Natural gas exploration and production
The Viura natural gas deposit is located in the subsoil of the Autonomous Community of La Rioja, about 12 kilometres from Logroño.
It is a geological structure composed of sandstone which was deposited more than 100 million years ago, during the Cretaceous Period, and the pores of the sandstone contain natural gas at about 4,000 metres below ground level. Since then, successive layers of clays have been deposited over this sandstone, forming a perfect seal that has preserved this deposit.
This deposit is estimated to contain at least a proven volume of three billion cubic meters (3 BCM) of natural gas. This quantity would be equivalent to10% of the anual consumption of natural gas in Spain.
Hydrocarbon exploration in La Rioja goes back to the Fifties of the last century. Since then, many companies have dedicated important technical resources and made numerous investments in this area but without success.
The prize came in July 2010 when the consortium led by Unión Fenosa Gas Exploración y Producción, S.A., a subsidiary of the Union Fenosa Gas Group ('UFG' 58.8%), along with Sociedad de Hidrocarburos de Euskadi, S.A. ('SHESA' 37.7%) and Oil Gas Skills, S.A. ('OGS' 3.5%) discovered a conventional, natural gas deposit, after the completion of an exploratory well called Viura-1.
This well, located in the municipality of Sotés, reached the depth of 3,788 metres (from December 2009 to February 2010). In the tests that were made after its drilling, sufficient volumes of natural gas production were registered which justified going ahead with the project.
The promoters decided to complete a series of additional works which would allow the geometry of the deposit to be better defined to evaluate its real production potential.
Firstly, a three-dimensional study was made of the subsoil geometry under a surface area of 232 Km2, which extended over 23 municipalities of La Rioja during serveral months (November 2012-March 2013).
To achieve this study, thousands of geophones were installed on the surface, capable of detecting the reflection of the waves generated by vibrating trucks and small, superficial and innocuous, explosive charges.
The system used would determine the time taken for the waves to return to the surface, after being reflected, as if by mirrors, from the different layers of the subsoil. Once processed, the thousands of millions of data collected in this way allowed a precise three-dimensional image of the subsoil to be obtained down to a depth of 6,000 metres.
In June 2013, a new exploratory well was begun, called Viura 3, located in the municipality of Hornos de Moncalvillo, 1.3 km from Viura 1, with the purpose of confirming the lateral continuity of the deposit and its total thickness, as well as to determine the connectivity between both wells.
A long term production test of the two wells, Viura-1 and Viura-3, was begun in the first months of 2015, the objective of which will be to study the behaviour of the deposit regarding its gas extraction capacity, and to predict its future evolution and to thus optimize its development, from both a technical and economic point of view.
To carry out this test it was necessary to construct facilities for the transport and treatment of the gas extracted from these wells.
The process plant was constructed in lands adjacent to Viura-1, which treats the extracted gas before its delivery to the national gas pipeline network, for the necessary separation of water and condensate, the reduction of the CO2 content and its odourization.
The Viura 3 well is connected to this plant thanks to a new 1,400 metre long and 10 centimetre diameter underground gas pipeline.
In order to guarantee the electrical supply to the plant, a 1,500 metre long overhead cable was installed, which connects with the nearby electricity transport network.
A 2,400 metre long and 30 centimetre diameter gas transport pipeline takes the gas treated at the plant to the delivery point, located at the junction with the Enagas national gas pipeline network, in the municipality of Navarrete.
The concession to operate is granted
On 21 July, a Royal Decree, published in the Official State Journal –BOE–, awards the concession to operate the natural gas deposit. It is granted for a period of thirty years, with the possibility of two extensions of ten years each. A positive report by the La Rioja regional government and a favourable environmental impact assesment have been issued for the concession.
The Royal Decree also establishes a set of measures to guarantee safety throughout the lifetime of the concession. No adverse effects of any nature at all were found during the exhaustive tests carried out.
Putting the deposit into production contributes to partially mitigate the need for natural gas imports into Spain, which satisfies practically 100% of the national demand.
The Viura project has been developed in an environmentally respectful manner and has brought about important investments in the region which have contributed to the creation of employment and favoured the economic and social development of the whole community.