“Missed” gas deposits are being searched for in Yamal with use of a new technology
16:53 27 мая 2020
Категории: News in English
Scientists of Tomsk Polytechnic University developed a technology that allows detecting previously “missed” oil and gas deposits and thereby prolonging life of extractive fields. It is not necessary to conduct additional research for searching — the existing data set is enough. The technology is used on the Yamal Peninsula — Tambeyskoye and Malyginskoye areas.
With help of the developed algorithms the polytechnic specialists analyze logging data. Logging is the most widespread type of geophysical research. When drilling, a geophysical probe is lowered into the well. The probe examines it and adjoining rocks for a number of parameters. They are used to judge presence or absence of mineral resources, their quantity and quality of the host rock. The technology offered by Tomsk Polytechnic University is a complex of the specially developed algorithms; it is suitable for searching for both oil and gas, as the press service of the University reports.
“Hydrocarbons in the well are not spilled like a lake. They are located there in the form of fluids, in other words, mixed with water in pores of sandy rocks. How to determine whether the sandstone contains just water or a water-oil or gas fluid? This is done according to logging data and indicators of rock resistivity”, said Igor Melnik, a developer of the technology and professor of the division of oil and gas engineering at Tomsk Polytechnic University.
If the rock contains only water, resistance is low, since natural water with its minerals and salts is a good conductor of electricity. If there is oil or gas in the rock, resistance is increased, since hydrocarbons are insulators.
“This is how it should be in theory. But in practice it turns out that sometimes well logging operations show low resistance, and there is still oil or gas in the rock. The problem was discovered in the 80-ies, and specialists are still looking for effective methods to detect “missed” layers, because the “missed” layer is lost money. It turns out that confusion is caused by a mineral pyrite and clay, which can be a conductor under certain conditions. If they are in the rock, well logging operations show low resistance, and it seems that there is no oil”, the scientist explained.
The algorithms developed by the polytechnic specialists distinguish layers with geochemical indicators of presence of hydrocarbons and low resistance, which contain pyrite or metamorphosed clays, from the arrays of logging data on various parameters. Such layers can be considered potentially containing hydrocarbons.
“It took long time to work out the algorithms, and now we reached the level of reliability of 70-80%. Being based on data from Tomsk Oblast, we can say that standard methods of interpretation of logging of appraisal and exploration wells give confidence of 18-20%”, said Igor Melnik. “The technology has been successfully tested in eight state programs on study of Cretaceous and Jurassic strata in more than 200 wells of old and undistributed fund of Tomsk Oblast”.
For the present day the researchers identified more than ten layers potentially containing hydrocarbons in Tambeyskoye field in Yamal-Nenets Autonomous Okrug.
“Further the customer will make a decision to check these layers. This is usually done by perforation of a well”, said the developer of the technology.