By LOUISE S. DURHAM
The paper "Exploration Potential of an Underexplored Passive Margin: New Plays and Petroleum System in the Suriname Offshore Basin" will be presented at 8:30 a.m. Wednesday, Sept. 14, during the AAPG International Conference and Exhibition in Paris, France.
The paper is the first in an eight-paper session on "New Plays in Rift and Passive Margin Settings," chaired by Salle Ambroisie.
Graphic courtesy of Max A. Torres, Repsol YPF
With global oil demand expanding at a still-rapid clip and hydrocarbon production going full-throttle in fields around the world, oil companies are on the prowl most everywhere looking for the next big find.
One appealing potential target is the Suriname Basin, which encompasses the coastal area of French Guyana, Suriname, Guyana and the eastern part of Venezuela. The basin reaches outward from the coast to the offshore where it grows deeper and the sedimentary package thickens, according to Staatsolie, the Suriname National Oil Co.
The entire on- and offshore basin region is underexplored. Twenty-two wells have been drilled offshore, encountering oil and gas shows in most instances but no commercial quantities of hydrocarbons.
Staatsolie operates the only two producing fields in the basin -- Tambaredjo and Calcutta -- both of which are located onshore. These two fields are credited with harboring 900 million barrels in place and 150 million barrels in place, respectively. Current daily production stands at 12,000 barrels.
Recent regional studies have indicated there is significant potential for additional oil production from the basin and also gas, to a lesser extent.
"The presence of a world-class organically rich source rock (of Cenomanian-Turonian age), a proven petroleum system, several potential trapping mechanisms and very few deepwater penetrations makes the offshore Suriname Basin an attractive target for exploration," said Max Torres, exploration manager for the Caribbean region at Repsol YPF.
In fact, the U.S. Geological Survey tags estimated undiscovered resources for the basin to be an impressive 15.2 billion barrels of oil.
Torres is the co-author of a paper on the basin to be presented in Paris for the AAPG International Conference and Exhibition.
Repsol has diligently evaluated the basin where it holds two offshore blocks. The current focus is on the sizeable Block 30, which encompasses 19,000 square kilometers in water depths ranging between 300 and 2,000 meters.
The proven established petroleum system requires a migration distance of as much as 200 kilometers from the deepwater source basin to the onshore Tambaredjo Field, according to Torres. The areas of proved reserves lack any established source rocks of sufficient maturity for oil generation, and the entrapped oils are typed to source rocks penetrated by offshore wells where they exhibit the maturity needed for oil generation and expulsion.
"The fact we have a billion barrels of oil on the coast tells us we have effective migration from the source to the coastal areas," Torres said. "Our block is on top of what we interpret as the kitchen of the petroleum system, so we think we're definitely in the migration pathway, putting us in a good position to capture oil generated in this kitchen.
"From studying the source rock, we have reason to believe it has tremendous potential," Torres noted. "Based on geochemical studies of the North Coronie well drilled by Elf in 1975 and 3-4 wells drilled in deeper water, we've established that the source rock has above average ability to generate oil."We determined TOC (total organic carbon) values between 5 and 20 percent. These are very important TOC values for a source rock and its generation potential."
More to Come
Repsol acquired 4,000 kilometers of 2-D seismic data from Block 30 last year, which it is currently interpreting. Repsol also has reprocessed 4,000 kilometers of previously existing 2-D, providing them with a total 2-D inventory of 8,000-plus kilometers to work with.
The seismic is revealing features Repsol interprets as slope fan complexes. The Oligocene features are potential deepwater reservoir targets, according to Torres.
"Our next step is to shoot a 3-D program by the end of this year," he said. "These are mainly stratigraphic traps, so we need 3-D -- it's the only way."
Repsol's partner in Block 30 is Occidental, which holds a 30 percent stake. The initial exploratory well in the block likely will get under way by the end of 2007.