?: 
(uncertainty of fixed but unknown values)
               
Oil fields:……………..….……... …………..min. no. (>0)     200     median no.     580     max no.     1000   
Gas fields:…………………..….. …………..min. no. (>0)     100     median no.     250     max no.     400    
               
Size of Undiscovered Fields: What are the anticipated sizes (grown) of the above fields?:
(variations in the sizes of undiscovered fields)
               
Oil in oil fields (mmbo)………………..…… ...min. size     1     median size     12     max. size     1500    
Gas in gas fields (bcfg):…………………... ...min. size     6     median size     60     max. size     7000    
               
               
AVERAGE RATIOS FOR UNDISCOVERED FIELDS, TO ASSESS COPRODUCTS
(uncertainty of fixed but unknown values)
Oil Fields: minimum   mean   maximum
Gas/oil ratio (cfg/bbl oil)………………………...………    1000         1770         3000   
NGL/gas ratio (bbl ngl/mmcfg)…………………....….    20         34         45   
               
Gas fields: minimum   mean   maximum
Total liquids/gas ratio (bngl/mmcfg)………………..………     50           61           70    
               
               

SELECTED ANCILLARY DATA FOR UNDISCOVERED FIELDS
(variations in the properties of undiscovered fields)
Oil Fields: minimum   median   maximum
API gravity (degrees)…………………….………….     10           40           60    
Sulfur content of oil (%)………………………...…..    0.07         0.15         0.60   
Drilling Depth (m) ……………………..………….…    350        2100       4500  
Depth (m) of water (if applicable)……………...…..     0          40         200   
               
               
Gas Fields: minimum   median   maximum
Inert gas content (%)……………………….....……    low                           
CO2 content (%)……………………………….....…    low                           
Hydrogen-sulfide content(%)………………...……  low-nil                         
Drilling Depth (m) ………………………..……..……    680        2200       4500  
Depth (m) of water (if applicable)………………...…     0           40          200   
               
ALLOCATION OF UNDISCOVERED RESOURCES IN THE ASSESSMENT UNIT
TO COUNTRIES OR OTHER LAND PARCELS
(uncertainty of fixed but unknown values)
1. Nigeria represents     90     areal % of the total assessment unit
               
Oil in Oil Fields:     minimum   median   maximum
Richness factor (unitless multiplier):……….…..…..                     1                
Volume % in parcel (areal % x richness factor):….                    90               
Portion of volume % that is offshore (0-100%)…….                    40               
               
Gas in Gas Fields:     minimum   median   maximum
Richness factor (unitless multiplier):…………..…..                     1                
Volume % in parcel (areal % x richness factor):….                    90               
Portion of volume % that is offshore (0-100%)…….                    40               
               
2. Cameroon represents      5     areal % of the total assessment unit
               
Oil in Oil Fields:     minimum   median   maximum
Richness factor (unitless multiplier):……….…..…..                     1                
Volume % in parcel (areal % x richness factor):….                     5                
Portion of volume % that is offshore (0-100%)…….                    70               
               
Gas in Gas Fields:     minimum   median   maximum
Richness factor (unitless multiplier):…………..…..                     1                
Volume % in parcel (areal % x richness factor):….                     5                
Portion of volume % that is offshore (0-100%)…….                    70               
               
*Uncertainty about this mean will be calculated using statistical methods
               
3. Equitorial Guinea represents      5     areal % of the total assessment unit
               
Oil in Oil Fields:     minimum   median   maximum
Richness factor (unitless multiplier):……….…..…..                     1                
Volume % in parcel (areal % x richness factor):….                     5                
Portion of volume % that is offshore (0-100%)…….                    100               
               
Gas in Gas Fields:     minimum   median   maximum
Richness factor (unitless multiplier):…………..…..                     1                
Volume % in parcel (areal % x richness factor):….                     5                
Portion of volume % that is offshore (0-100%)…….                    100               


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U. S. Geological Survey Open File Report 99-50H