Drilling Terms: A Buyer’s Glossary

39 definitions of the terms we use in quotations and specifications — from wireline coring and BTW/BQ to PQ hole sizes to make-up torque and thread galling.

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Rigs and drilling methods Diamond products and bits Wireline components Rods, casing and threads Operation, wear and diagnostics

Definitions of the drilling terms we use in quotations, specifications and technical discussions. Written for buyers comparing rigs, rods and bits — not for a textbook.

Rigs and drilling methods

Core drilling 岩心钻探: Rotary drilling with an annular bit that leaves a cylindrical rock core intact inside the inner tube, so the core can be recovered and logged. The method used for mineral exploration, geotechnical investigation and concrete coring.
Wireline coring 绳索取芯: A coring system where the inner tube is retrieved through the drill string by a wireline overshot instead of pulling the whole rod string. Trips take minutes rather than hours, which is why deep holes use wireline.
Conventional coring 常规取芯: Coring where the entire rod string is pulled to recover the core. Still used for shallow holes and large-diameter sampling, and for ground where wireline tools jam.
Surface core drill 地表岩心钻机: A core rig set up on the surface and used for deep holes, typically skid- or crawler-mounted with a mast and a wireline winch.
Underground core drill 坑道岩心钻机: A compact, often split-type rig designed to work inside mine drifts and tunnels, where headroom, transport width and ventilation are limited. Usually electric drive.
Reverse circulation (RC) 反循环钻探: Drilling with dual-wall rods where cuttings return up the inner tube by air or water. Fast samples for grade control, but no continuous core.
BQ / NQ / HQ / PQ · BTW / NTW / HTW 岩芯规格与绳索取芯（Wireline）W 系列: Standard wireline hole sizes defined by DCDMA. BQ is the smallest (about 60 mm hole), then NQ (75.7 mm), HQ (96 mm) and PQ (122.6 mm). Depth ratings are always quoted against a hole size, because a rig drills less HQ than NQ. Wireline rod strings carry a W after the size: BTW, NTW and HTW — the same hole diameters in a wireline string.
Depth rating 钻孔深度: The maximum depth a rig can drill with a stated rod size — normally NQ for wireline rigs. A figure without a hole size is not a specification.

Diamond products and bits

Impregnated diamond bit 孕镶金刚石钻头: A bit whose crown is a metal matrix with synthetic diamond distributed through its whole depth. As the matrix wears, fresh diamond is exposed — suited to hard, abrasive, homogeneous rock and long runs.
Surface-set bit 表镶金刚石钻头: Natural diamond set on the surface of the crown. Larger stones cut faster in softer or broken formation but are damaged more easily by shock.
PCD bit PCD 复合片钻头: Polycrystalline diamond compact cutters on a steel or matrix body, usually for soft to medium rock, coal and concrete where fast penetration matters more than abrasion resistance.
TC (carbide) bit 硬质合金钻头: Tungsten carbide insert bit for medium-hard rock, overburden and casing shoes. Cheap, robust, but not for hard abrasive rock.
Reaming shell 扩孔器: A short tool above the bit that maintains hole diameter and stabilises the bit, reducing deviation and vibration.
Casing shoe 套管鞋: A hardened ring on the bottom of the casing string that guides the casing down and cuts through obstructions in the hole wall.
Matrix hardness 胎体硬度: The wear resistance of the bit crown. Soft matrix suits hard, dense rock; hard matrix suits broken, abrasive ground. Selecting it is the main variable in bit performance.

Wireline components

Core barrel 岩心管: The assembly that receives the core: outer tube, inner tube, core lifter and head. Double-tube barrels keep the core away from the flushing fluid.
Inner tube assembly 内管总成: The removable inner part of a wireline barrel, retrieved by overshot and containing the core lifter case and core.
Overshot 打捞器: The wireline tool that latches onto the spearhead of the inner tube assembly to pull it to surface, and can also recover dropped rods.
Water swivel 水接头: A rotating seal that lets drilling fluid enter the rotating rod string from a stationary hose.
Sub / adaptor 短节/转换接头: A short threaded piece used to join two different thread forms or sizes in the string.
Hoisting plug 提升塞: A plug screwed into the rod head so the string can be lifted by the elevators or wireline.

Rods, casing and threads

Wireline drill rod 绳索取芯钻杆: Thick-walled tubing with a flush internal bore so the inner tube passes through, and a tapered thread at each end. Usually 1.5 m or 3.0 m.
Q thread Q 螺纹: The long-established tapered thread standard for wireline rods, with a coarse pitch and a shoulder that carries make-up load. Being superseded by RQ in fatigue-critical deep holes.
RQ thread RQ 螺纹: A patented stress-relieved thread profile: the thread root is shaped to reduce stress concentration, extending rod life in deep, deviated or high-torque holes.
WJ thread WJ 摩擦焊螺纹: The DCDMA standard thread for friction-welded rods, common in conventional and geotechnical coring.
V-Wall rod V-Wall 变壁厚钻杆: A rod with variable wall thickness — thicker at the ends where bending stress concentrates — giving a lighter string with similar fatigue life.
Casing 套管: Steel pipe run into the hole to hold back loose ground or water. Flush-joint casing (AW/BW/NW/HW) is rotated with the string; welded casing is permanent.
Make-up torque 上扣扭矩: The torque applied when tightening a joint. Too little and the shoulder does not seat, so the thread carries load and cracks; too much and the box bulges or galls.
Break-out torque 卸扣扭矩: The torque needed to unscrew a joint. Rising break-out torque is an early sign of galling or cross-threading.
Galling 螺纹胶着: Cold welding and tearing of thread surfaces under pressure and sliding, usually from insufficient or wrong thread compound. Once galled, the joint leaks and must be re-cut.

Operation, wear and diagnostics

Thread compound 丝扣油: A metal-bearing grease applied to pin and box before make-up. It lubricates the sliding surfaces and fills the gap so fluid cannot leak through the thread.
Fluid seal 流体密封: The seal formed at the shoulder and thread of a made-up joint. Loss of seal shows as flush loss at the collar or a wet joint.
Pressure test 试压: Pumping the string to a set pressure and holding it to prove joints seal before drilling ahead. Flow loss indicates a leaking joint.
Rod string 钻柱: The assembled rods from the bit to the swivel. Its weight, torque and bending load define what the rig and rods must survive.
Pullback load 回拉载荷: The upward force the rig can apply to the string — used to break out stuck rods and to hoist the string. A rig's pullback and its depth rating are separate numbers.
Hole deviation 孔斜: Departure of the hole from its intended path, caused by rod bending, wrong bit load or fractured ground. It adds bending stress to rods and can miss the target.
Fatigue failure 疲劳失效: Cracking from repeated cyclic stress below the material's yield strength — the normal failure mode of drill rods, usually starting at a thread root.
Heat-check cracking 热裂纹: Fine surface cracks from friction heating at the shoulder of a joint that spins or slips under load, often after spin-out or a dry joint.
Flush loss 冲洗液漏失: Drilling fluid escaping into the formation rather than returning to surface. Distinguishes a leaking joint from a permeable or cavernous hole.

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