1. Classification of Internal BOP Tools
(1) Kelly Cock Valve
The kelly cock valve is a manually operated valve installed on the kelly. It consists of an upper kelly cock and a lower kelly cock. Using a dedicated wrench, the valve can be rotated 90° to open or close it as required.
(2) Drill String Check Valve
The drill string check valve is installed at predetermined positions in the drill string. It allows fluid to flow only downward (from top to bottom) while preventing reverse flow, thereby preventing internal blowouts.
(3) Drill String Bypass Valve
The drill string bypass valve serves as a backup safety valve. If the drill bit nozzles become clogged and circulation is blocked, opening the bypass valve restores normal drilling fluid circulation.
2. Performance Testing
All internal BOP tools (except bypass valves) must undergo seal integrity testing using water as the test medium.
Low-pressure test: 2.1 MPa, held for **≥5 minutes**, pressure drop **≤0.3 MPa**.
High-pressure test: Performed at the rated working pressure of the dart-type check valve, held for **≥5 minutes**, pressure drop **≤0.7 MPa**.
3. Installation Positions in the Drill String
The placement and quantity of internal BOP tools are determined based on drilling design or specific well conditions.
Kelly cock valves are installed at the upper and lower ends of the kelly.
Check valves should be installed as close to the bottom of the drill string as possible.
Exceptions Where Check Valves Cannot Be Installed:
Lost circulation tool assemblies
Drill string assemblies for tailpipe weight measurement
Explosive back-off assemblies for stuck pipe incidents
Wireline fishing and logging tool assemblies
Logging-while-drilling (LWD) assemblies
In such cases, alternative blowout prevention measures must be implemented.
Recommended Check Valve Positions:
Conventional drilling/reaming: Installed between the drill bit and the first drill collar.
Downhole motor assemblies: Installed between the motor and the first drill pipe.
Core drilling in hydrocarbon zones (non-drop-ball type): Installed between the core barrel and the first drill pipe.
Underbalanced drilling: At least two check valves must be installed, with one being a normally closed valve at the bottom.
Recommended Bypass Valve Positions:
Installed between drill collars and drill pipes or 30–50 m above the check valve.
In horizontal or highly deviated wells, install within the 50°–70° inclination section.
Emergency Installation of Dart-Type Check Valves:
Can be installed at the surface drill pipe during underbalanced operations for safe pipe connection.
In emergencies, the valve can be quickly installed on the drill string.
A push-open device is pre-installed on the female connection to hold the valve open.
After installation, the push rod is released, allowing well pressure to close the valve.
4. Maintenance and Inspection
After each trip, internal BOP tools must be removed, cleaned, and inspected.
Lubricate threads and install protective caps.
Emergency-installed tools must have push-open devices secured and be stored on the rig floor for quick access.
5. Testing and Certification
Testing includes:
Hydrostatic body test
Upper/lower pressure tests
Thread inspection (internal/external)
Dimensional and visual inspection
Non-destructive testing (NDT)
New Tool Acceptance Testing:
10% sampling rate (minimum 1 tool if batch <10).
Gas testing may be performed if applicable.
Hydrostatic Test Standards:
≤35 MPa: 2× rated working pressure
≥70 MPa: 1.5× rated working pressure
Low-pressure test: 1.4–2.1 MPa
High-pressure test: Rated working pressure
Hold time: ≥10 minutes (no pressure drop or leakage = pass)
6. Pre-Job Preparations
Verify user manuals, certificates, and markings (manufacturer, model, serial number, date, thread specs).
Ensure "OPEN/CLOSE" markings are clear.
Inspect threads, seals, and handles for damage.
Confirm operating wrenches and emergency tools are available.
Test kelly cock valves for smooth operation before use.
Store wrenches securely to prevent loss or dropping.
Responsibilities:
The drilling engineer is responsible for daily management.
Maintain usage logs and retrieval records.
7. Operational Procedures
Before running in hole (RIH): The toolpusher must inspect, measure, and sketch the tool.
Follow manufacturer guidelines for load limits, torque, pressure, and service life.
Reused tools must be inspected and tested (including NDT) before re-entry.
8. Safety Measures and Requirements
In case of a kick: Close the nearest kelly cock valve.
If pressure differential prevents opening, apply pressure above the valve to assist.
While tripping in: Fill drill pipe every 20–30 stands.
Before entering hydrocarbon zones: Circulate to remove compressed air.
Store tools properly and perform routine maintenance.
Post-use cleaning and inspection are mandatory.
NDT required if tools show signs of wear.
During emergency installation: Keep clear of pressure relief ports to avoid injury.
9. Retirement Criteria
Service life: 800 operating hours (mandatory retirement).
Thread/seal damage beyond repair.
Body/seal failure beyond repair.
Failed pressure/NDT tests.
This document provides comprehensive guidelines for the selection, testing, installation, and maintenance of internal BOP tools to ensure well control safety.