Ⅰ Derrick
 

As the core load-bearing structure of a drilling rig, the derrick is mainly used to bear various loads such as the dead weight of drilling tools, construction dynamic loads, wind loads and guy rope tension. The commonly used structural forms of derricks in engineering include single-pole mast type, double-leg A-type, three-leg type, four-leg tower type and portal frame type. Among them, A-type and portal derricks are the mainstream types applied in current engineering drilling.

1. Core Technical Parameters

（1）In terms of load-bearing capacity, the derrick is designed to comprehensively withstand static loads of drilling tools and mechanical equipment, as well as construction dynamic loads, wind loads and additional friction loads. The design safety factor is no less than 1.4 to ensure sufficient safety margin.
 

（2）The derrick height is divided into effective height and total height. The effective height shall meet the operational requirements of the longest components such as casing running, drilling tools, swivels and torque-transmitting drill pipes, with a 1.2-fold safety margin reserved in type selection to avoid potential risks in lifting operations.
 

（3）The base span dimension is comprehensively determined according to the layout specifications of wellhead equipment, wellhead operation space, maximum dimensions of drilling tools and casings, and overall structural stability, so as to ensure convenient wellhead operation and stable equipment operation.
 

2. Applicable Scenarios of Mainstream Derricks

（1）The double-leg A-type derrick features a simple structure, economical cost, convenient lifting and lowering, and spacious wellhead operation space. It can realize independent erection and posture adjustment relying on the main winch, and is compatible with various medium-sized drilling equipment. Widely used in conventional engineering drilling with a well diameter within 2.5 m and well depth of about 150 m, it is the most widely adopted derrick type at present.
 

（2）The three-leg derrick is lightweight and easy to disassemble and assemble, mostly made of lightweight materials. It is mainly applicable to simple drilling projects such as shallow wells and small-diameter cast-in-place piles.
 

（3）The four-leg tower derrick boasts high load-bearing capacity and excellent structural stability, suitable for heavy-duty, large-diameter and deep-well drilling projects and mostly matched with large shaft drilling rigs. Its disadvantages include a large number of components, high overall self-weight and low efficiency of disassembly, assembly and transportation.
 

（4）The portal derrick is a modular frame structure with light self-weight and small occupation space, supporting integrated vehicle-mounted and trailer-mounted configuration. It can be automatically lifted and lowered by hydraulic cylinders with high transportation and installation efficiency. However, it has a small base span and limited wellhead operation space, only applicable to small and medium-sized engineering drilling rigs with well diameter and depth both within 1.2 m and 150 m respectively.
 

Ⅱ Pulley Block
 

Composed of a crown block (fixed pulley) and a traveling block (movable pulley), the pulley block serves to convert the rotary power of the winch into vertical lifting power of the hook, and realize deceleration and force amplification, thereby completing the lifting and suspension of large-tonnage drilling tools with small single-rope tension of steel wire ropes.
 

1.The specification of the pulley block is jointly determined by the rated load of the hook, the single-rope tension of the winch and the strength of steel wire ropes. With a fixed rated load, more pulleys and effective ropes lead to smaller single-rope stress and more stable equipment operation, accompanied by a relatively lower lifting speed.

2.The number of effective ropes follows fixed calculation rules: when the dead rope is fixed on the base, the number of effective ropes is twice the number of traveling pulleys; when the dead rope is fixed on the traveling block, the number of effective ropes is twice the number of traveling pulleys plus one.
 

3. The diameter of matched pulleys is conventionally 23 times the diameter of the steel wire rope, and the safety factor for steel wire rope selection is 3 to 5 times the single-rope tension of the winch.
 

4.On-site steel wire rope threading technologies include straight threading and cross threading. 
（1）Straight threading is simple to operate but prone to uneven stress, hook deflection and torsional wear of steel wire ropes. 
（2）Cross threading features uniform stress and good hook centering performance, suitable for heavy-load operations, yet it causes large cross friction loss of steel wire ropes and is not applicable to high-speed lifting. The optimal method shall be selected according to actual working conditions in construction.
 

Ⅲ Drilling Hook
 

As the core load-bearing device for hoisting and suspending drilling tools and casings, the drilling hook takes rated bearing capacity as its core performance index. It is structurally divided into pin-type, single-hook and double-hook types. The pin-type hook adapts to light-duty drilling rigs, the single-hook type to medium-duty rigs, and the double-hook type to heavy-duty high-load rigs.
 

The bearing capacity design of the hook takes into account both conventional static loads and transient dynamic loads under special working conditions, including emergent conditions such as drilling tool sticking and forced lifting. The safety factor is set at 1.2 to 1.5 to fully ensure operational safety under heavy-load and accidental working conditions.
 

Ⅳ Winch
 

As the core executive mechanism of drilling rigs, the winch is mainly responsible for drilling tool lifting, suspension drilling, equipment hoisting, drill pipe make-up and break-out, and equipment displacement. A single drilling rig is equipped with 3 to 5 winches according to construction requirements, with two transmission forms: centralized transmission and independent transmission. The independent transmission system, featuring strong working condition adaptability and low mutual equipment interference, is the mainstream configuration of modern drilling rigs.
 

Each type of winch has a clear division of labor. The main winch undertakes heavy-load drilling tool suspension and constant-pressure feeding operations, equipped with a slow rope releasing mechanism to realize uniform-speed and constant-pressure drilling in cooperation with electric control and weighing systems. The auxiliary winch is mainly used for component hoisting and wellhead auxiliary operations. The slow-speed winch is dedicated to low-speed and high-precision operations such as drilling tool dragging, rotary table displacement and drill pipe disassembly.
 

The braking system is the core safety component of the winch, mainly classified into band brake, shoe brake and hydraulic end-face brake. Band brakes apply to light-duty drilling rigs, shoe brakes to electric slow-speed equipment, and hydraulic end-face brakes are widely used in heavy-duty large-diameter drilling rigs due to their high load-bearing capacity and operational stability.
 

Ⅴ Rotary Table
 

The rotary table is the core power component of rotary drilling rigs, mainly used to drive drilling tools to rotate and break rocks. Its core performance indicators, namely rated torque and load-bearing capacity, directly determine the rock-breaking efficiency and formation adaptation range of drilling rigs.
 

The through-hole size of the rotary table is a key structural parameter. Large-through-hole rotary tables allow direct lifting of drilling tools without additional displacement mechanisms, featuring a concise structure but high design, manufacturing cost and difficulty. Small-through-hole rotary tables require matched displacement mechanisms, with low processing cost and high practicality, serving as the mainstream choice for current engineering drilling rigs.
 

The rotary table torque is selected comprehensively according to formation characteristics, rock-breaking area and well diameter parameters. Dense cohesive strata such as soil and overburden usually require higher rock-breaking torque than conventional bedrock strata, and the selected torque shall cover all construction working conditions. The transmission forms of rotary tables include independent transmission and centralized transmission; the former adapts to heavy-duty drilling rigs, while the latter is mostly used for light-duty ones.
 

Ⅵ Power Head
 

Also known as a power swivel, the power head has similar functions to rotary tables, with advantages of high integration, no need for torque-transmitting drill pipes and stepless speed regulation, making it the core configuration of modern intelligent drilling rigs. The power head does not bear the static load of drilling tools, suspends the entire drilling tool assembly throughout the operation, and integrates the medium conveying function of conventional swivels.
 

Power heads are divided into mechanical transmission and hydraulic transmission types. Mechanical transmission power heads have a large volume and limited speed regulation range. Hydraulic transmission power heads feature a compact structure, high transmission efficiency and stepless speed regulation, suitable for high-precision and high-efficiency drilling operations. Equipped with a hydraulic chuck at the lower end, the power head can directly clamp drill pipes to transmit torque and seal flushing media to prevent slurry leakage. It can move vertically along the derrick slideway to independently complete drill pipe make-up, break-out and lifting operations, with unobstructed wellhead and spacious operation space.
 

Ⅶ Swivel
 

The swivel is a multifunctional supporting component integrating drilling tool suspension, medium conveying, slag discharge and ventilation, with load-bearing capacity and through-hole diameter as its core technical parameters. It is mainly composed of a core pipe, bearing assembly, sealing components, shell, medium interface and lifting ring.
 

The commonly used through-hole diameter of engineering drilling swivels ranges from 120 mm to 200 mm, which needs to match the through-hole parameters of drill pipes and gravel pumps. The conventional load-bearing capacity is no more than 40 tons, and 60 to 80-ton specifications are adopted for heavy-load construction conditions. The lower connection mode of swivels has been upgraded from traditional left-hand thread connection to flange connection, which is convenient for disassembly and assembly with reliable sealing performance, meeting the long-term continuous operation requirements of equipment.
 

Ⅷ Torque-Transmitting Drill Pipe
 

The torque-transmitting drill pipe is the core force-transmitting component of rotary table drilling rigs. Installed inside the square sleeve at the center of the rotary table, it can rotate synchronously with the rotary table and slide vertically along the square sleeve to realize stable torque transmission. It is divided into square and hexagonal structures. The hexagonal drill pipe has a large contact area and high bearing strength, suitable for heavy-duty drilling rigs with large diameter and high torque. The square drill pipe features simple processing technology and good economy, mostly used for small and medium-sized drilling rigs.
 

The manufacturing processes include integral special-shaped seamless steel pipe forming and round pipe welding reinforcement forming. The welding forming process is widely applied for its high cost performance. The length of torque-transmitting drill pipes is comprehensively determined by the effective derrick height, single drill pipe length and well flushing technology. Under reverse circulation well flushing conditions, the pipe length should not exceed 5 m to avoid affecting bottom-hole slag discharge efficiency.
 

Ⅸ Drill Pipes and Connection Joints
 

Conventional round drill pipes undertake core functions such as torque transmission, drilling tool suspension and medium conveying, with torsional strength as the key performance parameter. The type selection shall accurately match formation lithology, slag particle size and drilling depth. For reverse circulation drilling, the optimal length of a single drill pipe is 4.5 m, with a maximum length of 6 m. Matching short joints are required to accurately adjust the total assembly length of drilling tools.
 

To adapt to complex strata and high-efficiency well flushing technology, double-layer hollow drill pipes have been gradually popularized. The annular channel formed by inner and outer pipes can convey compressed air, adapting to new drilling technologies such as air-lift reverse circulation with excellent sealing, anti-seepage and air leakage prevention performance. Drill pipes are generally made of special FG70V steel, and the material accuracy and structural strength of accessories such as joints and connecting bolts are strictly matched to ensure overall stress stability.
 

Drill pipe connection forms include lock joint connection and flange connection. Small-diameter drill pipes below 168 mm adopt petroleum standard lock joints for high disassembly and assembly efficiency. Large-diameter drill pipes adopt flange bolt connections for higher load-bearing capacity. To solve the defects of traditional flange joints such as uneven tightness, easy loosening and cumbersome disassembly, new spline-type quick joints have been widely applied. Realizing rapid disassembly and assembly through plug-in locking structures, they feature stable torque transmission and high safety, and have been gradually popularized in medium and large-diameter drilling construction as the mainstream upgrading direction of drilling joints.