kelly bushing and rotary table in stock

B.Roller Kelly bushing can be square drive or pin drive, and can be applicable for rotary table size from 17½ to 37½. By changing roller sizes, the bushing can accommodate square kellys from 2½ to 5¼ or hex kellys from 3 to 6. Roller Kelly bushing has three series: SD(light duty), MD(medium duty) and HD(heavy duty).

Square drive Roller Kelly bushing consists of lower body half, upper body half, roller, roller pin and etc. when the bushing is installed to square kelly or hex kelly, the square part of the lower body half can be fitted in the square of the master bushing. When operating, the rotary table drive master bushing and master bushing drive Roller Kelly bushing and Roller Kelly bushing drive square kelly or hex Kelly to rotate, such is the torque transporting. The lower body half is conically shaped to readily enter the bore of the master bushing and automatically center bushing and drill string within the bore of the master bushing. Inside rollers are journal bearings which are fitted to the roller pin, when kelly rotates and moves downward, the rollers rotates with Kelly, such change sliding friction to rolling friction and minimize the abrasion of the kelly. The bushing is equipped with mud-scrapper assembly to clean the mud.

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The College of Earth and Mineral Sciences is committed to making its websites accessible to all users, and welcomes comments or suggestions on access improvements. Please send comments or suggestions on accessibility to the site editor. The site editor may also be contacted with questions or comments about this course.

This is the brief explanation of a Kelly rotating system on the rig. Kelly rig is on an old style rigs and  nowadays it is mostly used on land operations. For offshore operation, a top drive system is used instead.

First of all, it is important for new people to look at these images before reading the information below because they show the equipment’s name and where they are on the rig.

The upper end of the drill pipe is screwed onto the saver sub. The saver sub is used to protect and minimize wearr and tear on the threads at the bottom of the Kelly. The Kelly is about 40 ft in length with a square or hexagonal shape and it is hollow throughout in order to transport the drilling mud.  Kelly moves freely through a Kelly bushing even though the drill stem is rotated.

A Kelly cock valve is located at the top of a Kelly and it is a safety valve which can be closed to stop back pressure from coming back to damage other surface equipment.

A swivel attached to the hook does not rotate, but at the bottom part it supports the Kelly which is being rotated while drilling.  Drilling mud is pumped from a mud pump to a stand pipe manifold, Kelly hose and then to a gooseneck connection at a swivel.

A rotary table rotates a Kelly bushing and it simultaneously rotates a Kelly and a drill string and a drill bit. A rotary table has two main functions. The first one is to provide rotation to a drill stem and a bit and the second function is to hold slip in order to support the weight of a drill stem when it is not connected to a Kelly.

Generally, a rotary drive consists of  a chain and rotary-drive sprocket. A rotary-drive sprocket is a part of the draw-works. In other rig power systems, an independent electric motor or engine with a direct drive to a rotary table is utilized. For this case, the rotary is normally driven by a drive shaft instead of a chain and rotary-drive sprocket.

A master bushing severs its function as a rotary motion transmission from a rotary table to a Kelly. Additionally, it is a link between a slip and a rotary table.

A Kelly bushing (some people call “rotary Kelly bushing”) engages a master bushing via four pins and rollers inside a Kelly bushing to allow a Kelly to move up or down freely while it is rotated or in a static mode.

In the oil and gas industry, depth in a well is the measurement, for any point in that well, of the distance between a reference point or elevation, and that point. It is the most common method of reference for locations in the well, and therefore, in oil industry speech, "depth" also refers to the location itself.

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).

Example: the top of a reservoir may be found at 1,500 mMDRT in a particular well (1,500 m measured depth below the rotary table), which may be equal to 1,492 mTVDMSL (1,492  m true-vertical-depth below mean sea level) after correction for deviations from vertical.

Well depth values taken during the drilling operation are referred to as "driller"s depth". The "total depth" for the well, core depths and all analysis of core / mud and other materials from the drilling hole are measured in "drillers depth".

The differences between loggers and drillers depths are due to different stretch in the drilling string when drilling, and the wire line entered into the bore hole during wireline logging operations. This difference is estimated and referred to as "core shift". A core from a certain drillers depth is lined up with a wireline log (loggers depth) and structures in the core are compared with the log and matched.

Sign Convention - Depth increases positive in the downward direction. This may seem intuitive but confusion can arise when using certain references while integrating data from different sources. Workers mapping surfaces typically use elevation which, by convention, increases positive in the upward direction. Be mindful when integrating depth and elevation. For example, shallow wells drilled onshore often encounter reservoir at negative depths when referenced to sea level, mappers would define these same reservoirs at positive elevations when referenced to sea level.

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.

Differential (or relative) depths or thicknesses should generally be specified with at least two components: a unit and a path, plus any eventual specifiers to remove any possible ambiguity. No specifier should ever be left "implicit" or "understood". There are cases where a path is not needed and in fact should not be specified, because it is defined by the specifier, e.g. isochore (true stratigraphic thickness, independent of well path or inclination).

The distinction between "loggers" depth" and "drillers" depth" is becoming blurred due to the increasing use of logs acquired while drilling (LWD). At the time of writing, the common practice remains that the petrophysicists or geologists define the "official depths" in a well, and these depths are frequently different from the "drillers" depth", after various corrections, tie-ins, etc., have been applied.

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.

Path: common expressions of path are measured depth (MD) – elsewhere often known as along hole depth (AHD) – and true vertical depth (TVD). Note that using TV for true vertical depth is not consistent with the use of MD for measured depth, hence the recommended TVD.

the legal datum offshore Australia is Lowest Astronomical Tide (LAT) – (Ref. 1 & 2). Note that this requirement in itself can cause difficulties as it is difficult to measure offshore and can vary greatly between locations and even with time. There is, however, an advantage to this convention: tidal corrections should always be of the same sign (negative depth), i.e. the sea level is always higher than or equal to LAT.

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).

Any combination of unit, path, and reference can be used, as long as they result in fully specified, unambiguous depths. A well may reach to many kilometers.

Specification of an absolute depth: in Figure 1 above, point P1 might be at 3207 mMDRT and 2370 mTVDMSL, while point P2 might be at 2530 mMDRT and 2502 mTVDLAT.

Specification of a differential depth or a thickness: in Figure 2 above, the thickness of the reservoir penetrated by the well might be 57 mMD or 42 mTVD, even though the reservoir true stratigraphic thickness in that area (or isopach) might be only 10 m, and its true vertical thickness (isochore), 14 m.