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Drilling Personnel Baseline Test: See How Many You Can Get Right! (Part 1)
Drilling operations involve complex geological conditions, sophisticated equipment operation, and stringent safety regulations—every single detail is critical to both construction efficiency and personnel safety. This article compiles 100 frequently asked practical questions and answers from the drilling industry, covering core scenarios such as downhole operations, equipment usage, safety protocols, and geological logging. It serves as both a beginner’s learning guide and a comprehensive reference for experienced professionals looking to fill in any knowledge gaps. We recommend saving it for future use!
I. Core Technology Operations (30 Questions)
1. Fundamentals of Underground Operations
How do you perform a reverse eye sweep?
Answer: ① When drilling reaches the stuck section, connect the square drill pipe, start the pump to circulate the drilling fluid, and adjust the drilling fluid properties accordingly. ② Adjust the suspension weight indicator and the sensitivity gauge pointer to zero. ③ While observing the suspension weight indicator, use first gear at low speed to slowly raise the drill string, applying a tensile force of 10 kN. Immediately brake the drawworks and closely monitor the pump pressure to prevent pump blockage. ④ At the wellhead, insert the drill pipe slips to securely clamp the drill string; secure the drill pipe slips with a safety rope made of 10 mm diameter steel wire. ⑤ Slowly rotate the rotary table in the forward direction to begin reverse reaming. Once the rotary table’s rotational load decreases and you confirm that the downhole conditions are normal, stop rotating the rotary table, then apply another tensile force of 10 kN to the drill string, seat the drill pipe slips, and continue rotating. Repeat this procedure until the drill string is pulled out.
Directional well What are the three elements?
Answer: Well depth, well inclination angle, and azimuth angle.
What is the working principle of a screw drill?
Answer: As the drilling fluid flows through the motor, a pressure difference is created at the motor’s inlet and outlet, which drives the rotor to rotate. The torque and rotational speed are then transmitted to the drill bit via the universal joint shaft and transmission shaft, thereby converting the fluid’s pressure energy into mechanical energy.
What is drilling time logging?
Answer: Drilling time logging is the process of using a timer to record and document the time required to drill a specified unit of footage; it is typically expressed in “minutes per meter.”
What is core recovery rate?
Answer: The core recovery rate refers to the ratio of the length of core recovered during a single drilling run to the total footage drilled.
2. Drilling and Cementing Operations
What are the main methods and objectives of well completion testing?
Answer: Well completion testing primarily includes electrical logging, radioactive logging, and engineering logging. The purpose is to inspect the wellbore quality and cementing quality, providing a basis for accurate perforation.
What are the common types of drill bits?
Answer: They are classified into four types: scraper drill bits, roller cone drill bits, diamond drill bits, and PDC drill bits.
What factors does the magnitude of hydrostatic pressure depend on?
Answer: Its magnitude is related to the density of the liquid and the vertical height or depth of the liquid column.
How can we describe the process of “drilling in”?
Answer: Drilling involves applying a certain pressure to the drill bit and rotating it to break up the rock formation at the bottom of the well. As the rock at the bottom of the well is broken, the resulting cuttings are carried to the surface by the circulating drilling fluid. This entire process is known as drilling.
What is “cementing”?
Answer: Cementing is the process of running casing into a wellbore that has already been drilled, and then injecting cement slurry into the annular space between the casing and the wellbore wall to bond the casing securely to the formation.
How do you perform dual-pump drilling?
Answer: After connecting a single drill pipe, first start one pump. Once the drilling fluid begins to return normally from the wellhead, then start the second pump. After completing the single drill pipe run, first stop one pump, raise the square drill pipe, and after securely seating the elevator at the wellhead, stop the other pump. Start the pumps early and stop them late to prevent drill cuttings from settling and causing downhole complications.
What are the precautions for drilling through cement plugs?
Answer: ① Work at the wellhead must strictly prevent hazards from below the well. Falling object stuck in the drill string ② When drilling down, control the drilling speed carefully, especially in wells where “casing is being cemented”—pay attention to any resistance encountered by the cement plug. ③ When drilling through cement plugs in production casing, perform segmented circulation and select an appropriate flow rate. Due to the narrow annular space, avoid pump surges; adjust the drilling pressure appropriately based on the drilling rate. ④ After completing the drilling of a cement plug in production casing, thoroughly flush the well to prevent cement fragments from settling inside the wellbore and causing other problems. ⑤ Drilling through cement plugs can easily lead to stuck pipe; therefore, avoid excessive torque that might cause the lower casing to unscrew.
What are the wellbore preparations required before logging?
Answer: ① Before logging, it is essential to thoroughly circulate the drilling fluid to ensure uniformity and stable performance throughout the wellbore. ② Sections where the drill string encounters resistance or gets stuck must be properly treated to guarantee the safe and smooth execution of the logging operation.
What factors does the magnitude of the hydrostatic pressure gradient depend on?
Answer: It is related to the concentrations of minerals and gases dissolved in the liquid.
What is formation pressure?
Answer: The pressure exerted by fluids in rock pores.
How to describe a certain location in a geological stratum Overlying rock layer pressure ？
Answer: It refers to the total weight exerted by the rock matrix and fluids in the pores above that location.
What is formation fracture pressure?
Answer: Refers to the pressure at which the formation fractures when the fluid pressure reaches a certain value.
During formation fracture pressure testing, in which areas is fracturing most likely to occur?
Answer: During formation fracture pressure testing, formation fracturing tends to occur at the casing shoe.
What causes the pressure balance within the well to be easily disrupted during the cementing and setting period?
Answer: The loss of cement slurry weight and gas migration are the primary causes of disruption to the pressure balance within the well.
What method is typically used for waiting and curing after cementing?
Answer: Based on the operating conditions of the back-pressure valve, either open-pressure or closed-pressure methods can be used for waiting-on-cementing.
3. Wellbore Trajectory and Structure
What parameters can be measured to determine the wellbore trajectory?
Answer: The wellbore trajectory can be determined by directly measuring the well depth, well inclination, and azimuth.
What are the main bases for wellbore structural design?
Answer: Formation pressure and formation fracture pressure.
What methods are currently mainly used to detect cementing quality?
Answer: The main methods used are acoustic amplitude logging and acoustic variable-density logging, and... Well temperature logging Method detection.
Among the geological factors that influence well deviation, which factor plays the primary role?
Answer: Stratigraphic dip.
In casing size design, what is the most appropriate clearance between the casing and the wellbore?
Answer: The ideal clearance between the casing and the wellbore is 19 mm.
What are the main contents of wellbore quality indicators?
Answer: The main quality indicators for wellbore include the horizontal displacement at the bottom of the well (in directional wells, this is the target center distance), the maximum total well inclination angle, wellbore curvature, and the wellbore enlargement rate.
4. Special formations and drill bit usage
Can PDC drill bits be used in formations containing gravel?
Answer: The formation drilled by a PDC bit must be homogeneous; formations containing gravel cannot be drilled with this type of bit.
What phenomenon is extremely likely to occur when drilling through a gravel layer?
Answer: These refer to the phenomena of stuck drill, bit jamming, and wellbore collapse.
What precautions should be taken when drilling with a roller cone bit?
Answer: ① After the drill bit reaches the bottom of the well, apply light pressure and run in for about 0.5 hours before gradually increasing the pressure to the specified drilling load. It is strictly prohibited to start the rotary table by applying excessive pressure immediately. ② When operating the brake lever, maintain full concentration, ensure even weight-on-bit application, and strictly prevent incidents such as bit slippage and bit bumping. ③ During drilling, continuously analyze the drilling time changes and the drill bit’s operational condition to promptly identify variations in rock properties and adjust parameters accordingly to meet the requirements of the formation being drilled. ④ Properly manage the timing of trip-out operations; under normal circumstances, the working life of the drill bit depends on the lifespan of its teeth and bearings.
How should a PDC drill bit be operated when it first starts drilling after being lowered into the well?
Answer: After the drill bit contacts the bottom of the well, first perform bottom-of-well shaping by drilling at a light weight-on-bit (5 kN to 10 kN) for 0.5 to 1 meter, thereby forming a new bottom-of-well surface that closely matches the profile of the PDC drill bit before commencing normal drilling operations.
