derrick floor versus kelly bushing for sale

LEE C. MOORE, Set back capacity 700 klb. Height to rotary beams 24 ft. Drill Floor Height 30 ft.; Complete with: Catwalk, 1 Set of Skidding Gear, Hydraulic jack up unit

Every signed oil well drilling contract includes some form of conditions and agreements. For example, the drilling rig contractor will agree to a specific drilling depth, financial obligations, or where the well will be drilled. Once everything has been agreed upon, the drilling rig will be moved in to prepare for drilling. This is most commonly referred to as the MIRU, or the “Move In and Rig Up”; and in most cases, will include drilling with a jackknife rig instead of the derricks that are built in place. Other important personnel often comprise of:

Commonly referred to as the derrick man, a derrick worker cannot be afraid of heights. This position requires working high above the floor, and is used during regular operations to help when the pipe is being pulled or run. In many of the modern rigs, a rack will vertically hold various sections of drill pipe along the side of the derrick. Each is then added to the drilling string as the bit makes it way deeper and deeper into the ground.

One of the common duties of derrick workers is to add (or remove) sections of pipe from the drill string. During drilling, the pipe is added the deeper into the ground they drill; while sections are removed from the drill string and pulled out of the ground once the drilling has been complete. Sections of pipe are also removed for replacement, or to deal with any drilling issues.

While running and pulling pipe, there are always two floor workers. These two personal are generally referred to as either roughnecks or floor hands, with the more experienced worker being referred to as the lead. The lead operates the lead tong, while the other floor worker operates the back-up tong (or back-up). In most cases, these workers are the most inexperienced members of the rig crew.

As the crew drills the well, the distances are calculated starting from the top of kelly bushing (refers to the sliding bushing located on the drilling rig floor on top of the rotary table that permits the drill kelly  to go down through it when the pipe is turning and the hole is drilled.

Once the casing pipe is permanently cemented into the hole (or set) and either the braiden head or wellhead installed, the measurements from the top of the wellhead to the top of the kelly bushing are calculated and subtracted from all drilling records. This allows precise well records for once the drilling rig is no longer there.

RFRMRD89–Oklahoma City, Oklahoma, United States of America - January 18, 2017. Portable drilling derrick in Devon Oil and Gas Exploration Park in Oklahoma City

RFRMRD8D–Oklahoma City, Oklahoma, United States of America - January 18, 2017. Drilling rigs and derricks located in Devon Oil and Gas Exploration Park in Okla

Because wells are not always drilled vertically, there may be two "depths" for every given point in a wellbore: the borehole, and the datum and the point in the wellbore. In perfectly vertical wells, the TVD equals the MD; otherwise, the TVD is less than the MD measured from the same datum. Common datums used are ground level (GL), drilling rig floor (DF), Rotary table (RT), kelly bushing (KB or RKB) and mean sea level (MSL).

The term "subsea" (SS) by itself should not be used, as it is ambiguous. It could mean: below sea floor or bottom, below mean sea level (MSL), below lowest astronomical tide (LAT), etc.

The acronym TVDSS is commonly used in the oil industry to represent TVD minus the elevation above mean sea level of the depth reference point of the well. The depth reference point is the kelly bushing in the United States and a few other nations, but is the drill floor in most places.

Petrophysicists and drilling operations tend to express depths with reference to the rotary table or the original drill floor; geologists tend to use a common datum such as the mean sea level; geophysicists use the mean sea level. This can introduce much confusion when a unit is not specified with all 3 components: unit, path, and reference.

Common references used in operations include: Rotary Table (RT), Drill Floor (DF), Kelly Bushing (KB), Sea Bottom (SB), Ground Level (GL), Casing Bowl Flange (CBF).