S

Saddle

A saddle that is partly mounted to a pipe in order to stop a leak or to create an outflow. 
 

Safety valves

Safety valves are located on the surface where they close off the production flow in case a disaster like fire, collision or sabotage should occur. 
 

Scale

A deposit of mineral salt, which may occur on wellbore tubulars and/or other elements since changing temperatures affect the saturation of produced water and pressure conditions in the production conduit. 
 

Scrubbing

To remove impurities from a fluid or gas. 
 

Secondary recovery

To maintain or increase the pressure in the subsoil by injecting gas, water or other substances. 
 

Sector

A specified area on the continental shelf where the rights to the minerals in that area belong to a certain country. 
 

Sediments

Lose materials or particles that settle on the bottom of wet areas. 
 

Sedimentary basin

An area with heavy sediments that have settled through million of years, which has generated oil or gas. 
 

Shale shaker

This is probably the most important equipment on the rig. It is used to drill out solids from the drilling mud. It works like a very efficient vibrating sieve. 
 

Shaped charge

A small container loaded with explosives, which are put into a perforating gun. The load frees a small stream of high-velocity particles that penetrate the casing collar, the cement and the formation. 
 

Show

Evidence of proven carbon hydrates in an exploration well. 
 

Shut in

To close the valves at the top of the well, which causes the oil to stop flowing. Also a term used to describe a well where the valves have been closed. 
 

Shut down

When work is temporarily stopped on a platform. 
 

Sidetrack drilling

To drill a secondary hole from another point in the well. Also called sidetracking. 
 

Sidewall cores

Faster than core samples but not sufficient alone to assess the potential of a field. 
 

Skid

To push the rig, for instance moving it from one well slot to another. 
 

Skimmer

Special equipment that is able to dross or suck up a layer of oil on the surface of the sea. They are typically mounted on catamarans. 
 

Skin factor

The degree of deterioration of the permeability in close vicinity to the wellbore. 
 

Sleeve fitting

Joint used to cover another pipe in order to stop a leak. 
 

Slick

Pool of oil (on sea surface). 
 

Slick Line

A single-strand wireline used to run and retrieve tools as well as flow control elements. 
 

Slips

Steel wedges used to hold the drill string in place in the rotary drill. 
 

Slush pumps

Pumps used to keep the drilling mud in circulation. 
 

Snubbing

A technique that enables drill pipes to be run up and down in the hole despite pressure on the drill bit and its equipment. 
 

Solution gas driver

The most common way to retrieve oil to surface. The oil is pushed up due to the expansion pressure from the gasses that are set free when the boiling point is surpassed. 
 

Sour crude

Crude with a high content of sulphur. 
 

Sour gas

Natural gasses with high contents of hydrogen sulphide or hydrocarbons. Should not be inhaled as it may be deadly. 
 

Spacing

The distance between several wells all producing from the same reservoir. Spacing is typically measured in hectares. 
 

Specific gravity

The number of grams that 1 cubic meter of a material weighs at a certain temperature. Mass per unit of volume. 
 

Spudding in

To drill a new hole at the bottom of the sea with a large-diameter drill bit. 
 

Spur line

An undersea pipe line with a relatively small diameter. It connects a production platform with a storage tank or with another pipeline, leading oil or gas into the shore.

Squeeze

To inject fluids under high pressure, especially during cementing. 
 

Stand-down

When it is no longer possible to employ people on the platform. People are not laid off but they receive reduced payment. 
 

Stand of pipe

The length of one or more sections of pipes that are kept ready in the derrick or during drilling. A single section of pipes is called a joint. 
 

Stand pipe

The pipe that leads the drilling mud into the derrick and from there into the rotary tube. 
 

Step out well

See outstep well
 

Stimulation

A way to make the well produce larger amounts of oil or gas. Methods are injecting acid into the wellbore, blowing holes in the side or cleaning the hole for debris. 
 

Straddle

A method to shield the inside of connection(s) from the flow of fluids and/or from the reservoir pressure. 
 

Stripper

An almost dried out oil well. 
 

Success ratio

The relationship between the number of proven wells and the number of dusters or non-profitable wells. 
 

Swab valve

The upper valve on the christmas tree, giving horizontal access to the wellbore. Also see christmas tree
 

Swabbing

When fluids are sucked into the wellbore due to the piston effect produced when pulling out the drilling equipment. 
 

Sweet crude

Crude with a low content of sulphur. 
 

Swivel

A type of rotating coupling that the entire drill string is connected to.

Synthetic natural gas (SNG)

Gas produced from carbons or oil.

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