Although some exploration work (map) has been carried out in the Portuguese sedimentary basins, even the Lusitanian basin, the most explored one, with a drilling density of only 2.4 wildcats per 1000 km2 must still be considered under explored.
Well results were often encouraging, and there is no question about the presence - at least in some of the basins - of all the necessary ingredients (mature source rocks, sealed reservoirs and traps) for potential economic accumulations. However, no commercial production has yet been achieved.
Further exploration efforts are warranted in the "traditional" basins (Porto, Lusitanian and Algarve) since there is scope for new plays to provide for commercial discoveries, as attested by the companies which continue to find worthwhile to invest in Portugal.
In addition, the frontier areas - the outer, deep offshore basins to the West and South of the continental platform - present new opportunities, particularly in view of the very favorable contractual terms and fiscal regimen.
The first
exploration wells were drilled in the early years of the last century. These
were mostly very shallow wells located in the proximity of
occurrences of petroleum impregnated rocks at surface (seeps),
in both the northern and southern parts of the Lusitanian basin onshore.
A petroleum exploration and production concession, covering most of the Lusitanian and Algarve basins onshore, was granted in 1938. Transmission of concession rights occurred a few times but it remained in force until 1969. During the life of the concession some 3264 km of mostly single fold reflection land seismic and gravity surveys were acquired in the Lusitanian basin and a small magnetic survey was executed near Lisbon. A total of 78 wells were drilled in the Lusitanian basin, of which, only 33 were deeper than 500 m. Many of the wells had strong shows and some of them achieved sub-commercial production. During this period only gravity data was acquired in the Algarve basin.
After the relinquishment of the above concession, under a new oil legislation, the prospective areas on- and offshore were divided in blocks in a regular grid, and offered for bidding to the industry in general. This bidding round resulted in the signing of 30 contracts for offshore areas in 1973 and 1974. The last of these contracts was terminated in 1979. During this period, about 21237 km of offshore seismic plus gravity and magnetics were acquired and 22 wells were drilled, of which 5 in the Porto basin, 14 in the Lusitanian basin and 3 in the Algarve basin. All wells were plugged and abandoned, although many encountered good shows and 2 wells, Moreia-1 and 14A-1, produced small amounts of oil on drillstem tests.
After 1979 the rate of offshore exploration decreased considerably. However, in 1978 the interest in the onshore returned. From 1978 to 2004, 39 areas were granted, of which 23 concessions in the onshore of the Lusitanian basin (2 of them with onshore and offshore lots), 15 concessions in the offshore (11 in the Porto basin, 3 in the Algarve basin and 1 in the Lusitanian basin) and 1 preliminary evaluation license in the deep-offshore Algarve basin. During this period, 28 wells were drilled of which 23 in the onshore of the Lusitanian basin and 5 in the offshore (3 in the Porto basin and 2 in the Algarve basin). Again, many of these wells had good shows, mainly of oil. During this period about 36000 km of conventional seismic were acquired, of which about 27600 km under multi-client seismic campaigns - 4600 km by GSI in 1984 and 23000 km by TGS between 1999 and 2002.
Following the TGS campaign, Portugal launched in 2002, a bidding round for 14 blocks in the deep offshore. Two blocks, block 13 and 14, were subject to bids by a group formed by Repsol-YPF (Spain) and RWE/Dea (Germany) and in 2005 these blocks were granted.
At the end of 2006, only one company operated in Portugal, Mohave Oil & Gas Corporation, holding 2 concession areas in the onshore of the Lusitanian basin. In Alcobaça region, Mohave found strong gas shows in two of the wells drilled. In the Torres Vedras region, Mohave drilled a number of wells with oil recovered from fractures and began to perform production tests. The company also acquired 760 km of seismic in the offshore and 224 in the onshore. This seismic and these wells were already accounted in the above totals.
In 2007 there was a significant increase in oil exploration in Portugal, with the signature of 12 new concession contracts:
- on February 1, 2007, 3 concessions contracts were signed with the companies Hardman Resources Ltd., Petróleos de Portugal - Petrogal S.A. and Partex Oil and Gas (Holdings) Corporation, in consortium "Hardman / Galp / Partex", for the areas Lavagante, Santola and Gamba, in the deep-offshore of the Alentejo basin (map).
Since March 25, 2010, by transmission of contractual positions, these areas are held by the companies Petrobras International Braspetro B.V. e Petróleos de Portugal - Petrogal S.A., in consortium ("Petrobras / Galp");
- on May 18, 2007, 4 concessions contracts were signed with the companies Petrobras International Braspetro B.V., Petróleos de Portugal - Petrogal S.A. and Partex Oil and Gas (Holdings) Corporation, in consortium "Petrobras / Galp / Partex", for the areas Camarão, Amêijoa, Mexilhão and Ostra, in the deep-offshore of the Peniche basin (map) and
- on August 3, 2007, 5 concessions contracts were signed with the company Mohave Oil & Gas Corporation, for the areas Cabo Mondego-2, S. Pedro de Muel-2, Aljubarrota-3, Rio Maior-2 and Torres Vedras-3, in the onshore and offshore of the Lusitanian basin (map).
In 2008 the consortium Hardman / Galp / Partex acquired 3.307 km of 2D seismic in the Alentejo basin (map) in order complement and tighten the spacing between seismic lines from the previous seismic survey shot in the area - the TGS-NOPEC's survey shot between 2000-2002.
Also in 2008 the consortium Petrobras / Galp / Partex acquired 8.615 km of 2D seismic in the Peniche basin (map) in order complement and tighten the spacing between seismic lines from the previous TGS-NOPEC's survey, shot between 2000-2002.
Mohave Oil & Gas Corporation, will continue with the onshore acquisition of two surveys of 3D seismic.
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