Written in the rocks

10/10/2006 Thick sedimentary sequences exposed to view make the far northern Svalbard islands a veritable archive for petroleum geologists. They provide significant help in the hunt for oil and gas deposits on the NCS.

This article was first published in Norwegian Continental Shelf no. 2-2006

Norway's continental shelf is completely different in geological terms from the Norwegian mainland, which consists primarily of igneous or metamorphic rocks. Including such types as gneiss, granite, quartz and mica schists, these either originated deep beneath the Earth's crust or have been fundamentally altered by folding and compression. The NCS, on the other hand, has been formed by another process altogether. Here lie the last residues of earlier landscapes and mountain chains eroded down to gravel, sand and clay. These materials are encountered today after compression into sedimentary rocks such as conglomerates, sandstones, siltstones and shales. So studying  geological processes on the Norwegian mainland is little use for understanding how sediments have formed on the seabed. But Svalbard provides an exception. This Arctic archipelago, and the main Spitsbergen island in particular, is particularly interesting for anyone wanting to learn about strata beneath the bed of the Barents Sea.

Unlike the mainland, with its very ancient basement rocks, Svalbard is nothing special in geological terms. But petroleum geologists love its thick sequences of sedimentary rocks. These show what was deposited and how - crucial knowledge when searching for new petroleum deposits or seeking to improve the performance of producing fields. Sediments from all the most important geological periods in the Barents Sea have been preserved on Svalbard. The islands also have another major advantage - accessibility. Despite lying 567 kilometres from the northernmost point of mainland Norway, large parts of them are free from snow and ice for at least part of the year. And an airport as well as other infrastructure at Longyearbyen and Ny Ålesund provide good jumping-off points for conducting field work.

Scale

People are small compared to the size of the planet, which can make it hard to  comprehend the difference in scale when studying and understanding the Earth's crust or a mountain chain. Anyone who looks at a
detailed satellite image of Svalbard or flies over the islands will be struck by the diversity of landscape forms and colours in its highlands. Steep-sided mountains and cross-cutting valleys provide insights into the three-dimensional structure of the bedrock. The various strata are piled on each other in full view. In many places, movements in the Earth's crust have displaced the originally horizontal layers so that they are now tilted. That allows geologists to follow continuous strata over large areas. They can almost leaf backwards and forwards through the geological eras. Fossils - both microscope and huge - provide the "page numbers" in this history book. Such long and continuous time series are seldom encountered anywhere but on Svalbard. The oil industry has devoted much time and money to geological studies in the islands. Universities pursue field courses there, postgraduate students find thesis subjects, and consultants pursue company-funded investigations. In addition to collecting rock samples, maps have been compiled and scientific articles published about Svalbard's geological development. Petroleum specialists ultimately want to create models of the geology and its structures, and relate these to information gathered from the NCS.

Claimed



Two signs found in the Svalbard Museum at Longyearbyen and dated July 1919 announce that Birger Jacobsen claimed the rights to possible oil deposits in a radius of 300 metres. The first drilling for oil was carried out by Britons near Barentsburg at the mouth of the Is Fjord in the late summer of 1920. This site was probably selected because small natural deposits of gas and asphalt were known to exist in Triassic rocks, which could be a sign of hydrocarbons deeper down. But the well had only reached a depth of four metres when coal mining company Store Norske Spitsbergen Kullkompani intervened and maintained that it had exclusive rights to the whole area. Its demand that drilling be halted immediately was backed by an overwhelming superiority of personnel, and the British were compelled to pack up and quit.

Exploration for oil got seriously under way in 1963, when Norsk Polarnavigasjon drilled in the Grøn Fjord area as an extension of pre-1914 surveys and geological fieldwork in 1926. These had found free oil and asphalt in thick Triassic rocks, but the 1926 survey's  recommendation that a well be drilled to a depth of 1 200 metres took almost 40 years to be implemented. Even with relatively simple equipment, the 1963 well reached a depth of almost 1 000 metres three years before Ocean Traveler spudded the first well in the Norwegian North Sea. Norsk Polarnavigasjon also drilled a well on the Bell Sound in southern Svalbard during 1967, again with a simple rig which featured a home-made blowout preventer. This structure is now to be restored and erected at the Svalbard Museum. Interest in oil exploration increased during the 1960s and 1970s, and several projects were mooted. Texaco and the Caltex group drilled as deep as 3 304 metres on Ishøgda in 1965. A total of 20 oil wells have been completed in the islands, although their locations were chosen for accessibility rather than on the basis of detailed geological assessments. Mainly pursued in Jurassic and Cretaceous rocks on the west coast, this work never yielded any specific results. Traces of petroleum were found, but nothing in commercial quantities. Seismic surveying was actively pursued in 1984-92 to learn more about Svalbard's sub-surface. About 1 000 kilometres were shot on land and 1 500 in fjords and around the coast. Based on these data, the last major exploration drilling projects in the archipelago were carried out by Norsk Hydro and Store Norske Spitsbergen Kullkompani in 1991 and 1994 respectively - with disappointing results. The only real strike has been made by the Russians when they were drilling for coal in Petunia Bay in 1992. Trust Artikugol encountered hydrocarbons - and problems. No BOP had been required because coal was the target, and the mining company suffered two minor uncontrolled blowouts. One of these caught fire, and the rules have since been tightened. Russians still have plans for to drill more wells in a search for gas, and the final chapter in Svalbard's petroleum exploration history almost certainly remains to be written.

Updated: 04/09/2009