Hasła / Terms beginning with S
- Sealing rock
A lithological interval of a petroleum formation of which petrographic composition and structural patterns make it impervious to hydrocarbons.
- Sedimentary basin
A natural depression in the Earth's crust in which sediments are deposited (those rich in organic matter may become the source of hydrocarbons). Usually, sedimentary basin is located lower than areas that are adjacent thereto or tends to subsidize. Normally, a water reservoir (a lake, sea or an ocean) or (in arid or semi-arid climate regions) a sand-filled landlocked basin is a sedimentary basin.
Source: Jaroszewski W., Marks L. i Radomski A. Słownik geologii dynamicznej. Wydawnictwa Geologiczne. Warszawa, 1985
- Seismic surveying
A method used in geological structure investigations, based on generation of seismic waves that reflected by subsequent rock layers return to the ground surface where they are recorded by special instruments. Processed (e.g. in the form of an image) and interpreted seismic data provide an insight into the deep geological structure of the Earth. Seismic surveying results enable geologists to draft geological maps, cross-sections, etc.
- Sets of lithofacies
Genetically related lithofacies that were formed in a similar sedimentary environment, but by different depositional processes, e.g. a set of sand coast lithofacies will include dune, beach and littoral lithofacies.
Fine-grained sedimentary rock with specific shale texture, which is characterized by breaks along parallel bedding called fissility (breaking along flat planes). Besides predominant clay minerals and quartzite (silica), shale contains in various proportions the following key minerals: carbonates (calcite, dolomite), feldspars, pyrite and phosphates. In addition, a shale may contain calcareous, silicious or phosphatic remains of skeletons. Among traditionally distinguished rock types, fissility is typical to some sedimentary (sedimentary shales) and metamorphic (crystalline shales) rocks – both of them fall into several subtypes. Sedimentary shales are fine-grained (claystone/mudstone) rocks formed by diagenesis of sediments in a marine or lacustrine environment. Exposed on the ground, they are characterized by specific fissility, but deep below the ground, subjected to high pressures and temperatures they are solid, very hard and impermeable. Black shales, in Poland formed in Ordovician and Silurian (approx. 420-480 million years ago), have attracted attention of upstream industry due to the presence of oil and gas in rock pores.
Ring-shaped end of the casing string or of a bailer.
- Slick water
A fluid used in hydraulic fracturing, composed mostly of water with a small admixture of a natural polymer (e.g. guar gum). Slick water initiates propagation of fractures, opens micro- and natural fractures and establishes a wide area of the well contact with the reservoir. Since slick water has very low viscosity, it is unsuitable for transport of proppant to the fractures. It is used primarily for fracturing brittle shales with a small share of clay minerals.
Source: Piotr Kasza, Instytut Nafty i Gazu, Oddział Krosno Zabiegi hydraulicznego szczelinowania w formacjach łupkowych. Nafta-Gaz, December 2011.
- Smectite illitization
The process of smectite (a clay mineral) transformation into illite, a different clay mineral. The transformation occurs during the process of rock formation (diagenesis) with increasing sediment burial depth. Changes in the illite to smectite ratio are used for the determination of the thermal maturity of organic matter.
- Sonic log (SL)
Measurement of velocity rate of acoustic wave propagation in the borehole. Acoustic wave emitted by the logging tool propagates across the rocks and returns to receivers installed in the tool. The measurements provide information, among other things, on the porosity of the rocks.
- Sound screen
Soundproof barrier built around the drill site to minimize the level of noise that is associated with drilling operations.
- Source rock
A lithological interval of a petroleum formation of which petrographic composition contains an adequate quantity of fossil organic substance that enabled generation and expulsion of hydrocarbons as a result of thermocatalytic processes.
Agents that prevent re-precipitation of dissolved reaction products from the solution in the pores of the pay horizon. They form soluble chemical bonds with metal hydroxides and oxides.
Source: Witold Górski Wykonywanie zabiegów intensyfikacji wydobycia ropy naftowej. Instytut Technologii Eksploatacji – Państwowy Instytut Badawczy. Radom, 2007
- Stratigraphic correlation
A key method applied in geology to determine the geological age and position of rocks, geologic events and processes by comparing them in different geological profiles.
The process of sedimentary basin sinking (deepening).
- Sweet spot
A location within a reservoir with the best reservoir parameters.