1. Well: A cylindrical hole drilled into the formation to a certain depth for the purpose of exploring and developing oil and natural gas.
2. Wellhead: The opening end of the well.
3. Well bottom: The lowermost end of the well.
4. Open hole: The section of the well that has not been cased.
5. Well depth: The depth from the top of the rotary table to the bottom of the well.
6. Wellbore wall: The cylindrical surface of the wellbore.
7. Annulus: The cylindrical space between the wellbore wall and the tubing or between different tubings when tubing is present in the well.
8. Wellbore axis: The center line of the wellbore.
9. Well structure: Refers to the drilling bit depth, corresponding drill bit diameter for each section, number of casing strings and their diameters and depths, cement returns outside each casing string, and artificial bottoms.
10. Artificial bottom: The obstruction ring or cement plug below the lowest producing zone as designed. (Note: This definition is incomplete; the artificial bottom can vary.)
11. Types of wells: Wells classified according to certain criteria. They can be divided into exploration wells and development wells based on drilling purpose; shallow wells (<1200m), medium-depth wells (1200-3000m), deep wells (3000-5000m), and ultra-deep wells (>5000m) based on final depth; and vertical wells and directional wells based on the shape of the wellbore axis.
12. Exploration well: Wells drilled for understanding the age, lithology, thickness, combination of source-reservoir-cap rocks, regional geological structures, local structural sections, discovering oil and gas reservoirs, further delineating hydrocarbon boundaries and reserves, and understanding the structure of oil and gas layers. Includes stratigraphic exploration wells, preliminary exploration wells, appraisal wells, and geological shallow wells.
13. Development well: Wells drilled for oil and gas production, water or gas injection, adjustment, supplementation, expansion, and logging in already developed oil and gas fields to maintain production levels and study changes in underground conditions.
14. Vertical well: A well where the wellbore axis is generally along the vertical direction, with limited deviation angle, horizontal displacement at the bottom, and total angular change rate.
15. Directional well: A well drilled along a pre-designed wellbore trajectory, deviating from the vertical axis of the wellhead by a certain distance to reach the target.
16. Pad well: Two or more directional wells (can include one vertical well) drilled from a single pad or drilling platform.
17. Relief well: A directional well designed and constructed to rescue a blowout or fire at another well.
18. Multilateral well: A directional well with two or more bottom holes from a single wellhead.
19. High-angle well: A directional well with a maximum deviation angle between 60° and 86°.
20. Horizontal well: A directional well with an inclination angle greater than or equal to 86°, and maintaining this angle while drilling a certain length of horizontal section.
21. Drilling operations: Various components of the drilling process. Generally includes pre-drilling preparation, drilling, coring, intermediate testing, logging, cementing, and completion.
22. Casing hanger to rotary table distance: Distance between the top of the casing head and the rotary table.
23. Tubing hanger to rotary table distance: Distance between the top of the tubing head and the rotary table.
24. Rig site: Required working area for drilling operations.
25. Sump: A circular or square pit dug for installing well control equipment.
26. Kelly bushing: A hole located directly in front of the wellhead used for placing a single stand of drill pipe in advance to speed up the make-up operation.
27. Kelly hole: A hole located on the left front side of the derrick leg line, used for storing the kelly and water龙头龙带 when not in use.
28. Drill floor: Platform mounted on the base of the derrick serving as the working area for drilling operations.
29. Drill string: A general term for downhole drilling tools. Typically includes kelly, drill pipes, drill collars, connections, stabilizers, reamers, shock absorbers, bits, and other downhole tools.
30. Kelly: A thick-walled pipe with a square or hexagonal cross-section and a round inner hole made of high alloy steel. It has threaded ends primarily used for transmitting torque and supporting the weight of the drill string.
31. Drill pipe: Seamless steel tubing made of high alloy steel with connections at both ends. Used for extending the wellbore, transmitting torque, and forming a circulation path for drilling fluid. Can be classified as internal flush, external flush, and regular drill pipes.
32. Drill collar: Thick-walled seamless tubing made of high alloy steel with threaded ends. Its wall thickness is usually 4 to 6 times that of drill pipes. Primarily used for applying weight to the bit, transmitting torque, and forming a circulation path for drilling fluid.
33. Connection: Short sections used to connect and protect drill string components.
34. Drill string makeup: Selection and assembly of drilling tools that make up the drill string.
35. Bottom hole assembly (BHA): Composition of the lowermost part of the drill string.
36. Drill string: General term for the series of drill pipes extending from the kelly below the rotary table to the bit. Consists of kelly, drill pipes, drill collars, connections, stabilizers, etc.
37. Full-bore drill string: BHA composed of multiple stabilizers and large-size drill collars with outer diameters close to the bit diameter. Used for maintaining the wellbore direction.
38. Step drill string: BHA composed of drill collars of different diameters, smaller at the top and larger at the bottom. Used for preventing well deviation.
39. Pendulum drill string: In a deviated wellbore, the section of drill collars above the bit but below the hinge point acts like a pendulum, causing the bit to cut towards the low side of the wellbore under the lateral component of gravity force. Known as pendulum drill string.
40. Downhole tools: Refers to stabilizers, shock absorbers, and jars.
41. Stabilizer: A tool used in the BHA with an enlarged middle outer diameter to help stabilize the drill string’s axis. Available in straight, helical, and roller designs.
42. Shock absorber: Tool installed in the drill string to absorb vertical and rotational vibrations from the bit.
43. Jar: Tool capable of generating upward or downward impact vibrations.
44. Rig floor tools: Tools used on the drill floor for wellhead operations. Includes tongs, slips, elevators, safety slips, lifting sub, bit wrenches, swivels, etc.
45. Hookload indicator: Instrument that reflects the load changes on the hook, showing suspended weight, bit weight, and drilling pressure.
46. Drilling: Process of continuously breaking rock using a cutting tool to deepen the wellbore.
47. Drilling parameters: Controllable parameters during drilling, including drilling pressure, rotational speed, drilling fluid properties, flow rate, pump pressure, and other hydraulic parameters.
48. Drilling pressure: Force applied to the bit along the direction of the wellbore during drilling.
49. Suspended weight and bit weight: In a well filled with drilling fluid, the axial load indicated by the hookload indicator when the drill string is suspended is called suspended weight (drill string weight minus buoyancy); the axial load indicated by the hookload indicator when drilling is called bit weight. The difference between suspended weight and bit weight is drilling pressure.
50. Rotational speed: The rotation speed of the bit, typically measured in revolutions per minute (RPM).
51. Flow rate (displacement): The volume of liquid passing through the pump’s outlet per unit time. Usually measured in liters per minute (L/min).
52. Spudding in: Refers to the start of drilling after setting the conductor pipe or casing strings. Subsequent starts are called first spud, second spud, etc.
53. Total depth reached: The end of the drilling phase for the entire well.
54. Feeding: Process of continuously lowering the drill string to maintain a certain drilling pressure as the wellbore deepens.
55. Kelly in and out: Length of the kelly below the rotary table face during drilling is called kelly in; length of the kelly above the rotary table face is called kelly out.
56. Footage: Cumulative length drilled by the bit.
57. Mechanical drilling rate: Length drilled by the bit per unit time. Typically measured in meters per hour (m/h).
58. Rate of penetration (ROP): Time taken to drill a unit length of footage. Typically measured in minutes per meter (min/m).
59. Reaming: Process of rotating and circulating while lowering or raising the drill string within the existing wellbore to smooth the wellbore walls and remove debris, ensuring free passage. Divided into forward and backward reaming.
60. Reaming out: Process of enlarging the wellbore diameter using a reamer bit.
61. Sticking: Phenomenon of uneven torque on the bit causing abnormal rotation of the rotary table.
62. Bucking: Phenomenon of significant longitudinal vibration of the drill string caused by unstable bit operation during drilling.
63. Standby: Ceasing the drilling operation.
64. Bottoming: Phenomenon of the drill string uncontrollably striking the bottom of the well or other obstructions.
65. Slipping: Phenomenon of the drill string sliding down due to uneven feeding or loss of control, resulting in instantaneous excessive drilling pressure.
66. Slipping off: Phenomenon of reverse rotation of the rotary table under severe sticking.
67. Running-in hole: Operation of running-in the drill string with a pilot shoe or bit to keep the wellbore open.
68. Whistling: Phenomenon of the drill string being able to slide into the well without resistance.
69. Feather drilling: Process of drilling with minimal drilling pressure applied to the bit.
70. Correction: Process of correcting the well deviation back to within specified limits when it exceeds them.
71. Milling cement plugs: Process of removing hardened cement left in the casing or wellbore after cementing.
72. Shrinkage: Phenomenon of the wellbore diameter becoming smaller due to formation collapse or swelling.
73. Enlargement: Phenomenon of the wellbore diameter becoming larger due to formation collapse or swelling.
74. Single joint: One piece of drill pipe.
75. Double joint: Two pieces of drill pipe connected together.
76. Stand: A column of drill pipe that can be placed vertically in the drill floor racks during tripping operations, typically three joints long.
77. Tripping in: Operation of lifting a single joint of drill pipe and placing it in the kelly bushing.
78. Making a connection: Operation of adding a single joint of drill pipe to the drill string when the kelly reaches its effective length.
79. Tripping: The operation of pulling the drill string out of the wellbore is called tripping out; inserting the drill string into the wellbore is called tripping in. The whole process is called tripping.
80. Short tripping: Operation of pulling several stands of drill pipe out of the well and then running them back in during drilling.
81. Moving pipe: Sometimes during drilling operations, the drill string is raised, lowered, or rotated.
82. Breaking down pipe: Separating the drill string into singles and pulling them off the drill floor.
83. Changing bit: Operation of changing the bit by tripping the drill string.
84. Pumping mud: Pumping drilling fluid into the wellbore or casing during tripping, casing running, or lost circulation to ensure the wellbore remains full.
85. Bit run: One complete round trip of a bit from entering the well to being pulled out.
86. Circulating drilling fluid: Pumping drilling fluid through the circulation system.
87. Circulation period: Time required for drilling fluid to enter the wellbore at the wellhead and return to the surface.
88. Target point: Underground coordinate point of a directional well determined by geological design.
89. Target area: Specified range within which the actual wellbore axis can deviate from the designed target point when penetrating the objective formation.
90. Target radius: Radius of the target area circle.
91. Deviation point: Depth at which directional deviation begins.
92. Deviation: Process of drilling an inclined section in a specific direction using deviation tools.
93. Steepening: Process of continuously increasing the deviation angle.
94. Flattening: Process of continuously decreasing the deviation angle.
95. Stabilizing: Process of keeping the deviation angle constant.
96. Deviation tool: Downhole tool used to alter and control deviation and azimuth.
97. Bent sub: A downhole tool used with a downhole motor for directional deviation. It has a bent axis and the male thread axis forms an angle with the female thread axis, typically between 1° to 3°.
98. Downhole motor: Power unit installed at the bottom of the drill string to drive the bit.
99. Turbine motor: Motor that converts hydraulic energy of drilling fluid into mechanical energy via turbine wheels.
100. Screw motor: Motor that converts hydraulic energy of drilling fluid into mechanical energy via a screw mechanism.
101. Oriented connection: Connection used to mark the orientation of deviation tools.
102. Non-magnetic drill collar: Drill collar made of alloy material with a magnetic permeability close to 1.
103. Oriented elements: Basic elements of a directional well, including deviation angle, azimuth, and depth.
104. Deviation angle: Angle between the tangent line at a given point on the wellbore axis and the vertical line at that point.
105. Maximum deviation angle: Maximum deviation angle value across the entire wellbore axis.
106. Azimuth: Angle between the projection of the tangent line at a given point on the wellbore axis onto the horizontal plane and the true north direction (measured clockwise).
107. Measured depth (inclined depth): Measured length of the wellbore axis from the drill rig rotary table face (reference point) to a measurement point inside the well.
108. True vertical depth: Vertical distance from a measurement point on the wellbore axis to the horizontal plane of the rotary table face at the wellhead.
109. Horizontal displacement (closure distance): Distance from a measurement point on the wellbore trajectory to the vertical line from the wellhead.
110. Closure azimuth: Angle between the true north direction and the horizontal displacement direction.
111. Coring: Operation of extracting core samples from the formation using machinery and coring tools.
112. Core: Rock extracted from the well during coring operations.
113. Core recovery: Percentage ratio of the core length to the coring footage.
114. Core length: Actual length of the core extracted from the well.
115. Coring footage: Actual length drilled during coring operations.
116. Drilling fluid (drilling mud): Circulating fluid used in drilling operations.
117. Filter cake: Solid deposit formed by the drilling fluid on the filtration medium during filtration.
118. Filtrate: Liquid that passes through the filtration medium from the drilling fluid.
119. Hydrostatic pressure of drilling fluid: Pressure caused by the weight of the drilling fluid column, which depends on the density of the drilling fluid and the vertical height of the fluid column.
120. Formation fracturing pressure: Pressure value at which a formation at a certain depth fractures under hydraulic action.
121. Equivalent mud weight: Pressure at a given depth divided by the product of the depth and gravitational acceleration.
122. Overflow: Phenomenon where the volume of drilling fluid returning to the surface is greater than the volume pumped in, or the drilling fluid spontaneously overflows when the pumps are stopped.
123. Surge: Further development of overflow, where drilling fluid surges out of the wellbore.
124. Blowout: Uncontrolled influx of formation fluids (oil, gas, or water) into the wellbore and onto the surface.
125. Cementing: Operation of pumping high-density drilling fluid into a well that has lost pressure balance to rebuild and restore pressure equilibrium.
126. Stuck pipe: Phenomenon where the drill string cannot be raised, lowered, or rotated in the well. (Includes various types such as ball-stuck, bridge-stuck, sand-stuck, keyseat-stuck, collapse-stuck, differential-pressure-stuck, small-diameter-stuck, shrinkage-stuck, stuck-on-bottom, object-stuck, cement-stuck, etc.)
127. Stuck point: Highest point of the stuck drill string.
128. Fish: Drill string left in the well due to an incident.
129. Fish head: Top end of the fish.
130. Fish tail: Bottom end of the fish.
131. Fish head depth: Distance from the fish head to the rotary table face.
132. Fish tail depth: Distance from the fish tail to the rotary table face.
133. Fish length: Length of the fish.
134. Oilwell cement: Cement or any mixture of cement and other materials suitable for cementing oil, gas, or water wells.
135. Initial set: When the needle of the setting time tester (Vicat apparatus) sinks into the cement slurry to within 0.5 to 1.0 mm of the bottom plate, it indicates the initial set of the cement slurry.
136. Initial setting time: Time from the addition of water until the initial set of the cement occurs.
137. Final set: When the needle of the setting time tester (Vicat apparatus) sinks into the cement slurry no more than 1 mm, it indicates the final set of the cement slurry.
138. Final setting time: Time from the initial set to the final set of the cement slurry.
139. Setting time: Total time from initial set to final set.
140. Cementing: Process of cementing the uncased borehole by running casing and injecting cement to isolate formation fluids and strengthen the wellbore.
141. Cement return depth (height): Depth of the cement column in the annulus.
142. Cement plug: Operation of pumping cement slurry into the well at a designated position to form a cement plug.
143. Spotting cement: Injecting cement slurry into the annulus between the casing and the formation to form a seal.
144. Casing accessories: Accessories attached to the casing string (such as float shoes, float collars, washers, cement umbrellas, centralizers, packers, etc.).
145. Lower end of casing string: Total name for accessories attached to the lower end of the casing string.
146. Guide shoe: Conical body attached to the bottom of the casing string to guide it smoothly into the well.
147. Casing shoe: Special short section with an internal chamfer at the top and threaded or otherwise connected to the guide shoe at the bottom.
148. Float shoe: Device that integrates the guide shoe, casing shoe, and valve.
149. Float collar: Drillable check valve installed in the coupling above the casing shoe.
150. Washer (choke ring): Casing accessory used to control the position of the plug during cementing, ensuring the length of the cement plug in the casing.
151. Plug: Rubber plug with multi-tiered disc wings used to isolate and scrape drilling fluid and cement slurry adhered to the casing during cementing. Types include upper plug, lower plug, and liner plug.
152. Cake scraper: Wire brush installed on the casing during cementing to remove filter cake from the wellbore wall.
153. Cement umbrella: Device installed at the bottom of the casing to prevent the cement slurry from settling.
154. Centralizer: Device installed on the casing string to center the casing in the wellbore.
155. Rigid centralizer: Centralizer with spiral grooves or straight ribs that does not have elasticity. Commonly used in directional wells.
156. Packoff: Special coupling with opening and closing functions installed at a designated position on the casing for graded cementing.
157. Liner hanger: Special tool used to suspend the liner at the bottom of the upper casing and perform cementing. There are mechanical and pressure types, both using slip hangers to suspend the liner on the upper casing.
158. Casing packer: Expandable packer installed on the casing string to seal the annular space above and below the packer.
159. Top joint: Short section of casing attached to the last casing joint to adjust the top position of the casing string and connect to the cement head.
160. Cementing head: High-pressure wellhead device used during cementing operations containing plugs and equipped with gates for connecting to circulation lines.
161. Gauge plug: Tool used to check the passable inner diameter of the casing.
162. Bumping pressure: Phenomenon where the pump pressure suddenly increases when the plug hits the washer during cement displacement.
163. Waiting on cement: Time required for the cement sheath to reach sufficient strength for subsequent operations.
164. Cement sheath: Cement stone formed by the cement slurry in the annular space.
165. Casing: Special steel pipe used to isolate formations and strengthen the wellbore.
166. Casing program: Number, type, diameter, and depth of casings run into the well.
167. Surface casing: Casing run to prevent the collapse of loose formations near the surface, protect freshwater sources, prevent fluid intrusion, and provide a base for surface equipment.
168. Intermediate casing: Casing run between the surface and production casing to overcome complex formations or limitations imposed by drilling fluid densities used in completion.
169. Production casing (reservoir casing): Last casing string run to create a solid conduit for production, protect the wellbore, and enable zonal production, testing, and treatment.
170. Casing string: Column of casings connected with different grades, wall thicknesses, materials, and threads based on strength design requirements.
171. Tail pipe: Casing run into the uncased section of the wellbore, suspended from the upper casing, and not extending to the surface.
172. Screen pipe: Casing with screened holes located in the reservoir section.
173. Magnetic locator short joint: Short section of casing near the production zone for calibrating perforation depth.
174. Casing stub: Short section of casing shorter than standard length.
175. Casing head: Heavy-duty steel flanged device with slips and sealing components used to suspend and seal the annulus of casings at the wellhead.
176. Nominal outer diameter of casing: Outer diameter of the casing body in cross-section.
177. Casing strength: Combined load-bearing capacity of the casing (including collapse resistance, burst strength, and tensile strength).
178. Drilling cycle: Total time from the start of drilling until reaching total depth.
179. Well construction cycle: Total time from rig moving in, setup to well completion, including rig moving and setup time, drilling time, and completion time.
180. Well history: Archive of a well, including data and records from drilling, geological surveys, and completion operations.
