What drilling tools are there, and what are their functions?-Jiangsu Hengda Machinery Manufacturing Co., Ltd.

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What drilling tools are there, and what are their functions?

Release Date:

2020-03-19

Drilling Tools Overview: This includes drill bits, drill strings, downhole power drilling tools, as well as stabilizers, vibration dampers, and jar tools. Drill Bits: An indispensable tool for breaking rock during drilling, primarily categorized into three types: roller cone bits, diamond bits, and scraper bits. ① Roller cone bits consist of a bit body, cutting teeth, a cone, bearings, and nozzles, among other components.

Drill String Introduction

　　Includes drill bits, drill strings, downhole power drilling tools, as well as stabilizers, vibration dampers, and impact tools.

　　Drill bits are indispensable tools for breaking rock during drilling, and they are mainly classified into three types: roller cone bits, diamond bits, and scraper bits.

　　① Toothed roller bit: This type of drill bit consists of a bit body, cutting teeth, a roller cone, bearings, and water nozzles. Based on the roller-cone structure, it is classified into milled-tooth and insert-type bits; based on the bearing configuration, it is further divided into sealed (or unsealed) rolling-bearing bits and sealed (or unsealed) plain-bearing bits. Toothed roller bits are suitable for drilling a wide range of formations and are currently in widespread use.

　　② Diamond drill bits were initially used only in hard formations, but their varieties and application ranges are steadily expanding.

　　③ Scraper-type drill bits have a simple structure and are easy to manufacture, enabling relatively high penetration rates in soft formations; however, they generate substantial torque during drilling, which can easily damage the drill string and equipment. In recent years, a new type of cutting-bit has been developed, in which novel wear-resistant materials with various geometric shapes are inlaid into the bit body, allowing it to adapt to a wide range of lithological formations and to operate at high rotational speeds, with increasingly significant economic benefits.

　　The drill string is the collective term for all downhole drilling tools, ranging from the kelly to the drill bit, and comprises the kelly, drill pipes, heavy-weight drill pipe, stabilizers, joints, and various other accessories. Its functions include running the drill bit into and out of the well, transmitting the mechanical energy required for rock breakage to the bit, applying bottomhole weight, circulating drilling fluid into the wellbore, and performing other downhole operations.

A downhole power drill is a power unit connected to the lower end of the drill string and lowered into the wellbore along with the drill string.

The main types include turbodrills and screw drills, among others.

　　① Turbine drilling tools rely on high-pressure fluid flowing through the turbine to convert fluid energy into mechanical energy on the central shaft, thereby driving the drill bit to break rock. They consist of hundreds of turbine stators and rotors mounted in series within a casing, along with bearings, a central shaft, and other components. The blades of the turbine stator and rotor are curved in opposite directions; high-pressure mud flows along the skewed direction of the stator blades, striking the rotor blades with force and causing the rotor to drive the central shaft in rotation. Turbine drilling tools are the primary drilling equipment used in the Soviet Union, where various new types of high-performance turbine drills have been developed and widely employed in drilling operations at different depths and in diverse formations—including wells that have already reached depths of 10,000 meters. Other countries are also actively developing such tools.

　　② The screw-type drilling tool relies on high-pressure mud flowing through the stator and rotor passages to drive the rotor to rotate within the stator’s helical flow path, generating torque that in turn drives the drill bit to break the rock. It consists of a helical rotor housed within the outer casing, a rubber stator liner with helical flow passages, as well as a rotating shaft and bearings. This is a positive-displacement downhole power drilling tool whose rotational speed is directly proportional to the pump displacement, while its torque is directly proportional to both pump pressure and weight on bit; moreover, pump pressure can be used as an indirect indicator of weight on bit. Due to its relatively low rotational speed, it is particularly advantageous when used with roller-cone bits.

Other tools

　　Stabilizers, commonly referred to as centralizers, are connected to the bottom hole assembly of the drill string to prevent wellbore deviation or to enable directional drilling, while also promoting smooth and stable bit operation.

Drilling tools

　　Shock absorbers are used to absorb the impact and vibration loads generated during drilling, thereby extending the service life of the drill bit and other drilling tools. The key components are shock-absorbing elements of various types.

　　A jar is a tool that accumulates elastic energy when the drill string is subjected to tensile stress and undergoes elastic elongation, thereby generating a jarring action. It can be used to address stuck‑pipe incidents and promote safe drilling operations.

　　Fishing tools are specialized equipment used to retrieve downhole objects and address downhole incidents. Common fishing tools include male cones, female cones, fishing jars, fishing spears, fishing baskets, magnetic fishing tools, milling shoes, and safety subs. When a stuck pipe incident occurs, a stick-point locator is used to accurately identify the stuck point, after which an explosive method is employed to loosen the threaded connections of the stuck drill string; this approach is highly effective for resolving stuck-pipe problems.