In 1989 Neste Gas prepared a survey on different ways to store natural gas, which resulted m a job to plan a deep unlined hard rock storage for natural gas with an active volume of 100 million m3. Field work in Mantsala (60 km north of Helsinki) consisted of geological and geophysical surveys followed by diamond drilling, drill hole seismics and rock stress measurements. A way to diminish the volume of gas was to chill it down to temperatures of about - 60°C. This required measurements of rock material characteristics down to that temperature to allow for stability calculations of the frozen rock mass. The standard strength and deformation characteristics (compressive strength, tensile strength, Young's modulus, Poisson's ratio) of the Mantsala gabbro were measured down to - 60°C. The results are compared to earlier frozen rock characteristics in the literature.
ln 1989 ausarbeitete Neste Gas eine Studie ueber verschiedenen Wei sen Erdgas zu lagem, die zu einem Beschaftigung fuehrte, einen unbekleideten Erdgastieflager in harten Gesteinen mit einem Aktivvolumen von 100 MiIIionen m3 zu projektieren. Die Feldarbeiten in Mantsala(60 Km nord von Helsinki) entfassten geologische und geophysikalische Studien gefolgt mit Diamantbohrungen, Bohrlochseismik und Bergspannungsmessungen. Eine Weise das Gasvolumen zu vermindem war es zu abkuehlen bis Temperaturen von - 60°C. Diese forderte Messungen der Felsmaterialseigenschaften bis diesen Temperaturen, die Stabilitatsberechnungen des gefrorenen Gebirges môglich zu machen. Die normalen Festigkeits- und verformungseigenschaften (Druckfestigkeit, Tragfestigkeit, Elastizitatsmodul, poisson's Verhaltnis) der Mantsala Gabbro wurden bis - 60°C gemesst. Die Resultaten werden mit frueheren Eigenschaften des gefrorenen Gebirges im Litteratur vergleicht.
En 1989 Neste Gas preparait une analyse sur les moyens differents de stocker le gaz naturel, qui aboutissait au travail de la planification d'une cavite non revêtue profonde en roche dure pour le gaz naturel avec un volume actif de 100 million m3. Le travail de gisement à Mantsala (60 km au nord d'Helsinki) se composait des recherches geologiques et geophysiques suivies par le forage de diamente, les etudes sismiques du trou fore et les mesurages des contraintes de la roche. Un moyen de diminuer le volume de gaz etait de le refroidir jusqu'à les temperatures d'environ −60°C. Cela exigait les mesurages des caracteristiques du materiel rocheux jusqu' à cette temperature pour rendre possible les calculs de stabilite de la masse rocheuse refroidie. Les resistances et les caracteristiques de deformabilite (resistance à la compression, resistance à la traction, coefficient d' elasticite, coefficient de poisson) du gabbro de Mantsala etait mesurees jusqu'à −60 °C. Les resultats sent compares avec les caracteristiques anterieures de roches refroidies dans la litterature.
Natural gas has been imported to Finland from Soviet Union since 1974. Ten years the annual usage was about I billion m3. Then gas was mainly used by pulp and paper industry. Nowadays more and more gas has been utilised for district heating and electricity production. In 1992 natural gas covered about 8 % of the energy supply of the country with a gas consumption of about 3 billion m3 (+20°C). Locally, in south-eastern Finland, it has a more than 30 % share in energy production (Fig.1). The distribution network now reaches the most important cities on the south-southeastern part of Finland. Its extension to the west coast together with a possible second supply line from Norway through Sweden is discussed as well as a connection to the Baltic gas network through Tallinn. 1.1 Storage needs The Finnish consumption of natural gas varies in cycles of different length. The most important of these are the daily and the annual variation.