The derrick is used to place lifting equipment and tools such as overhead cranes, traveling blocks, hooks, etc., to bear the load generated by the drilling, casing and other operations, and provide the height and space for the operation of drilling and storing the pipe string. It is a tower mast steel structure.
The derrick is composed of main body, overhead crane platform, overhead crane frame, two-story platform, riser platform and working ladder.
Derrick classification
According to the structural characteristics of the derrick, it can be divided into the following 4 categories:
1. Tower derrick
The tower derrick is one of the widely used derricks in the early days of domestic land drilling. It is a spatial structure of a quadrangular truncated cone with a generally square cross section. This kind of derrick is generally a single rod assembly structure, which is time-consuming to install and disassemble, and is a high-altitude operation. However, it has a wide bottom foundation support, and the derrick body is a closed overall structure, so its overall stability is good, and the bearing capacity is large.
Tower derrick is also the most important structural form of offshore rig derrick.
2. Type A derrick
As the name suggests, the A-type derrick is a derrick with the appearance of the capital letter A. It consists of two trellis or column-type thighs, which are connected to the additional rods on the top of the derrick and the two-tier platform by an overhead platform to form an "A" shape. Spatial structure. The cross section of the thigh has a rectangular or triangular shape. The load capacity and overall stability of this type of derrick are relatively good. Pins are used to connect between the sections. The derrick is installed at a low position. The herringbone or brace is used to lift up and down based on the winch power. The derrick is open front and back, and the driller has a good field of vision, which is called "full-view derrick".
3. Mast derrick
The mast-type derrick is mainly used as a truck-mounted drilling rig and workover rig derrick. It is a spatial structure composed of one or several sections of lattice or tubular thighs. Tilt 3°～8° to the wellhead during work, and the rope needs to be used to maintain the stability of the structure.
The mast derrick can be divided into telescopic type and non-telescopic type, and the derrick of truck mounted drilling rig and workover rig are mostly telescopic type.
4.K type derrick
At present, the commonly used derricks for land drilling are front open derricks, the front fan is open, the cross-section is П-shaped space truss structure, the two sides are divided into pieces or blocks welded into several sections, and the back is the truss rod system. Each section and each member are connected by pins or bolts, which can be installed at a low position, and the whole lift is made by the power of the winch or the thrust of the liquid cylinder, which has the advantage of good overall rigidity. This kind of derrick can also be made into a telescopic derrick. Wanweier
The main structure of the derrick (take the K-type derrick without tension rope commonly used in major oil fields as an example)
The main body of the derrick: generally divided into 4~5 sections, and the sections are connected together by a pin. The upper section is a quadrilateral closed structure, and the remaining sections are front-opening Л-shaped structures, and the rigid frame and diagonal braces on the back can be removed.
Two-story platform: It is composed of platform body, operation platform, finger beam and inner and outer railings.
Cage ladder: installed on both sides of the derrick for operators to go up and down the crane and the second floor platform.
Hoisting device: including hoisting herringbone frame, buffer cylinder, hoisting big rope and hoisting pulleys, etc.
Derrick accessories: including stand pipe operation table, casing centering table, large clamp balance weight, etc.
The role of the base: used to install drilling equipment (rig winches, turntables, drive units, diesel engines, etc.), place drill collars, install derricks, and provide installation space for wellhead devices and operating platforms for drilling operations. It bears the drilling work load, derrick lifting load and equipment self-weight load, and transfers these loads to the foundation and foundation.
Classification of the base:
Box stack base
Block base (also known as block mount)
Swing-up base Wanweier
Slingshot base (also known as double lift base)
Telescopic base
Note: The last three of them are jack-up bases
The main structure of the base (take the slingshot base as an example)
Bottom layer: It is mainly composed of the left and right bases and the pull frame connecting the left and right bases.
Middle layer: Mainly composed of front and rear uprights, inclined uprights, lifting device and lowering device.
Top layer: mainly including left and right upper seats, standing box beams, turntable beams, winch beams, motor beams, and BOP guide rail devices.
Countertop: It is mainly composed of railings around paving boards, walkways, floating platforms and drilling platforms.
Peripheral auxiliary components: including ramps, escape slides, and ladders leading to the drill floor.
The safe bearing capacity of the derrick is usually expressed by the maximum hook load of the equipped drilling rig or workover rig. It refers to the maximum load (including the weight of the travel system) that the hook can bear under the condition that there is no wind load, the dead rope is fixed at the specified position, and the two-stage platform does not store the stand or sucker rod, tubing.
height
Nominal height of the derrick: refers to the vertical height H from the surface of the derrick thigh floor to the bottom surface of the overhead crane beam, and the effective height of the derrick: refers to the vertical height from the top plane of the drill floor frame to the bottom surface of the overhead crane beam.
The effective height of the derrick is determined according to the requirements of the drilling operation and the relevant equipment and considering the requirements for the removal of the derrick, such as the height of the travel system (the height from the top of the traveling car to the bottom of the elevator), the limit length of the stand and the safety distance of collision prevention (ie The collision prevention distance to prevent the traveling car from colliding with the overhead crane due to operation failure during work), etc. Wanweier
The height of the second floor of the derrick refers to the vertical height from the drilling floor level to the bottom of the second floor.
It depends on the length of the stand and the position of the two-stage console. In order to facilitate the derrick to pick up the elevator on the second floor, the bottom surface of the operation platform (usually also the bottom surface of the second floor) should be 1.8～2.0m lower than the height of the stand stored on the stand box. Usually the second floor has two or three Different height installation positions to meet the needs of different lengths of upright operation.
Second floor capacity
The capacity of the two-story platform refers to the number of uprights that can be stored in the second-story finger beam (mounted on the minimum height of the two-story platform), which is expressed by the total length of the uprights (drill pipe, tubing or sucker rod).
The finger beams of the derrick should be able to meet the needs of storing all the uprights, so the capacity of the second floor platform mainly depends on the height of the finger beams and the effective area enclosed by them (the number of stored uprights). Wanweier
Tower derrick upper and lower bottom dimensions and gate height
The size of the upper and lower bottom of the tower derrick refers to the horizontal distance between the bottom surface of the overhead crane beam and the thigh axis of the derrick top surface of the drilling rig girder, respectively. They should meet the needs of convenient operation and safety. The size of the upper base is determined according to the outer dimensions of the crown block and the work requirements of the traveling block, while the size of the lower base should be based on the layout of the relevant equipment tools. Need to determine the size of the drill floor area.
The height of the gate of the tower derrick refers to the vertical height from the plane of the bottom plate of the derrick thigh to the top surface of the gate, which should generally be higher than 8m in order to lift the single root on the drill floor.