INTEREST offshore Kenya is set to revive thanks to Origin Energy finding evidence of natural oil seepage from the sea floor which lines up with “very large” structures identified from seismic surveys.
Clues pointing to what may be an active petroleum province emerged as a direct result of a satellite oil seep survey covering Lamu Basin blocks L8 and L9 conducted by the Australian company.
“The slicks seen in block L8 are the largest and highest ranked in offshore Kenya and coincide with several main prospects mapped from seismic,” said Barry Rushworth, director at Pancontinental Oil & Gas (PCL), another Australian firm that partners Origin in the licences.
“This survey, which was commissioned by operator Origin Energy from Fugro NPA, gives considerable encouragement to PCL’s interpretation that a working petroleum system may be present in our Lamu Basin acreage.”
In September, 2006, PCL farmed out 75% of blocks L8 and L9 to Origin Energy in return for full funding of a seismic programme and the drilling of an exploration well in each block. PCL also holds a 40% interest in nearby block L6 with 60% joint-venture partner Gippsland Offshore Petroleum, which is also Australian.
A number of unassigned slicks were also seen in block L6 and interim mapping results also show significant potential from seismic in that block.
This acreage is next door to block L5 where, in 2006, Aberdeen company Dana Petroleum drilled the abortive Pomboo-1 exploration well, which was partnered by Global, Repsol and operator Woodside.
A second scheduled well was cancelled by Woodside and, more recently, it was reported that Dana with Global were contemplating suing their Australian partner for that cancellation.
PCI said that 3,759km of new seismic data had been acquired across L8 and L9, and in block L6, an extensive airborne gravity survey and a 1,240km seismic survey have been completed.
The characteristics of some slicks identified in the survey are consistent with seepages of light oil or condensate, according to the company.
Oil&gas geological systems are “dynamic” and may leak along permeable zones such as faults while still retaining large volumes of trapped oil&gas.
A number of notable prolific oil provinces have oil seeps, including offshore Angola, the Niger Delta and the Gulf of Mexico.
The phenomenon is commonplace and far more oil escapes into the natural environment this way than through man-made spills.
However, seismic mapping and oil-slick studies give just an indication of the potential for oil or gas reserves. Only drilling and further work can establish the size and value of any oil and/or gas discovery.
PCI said that, in L8 and L9, seismic mapping showed a number of very large geological prospects. The largest of these is the Mbawa prospect, which covers 360sq km at the Jurassic level and about 140sq km at the shallower Tertiary mapped level.
“These areas are very large by oil industry standards,” it claimed.
At an intermediate Tertiary/Cretaceous level within the Mbawa prospect, Origin has calculated potential exceeding 5billion barrels oil-in-place or 7trillion cu ft of gas-in-place.
The Nanaa Central prospect is said to possess similar potential, and a number of other prospects are also said to offer significant potential.
Rushworth said: “Continued exploration of this under-explored region is increasingly justified by the results of this survey and the very large structures identified on the seismic data. These structures are sufficiently large to easily contain more than 1billion barrels of oil or several TCF of gas, but only drilling will confirm the real potential of these areas.”
Origin is the operator of blocks L8 and L9 with a 75% interest. Pancontinental holds the remaining 25%.