Seismics give good hope for Cuban findings

June 18, 1997 MacDonald Oil Exploration Ltd., has completed processing of an initial 110 km seismic survey, following a year of field work on its onshore Block 22 concession in Cuba. The seismic data, reprocessed by CGG Geophysics of Canada, is very encouraging. The data was examined by MacDonald Oil's geologist and an independent geophysical consultant who have confirmed the identity of four possible structures on the western portion of Block 22. Based on these positive results MacDonald Oil plans to complete additional seismic acquisition and a possible first well later in the year, as funds become available.
The four structures are all fault related roll-overs, with multiple reservoirs within a clastic section that is most likely Tertiary in age. The reservoirs of all these structures appear to be Tertiary clastics (sandstones) and perhaps platform carbonates, but not reefal buildups. Because each structure is faulted, the reservoir would be compartmentalised and since several faults cut to the surface,there is a possibility of a breached reservoir. Under this Tertiary, good reflections were obtained of possible upper cretaceous clastics and carbonate reservoir rocks.

Cuatro Caminos structure: The largest of the four structures, the Cuatro Caminos, is a 72 sq km structure with an 18 sq km independent closure. The main thrust fault on this structure does not cut to surface. A small additional amount of seismic data is needed to confirm closure in the south-west and east part of the structure to upgrade Cuatro Caminos to a drillable prospect.
The second structure identified, named Laguna de Guano, is about 10 sq km in size. It appears to have multiple reservoir enclosures although there are numerous tension faults, some of which appear to go to the surface.
The third structure is smaller and less well-defined than the second structure. It is not possible to confirm the fault orientations on this structure, from existing data.
The fourth structure is a poorly-defined fault-dependent roll. More seismic is needed to confirm closure on these three structures.
A surface soil geochemistry survey completed over the seismic lines, has provided encouraging evidence tending to indicate the presence of heavy gases in clusters within the limits of the four structures.

MacDonald Oil is operator of the exploration program for Block 22, a 9,900 sq km concession in Camaguey, Las Tunas, and Granma provinces of south-east Cuba. It is the largest on-shore hydrocarbon exploration block in the southern Cuba petroleum province, known to contain light oil in the Pina field north-west of this very prospective back arc basin.