1. Exploration Opportunities Onshore Suriname
Presentation for AAPG Annual Convention, Dallas, April 2004

2. Geographical Position

3. Available Exploration Blocks
Tambaredjo, Calcutta Staatsolie Licenses, excluded
The onshore exploration blocks on offer are indicated in blue. The locations of the Tambaredjo and Calcutta fields are located in separate blocks (not included in the offer). Tambaredjo is producing since 1982 and Calcutta started production in 2003, shortly after discovery. Reserves are estimated respectively at 170 and at least 15 MMbbls. To date some 45 MMbbls have been produced. In 2004, oil has been discovered in Miocene reservoirs west of Calcutta. This discovery, conservatively estimated at 5 MMbbls reserves, is being appraised.
The area of the blocks varies between 680 (Wayombo block) and 2,774 km2 (Coronie block). All blocks are located in the coastal lowlands.

4. Presentation Outline Regional Setting Petroleum Geology
Onshore Play Concept
Onshore Prospectivity
Conclusions

5. Outline of Guyana basin and petroleum occurrences
Regional Setting
Paramaribo
200 m
2000 m
Suriname
Venezuela
Brazil
Fr. Guiana
100 Mi
100 km
Trinidad
Atlantic Ocean
Takutu Basin
6 N o
4 N
8 N
10 N
55 W
57 W
51 W
53 W
59 W
Outline of Guyana basin and petroleum occurrences
Demerara high
DSDP+ODP wells
Tambaredjo + Calcutta
oil fields
Guyana
Suriname-Guyana Basin Petroleum Occurrence
200 m
Trinidad
Atlantic Ocean
2000 m
10 N o
DSDP+ODP wells
Demerara high
2000 m
8 N o
Venezuela
200 m
Guyana
6 N o
The Suriname-Guyana Basin (after the USGS) stretches from the Venezuelan boundary (Antillean Arch) to French Guyane. The southern limit is the outcrop of the crystalline Proterozoic basement.
Oil is being produced onshore Suriname in the Tambaredjo and Calcutta fields (the Staatsolie heartland). Some 900 shallow wells (mostly production wells in the heartland) have been drilled onshore. Most of the onshore wells date from the eighties onwards, except for the western onshore, where drilling started in Although most wells had oil and gas shows, no commercial quantities of hydrocarbons were found outside the Staatsolie heartland, mainly due to lack of structure and/or trap.
22 exploration wells have been drilled offshore, most of them with oil and gas shows. The deeper shelf wells have been drilled in the late sixties and the seventies, with Cretaceous shelf carbonates as main objective. The wells near the coast have been drilled during the eighties.
Oil has also been discovered in the Takutu basin (1981), a graben straddling the boundary of Guayana and Brazil. The Takutu graben is the southernmost extension of an early Jurassic rift valley which preceded the drift phase of Africa and North America. The V-shaped palaeo-coast line suggests that a proto-Orinoco or proto-Amazon rivers drained into the early Central Atlantic Ocean.
One well has been drilled on the Demerara high, a remnant of continental crust.
The onshore prospective area covers about 12,000 km2.
Fr. Guyane
Tambaredjo/Calcutta oil fields
> 1 billion barrels in place
4 N o
Brazil
Suriname
Takutu Basin
Brazil
100 Mi
59 W o
57 W o
55 W o
53 W o
51 W o
100 km

6. Tambaredjo/Calcutta oil fields > 1 billion barrels in place
Regional Setting
Coastal Belt Basement Depth
Tambaredjo/Calcutta oil fields
> 1 billion barrels in place
Top of the crystalline basement underneath the Cretaceous and Neogene sediment wedge.
The horizon has been mapped using a variety of sources. Offshore, mainly seismic has been used, calibrated to some of the near shore wells which bottomed in the basement. Onshore, a number of wells have reached basement. Over the Nickerie area (West Suriname), pre-second world war, refraction data has been used.

7. Onshore Play Cartoon Coastal Plain Tidal Flats Coastal Marine
Cartoon depicting the mostly Palaeocene-Eocene stratigraphic trapping conditions in the Suriname coastal belt in the Cretaceous-Cenozoic sedimentary wedge. The onshore sedimentary sequence belongs to the post-rift sedimentary history. There is no evidence of Jurassic age pre-rift of Cretaceous syn-rift sediments onshore Suriname. The maximum thickness of the sedimentary sequence onshore is about 2,000 m in the northwest of the country.

8. Source Rock Distribution
Turonian/
Cenomanian Petroleum System 34
The Turonian/Cenomanian marine source rock is considered the most important one. Thickness up to 550 m have been observed with Total Organic Carbon levels between 4 and 7%. It is mature for oil over large parts of the basin off the main flexure zone
A biomarker study on the oils from Tambaredjo and Calcutta indicated that they are sourced from a Late Cretaceous fully mature marine source rock
Towards the kitchen area oil gravity decreases.
Migration routes exceed 100 km (possibly 200 km from hot part of kitchen
Modelling of the maturity indicates that over the basin north of the shelf (north of the non-active transfer zone) the source rock is in the oil window, locally possibly in the early gas window. Oil expulsion started during Eocene times.
In addition, a Jurassic and Tertiary petroleum system has been inferred. However, data is limited and the implication for the onshore play is as yet speculative.
Tambaredjo/Calcutta oil fields
> 1 billion barrels in place

9. Turonian/Cenomanian System (1)
Source rock present in all wells off deep shelf
Thickness between 120 and 550 meters
Type II organic matter (oil-prone)
TOC 4-7%; 14% in the DSDP wells
Oil expulsion started in Eocene times
Source rock currently mature for oil
Summary of Cenomanian-Turonian source rock data. Note that the TOC (total organic carbon) levels have been recorded in wells on the edge of the shelf. It is likely that off the shelf, in the so-called hot pod, TOC levels might be higher (ref. the DSDP wells of the the Demerara high).

10. Turonian/Cenomanian System (2)
Oil gravity decreases towards the kitchen area
Migration routes exceed 100 km
Tambaredjo and Calcutta crude sourced from Cretaceous marine organic matter
World-class source rock equivalent to Naparima Hill (Trinidad) and La Luna (Venezuela)
The Canje source rock has been deposited in the same realm as the world-class rource rocks known from Trinidad, Venezuela and Colombia. Also the Tarfaya oil shales in Morocco occur in the same time interval.

11. Events Chart Turonian/Cenomanian Petroleum System Source Rock
Cretaceous
Palaeocene
Eocene
Oligocene
Neogene
Source Rock
Reservoirs
Seals
Trap Formation
Oil Generation
Retention
Tectonics
Critical Moment
Time
Habitat
Chart showing the timing of events contributing to the hydrocarbon habitat of the Suriname coastal belt. The petroleum system is assuming access to the world-class Cenomanian/Turonian source rock and kitchen mapped offshore.
Post-rift thermal subsidence in transform passive margin setting

12. Onshore Play Concept Tambaredjo Field
Depth contour map of the top of the Lower Saramacca member (Palaeocene), represented by a possible high-stand clay.
The oil column is some 500 ft. Several OWC’s have been observed
Note that no structural control exists. Towards the West and East similar depth are observed, but no hydrocarbons occur.
Towards the south, reservoirs either onlap or shale out.
Depth Contour Map Top Lower Saramacca Member

13. Onshore Play Concept Tambaredjo Field Foreshore Estuary Tidal Flats
Coastal Plain
Map showing the clay percentage distribution of the Lower Saramacca member (Palaeocene) and an interpretation of the depositional environment. This incorporates three (or four) sequences. Large variations in shaliness can be observed. Blue represent 100% shale, red (yellow) 100% sand. The relation between increased shale levels and the presence of oil is striking (note the outline of the Tambaredjo field). The same is valid for the Weg naar Zee area where encouraging oil shows have been observed.
Outboard, this member becomes increasingly more sandy. The same is observed towards the west and east. In addition between the Weg naar Zee area and the Wayombo area a sand-prone “corridor” is observed.
Blue high percentage
Yellow and red low percentage
Clay % Distribution Lower Saramacca Member

14. Onshore Play Concept Calcutta Field
Depth contour map of the top of the Upper Saramacca Member (Eocene), representing an unconformity. The strata underneath the unconformity dip slightly more towards the north. This unconformity is the same as the so-called bauxite unconformity further inland. This map shows that there is no structural element at he location of the Calcutta field. West and East of the oil field similar depth occur, but no hydrocarbons.
Depth Contour Map Top Upper Saramacca Member

15. Onshore Play Concept Calcutta Field Foreshore Estuary Tidal Flats
Coastal Plain
Unit 2 of the Upper Saramacca member is more clay-prone. The extension of the Suriname rivers becomes evident. The offshore wells are sandy. A biostratigraphical study pointed to a coastal marine to shallow marine setting. The Calcutta field is interpreted as being located in a tidal fat setting. From south to north the environment of deposition changes from coastal plain to shallow marine. In between, a tidally influenced area can be inferred.
In this unit several independent oil accumulations have been observed.
Blue high percentage
Yellow and red low percentage
Clay % Distribution Upper Saramacca Member (Unit 2)

16. Tambaredjo/Calcutta Fields
Stratigraphic traps (up-dip pinch-outs)
No structural trapping
Best trapping potential in tidal flat setting
Tidal channels not connected to the coastal plain possess the best trapping chance when sealed by high-stand clays
Palaeo-estuaries fixed from PC to MI
Westward drift relatively young
Summary of observations in Tambaredjo/Calcutta area.

17. Onshore Play Concept Explains:
Presence of oil in Tambaredjo and Calcutta
> Good seal in clay-dominated tidal flat setting
Absence of hydrocarbons in wells drilled close to present-day estuaries, or in a palaeo-estuary (e.g. Wageningen area)
> Lack of seal
The newly developed play concept gives an adequate explanation for the oil occurrence in Tambaredjo and Calcutta and the absence of oil elsewhere.

18. Play Map
Compilation play map of the Suriname coastal plain, based on observations in the area of the Tambaredjo and Calcutta fields. The estuaries have been indicated in yellow. Note the presence of an extensive carbonate bank offshore. Carbonates persisted through most of the Late Cretaceous and the early Tertiary (Paleogene). After the Miocene the Amazon river probably broke through and the equatorial current started to supply mud along the shore of Suriname, effectively killing off carbonate growth. The carbonates also prevented strong long-shore currents, giving further support to the observation that the estuaries must have been perpendicular to the then existing coast line.
The concept of estuaries, alternating with mud flats is extrapolated to un-drilled areas on the coastal plain. The Nickerie rivers draining the area west of the Bakhuis mountains, explain the sandy nature of the Wageningen wells and the lack of seal. The Corantijn river is also suspected to have been associated with an estuary. In between these rivers mud flats with tidal inlet complexes are expected. These areas are indicated in green. Within these areas the chance of finding another Tambaredjo-like oil field is considered high.

19. Onshore Prospectivity
Access to mature Turonian-Cenomanian source rock
The offshore study provided information to reconstruct the outline of the hydrocarbon kitchen area. The green area encompasses the area where the Turonian-Cenomanian Canje source rock is thought to be mature. Mature means that organic matter starts to break up into mobile carbon chains. In order for these chains to start moving (migration), pressure within the source rock has to built up sufficiently over time to fracture shales, enabling hydrocarbons to move out of the source rock into sand beds (the so-called carrier beds). This expulsion usually happens at slightly higher temperatures (VRe>0 .7% at 90 degrees Celcius).
Tambaredjo/Calcutta oil fields
> 1 billion barrels in place

20. Onshore Prospectivity
Material Balance Estimate
Mature Cenomanian/Turonian Source Rock
Prospective Area
Kitchen
Share (km2)
Average charge minus migration loss (MMbbls)
Nickerie
1,000-3,000
2,300
Coronie
1,500-2,000
2,040
Tambaredjo/
Calcutta/ Wayombo/WnZ
500-1,000
870
When the source rock thickness, area, TOC (total organic carbon) and the so-called HI index (hydrogen index) are known, it is possible to calculate how much hydrocarbons could have been generated. This process is called the material balance calculation.
Maturity modeling, based on the thermal burial history, indicates that hydrocarbon expulsion started in Eocene times (about 40 million years ago) and continues to the present day.
Input parameters:
Gross source rock thickness m, N/G 10-50%, TOC 7-9%, HI grHC/kgTOC, migration loss %
> 4 Billion Barrels
Total Charge Expectation

21. Play Map
Compilation play map of the Suriname coastal plain, based on observations in the area of the Tambaredjo and Calcutta fields. The estuaries have been indicated in yellow. Note the presence of an extensive carbonate bank offshore. Carbonates persisted through most of the Late Cretaceous and the early Tertiary (Paleogene). After the Miocene the Amazon river probably broke through and the equatorial current started to supply mud along the shore of Suriname, effectively killing off carbonate growth. The carbonates also prevented strong long-shore currents, giving further support to the observation that the estuaries must have been perpendicular to the then existing coast line.
The concept of estuaries, alternating with mud flats is extrapolated to un-drilled areas on the coastal plain. The Nickerie rivers draining the area west of the Bakhuis mountains, explain the sandy nature of the Wageningen wells and the lack of seal. The Corantijn river is also suspected to have been associated with an estuary. In between these rivers mud flats with tidal inlet complexes are expected. These areas are indicated in green. Within these areas the chance of finding another Tambaredjo-like oil field is considered high.

22. Onshore Prospectivity
Opportunity Ranking
2.7 Billion Barrels
Total Oil in Place Expectation
Prospective acreage size (potential oil in place volumes) have been plotted against the probability of success.
This plot allows the ranking of exploration opportunities and provides a powerful portfolio management tool.
The risk estimate has been based on the following assumptions:
Estimate based on prospective area size, calibrated with known Tambaredjo/Calcutta volumes

23. Conclusions Good oil potential onshore outside existing fields
Low reservoir and charge risks
High seal and trap risks
Best trapping possibilities away from present-day estuaries (corrected for present-day westward drift)
Expectation: billion barrels in place

24. Please visit our booth (#48) in the International Pavillion

25. Commewijne River Estuary
Staatsolie Maatschappij Suriname N.V.
Mrs. Marny Daal-Vogelland
Dr. Ir. H.S. Adhinstraat 21, Flora
P.O. Box 4069
Paramaribo, Suriname, South America
Phone: (597)
Fax: (597) ,
URL:
For more information, please contact:
Staatsolie Maatschappij Suriname N.V.
Mrs. Marny Daal-Vogelland
Dr. Ir. H.S. Adhinstraat 21, Flora
P.O. Box 4069
Paramaribo, Suriname, South America
Phone: (597)
Fax: (597) ,
URL:
Commewijne River Estuary
Suriname