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Year in review: 2017's Top 10 discoveries

Audrey Leon looks at some of 2017's 10 largest offshore discoveries. First published in the December 2017 OE.

While exploration hasn’t been as hot as it used to be, the finds this year have been big and plentiful. Wood Mackenzie has provided the year’s 10 biggest finds by volume.

#1 – Yakaar, Senegal

In May this year, Kosmos and partner BP discovered gas at the Yakaar-1 prospect, saying that the find could support the development of a second LNG hub. Yakaar-1 was drilled using the Atwood Achiever drillship. The well may contain 15 Tcf gross Pmean gas resource, according to Kosmos.

Yakaar, which is in the Cayar Offshore Profond block about 95km northwest of Dakar, was drilled in nearly 2550m water depth to 4700m total depth.

The well intersected a 120m gross hydrocarbon column in three pools within the primary Lower Cenomanian objective and 45m of net pay.

Kosmos estimates that Yakaar-1 discovered a gross Pmean gas resource of approximately 15 Tcf. An appraisal program is being planned to delineate the Yakaar discovery, the company said back in May.

“The result confirms our view of the potential scale of the petroleum system offshore Mauritania and Senegal, in particular the basin floor fan systems which have now been further derisked, with the well demonstrating that reservoir and trap both work in these previously untested fairways,” said Andrew G. Inglis, chairman and CEO, in May this year.

#2 – Zama, Mexico

Since Mexico’s historic oil reform was passed in 2013, the country has made significant strides by allowing in private and foreign investment. In July this year, Talos Energy backed by partners Sierra Oil and Gas and Premier Oil touted the 1+ billion bbl discovery at their Zama-1 exploration well, offshore Mexico.

The find has been described as one of the 20 largest shallow water finds in the past 20 years and the first private sector oil discovery in Mexico. Zama-1 was spud in May this year and drilled in 166m water depth, about 37mi off Tabasco, in Block 7 in the Sureste Basin, using the Ensco 8503 semisubmersible.

The well reached an initial shallow target vertical depth of approximately 11,100ft (3383m). Talos says it hit a 1100ft (335m) oil bearing interval, with 558-656ft (170-200m) of net oil pay in Upper Miocene sandstones with no water contact. Oil samples indicate light oil, with API gravities between 28° and 30° and some associated gas.

Talos reported later that same month that Zama-1 failed to find further volumes in a deeper target. Zama-1 was drilled to a total depth of 4108m (13,478ft).

Map from Premier Oil.

According to partner Premier Oil, the estimated recoverable P90-P10 gross unrisked resources are in the range of 400-800 MMboe, including the volumes that extend into the neighboring block.

#4 – Snoek, Guyana

In March this year, supermajor ExxonMobil confirmed a new discovery offshore Guyana at the Snoek well, in the southern portion of the Stabroek block – the same block containing the major Liza discovery currently under development.

Exxon encountered more than 82ft (25m) of high-quality, oil-bearing sandstone reservoirs. The well was spud in February this year by the Stena Carron drillship, and drilled to 16,978ft (5175m) at 5128ft (1563m) water depth.

Snoek is about 5mi (9km) to the southeast of the 2015 Liza-1 discovery. Stabroek covers 6.6 million acres (26,800sq km). Exxon said Snoek targeted similar aged reservoirs as encountered in previous discoveries at Liza and Payara. In March, Wood Mackenzie said Snoek adds another 220-370 MMbbl to its estimate of the block.

Exxon and its partners are continuing to have success at Stabroek. In October 2017, ExxonMobil confirmed further potential with a fifth oil discovery in the Turbot-1 well, which is in the southeastern portion of the block, approximately 30mi (50km) to the southeast of the Liza phase one project.

#6 – Neptune, Russia

In early October, Gazprom Neft subsidiary Gazpromneft-Sakhalin, completed drilling at its Neptune appraisal well at the Ayashsky license in the Sea of Okhotsk. Gazprom Neft reports initial in-place reserves estimated at 255 million tonnes of oil equivalent. A detailed assessment of these reserves will be prepared by mid-2018.

The Ayashsky block in the Okhotsk Sea forms part of the Sakhalin-3 project. The block is in the northeastern part of Sakhalin Island’s continental shelf, 55km from the coast. Water depth at the field is 62m. Gazprom Neft says that 2150sq m of 3D seismic has been shot inside the Ayashsky block.

#8 – Macadamia, Trinidad

BP's Juniper platform, offshore Trinidad and Tobago. Photo from BP.

In May this year, BP Trinidad & Tobago (bpTT) found success at the Macadamia wildcat, which was drilled to test exploration and appraisal segments below the existing SEQB discovery, which sits 10km south of the producing Cashima field, offshore Trinidad.

The well penetrated hydrocarbon-bearing reservoirs in seven intervals with approximately 600ft of net pay. Combined with the shallow SEQB gas reservoirs, the Macadamia discovery is expected to support a new platform within the post-2020 timeframe, BpTT said at the time.

“Savannah [another discovery made at the time] and Macadamia demonstrate that with the right technology we can continue to uncover the full potential of the Columbus Basin,” said Norman Christie, regional president for bpTT, back in June.