Exploration diamond drilling, a pivotal technique in the mining and geological exploration industry, has a rich history dating back to the mid-19th century. This article delves into the historical evolution of exploration diamond drilling, tracing its roots from its invention to its impact on mineral exploration in remote regions.
Invention and Early Advancements
The credit for inventing the first core bit in 1863 goes to Rodolphe Leschot. His groundbreaking innovation laid the foundation for diamond drilling, marking a departure from conventional mineral prospecting methods. Before the advent of portable diamond drills, exploration was primarily restricted to surface outcrops and manual digging. Leschot's invention opened up new avenues for mineral exploration, allowing prospectors to explore deeper into the Earth's crust.
Diamond Drilling Technology Emerges
One of the significant milestones in the evolution of diamond drilling was the development of polycrystalline diamond compacts (PDCs) by General Electric in the late 1970s. PDCs revolutionized the industry by replacing natural diamonds in drill bits, making the process more efficient and cost-effective. This innovation brought about a seismic shift in the way mineral exploration was conducted, enabling drilling in challenging terrains and at greater depths.
The Core of Diamond Drilling
At the heart of exploration diamond drilling lies the diamond-encrusted drill bit. These bits consist of industrial diamonds embedded in a soft metallic matrix. The diamonds are strategically placed within the matrix, with their exposure relying on the gradual wear of the matrix during drilling. The drill bit is mounted onto a core barrel, which is connected to a drill string attached to a rotary drill rig. Drilling mud is injected into the drill pipe to wash away rock cuttings and reduce friction-induced heat, prolonging the life of the bits.
Core Extraction and Retrieval
As drilling depth increased, a critical challenge emerged: how to extract and retrieve the core from the depths efficiently. Simply withdrawing the heavy drill pipe was not a practical solution. Wireline drilling methods were developed to tackle this issue, particularly in situations where an undisturbed core in fractured rock was essential. These wireline systems, exemplified by the triple-tube method, played a crucial role in core extraction, even in challenging environments like fault zones such as the San Andreas Fault.
Tube Sizes and Their Significance
The choice of tube size in wireline drilling is a crucial consideration, balancing the desired core diameter with the drilling rig's capabilities. Larger tubes produce larger diameter rock cores but demand more drilling power. Standard "Q" wireline bit sizes, including AQ, BQ, NQ, HQ, HQ3, PQ, PQ3, CHD 76, CHD 101, and CHD 134, cater to various drilling needs based on core size and drilling depth.