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Oil & Gas IQ's A to Z of Drilling - Part I - A to M

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Posted: 11/01/2011
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A is for Annulus

Annulus is the latin word for ring, and in a drilling context it is the ring of empty space that surrounds a pipe in a well bore. For this reason it is sometimes referred to as the "annular space."

B is for Borehole

The borehole is also referred to as the wellbore, and essentially is the portion of the well that is excavated during the drilling process.

C is for Cementing

This is the process undertaken by the cementing crew to pump cement into a wellbore, either for the purpose of sealing components in e.g. to seal the annulus or to plug a well before abandonment.

D is for Derrick


This is the load-bearing structure, used to support the crown block (topmost part of the tower) and the drillstring (tube that pumps drilling fluid to the drill bit) in a rig. Usually these are assembled piece by piece in a bolted construction and are disassembled if relocation is necessary.

E is for Evening Tour


The evening tour, pronounced "tower" in many places, is the duty shift on a drilling rig that starts in the afternoon and runs throughout the evening. There will usually be two separate crews working twelve-hour tours to maintain the rig at its operational peak.

F is for Fluids

Fluids in oil and gas can refer to a number of specific substances, from the clay/chemical/water mix that is pumped down the drill pipe to lubricate the drilling bit, to the fracturing fluids that are injected under high pressure into rock formations to crack them and enable ease of drilling.

G is for Geophysics

This is the study of the planet’s physical properties and the physical processes acting upon it above and within the earth. It includes geomagnetism, seismology, meteorology, and oceanography. Geophysics is crucial in the petroleum industry as geophysical information is used by exploration and development (E&D) teams to make predict the whereabouts, nature and size of subsurface hydrocarbon deposits.

H is for HPHT

HPHT stands for High-Pressure, High-Temperature and refers to the types of well that experience extremes of both of these variables. HPHT wells are increasingly more common in the oil and gas sector as "easy oil" deposits are running out across the globe.

I is for the International Association of Drilling Contractors (IADC)

This is a body made up of drilling contractors, oil and gas operators and service companies that undertakes or sponsors education, research into accident prevention, and novel drilling technologies on behalf of the drilling community.

J is for Jackup

A jack-up rig is a floating drilling rig that can be towed from field to field. When the jackup arrives at the drilling location, retractable legs are "jacked down" onto the seafloor and weighed down to securely drive them into the seabed. The "jacking mechanism" begins when all of the jackups legs are rooted and the barge and drilling structure are raised above the water so that tidal pressures affect only the legs and not the greater drilling apparatus.

K is for Kick

A kick is experienced when water, gas, oil, or other fluids enter into the wellbore during drilling. The kick occurs because the pressure exerted by the column of drilling fluid is not great enough to overcome the pressure exerted by the fluids in the rock formation being drilled. If kicks are not swiftly dealt with, there is the possibility of a well blowout.

L is for Licensing Round

Licensing rounds are initiated by governmental bodies offering acreage for leasing by exploration and production (E&P) companies in return for a fee and obligations, such as drilling a well. Exploration licenses are usually valid for a period of 5 years, in which time, if hydrocarbons are discovered a separate production license or production-sharing agreement is drawn up before drilling begins.

M is for Managed-Pressure Drilling

Managed Pressure Drilling (MPD)is increasingly used in HPHT and extreme HPHT circumstances to control the annular pressure throughout the wellbore, this limits the amount of potential for kicks to occur during the drilling process.


Thank you, for your interest in Oil & Gas IQ's A to Z of Drilling - Part I - A to M.
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