Explorers finding more success in stratigraphic traps

Feb. 27, 2020
A new report from Westwood found that more oil and gas were discovered in stratigraphic traps than any other trap type in the last decade.

Offshore staff

LONDON – A new report from Westwood found that more oil and gas were discovered in stratigraphic traps than any other trap type in the last decade. 

According to Dr. Keith Myers, president, Research at Westwood, excelling in stratigraphic trap exploration is now the key to top quartile exploration performance.

In the report “Clastic Stratigraphic Traps – What has Driven Exploration Performance?,” the firm has analyzed stratigraphic trap exploration between 2008 and 2019 in 66 basins and 113 different plays. It found that 35 Bboe has been discovered in clastic stratigraphic traps since 2008, comprised of 22 Bboe (132 tcf) of gas and 13 Bbbl of oil. Seventy five percent of the oil resources and 95% of the gas resources were discovered in deepwater.

The most prolific basins were Suriname-Guyana, the MSGBC, the Rovuma-Rufiji and the Colville, where major new plays dominated by stratigraphic traps emerged in the period. Upper Cretaceous aged stratigraphic traps delivered 42 commercial discoveries, with a total of 9 Bbbl of oil and 39 tcf of gas, of which 7 Bbbl of the oil is in the Suriname-Guyana basin and 20 tcf is in the MSGBC basin. Oligocene aged plays delivered seven commercial discoveries with a total 40 tcf of gas – of which 36 tcf was in the Rovuma basin in Mozambique.

There were also notable disappointing campaigns targeting stratigraphic traps in the Carnarvon, Sierra Leone-Liberia, and Central North Sea basins from which important lessons have been learned, Myers said.

Stratigraphic traps had a larger average discovery size of 280 MMboe, and a lower drilling finding cost of 0.5 $/boe, compared to other traps types in the period.  Stratigraphic traps had a commercial success rate (CSR) of 32%, in line with other trap types. According to Myers, the evidence shows they are not higher risk than other traps, contrary to many explorers’ preconceptions.

Industry is also getting better at exploring for stratigraphic traps with the CSR increasing to 50% in the 2017-2019 period from 21% between 2014-2016. The more effective use of seismic attributes and better integration with geological models has had an impact in some basins.

Marine turbidite sandstones in stratigraphic traps in passive margin settings were the most targeted delivering 31 Bboe (90%) of discovered commercial resources. For marine turbidite plays, stratigraphic traps on graded slopes in the lower slope to basin floor settings performed best in terms of both discovered volumes and success rates. Finding stacked traps or extensive traps was key to commercial success.

Commercial deepwater standalone discoveries of more than 300 MMbbl in clastic reservoirs are now most likely to be found in stratigraphic traps and traps with stratigraphic components, Myers concluded.