ALBERT

Description: The Ayoluengo Field, commonly cited as the only onshore oil field in Spain, was discovered in June 1964 by Amospain, a joint venture of Chevron, Texaco and CAMPSA, by then the state-owned company. Ayoluengo is located about 300 km north of Madrid in the southern part of the Basque–Cantabrian Basin, a geological region where natural oil seeps, tar sands and asphalt have been recognized in outcrops since the early twentieth century. Now, 50 years after the first oil in 1967, the field has a cumulated production of 17 million barrels of oil. The 50-year production concession expired at the end of January 2017 and the field is now closed, awaiting a bidding process for a new concession to be awarded. The Ayoluengo Field consists of a NE–SW-orientated salt-cored anticline, related to Triassic salt movements. The field is divided into two large structural blocks by a normal fault. Oil and gas production comes from a series of thin lenticular fluvio-lacustrine sandstone packages of Late Jurassic–Early Cretaceous age. More than 50 separate oil and gas sandstone beds have been identified by drilling. This multilayer reservoir, together with the structural component, means that Ayoluengo is considered to be a grouping of hundreds of small oil and gas fields. After years of intense exploration activity, the Ayoluengo Field still, surprisingly, remains a unique oil discovery and is the only onshore commercial oil field in Spain and also the only one in the entire Iberian Peninsula. This geological singularity has resulted in recurrent discussions between petroleum geologists because it is difficult to explain why a petroleum system is working uniquely at this particular spot and nowhere else within such a vast territory.

Description: The onset of hydrocarbon exploration and production activity in Spain dates back to 1860, mainly consisting of rudimentary mining of tar sands, asphalts and bituminous shales. Petroleum exploration drilling started properly in 1900 by simply locating wells in the vicinity of petroleum impregnations at the surface, often with little or no geological input. Until 1940, most of these early exploration wells were shallow tests (less than 500 m deep), commonly operated by small private companies with foreign investment, but no oil and gas accumulations were found. Systematic hydrocarbon exploration in Spain began in 1940 after the Spanish Civil War (1936–39). Two oil companies led these activities: CAMPSA, a state-run petroleum monopoly established in 1927; and CEPSA, a fully private Spanish company founded in 1929, which created the exploration subsidiary CIEPSA in 1940. However, the poor economic situation in Spain, the currency shortage and the international embargo after the Civil War made it very difficult to import any rig capable of deep drilling until the late 1940s. During the early 1950s, the domestic and international position of Spain started to improve. Slowly, foreign hydrocarbon exploration companies (especially German and American) began to form partnerships with national and Spanish private companies. They conducted the acquisition of the first seismic reflection surveys and were responsible for a considerable increase in deep drilling and pioneering borehole logging. Noteworthy amongst these were the intense activities of the VALDEBRO, a consortium formed in 1952 by American companies and the state. In 1960, 100 years after the initiation of petroleum production in Spain, the first commercial success was obtained with the discovery of dry gas in the Castillo-1 well, drilled by CIEPSA in the onshore Cantabrian–Basque Basin. This find was later complemented by the oil discovery at Ayoluengo in 1964 by a joint venture led by CAMPSA and which still remains the only commercial oil field discovered onshore Spain.

Description: The San Pedro basin (SPB) is located at the south-eastern margin of Hispaniola Island (Dominican Republic and Haiti). It is the largest offshore basin of the Dominican Republic with an extension of 6000 km2. The basin has a maximum water depth of 1600 m and is positioned to the rear of the Muertos Thrust Belt (MTB). The SPB bounds to the West by The Azua basin which has a proven petroleum system and small oil production has been recovered from the Maleno and Higuerito fields. While in the scientific literature the SPB and the Azua basins have been considered as disconnected sedimentary systems, our current study suggests both are shared a common tectonic evolution and therefore the presence of an untested petroleum system in the SPB can be expected. We have carried out a detailed review and synthesis of the onshore systematic geological mapping (SYSMIN I & II Programs) together with the integration of a large volume of sub-surface geophysical data. This includes analysis of 60 exploration wells provided by Banco Nacional de Datos de Hidrocarburos (BNDH) of the Dominican Republic, processing of new 2D multi-channel seismic data from the Spanish Research Project NORCARIBE, re-processing of legacy seismic profiles and interpretation of gravity and magnetic data. Our results led us to propose a new evolution model for the SPB. Basement of both basins consists of Cretaceous sedimentary and volcanic rocks of intra- and back-arc settings. A change in the stress regime in the Campanian led to partial inversion of the basement units favouring the deposition of two main sequences of Campanian to Maastrichtian and Palaeocene? -Eocene age in a submarine foreland setting. Due to collision between the Carbonate Bahamas Province and Hispaniola in middle Eocene, compressional stresses were transferred to the south where Cretaceous and Paleogene sediments were deformed forming the current configuration of MTB and generating a new accommodation space where SPB was developed since Upper Eocene / Oligocene until Present. While the Azua basin was finally exhumed after Miocene/Pliocene, most of SPB continued as an actively subsiding basin. This new model has allowed identification of the main elements of the petroleum system in the SPB basin: a mature Upper Cretaceous source rock and Oligocene to Miocene carbonate and clastic reservoirs interbedded with sealing shales and marls. Main traps (structural and stratigraphic) are of Oligocene to Miocene age and their formation seems to be synchronous to oil generation. While main elements of the petroleum system seem to be present in the basin, timing is a key issue that must be addressed and assessed in any future exploration in the basin.