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>Well costs are ~quadratic in depth. Anyone know as to why this is the case? At first pass it seems like your cutting tools should wear out in proportion to d

>Well costs are ~quadratic in depth. Anyone know as to why this is the case? At first pass it seems like your cutting tools should wear out in proportion to depth. But I suppose as things get warmer tool wear becomes faster. What types of tool materials are used for rock boring? Diamond? Tungsten carbide? Is is more of a "conventional machining" process, or an abrasive / water jet? Or explosive like in hard rock mining? What else has an effect on cost for deep holes? Shaft length gets longer, so the twist becomes more of a problem if your are driving rotating bits from the top? Does it have to do with removing the material from the bottom of the hole to the top? Others?

cnnsucks 9y ago
"Anyone know as to why this is the case?" Think of a telescopic antenna. That structure is similar to what is done to bore a well. You start with large casing diameter and add progressively smaller casings until you reach the target depth. The deeper you go the bigger the casing you must start with. Offshore deep water stuff can be a meter in diameter with 10cm solid steel walls; monstrously heavy and costly materials. And you use kilometers of the stuff. There are a lot of reasons why costs scale as they do with depth; casing is just one of the more obvious.
- GregBuchholz 9y ago
  Anyone recommend a good pop-sci book on deep hole boring? Seems like it could be an interesting light engineering read.
- lumost 9y ago
  For deep wells would the need for casing change depending on the material you're drilling into? once your into hard granite bedrock I'd imagine wells of a certain diameter are stable with minimal to no casing.
  - cnnsucks 9y ago
    Yes, geology is a big factor in engineering a well. Pressure is another. Every well is engineered to the prevailing conditions and requirements. Sometimes it is possible to elide heavy casing which can save large amounts of money.

cnnsucks 9y ago

"Anyone know as to why this is the case?" Think of a telescopic antenna. That structure is similar to what is done to bore a well. You start with large casing diameter and add progressively smaller casings until you reach the target depth. The deeper you go the bigger the casing you must start with. Offshore deep water stuff can be a meter in diameter with 10cm solid steel walls; monstrously heavy and costly materials. And you use kilometers of the stuff. There are a lot of reasons why costs scale as they do with depth; casing is just one of the more obvious.

GregBuchholz 9y ago
Anyone recommend a good pop-sci book on deep hole boring? Seems like it could be an interesting light engineering read.
lumost 9y ago
For deep wells would the need for casing change depending on the material you're drilling into? once your into hard granite bedrock I'd imagine wells of a certain diameter are stable with minimal to no casing.
- cnnsucks 9y ago
  Yes, geology is a big factor in engineering a well. Pressure is another. Every well is engineered to the prevailing conditions and requirements. Sometimes it is possible to elide heavy casing which can save large amounts of money.