Drilling engineering is accomplished by complete sets of specialized drilling equipment. The comprehensive performance, structural workmanship quality, operational reliability, as well as mechanization and intelligence level of equipment directly determine drilling efficiency, well-forming quality, operational safety and comprehensive economic benefits of the project. They constitute the core foundation for high-quality, efficient and stable implementation of drilling works.

I. Principles for Drilling Equipment Selection

In compliance with current industrial standards and requirements for modern green drilling construction, drilling equipment selection shall be closely matched with formation conditions, drilling technologies and construction scenarios, following the general criteria of technical adaptability, safety-reliability and economic energy-saving. Specific selection requirements are specified as follows:

(1) Process Adaptability Principle

The overall performance of equipment shall fully adapt to requirements of well type, well depth, formation characteristics and full-process drilling technologies. For core-drilling operations, equipment shall feature a wide speed-regulation range and high output torque. The supporting mud pump shall satisfy working conditions of large displacement and high pump pressure to ensure the upward-return flow velocity of flushing fluid in the well annulus meets specifications. Full-face drilling involves heavy drill string loads and high rock-breaking resistance; therefore, large-tonnage hoisting systems, high-strength rock-breaking cutters and high-efficiency slag-removal equipment shall be deployed to satisfy working conditions of heavy loads and high torque.

(2) High-efficiency & Energy-saving Principle

Priority shall be given to complete drilling equipment with high integration, mechanization and intelligence, so as to effectively reduce manual labor intensity and optimize operating conditions. Meanwhile, concepts of low-carbon energy conservation and green construction shall be strictly followed to cut equipment energy consumption and later-stage operation-maintenance costs, complying with the development trend of consumption reduction and quality improvement for modern drilling projects.

(3) Reliability & Durability Principle

Key components of equipment shall possess sufficient structural strength, rigidity and wear resistance, with excellent anti-fatigue and anti-impact capacity to accommodate long-term continuous operation in complex formations. Adopt standardized and modular structural design for the whole equipment to facilitate routine inspection, maintenance and rapid fault disposal, minimize equipment downtime losses and guarantee construction continuity.

(4) Mobility Adaptability Principle

Equipment shall feature compact overall structure and reasonable self-weight distribution, with good dismountability, mobility and versatility. Dismantling, transportation and positioning procedures shall be simple and efficient, adapting to complex operation scenarios characterized by limited field space and scattered construction points, and meeting demands for flexible equipment allocation and rapid construction.

(5) Safety & Environmental Protection Principle

Equipment shall be fitted with complete safety protection devices such as guards, brakes and limiters to effectively avoid various construction safety risks. Noise, vibration and pollutant emissions generated during equipment operation shall strictly comply with national and industrial standards, fully satisfying requirements for safe and civilized construction as well as on-site environmental control.

(6) Economic Applicability Principle

On the premise of meeting technical specifications, project quality and work safety standards, priority shall be given to equipment with reasonable cost, strong versatility and readily available spare parts. Balance shall be struck between one-time procurement cost and long-term operation-maintenance cost to maximize comprehensive economic benefits of drilling projects.

II. Overall Composition System of Drilling Equipment

Classified by core construction technologies, drilling operations fall into two categories: percussion drilling and rotary drilling, corresponding to differentiated complete-set equipment systems. Modern drilling equipment generally adopts modular integrated design, consisting of rock-breaking system, rotary system, hoisting system, slag-removal system and auxiliary support system, which are applicable to various formations, well types and complex working conditions.

1.Composition of Percussion Drilling Equipment

Percussion drilling equipment centers on rock breaking by percussion, tool hoisting and rock-slag removal. Its core components include percussion rock-breaking mechanism, traction-hoisting mechanism and bailing-slag-removal mechanism. Supporting systems are configured differentially according to well-flushing technologies: special slurry supply system is equipped for normal-circulation well-flushing; professional reverse-circulation slag-removal devices are added for reverse-circulation percussion drilling; for mud-wall-protection construction, mud preparation and purification equipment shall be deployed to realize stable borehole wall support and high-efficiency bottom-hole slag removal simultaneously.

2.Composition of Rotary Drilling Equipment

Rotary drilling applies to mainstream drilling technologies such as core drilling and full-face drilling, featuring higher equipment integration and automation. It is divided into five core functional modules, which cooperate to complete the whole drilling workflow.

（1）Hoisting & Lifting Module

The core equipment of this module is the winch system. Large-scale drilling rigs are usually equipped with three to five special winches, together with supporting drilling towers, pulley blocks, traveling hooks and various dedicated hoisting tools. It is mainly responsible for tripping drill strings, hoisting tools, making-and-breaking drill pipes and erecting drilling towers, serving as the primary load-bearing and execution mechanism of drilling rigs.

（2）Rotary Drive Module

Rotary drive structures are mainly divided into rotary-table type and power-head type:

1) The rotary-table type is integrated and matched with motors, gearboxes, reducers and rotary tables, mostly applied to heavy-duty drilling rigs; it requires position shifting to avoid the wellhead during operation.

2) The power-head type is an integrated independent drive structure, available in mechanical transmission and hydraulic stepless transmission forms. It boasts advantages of no position shifting requirement, rapid response and high speed-regulation precision. It adapts to high-efficiency drilling and can directly drive drill string rotation without special torque-transmission drill pipes.

（3）Rock-breaking Drilling Module

The core of this module is the large-diameter drill string assembly, mainly composed of rock-breaking cutters, cutter head (drill bit), connector, upper-lower centralizers, weight blocks and drill-pipe connection discs. As a key vulnerable component, rock-breaking cutters directly determine rock-breaking efficiency and overall drilling progress.

（4）Well-flushing & Slag-removal Module

This module is designed to timely remove broken rock slag at borehole bottom, prevent repeated crushing and excessive wear of cutters, keep the drill bit continuously fitted against borehole bottom, and improve drilling efficiency and service life of tools. Modern drilling rigs are standardly fitted with one set of normal-circulation equipment and two sets of reverse-circulation equipment. Well-flushing technologies can be flexibly switched according to formation lithology, hole diameter and drilling depth to satisfy construction requirements of diverse complex formations.

（5）Auxiliary Support Module

Auxiliary support module mainly includes water-supply equipment, underground drainage equipment, generator sets, maintenance tooling and other supporting facilities. It provides stable water supply, drainage, power supply and equipment maintenance support for the whole drilling process, acting as the fundamental guarantee for continuous drilling operations.