glossary

With reference to measurements-while-drilling (MWD), the data is transmitted to the surface shortly after being recorded.

Amount in % of crude oil produced from the total oil-in-place of a reservoir, depending on the individual reservoir parameters and the quality of the crude oil produced. Currently, the average global recovery factor is approx. 35 %.

A subsurface body of rock having sufficient porosity and permeability to store and transmit fluids. Sedimentary rocks (see sediments) are the most common reservoir rocks because they have more porosity than most igneous and metamorphic rocks and form under temperature conditions at which hydrocarbons can be preserved.

The term reservoir implies storage. Hence the reservoir rock is the rock in which the hydrocarbons can be stored and from which it can be produced (see also porosity). The reservoir rock can be, but must not be, the rock in which the hydrocarbon was generated (source rock)

The machine used to drill a wellbore. Major components of the rig include the mud tanks, the mud pumps, the derrick or mast, the drawworks, the rotary table or topdrive, the drillstring, the power generation equipment and auxiliary equipment.

The revolving or spinning section of the drillfloor that provides power to turn the drillstring in a clockwise direction. The rotary motion and power are transmitted through the kelly bushing and the kelly to the drillstring. Almost all rigs today have a rotary table, either as primary or backup system for rotating the drillstring. Topdrive technology, which allows continuous rotation of the drillstring, has replaced the rotary table in certain operations. A few rigs are being built today with topdrive systems only, and lack the traditional kelly system.

Member of the drilling crew who works under the direction of the driller to make or break connections as drill pipe is tripped in or out of the hole. On most drilling rigs, roughnecks are also responsible for maintaining and repairing much of the equipment found on the drill floor and derrick. The roughneck typically ranks above a roustabout and beneath a derrickman, and reports to the driller.

The complete operation of removing the drillstring from the wellbore and running it back in the hole. This operation is typically undertaken when the drill bit becomes dull or broken, and no longer drills the rock efficiently. A general estimate for a competent crew is that the round trip requires one hour per thousand feet of hole, plus an hour or two for handling collars and drill bits. At that rate, a round trip for a 30,000-ft (9230 m) well might take 32 or more hours, especially if intermediate hole-cleaning operations must be undertaken.

Any unskilled manual laborer on the rigsite. A roustabout may be part of the drilling contractor's employee workforce, or may be on location temporarily for special operations. Roustabouts are commonly hired to ensure that the skilled personnel that run an expensive drilling rig are not distracted by peripheral tasks, ranging from cleaning up location to cleaning threads to digging trenches to scraping and painting rig components.