Surface-to-Inseam Gas Drainage Program for Longwall Mining

Project Overview

A coal mining operator identified elevated virgin methane concentrations within a planned longwall mining panel, requiring accelerated gas drainage to ensure safe mine development. To achieve the required reduction in in-situ gas content within the limited pre-mining timeframe, the operator elected to supplement conventional underground drainage methods with oil and gas style directional drilling using surface-to-inseam wells. JJM personnel were engaged to design and deliver the program, applying directional drilling and reservoir engineering techniques to rapidly depressurise the coal seam ahead of mining operations.

Project Details

Location: Australia
Project Type: Coal Mine Gas Drainage
Scope: Surface-to-Inseam Directional Drilling Program
Role: Well Engineering, Subsurface Engineering and Project Management

Scope of Work

• Reservoir modelling to optimise well spacing, lateral design and drainage performance

• Development of well designs for surface-to-inseam directional wells

• Detailed drilling and completion program preparation

• Drilling of two multi-lateral inseam wells

• Drilling of two vertical wells for drainage and monitoring

• Horizontal-to-vertical well ranging and intersection operations

• Procurement and installation of artificial lift systems

• Design and installation of well site gas gathering and flaring facilities

• Commissioning and operation of surface production infrastructure

• Ongoing asset support and monitoring of drainage performance

Key Challenges

• Achieving significant methane reduction within a constrained drainage timeframe prior to longwall mining operations

• Designing directional well trajectories capable of maximising coal seam contact and drainage efficiency

• Integrating oil and gas style drilling techniques with coal mine gas management practices

• Muli well pad SIMOPs operations involving simultaneous drilling and workover operations on adjacent wells

• Managing drilling accuracy for horizontal-to-vertical well intersection operations

• Designing surface facilities capable of safely handling variable gas production rates

Outcome

The directional drilling and gas drainage program was successfully delivered on schedule and under budget. The surface-to-inseam wells achieved the required methane drainage performance, reducing in-situ gas content within the longwall panel to levels suitable for safe mining operations. The project enabled uninterrupted longwall development while demonstrating the effectiveness of directional drilling technology in accelerating pre-drainage of coal seam methane.