Jawaharlal Nehru Technological University Hyderabad B.Tech III MINING OF DEEP-SEATED DEPOSITS Previous Question Paper (March - 2021 - R18)

Modern exploration for complex coal deposits relies on high-resolution geophysical and remote sensing methods to delineate structural complexities and seam continuity. Key techniques include:

• High-Resolution 3D Seismic Reflection: Used to map geological structures, faults, and seam discontinuities at depth with high precision.
• Geophysical Well Logging: Utilizing density, resistivity, and gamma-ray logs to determine coal quality, seam thickness, and roof/floor rock characteristics.
• Directional Core Drilling: Allows for multiple intersections of a coal seam from a single surface location, providing detailed stratigraphic data in folded or faulted terrain.
• Remote Sensing and Hyperspectral Imaging: Employed to identify surface expressions of geological features and monitor subsidence or environmental impacts.
• In-seam Seismic (ISS): Specifically used in underground environments to detect small-scale faults or washouts within the coal seam that are not visible from surface surveys.

Coal deposits are classified based on their rank (degree of metamorphism), geological age, and structural complexity. The primary classification by rank is as follows:

• Peat: The precursor to coal, containing high moisture and low carbon content.
• Lignite (Brown Coal): Low-rank coal with high moisture content and low calorific value.
• Sub-bituminous Coal: Intermediate rank, often used for power generation.
• Bituminous Coal: The most common type, used extensively for steam raising and coking.
• Anthracite: The highest rank, characterized by high carbon content, low volatile matter, and high energy density.

Additionally, coal deposits are categorized by their geological occurrence:

• Gondwana Coal: Older, high-quality deposits (Permian age) found in the southern hemisphere regions.
• Tertiary Coal: Younger deposits (Eocene to Miocene age) typically characterized by higher sulfur content and lower rank.