UK Mining, the Oil & Gas Industry & the Rescue of the Chilean Miners
The rescue of the Chilean miners brought the world's attention to an application of directional drilling technology which had been used to locate, sustain, supply and to finally provide the rescue egress route out of the mine workings for the 33 miners who had become trapped in the workings.
Directional drilling as a technique was initially developed as a result of a specification requirement put out by the UK coal mining industry to drill very high accuracy wells with minimal departure from the vertical. This allowed the construction and placement of a ring of wells around a shaft sinking location. On completion, chilled brine was circulated through the wells creating initially a freeze curtain and then freezing (within the ground within the boundary set by the wells) the water in the aquifer rock formation.
Using this technique, with the aquifer frozen, conventional shaft sinking techniques could be used while preserving the environmental integrity of these formations which in the UK often provide the main source of water supply for the population. This technique was brought to a high state of refinement during the Selby coalfield development in the 1980s which has left the UK as a major source of expertise in projects of this type.
The oil and gas industry turned to directional drilling technology in the mid-1970s. Prior to this, hydrocarbons could be searched for and exploited with much less effort, reserves often under-exploited with low rates of recovery achieved before moving on as it was often cheaper and easier to move on to set up and start new wells elsewhere. In the 1950s exploratory drilling achieved discovery rates of around 900 barrels of oil equivalent (boe) per foot of well drilled in an area with no existing hydrocarbon production. By 1977 this had dropped to 200 boe, forcing the industry to increase recovery efficiency and exploit smaller reserves in poorer, less defined reservoirs with wells of greater depths and more complex well geometry.
The industry now regularly drills horizontal wells using this technology to horizontal departures from a surface location in excess of 10km, with ultra extended reach wells now being initiated in excess of 15km departure.
Extending the reach requires high accuracy measurements to define well location, its position relative to origin, trajectory and ultimately placement. The further the reach of these types of wells, the higher the accuracy of the basic measurements is required in order to keep target error models within accepted industry standards.
The Chilean miner rescue was enabled by accurate drilling and placement of a well from surface to a set of co-ordinates determined from mine survey information. The skills and procedures of the mining and oil and gas industries have much in common and in this case they came together to get the miners out and home.