NB/T 11467-2023
Technical Specifications for Surface Drilling Hole Expansion and Increased Pumping and Pressure Relief Gas (English Version)

Standard No.

NB/T 11467-2023

Language

Chinese, Available in English version

Release Date

2023

Published By

Professional Standard - Energy  CN  /  NB

Latest

NB/T 11467-2023

Introduction

Technical background and evolution of the standard

As an important technical specification in the field of coal mine gas control, this standard integrates advanced technologies such as PDC hole-digging drill bit and piston jet hole washer, marking the transformation of my country's coal mine pressure relief gas extraction technology from traditional drilling to refined operations. Compared with the NB/T 10366-2013 version, the quantitative index of hole-digging and hole-expansion radius ≥ 80mm and the innovative process of PH13.1 alkali solution well washing have been added.

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Comparison of key technical parameters

Technical links	Core parameters	Requirements of the old standard	Requirements of this version
Hole enlargement	Well wall radius increment	No clear regulation	≥80mm
Well washing process	Alkali solution concentration	No requirement	5% PH13.1
Well washing with air compressor	Segment height	≤300m	≤250m

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Key points for the implementation of core technology

5.1 Hole digging and hole enlargement technology

When using Φ420mm hole digging drill bit, it is necessary to pay attention to: The wing knife expansion angle should ensure that the cutting radius meets the standard, and the hole enlargement section should be controlled in the precise range of 7-10m from the top plate of the protective layer to 10m from the top plate of the protected layer. Typical cases show that the gas extraction concentration in Huainan mining area increased by 40% after the application of this technology.

6.3 Composite well washing process

The original "alkali solution softening-piston jet-air compressor shock" three-stage well washing method:

1. First, soak in alkali solution for 24 hours to destroy the mud colloidal structure
2. Then use a Φ73mm piston jet hole washer to achieve slow pull and fast release circulation flushing
3. Finally, use a 2MPa air compressor to perform staged depth reduction flushing

The practice of Shaanxi Taihe Drilling shows that this process can improve the well washing efficiency by more than 60%.

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Key control points for safety management

Drilling tower installation specifications:

• 8 guy ropes are arranged symmetrically and the included angle is ≤45°
• Lightning rod grounding resistance is ≤10Ω
• Fire extinguishers are configured with ≥4

An analysis of an accident in a mine in Anhui Province showed that 80% of drilling tower accidents were caused by excessive guy rope angles or poor grounding.

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Recommendations for the implementation of the standard

1. Process connection optimization: It is recommended to control the interval between the hole digging and well washing processes within 48 hours to prevent secondary contamination of the well wall
2. Parameter monitoring system: Establish a system for real-time monitoring of pH value and return water volume recording during the well washing process
3. Equipment selection guide: Give priority to hole digging drill bits equipped with automatic wing knife retraction and extension system to reduce the risk of drill sticking

NB/T 11467-2023 Referenced Document

• DZ/T 0250 Specifications for coalbed methane drilling engineering
• GB 50471 Standard for design of the gas drainage engineering of coal mine
• NB/T 10366 Coal mine pressure relief gas surface drilling and drainage technology methods

NB/T 11467-2023 history

• 2023 NB/T 11467-2023 Technical Specifications for Surface Drilling Hole Expansion and Increased Pumping and Pressure Relief Gas

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