Drilling on API Casing

API casing (conforming to API 5CT standards) is a steel pipe used in oil and gas wells to support the wellbore, isolate formations, and transport oil and gas. Common steel grades include J55, K55, N80, L80, P110, etc., with outer diameter ranges from 4.5 inches to 20 inches, and connection methods including STC, LTC, BTC, etc. Drilling or punching holes in the casing is usually for specific purposes, such as perforation to connect the reservoir, or other custom processing (such as sidetracking or sampling).

Drilling refers to the process of creating holes in the casing using mechanical methods (such as drilling machines or CNC machine tools), typically for special well types (such as sidetracked wells) or casing repair. Here are the key points:

• Mechanical Drilling: Using high-speed steel or cemented carbide drill bits, suitable for drilling holes of specific diameters and depths in the casing. It is necessary to ensure that the drill bit is suitable for the high-strength steel of API casing (such as P110 steel grade, tensile strength ≥ 758 MPa).
• Plasma or Laser Cutting: For high-precision or complex hole shapes, plasma cutting or laser drilling can be used, which has high precision but is more expensive.

• CNC drilling machine or machining center to ensure hole diameter and position accuracy.
• Coolant system to prevent the casing from overheating and causing material performance degradation.

• Material Strength: The steel grade of API casing is different, and the drilling parameters (such as speed, feed rate) need to be adjusted during processing to avoid tool wear or casing cracking.
• Hole Design: The hole diameter, spacing, and angle need to be designed according to the downhole purpose (such as sidetracking or cable threading) to avoid affecting the overall strength of the casing.
• API Standards: After processing, it must meet the inspection requirements of API 5CT (such as non-destructive testing) to ensure the integrity of the casing.