Seismic-reflection techniques are widely exploited in exploration for hydrocarbons, and have consequently reached a high state of development. Improvements in resolution and fidelity of recorded information, and in techniques for extracting and interpreting information contained in recorded data, are such that seismic techniques are increasingly attractive in both the resource-evaluation and mine-planning aspects of coal exploration. Field, processing, and interpretation methodologies consistent with the vertical and lateral resolution necessary for delineation of fine structure in a coal-bearing section differ significantly from those which are praxis in seismic exploration for hydrocarbon-bearing structures.
The key to improved resolution lies in maximizing signal bandwidth and dominant frequency, and minimizing signal-generated and other noise. Explosive charges detonated below the geophysical weathered layer are the richest sources of high frequencies available for seismic work; for high resolution, the smallest charges capable of providing the required penetration are preferred on the basis that the source spectra are displaced to higher frequencies. The technology necessary for detecting and recording high frequency information can be accurately specified in terms of dynamic range, bandwidth, and frequency discrimination. Processing high-resolution data is conceptually simple but demands extreme care.
Notwithstanding the capabilities of high-resolution seismic techniques, maximum resolution is ultimately limited by the complexity of the earth. In particular, the resolution of multiple seams is limited by internal multiples, which have a higher frequency content than transmitted primaries. Reflection data from two markedly different coal-bearing sections in Australia illustrate the scope, and indirectly the, viability of seismic exploration for coal.
Figures & Tables
The energy and mineral resources of the vast Pacific basin and its neighboring land areas play a vital role in meeting the ever-growing needs of society worldwide. Building on the foundation of a highly successful conference held in 1978, this volume contains 51 of the 135 papers presented there. Subjects included are general and specific in nature--oil, gas, and coal resources; geothermal fields, uranium; tin; evaporites, trace elements; water resources; magma energy and fuels from magma. Geological and geophysical techniques, and also the new tool of remote sending for petroleum and minerals exploration are represented. Tectonics, structure fundamentals, subsurface hazards, international treaties and the law of the deep sea are discussed. Seventeen countries and regions are represented in these papers: Thailand, Nicaragua, the United States, Japan, Peru, Antarctica, El Salvador, Australia, Mexico, Taiwan, New Zealand, China, Chile, Indonesia, Canada, and the Pacific Ocean.